- 10 Apr, 2019 16 commits
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Daniel Borkmann authored
Extend test_btf with various positive and negative tests around BTF verification of kind Var and DataSec. All passing as well: # ./test_btf [...] BTF raw test[4] (global data test #1): OK BTF raw test[5] (global data test #2): OK BTF raw test[6] (global data test #3): OK BTF raw test[7] (global data test #4, unsupported linkage): OK BTF raw test[8] (global data test #5, invalid var type): OK BTF raw test[9] (global data test #6, invalid var type (fwd type)): OK BTF raw test[10] (global data test #7, invalid var type (fwd type)): OK BTF raw test[11] (global data test #8, invalid var size): OK BTF raw test[12] (global data test #9, invalid var size): OK BTF raw test[13] (global data test #10, invalid var size): OK BTF raw test[14] (global data test #11, multiple section members): OK BTF raw test[15] (global data test #12, invalid offset): OK BTF raw test[16] (global data test #13, invalid offset): OK BTF raw test[17] (global data test #14, invalid offset): OK BTF raw test[18] (global data test #15, not var kind): OK BTF raw test[19] (global data test #16, invalid var referencing sec): OK BTF raw test[20] (global data test #17, invalid var referencing var): OK BTF raw test[21] (global data test #18, invalid var loop): OK BTF raw test[22] (global data test #19, invalid var referencing var): OK BTF raw test[23] (global data test #20, invalid ptr referencing var): OK BTF raw test[24] (global data test #21, var included in struct): OK BTF raw test[25] (global data test #22, array of var): OK [...] PASS:167 SKIP:0 FAIL:0 Signed-off-by:
Daniel Borkmann <daniel@iogearbox.net> Acked-by:
Martin KaFai Lau <kafai@fb.com> Signed-off-by:
Alexei Starovoitov <ast@kernel.org>
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Joe Stringer authored
Add tests for libbpf relocation of static variable references into the .data, .rodata and .bss sections of the ELF, also add read-only test for .rodata. All passing: # ./test_progs [...] test_global_data:PASS:load program 0 nsec test_global_data:PASS:pass global data run 925 nsec test_global_data_number:PASS:relocate .bss reference 925 nsec test_global_data_number:PASS:relocate .data reference 925 nsec test_global_data_number:PASS:relocate .rodata reference 925 nsec test_global_data_number:PASS:relocate .bss reference 925 nsec test_global_data_number:PASS:relocate .data reference 925 nsec test_global_data_number:PASS:relocate .rodata reference 925 nsec test_global_data_number:PASS:relocate .bss reference 925 nsec test_global_data_number:PASS:relocate .bss reference 925 nsec test_global_data_number:PASS:relocate .rodata reference 925 nsec test_global_data_number:PASS:relocate .rodata reference 925 nsec test_global_data_number:PASS:relocate .rodata reference 925 nsec test_global_data_string:PASS:relocate .rodata reference 925 nsec test_global_data_string:PASS:relocate .data reference 925 nsec test_global_data_string:PASS:relocate .bss reference 925 nsec test_global_data_string:PASS:relocate .data reference 925 nsec test_global_data_string:PASS:relocate .bss reference 925 nsec test_global_data_struct:PASS:relocate .rodata reference 925 nsec test_global_data_struct:PASS:relocate .bss reference 925 nsec test_global_data_struct:PASS:relocate .rodata reference 925 nsec test_global_data_struct:PASS:relocate .data reference 925 nsec test_global_data_rdonly:PASS:test .rodata read-only map 925 nsec [...] Summary: 229 PASSED, 0 FAILED Note map helper signatures have been changed to avoid warnings when passing in const data. Joint work with Daniel Borkmann. Signed-off-by:
Joe Stringer <joe@wand.net.nz> Signed-off-by:
Andrii Nakryiko <andriin@fb.com> Acked-by:
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Daniel Borkmann authored
Extend test_verifier with various test cases around the two kernel extensions, that is, {rd,wr}only map support as well as direct map value access. All passing, one skipped due to xskmap not present on test machine: # ./test_verifier [...] #948/p XDP pkt read, pkt_meta' <= pkt_data, bad access 1 OK #949/p XDP pkt read, pkt_meta' <= pkt_data, bad access 2 OK #950/p XDP pkt read, pkt_data <= pkt_meta', good access OK #951/p XDP pkt read, pkt_data <= pkt_meta', bad access 1 OK #952/p XDP pkt read, pkt_data <= pkt_meta', bad access 2 OK Summary: 1410 PASSED, 1 SKIPPED, 0 FAILED Signed-off-by: -
Daniel Borkmann authored
Add the ability to bpftool to handle BTF Var and DataSec kinds in order to dump them out of btf_dumper_type(). The value has a single object with the section name, which itself holds an array of variables it dumps. A single variable is an object by itself printed along with its name. From there further type information is dumped along with corresponding value information. Example output from .rodata: # ./bpftool m d i 150 [{ "value": { ".rodata": [{ "load_static_data.bar": 18446744073709551615 },{ "num2": 24 },{ "num5": 43947 },{ "num6": 171 },{ "str0": [97,98,99,100,101,102,103,104,105,106,107,108,109,110,111,112,113,114,115,116,117,118,119,120,121,122,0,0,0,0,0,0 ] },{ "struct0": { "a": 42, "b": 4278120431, "c": 1229782938247303441 } },{ "struct2": { "a": 0, "b": 0, "c": 0 } } ] } } ] Signed-off-by: -
Daniel Borkmann authored
This adds libbpf support for BTF Var and DataSec kinds. Main point here is that libbpf needs to do some preparatory work before the whole BTF object can be loaded into the kernel, that is, fixing up of DataSec size taken from the ELF section size and non-static variable offset which needs to be taken from the ELF's string section. Upstream LLVM doesn't fix these up since at time of BTF emission it is too early in the compilation process thus this information isn't available yet, hence loader needs to take care of it. Note, deduplication handling has not been in the scope of this work and needs to be addressed in a future commit. Signed-off-by:
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Daniel Borkmann authored
This work adds BPF loader support for global data sections to libbpf. This allows to write BPF programs in more natural C-like way by being able to define global variables and const data. Back at LPC 2018 [0] we presented a first prototype which implemented support for global data sections by extending BPF syscall where union bpf_attr would get additional memory/size pair for each section passed during prog load in order to later add this base address into the ldimm64 instruction along with the user provided offset when accessing a variable. Consensus from LPC was that for proper upstream support, it would be more desirable to use maps instead of bpf_attr extension as this would allow for introspection of these sections as well as potential live updates of their content. This work follows this path by taking the following steps from loader side: 1) In bpf_object__elf_collect() step we pick up ".data", ".rodata", and ".bss" section information. 2) If present, in bpf_object__init_internal_map() we add maps to the obj's map array that corresponds to each of the present sections. Given section size and access properties can differ, a single entry array map is created with value size that is corresponding to the ELF section size of .data, .bss or .rodata. These internal maps are integrated into the normal map handling of libbpf such that when user traverses all obj maps, they can be differentiated from user-created ones via bpf_map__is_internal(). In later steps when we actually create these maps in the kernel via bpf_object__create_maps(), then for .data and .rodata sections their content is copied into the map through bpf_map_update_elem(). For .bss this is not necessary since array map is already zero-initialized by default. Additionally, for .rodata the map is frozen as read-only after setup, such that neither from program nor syscall side writes would be possible. 3) In bpf_program__collect_reloc() step, we record the corresponding map, insn index, and relocation type for the global data. 4) And last but not least in the actual relocation step in bpf_program__relocate(), we mark the ldimm64 instruction with src_reg = BPF_PSEUDO_MAP_VALUE where in the first imm field the map's file descriptor is stored as similarly done as in BPF_PSEUDO_MAP_FD, and in the second imm field (as ldimm64 is 2-insn wide) we store the access offset into the section. Given these maps have only single element ldimm64's off remains zero in both parts. 5) On kernel side, this special marked BPF_PSEUDO_MAP_VALUE load will then store the actual target address in order to have a 'map-lookup'-free access. That is, the actual map value base address + offset. The destination register in the verifier will then be marked as PTR_TO_MAP_VALUE, containing the fixed offset as reg->off and backing BPF map as reg->map_ptr. Meaning, it's treated as any other normal map value from verification side, only with efficient, direct value access instead of actual call to map lookup helper as in the typical case. Currently, only support for static global variables has been added, and libbpf rejects non-static global variables from loading. This can be lifted until we have proper semantics for how BPF will treat multi-object BPF loads. From BTF side, libbpf will set the value type id of the types corresponding to the ".bss", ".data" and ".rodata" names which LLVM will emit without the object name prefix. The key type will be left as zero, thus making use of the key-less BTF option in array maps. Simple example dump of program using globals vars in each section: # bpftool prog [...] 6784: sched_cls name load_static_dat tag a7e1291567277844 gpl loaded_at 2019-03-11T15:39:34+0000 uid 0 xlated 1776B jited 993B memlock 4096B map_ids 2238,2237,2235,2236,2239,2240 # bpftool map show id 2237 2237: array name test_glo.bss flags 0x0 key 4B value 64B max_entries 1 memlock 4096B # bpftool map show id 2235 2235: array name test_glo.data flags 0x0 key 4B value 64B max_entries 1 memlock 4096B # bpftool map show id 2236 2236: array name test_glo.rodata flags 0x80 key 4B value 96B max_entries 1 memlock 4096B # bpftool prog dump xlated id 6784 int load_static_data(struct __sk_buff * skb): ; int load_static_data(struct __sk_buff *skb) 0: (b7) r6 = 0 ; test_reloc(number, 0, &num0); 1: (63) *(u32 *)(r10 -4) = r6 2: (bf) r2 = r10 ; int load_static_data(struct __sk_buff *skb) 3: (07) r2 += -4 ; test_reloc(number, 0, &num0); 4: (18) r1 = map[id:2238] 6: (18) r3 = map[id:2237][0]+0 <-- direct addr in .bss area 8: (b7) r4 = 0 9: (85) call array_map_update_elem#100464 10: (b7) r1 = 1 ; test_reloc(number, 1, &num1); [...] ; test_reloc(string, 2, str2); 120: (18) r8 = map[id:2237][0]+16 <-- same here at offset +16 122: (18) r1 = map[id:2239] 124: (18) r3 = map[id:2237][0]+16 126: (b7) r4 = 0 127: (85) call array_map_update_elem#100464 128: (b7) r1 = 120 ; str1[5] = 'x'; 129: (73) *(u8 *)(r9 +5) = r1 ; test_reloc(string, 3, str1); 130: (b7) r1 = 3 131: (63) *(u32 *)(r10 -4) = r1 132: (b7) r9 = 3 133: (bf) r2 = r10 ; int load_static_data(struct __sk_buff *skb) 134: (07) r2 += -4 ; test_reloc(string, 3, str1); 135: (18) r1 = map[id:2239] 137: (18) r3 = map[id:2235][0]+16 <-- direct addr in .data area 139: (b7) r4 = 0 140: (85) call array_map_update_elem#100464 141: (b7) r1 = 111 ; __builtin_memcpy(&str2[2], "hello", sizeof("hello")); 142: (73) *(u8 *)(r8 +6) = r1 <-- further access based on .bss data 143: (b7) r1 = 108 144: (73) *(u8 *)(r8 +5) = r1 [...] For Cilium use-case in particular, this enables migrating configuration constants from Cilium daemon's generated header defines into global data sections such that expensive runtime recompilations with LLVM can be avoided altogether. Instead, the ELF file becomes effectively a "template", meaning, it is compiled only once (!) and the Cilium daemon will then rewrite relevant configuration data from the ELF's .data or .rodata sections directly instead of recompiling the program. The updated ELF is then loaded into the kernel and atomically replaces the existing program in the networking datapath. More info in [0]. Based upon recent fix in LLVM, commit c0db6b6bd444 ("[BPF] Don't fail for static variables"). [0] LPC 2018, BPF track, "ELF relocation for static data in BPF", http://vger.kernel.org/lpc-bpf2018.html#session-3Signed-off-by: -
Joe Stringer authored
Adjust the code for relocations slightly with no functional changes, so that upcoming patches that will introduce support for relocations into the .data, .rodata and .bss sections can be added independent of these changes. Signed-off-by:
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Daniel Borkmann authored
Pull in latest changes from both headers, so we can make use of them in libbpf. Signed-off-by:
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Daniel Borkmann authored
Given we'll be reusing BPF array maps for global data/bss/rodata sections, we need a way to associate BTF DataSec type as its map value type. In usual cases we have this ugly BPF_ANNOTATE_KV_PAIR() macro hack e.g. via 38d5d3b3 ("bpf: Introduce BPF_ANNOTATE_KV_PAIR") to get initial map to type association going. While more use cases for it are discouraged, this also won't work for global data since the use of array map is a BPF loader detail and therefore unknown at compilation time. For array maps with just a single entry we make an exception in terms of BTF in that key type is declared optional if value type is of DataSec type. The latter LLVM is guaranteed to emit and it also aligns with how we regard global data maps as just a plain buffer area reusing existing map facilities for allowing things like introspection with existing tools. Signed-off-by:
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Daniel Borkmann authored
This work adds kernel-side verification, logging and seq_show dumping of BTF Var and DataSec kinds which are emitted with latest LLVM. The following constraints apply: BTF Var must have: - Its kind_flag is 0 - Its vlen is 0 - Must point to a valid type - Type must not resolve to a forward type - Size of underlying type must be > 0 - Must have a valid name - Can only be a source type, not sink or intermediate one - Name may include dots (e.g. in case of static variables inside functions) - Cannot be a member of a struct/union - Linkage so far can either only be static or global/allocated BTF DataSec must have: - Its kind_flag is 0 - Its vlen cannot be 0 - Its size cannot be 0 - Must have a valid name - Can only be a source type, not sink or intermediate one - Name may include dots (e.g. to represent .bss, .data, .rodata etc) - Cannot be a member of a struct/union - Inner btf_var_secinfo array with {type,offset,size} triple must be sorted by offset in ascending order - Type must always point to BTF Var - BTF resolved size of Var must be <= size provided by triple - DataSec size must be >= sum of triple sizes (thus holes are allowed) btf_var_resolve(), btf_ptr_resolve() and btf_modifier_resolve() are on a high level quite similar but each come with slight, subtle differences. They could potentially be a bit refactored in future which hasn't been done here to ease review. Signed-off-by: -
Daniel Borkmann authored
This adds the BTF specification and UAPI bits for supporting BTF Var and DataSec kinds. This is following LLVM upstream commit ac4082b77e07 ("[BPF] Add BTF Var and DataSec Support") which has been merged recently. Var itself is for describing a global variable and DataSec to describe ELF sections e.g. data/bss/rodata sections that hold one or multiple global variables. Signed-off-by: -
Daniel Borkmann authored
Trivial addition to allow '.' aside from '_' as "special" characters in the object name. Used to allow for substrings in maps from loader side such as ".bss", ".data", ".rodata", but could also be useful for other purposes. Signed-off-by:
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Daniel Borkmann authored
This patch adds a new BPF_MAP_FREEZE command which allows to "freeze" the map globally as read-only / immutable from syscall side. Map permission handling has been refactored into map_get_sys_perms() and drops FMODE_CAN_WRITE in case of locked map. Main use case is to allow for setting up .rodata sections from the BPF ELF which are loaded into the kernel, meaning BPF loader first allocates map, sets up map value by copying .rodata section into it and once complete, it calls BPF_MAP_FREEZE on the map fd to prevent further modifications. Right now BPF_MAP_FREEZE only takes map fd as argument while remaining bpf_attr members are required to be zero. I didn't add write-only locking here as counterpart since I don't have a concrete use-case for it on my side, and I think it makes probably more sense to wait once there is actually one. In that case bpf_attr can be extended as usual with a flag field and/or others where flag 0 means that we lock the map read-only hence this doesn't prevent to add further extensions to BPF_MAP_FREEZE upon need. A map creation flag like BPF_F_WRONCE was not considered for couple of reasons: i) in case of a generic implementation, a map can consist of more than just one element, thus there could be multiple map updates needed to set the map into a state where it can then be made immutable, ii) WRONCE indicates exact one-time write before it is then set immutable. A generic implementation would set a bit atomically on map update entry (if unset), indicating that every subsequent update from then onwards will need to bail out there. However, map updates can fail, so upon failure that flag would need to be unset again and the update attempt would need to be repeated for it to be eventually made immutable. While this can be made race-free, this approach feels less clean and in combination with reason i), it's not generic enough. A dedicated BPF_MAP_FREEZE command directly sets the flag and caller has the guarantee that map is immutable from syscall side upon successful return for any future syscall invocations that would alter the map state, which is also more intuitive from an API point of view. A command name such as BPF_MAP_LOCK has been avoided as it's too close with BPF map spin locks (which already has BPF_F_LOCK flag). BPF_MAP_FREEZE is so far only enabled for privileged users. Signed-off-by:
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Daniel Borkmann authored
This work adds two new map creation flags BPF_F_RDONLY_PROG and BPF_F_WRONLY_PROG in order to allow for read-only or write-only BPF maps from a BPF program side. Today we have BPF_F_RDONLY and BPF_F_WRONLY, but this only applies to system call side, meaning the BPF program has full read/write access to the map as usual while bpf(2) calls with map fd can either only read or write into the map depending on the flags. BPF_F_RDONLY_PROG and BPF_F_WRONLY_PROG allows for the exact opposite such that verifier is going to reject program loads if write into a read-only map or a read into a write-only map is detected. For read-only map case also some helpers are forbidden for programs that would alter the map state such as map deletion, update, etc. As opposed to the two BPF_F_RDONLY / BPF_F_WRONLY flags, BPF_F_RDONLY_PROG as well as BPF_F_WRONLY_PROG really do correspond to the map lifetime. We've enabled this generic map extension to various non-special maps holding normal user data: array, hash, lru, lpm, local storage, queue and stack. Further generic map types could be followed up in future depending on use-case. Main use case here is to forbid writes into .rodata map values from verifier side. Signed-off-by:
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Daniel Borkmann authored
Both BPF_F_WRONLY / BPF_F_RDONLY flags are tied to the map file descriptor, but not to the map object itself! Meaning, at map creation time BPF_F_RDONLY can be set to make the map read-only from syscall side, but this holds only for the returned fd, so any other fd either retrieved via bpf file system or via map id for the very same underlying map object can have read-write access instead. Given that, keeping the two flags around in the map_flags attribute and exposing them to user space upon map dump is misleading and may lead to false conclusions. Since these two flags are not tied to the map object lets also not store them as map property. Signed-off-by:
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Daniel Borkmann authored
This generic extension to BPF maps allows for directly loading an address residing inside a BPF map value as a single BPF ldimm64 instruction! The idea is similar to what BPF_PSEUDO_MAP_FD does today, which is a special src_reg flag for ldimm64 instruction that indicates that inside the first part of the double insns's imm field is a file descriptor which the verifier then replaces as a full 64bit address of the map into both imm parts. For the newly added BPF_PSEUDO_MAP_VALUE src_reg flag, the idea is the following: the first part of the double insns's imm field is again a file descriptor corresponding to the map, and the second part of the imm field is an offset into the value. The verifier will then replace both imm parts with an address that points into the BPF map value at the given value offset for maps that support this operation. Currently supported is array map with single entry. It is possible to support more than just single map element by reusing both 16bit off fields of the insns as a map index, so full array map lookup could be expressed that way. It hasn't been implemented here due to lack of concrete use case, but could easily be done so in future in a compatible way, since both off fields right now have to be 0 and would correctly denote a map index 0. The BPF_PSEUDO_MAP_VALUE is a distinct flag as otherwise with BPF_PSEUDO_MAP_FD we could not differ offset 0 between load of map pointer versus load of map's value at offset 0, and changing BPF_PSEUDO_MAP_FD's encoding into off by one to differ between regular map pointer and map value pointer would add unnecessary complexity and increases barrier for debugability thus less suitable. Using the second part of the imm field as an offset into the value does /not/ come with limitations since maximum possible value size is in u32 universe anyway. This optimization allows for efficiently retrieving an address to a map value memory area without having to issue a helper call which needs to prepare registers according to calling convention, etc, without needing the extra NULL test, and without having to add the offset in an additional instruction to the value base pointer. The verifier then treats the destination register as PTR_TO_MAP_VALUE with constant reg->off from the user passed offset from the second imm field, and guarantees that this is within bounds of the map value. Any subsequent operations are normally treated as typical map value handling without anything extra needed from verification side. The two map operations for direct value access have been added to array map for now. In future other types could be supported as well depending on the use case. The main use case for this commit is to allow for BPF loader support for global variables that reside in .data/.rodata/.bss sections such that we can directly load the address of them with minimal additional infrastructure required. Loader support has been added in subsequent commits for libbpf library. Signed-off-by:
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- 07 Apr, 2019 1 commit
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Andrey Ignatov authored
vsprintf() in __base_pr() uses nonliteral format string and it breaks compilation for those who provide corresponding extra CFLAGS, e.g.: https://github.com/libbpf/libbpf/issues/27 If libbpf is built with the flags from PR: libbpf.c:68:26: error: format string is not a string literal [-Werror,-Wformat-nonliteral] return vfprintf(stderr, format, args); ^~~~~~ 1 error generated. Ignore this warning since the use case in libbpf.c is legit. Signed-off-by:
Andrey Ignatov <rdna@fb.com> Acked-by:
Yonghong Song <yhs@fb.com> Signed-off-by:
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- 05 Apr, 2019 9 commits
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Daniel Borkmann authored
Andrey Ignatov says: ==================== v2->v3: - sanity check max value for variable offset. v1->v2: - rely on meta = NULL to reject var_off stack access to uninit buffer. This patch set is a follow-up for discussion [1]. It fixes variable offset stack access handling for raw and unprivileged mode, rejecting both of them, and sanity checks max variable offset value. Patch 1 handles raw (uninitialized) mode. Patch 2 adds test for raw mode. Patch 3 handles unprivileged mode. Patch 4 adds test for unprivileged mode. Patch 5 adds sanity check for max value of variable offset. Patch 6 adds test for variable offset max value checking. Patch 7 is a minor fix in verbose log. Unprivileged mode is an interesting case since one (and only?) way to come up with variable offset is to use pointer arithmetics. Though pointer arithmetics is already prohibited for unprivileged mode. I'm not sure if it's enough though and it seems like a good idea to still reject variable offset for unpriv in check_stack_boundary(). Please see patches 3 and 4 for more details on this. [1] https://marc.info/?l=linux-netdev&m=155419526427742&w=2 ==================== Signed-off-by:
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Andrey Ignatov authored
check_stack_access() that prints verbose log is used in adjust_ptr_min_max_vals() that prints its own verbose log and now they stick together, e.g.: variable stack access var_off=(0xfffffffffffffff0; 0x4) off=-16 size=1R2 stack pointer arithmetic goes out of range, prohibited for !root Add missing newline so that log is more readable: variable stack access var_off=(0xfffffffffffffff0; 0x4) off=-16 size=1 R2 stack pointer arithmetic goes out of range, prohibited for !root Fixes: f1174f77 ("bpf/verifier: rework value tracking") Signed-off-by:
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Andrey Ignatov authored
Test the case when reg->smax_value is too small/big and can overflow, and separately min and max values outside of stack bounds. Example of output: # ./test_verifier #856/p indirect variable-offset stack access, unbounded OK #857/p indirect variable-offset stack access, max out of bound OK #858/p indirect variable-offset stack access, min out of bound OK Signed-off-by:
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Andrey Ignatov authored
As discussed in [1] max value of variable offset has to be checked for overflow on stack access otherwise verifier would accept code like this: 0: (b7) r2 = 6 1: (b7) r3 = 28 2: (7a) *(u64 *)(r10 -16) = 0 3: (7a) *(u64 *)(r10 -8) = 0 4: (79) r4 = *(u64 *)(r1 +168) 5: (c5) if r4 s< 0x0 goto pc+4 R1=ctx(id=0,off=0,imm=0) R2=inv6 R3=inv28 R4=inv(id=0,umax_value=9223372036854775807,var_off=(0x0; 0x7fffffffffffffff)) R10=fp0,call_-1 fp-8=mmmmmmmm fp-16=mmmmmmmm 6: (17) r4 -= 16 7: (0f) r4 += r10 8: (b7) r5 = 8 9: (85) call bpf_getsockopt#57 10: (b7) r0 = 0 11: (95) exit , where R4 obviosly has unbounded max value. Fix it by checking that reg->smax_value is inside (-BPF_MAX_VAR_OFF; BPF_MAX_VAR_OFF) range. reg->smax_value is used instead of reg->umax_value because stack pointers are calculated using negative offset from fp. This is opposite to e.g. map access where offset must be non-negative and where umax_value is used. Also dedicated verbose logs are added for both min and max bound check failures to have diagnostics consistent with variable offset handling in check_map_access(). [1] https://marc.info/?l=linux-netdev&m=155433357510597&w=2 Fixes: 2011fccf ("bpf: Support variable offset stack access from helpers") Reported-by:
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Andrey Ignatov authored
Test that verifier rejects indirect stack access with variable offset in unprivileged mode and accepts same code in privileged mode. Since pointer arithmetics is prohibited in unprivileged mode verifier should reject the program even before it gets to helper call that uses variable offset, at the time when that variable offset is trying to be constructed. Example of output: # ./test_verifier ... #859/u indirect variable-offset stack access, priv vs unpriv OK #859/p indirect variable-offset stack access, priv vs unpriv OK Signed-off-by:
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Andrey Ignatov authored
Proper support of indirect stack access with variable offset in unprivileged mode (!root) requires corresponding support in Spectre masking for stack ALU in retrieve_ptr_limit(). There are no use-case for variable offset in unprivileged mode though so make verifier reject such accesses for simplicity. Pointer arithmetics is one (and only?) way to cause variable offset and it's already rejected in unpriv mode so that verifier won't even get to helper function whose argument contains variable offset, e.g.: 0: (7a) *(u64 *)(r10 -16) = 0 1: (7a) *(u64 *)(r10 -8) = 0 2: (61) r2 = *(u32 *)(r1 +0) 3: (57) r2 &= 4 4: (17) r2 -= 16 5: (0f) r2 += r10 variable stack access var_off=(0xfffffffffffffff0; 0x4) off=-16 size=1R2 stack pointer arithmetic goes out of range, prohibited for !root Still it looks like a good idea to reject variable offset indirect stack access for unprivileged mode in check_stack_boundary() explicitly. Fixes: 2011fccf ("bpf: Support variable offset stack access from helpers") Reported-by:
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Andrey Ignatov authored
Test that verifier rejects indirect access to uninitialized stack with variable offset. Example of output: # ./test_verifier ... #859/p indirect variable-offset stack access, uninitialized OK Signed-off-by:
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Andrey Ignatov authored
It's hard to guarantee that whole memory is marked as initialized on helper return if uninitialized stack is accessed with variable offset since specific bounds are unknown to verifier. This may cause uninitialized stack leaking. Reject such an access in check_stack_boundary to prevent possible leaking. There are no known use-cases for indirect uninitialized stack access with variable offset so it shouldn't break anything. Fixes: 2011fccf ("bpf: Support variable offset stack access from helpers") Reported-by:
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Alexei Starovoitov authored
clang started to error on invalid asm clobber usage in x86 headers and many bpf program samples failed to build with the message: CLANG-bpf /data/users/ast/bpf-next/samples/bpf/xdp_redirect_kern.o In file included from /data/users/ast/bpf-next/samples/bpf/xdp_redirect_kern.c:14: In file included from ../include/linux/in.h:23: In file included from ../include/uapi/linux/in.h:24: In file included from ../include/linux/socket.h:8: In file included from ../include/linux/uio.h:14: In file included from ../include/crypto/hash.h:16: In file included from ../include/linux/crypto.h:26: In file included from ../include/linux/uaccess.h:5: In file included from ../include/linux/sched.h:15: In file included from ../include/linux/sem.h:5: In file included from ../include/uapi/linux/sem.h:5: In file included from ../include/linux/ipc.h:9: In file included from ../include/linux/refcount.h:72: ../arch/x86/include/asm/refcount.h:72:36: error: asm-specifier for input or output variable conflicts with asm clobber list r->refs.counter, e, "er", i, "cx"); ^ ../arch/x86/include/asm/refcount.h:86:27: error: asm-specifier for input or output variable conflicts with asm clobber list r->refs.counter, e, "cx"); ^ 2 errors generated. Override volatile() to workaround the problem. Signed-off-by:
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- 04 Apr, 2019 2 commits
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Daniel T. Lee authored
Since, ksym_search added with verification logic for symbols existence, it could return NULL when the kernel symbols are not loaded. This commit will add NULL check logic after ksym_search. Signed-off-by:
Daniel T. Lee <danieltimlee@gmail.com> Signed-off-by:
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Daniel T. Lee authored
Currently, ksym_search located at trace_helpers won't check symbols are existing or not. In ksym_search, when symbol is not found, it will return &syms[0](_stext). But when the kernel symbols are not loaded, it will return NULL, which is not a desired action. This commit will add verification logic whether symbols are loaded prior to the symbol search. Signed-off-by:
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- 03 Apr, 2019 11 commits
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Daniel Borkmann authored
Alexei Starovoitov says: ==================== v1->v2: - fixed typo in patch 1 - added a patch to convert kcalloc to kvcalloc - added a patch to verbose 16-bit jump offset check - added a test with 1m insns This patch set is the first step to be able to accept large programs. The verifier still suffers from its brute force algorithm and large programs can easily hit 1M insn_processed limit. A lot more work is necessary to be able to verify large programs. v1: Realize two key ideas to speed up verification speed by ~20 times 1. every 'branching' instructions records all verifier states. not all of them are useful for search pruning. add a simple heuristic to keep states that were successful in search pruning and remove those that were not 2. mark_reg_read walks parentage chain of registers to mark parents as LIVE_READ. Once the register is marked there is no need to remark it again in the future. Hence stop walking the chain once first LIVE_READ is seen. 1st optimization gives 10x speed up on large programs and 2nd optimization reduces the cost of mark_reg_read from ~40% of cpu to <1%. Combined the deliver ~20x speedup on large programs. Faster and bounded verification time allows to increase insn_processed limit to 1 million from 130k. Worst case it takes 1/10 of a second to process that many instructions and peak memory consumption is peak_states * sizeof(struct bpf_verifier_state) which is around ~5Mbyte. Increase insn_per_program limit for root to insn_processed limit. Add verification stats and stress tests for verifier scalability. ==================== Signed-off-by: -
Alexei Starovoitov authored
Add a test to generate 1m ld_imm64 insns to stress the verifier. Bump the size of fill_ld_abs_vlan_push_pop test from 4k to 29k and jump_around_ld_abs from 4k to 5.5k. Larger sizes are not possible due to 16-bit offset encoding in jump instructions. Signed-off-by:
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Alexei Starovoitov authored
Add 3 basic tests that stress verifier scalability. test_verif_scale1.c calls non-inlined jhash() function 90 times on different position in the packet. This test simulates network packet parsing. jhash function is ~140 instructions and main program is ~1200 insns. test_verif_scale2.c force inlines jhash() function 90 times. This program is ~15k instructions long. test_verif_scale3.c calls non-inlined jhash() function 90 times on But this time jhash has to process 32-bytes from the packet instead of 14-bytes in tests 1 and 2. jhash function is ~230 insns and main program is ~1200 insns. $ test_progs -s can be used to see verifier stats. Signed-off-by:
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Alexei Starovoitov authored
Allow bpf_prog_load_xattr() to specify log_level for program loading. Teach libbpf to accept log_level with bit 2 set. Increase default BPF_LOG_BUF_SIZE from 256k to 16M. There is no downside to increase it to a maximum allowed by old kernels. Existing 256k limit caused ENOSPC errors and users were not able to see verifier error which is printed at the end of the verifier log. If ENOSPC is hit, double the verifier log and try again to capture the verifier error. Signed-off-by:
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Alexei Starovoitov authored
The existing 16Mbyte verifier log limit is not enough for log_level=2 even for small programs. Increase it to 1Gbyte. Note it's not a kernel memory limit. It's an amount of memory user space provides to store the verifier log. The kernel populates it 1k at a time. Signed-off-by:
Jakub Kicinski <jakub.kicinski@netronome.com> Signed-off-by:
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Alexei Starovoitov authored
Large verifier speed improvements allow to increase verifier complexity limit. Now regardless of the program composition and its size it takes little time for the verifier to hit insn_processed limit. On typical x86 machine non-debug kernel processes 1M instructions in 1/10 of a second. (before these speed improvements specially crafted programs could be hitting multi-second verification times) Full kasan kernel with debug takes ~1 second for the same 1M insns. Hence bump the BPF_COMPLEXITY_LIMIT_INSNS limit to 1M. Also increase the number of instructions per program from 4k to internal BPF_COMPLEXITY_LIMIT_INSNS limit. 4k limit was confusing to users, since small programs with hundreds of insns could be hitting BPF_COMPLEXITY_LIMIT_INSNS limit. Sometimes adding more insns and bpf_trace_printk debug statements would make the verifier accept the program while removing code would make the verifier reject it. Some user space application started to add #define MAX_FOO to their programs and do: MAX_FOO=100; again: compile with MAX_FOO; try to load; if (fails_to_load) { reduce MAX_FOO; goto again; } to be able to fit maximum amount of processing into single program. Other users artificially split their single program into a set of programs and use all 32 iterations of tail_calls to increase compute limits. And the most advanced folks used unlimited tc-bpf filter list to execute many bpf programs. Essentially the users managed to workaround 4k insn limit. This patch removes the limit for root programs from uapi. BPF_COMPLEXITY_LIMIT_INSNS is the kernel internal limit and success to load the program no longer depends on program size, but on 'smartness' of the verifier only. The verifier will continue to get smarter with every kernel release. Signed-off-by: -
Alexei Starovoitov authored
Larger programs may trigger 16-bit jump offset overflow check during instruction patching. Make this error verbose otherwise users cannot decipher error code without printks in the verifier. Signed-off-by:
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Alexei Starovoitov authored
Temporary arrays used during program verification need to be vmalloc-ed to support large bpf programs. Signed-off-by:
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Alexei Starovoitov authored
With large verifier speed improvement brought by the previous patch mark_reg_read() becomes the hottest function during verification. On a typical program it consumes 40% of cpu. mark_reg_read() walks parentage chain of registers to mark parents as LIVE_READ. Once the register is marked there is no need to remark it again in the future. Hence stop walking the chain once first LIVE_READ is seen. This optimization drops mark_reg_read() time from 40% of cpu to <1% and overall 2x improvement of verification speed. For some programs the longest_mark_read_walk counter improves from ~500 to ~5 Signed-off-by:
Edward Cree <ecree@solarflare.com> Signed-off-by:
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Alexei Starovoitov authored
Branch instructions, branch targets and calls in a bpf program are the places where the verifier remembers states that led to successful verification of the program. These states are used to prune brute force program analysis. For unprivileged programs there is a limit of 64 states per such 'branching' instructions (maximum length is tracked by max_states_per_insn counter introduced in the previous patch). Simply reducing this threshold to 32 or lower increases insn_processed metric to the point that small valid programs get rejected. For root programs there is no limit and cilium programs can have max_states_per_insn to be 100 or higher. Walking 100+ states multiplied by number of 'branching' insns during verification consumes significant amount of cpu time. Turned out simple LRU-like mechanism can be used to remove states that unlikely will be helpful in future search pruning. This patch introduces hit_cnt and miss_cnt counters: hit_cnt - this many times this state successfully pruned the search miss_cnt - this many times this state was not equivalent to other states (and that other states were added to state list) The heuristic introduced in this patch is: if (sl->miss_cnt > sl->hit_cnt * 3 + 3) /* drop this state from future considerations */ Higher numbers increase max_states_per_insn (allow more states to be considered for pruning) and slow verification speed, but do not meaningfully reduce insn_processed metric. Lower numbers drop too many states and insn_processed increases too much. Many different formulas were considered. This one is simple and works well enough in practice. (the analysis was done on selftests/progs/* and on cilium programs) The end result is this heuristic improves verification speed by 10 times. Large synthetic programs that used to take a second more now take 1/10 of a second. In cases where max_states_per_insn used to be 100 or more, now it's ~10. There is a slight increase in insn_processed for cilium progs: before after bpf_lb-DLB_L3.o 1831 1838 bpf_lb-DLB_L4.o 3029 3218 bpf_lb-DUNKNOWN.o 1064 1064 bpf_lxc-DDROP_ALL.o 26309 26935 bpf_lxc-DUNKNOWN.o 33517 34439 bpf_netdev.o 9713 9721 bpf_overlay.o 6184 6184 bpf_lcx_jit.o 37335 39389 And 2-3 times improvement in the verification speed. Signed-off-by: -
Alexei Starovoitov authored
In order to understand the verifier bottlenecks add various stats and extend log_level: log_level 1 and 2 are kept as-is: bit 0 - level=1 - print every insn and verifier state at branch points bit 1 - level=2 - print every insn and verifier state at every insn bit 2 - level=4 - print verifier error and stats at the end of verification When verifier rejects the program the libbpf is trying to load the program twice. Once with log_level=0 (no messages, only error code is reported to user space) and second time with log_level=1 to tell the user why the verifier rejected it. With introduction of bit 2 - level=4 the libbpf can choose to always use that level and load programs once, since the verification speed is not affected and in case of error the verbose message will be available. Note that the verifier stats are not part of uapi just like all other verbose messages. They're expected to change in the future. Signed-off-by:
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- 02 Apr, 2019 1 commit
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Andrii Nakryiko authored
This patch adds new config option to trigger generation of BTF type information from DWARF debuginfo for vmlinux and kernel modules through pahole, which in turn relies on libbpf for btf_dedup() algorithm. The intent is to record compact type information of all types used inside kernel, including all the structs/unions/typedefs/etc. This enables BPF's compile-once-run-everywhere ([0]) approach, in which tracing programs that are inspecting kernel's internal data (e.g., struct task_struct) can be compiled on a system running some kernel version, but would be possible to run on other kernel versions (and configurations) without recompilation, even if the layout of structs changed and/or some of the fields were added, removed, or renamed. This is only possible if BPF loader can get kernel type info to adjust all the offsets correctly. This patch is a first time in this direction, making sure that BTF type info is part of Linux kernel image in non-loadable ELF section. BTF deduplication ([1]) algorithm typically provides 100x savings compared to DWARF data, so resulting .BTF section is not big as is typically about 2MB in size. [0] http://vger.kernel.org/lpc-bpf2018.html#session-2 [1] https://facebookmicrosites.github.io/bpf/blog/2018/11/14/btf-enhancement.html Cc: Masahiro Yamada <yamada.masahiro@socionext.com> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: Daniel Borkmann <daniel@iogearbox.net> Cc: Alexei Starovoitov <ast@fb.com> Cc: Yonghong Song <yhs@fb.com> Cc: Martin KaFai Lau <kafai@fb.com> Signed-off-by:
David S. Miller <davem@davemloft.net> Acked-by:
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