- 18 Feb, 2016 11 commits
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Ard Biesheuvel authored
This introduces the preprocessor symbol KIMAGE_VADDR which will serve as the symbolic virtual base of the kernel region, i.e., the kernel's virtual offset will be KIMAGE_VADDR + TEXT_OFFSET. For now, we define it as being equal to PAGE_OFFSET, but in the future, it will be moved below it once we move the kernel virtual mapping out of the linear mapping. Reviewed-by:
Mark Rutland <mark.rutland@arm.com> Signed-off-by:
Ard Biesheuvel <ard.biesheuvel@linaro.org> Signed-off-by:
Catalin Marinas <catalin.marinas@arm.com>
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Ard Biesheuvel authored
This wires up the existing generic huge-vmap feature, which allows ioremap() to use PMD or PUD sized block mappings. It also adds support to the unmap path for dealing with block mappings, which will allow us to unmap the __init region using unmap_kernel_range() in a subsequent patch. Signed-off-by:
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Ard Biesheuvel authored
Currently, using BUG_ON() in header files is cumbersome, due to the fact that asm/bug.h transitively includes a lot of other header files, resulting in the actual BUG_ON() invocation appearing before its definition in the preprocessor input. So let's reverse the #include dependency between asm/bug.h and asm/debug-monitors.h, by moving the definition of BUG_BRK_IMM from the latter to the former. Also fix up one user of asm/debug-monitors.h which relied on a transitive include. Signed-off-by:
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Ard Biesheuvel authored
Since architectures may not yet have their linear mapping up and running when the initrd address is discovered from the DT, factor out the assignment of initrd_start and initrd_end, so that an architecture can override it and use the translation it needs. Signed-off-by:
Rob Herring <robh@kernel.org> Signed-off-by:
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Ard Biesheuvel authored
By default, early_init_dt_add_memory_arch() ignores memory below the base of the kernel image since it won't be addressable via the linear mapping. However, this is not appropriate anymore once we decouple the kernel text mapping from the linear mapping, so archs may want to drop the low limit entirely. So allow the minimum to be overridden by setting MIN_MEMBLOCK_ADDR. Acked-by:
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Catalin Marinas authored
This function was introduced by previous commits implementing UAO. However, it can be replaced with task_thread_info() in uao_thread_switch() or get_fs() in do_page_fault() (the latter being called only on the current context, so no need for using the saved pt_regs). Signed-off-by: -
James Morse authored
If a CPU supports both Privileged Access Never (PAN) and User Access Override (UAO), we don't need to disable/re-enable PAN round all copy_to_user() like calls. UAO alternatives cause these calls to use the 'unprivileged' load/store instructions, which are overridden to be the privileged kind when fs==KERNEL_DS. This patch changes the copy_to_user() calls to have their PAN toggling depend on a new composite 'feature' ARM64_ALT_PAN_NOT_UAO. If both features are detected, PAN will be enabled, but the copy_to_user() alternatives will not be applied. This means PAN will be enabled all the time for these functions. If only PAN is detected, the toggling will be enabled as normal. This will save the time taken to disable/re-enable PAN, and allow us to catch copy_to_user() accesses that occur with fs==KERNEL_DS. Futex and swp-emulation code continue to hang their PAN toggling code on ARM64_HAS_PAN. Signed-off-by:
James Morse <james.morse@arm.com> Signed-off-by:
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James Morse authored
CPU feature code uses the desc field as a test to find the end of the list, this means every entry must have a description. This generates noise for entries in the list that aren't really features, but combinations of them. e.g. > CPU features: detected feature: Privileged Access Never > CPU features: detected feature: PAN and not UAO These combination features are needed for corner cases with alternatives, where cpu features interact. Change all walkers of the arm64_features[] and arm64_hwcaps[] lists to test 'matches' not 'desc', and only print 'desc' if it is non-NULL. Signed-off-by:
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James Morse authored
'User Access Override' is a new ARMv8.2 feature which allows the unprivileged load and store instructions to be overridden to behave in the normal way. This patch converts {get,put}_user() and friends to use ldtr*/sttr* instructions - so that they can only access EL0 memory, then enables UAO when fs==KERNEL_DS so that these functions can access kernel memory. This allows user space's read/write permissions to be checked against the page tables, instead of testing addr<USER_DS, then using the kernel's read/write permissions. Signed-off-by: -
James Morse authored
ARMv8.2 adds a new feature register id_aa64mmfr2. This patch adds the cpu feature boiler plate used by the actual features in later patches. Signed-off-by:
Suzuki K Poulose <suzuki.poulose@arm.com> Signed-off-by:
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James Morse authored
Older assemblers may not have support for newer feature registers. To get round this, sysreg.h provides a 'mrs_s' macro that takes a register encoding and generates the raw instruction. Change read_cpuid() to use mrs_s in all cases so that new registers don't have to be a special case. Including sysreg.h means we need to move the include and definition of read_cpuid() after the #ifndef __ASSEMBLY__ to avoid syntax errors in vmlinux.lds. Signed-off-by:
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- 16 Feb, 2016 29 commits
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Ard Biesheuvel authored
The __reg_num_xNN symbols that are used to implement the msr_s and mrs_s macros are recorded in the ELF metadata of each object file. This does not affect the size of the final binary, but it does clutter the output of tools like readelf, i.e., $ readelf -a vmlinux |grep -c __reg_num_x 50976 So let's use symbols with the .L prefix, these are strictly local, and don't end up in the object files. $ readelf -a vmlinux |grep -c __reg_num_x 0 Acked-by:
Will Deacon <will.deacon@arm.com> Signed-off-by:
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David Brown authored
Although the arm64 vDSO is cleanly separated by code/data with the code being read-only in userspace mappings, the code page is still writable from the kernel. There have been exploits (such as http://itszn.com/blog/?p=21) that take advantage of this on x86 to go from a bad kernel write to full root. Prevent this specific exploit on arm64 by putting the vDSO code page in read-only memory as well. Before the change: [ 3.138366] vdso: 2 pages (1 code @ ffffffc000a71000, 1 data @ ffffffc000a70000) ---[ Kernel Mapping ]--- 0xffffffc000000000-0xffffffc000082000 520K RW NX SHD AF UXN MEM/NORMAL 0xffffffc000082000-0xffffffc000200000 1528K ro x SHD AF UXN MEM/NORMAL 0xffffffc000200000-0xffffffc000800000 6M ro x SHD AF BLK UXN MEM/NORMAL 0xffffffc000800000-0xffffffc0009b6000 1752K ro x SHD AF UXN MEM/NORMAL 0xffffffc0009b6000-0xffffffc000c00000 2344K RW NX SHD AF UXN MEM/NORMAL 0xffffffc000c00000-0xffffffc008000000 116M RW NX SHD AF BLK UXN MEM/NORMAL 0xffffffc00c000000-0xffffffc07f000000 1840M RW NX SHD AF BLK UXN MEM/NORMAL 0xffffffc800000000-0xffffffc840000000 1G RW NX SHD AF BLK UXN MEM/NORMAL 0xffffffc840000000-0xffffffc87ae00000 942M RW NX SHD AF BLK UXN MEM/NORMAL 0xffffffc87ae00000-0xffffffc87ae70000 448K RW NX SHD AF UXN MEM/NORMAL 0xffffffc87af80000-0xffffffc87af8a000 40K RW NX SHD AF UXN MEM/NORMAL 0xffffffc87af8b000-0xffffffc87b000000 468K RW NX SHD AF UXN MEM/NORMAL 0xffffffc87b000000-0xffffffc87fe00000 78M RW NX SHD AF BLK UXN MEM/NORMAL 0xffffffc87fe00000-0xffffffc87ff50000 1344K RW NX SHD AF UXN MEM/NORMAL 0xffffffc87ff90000-0xffffffc87ffa0000 64K RW NX SHD AF UXN MEM/NORMAL 0xffffffc87fff0000-0xffffffc880000000 64K RW NX SHD AF UXN MEM/NORMAL After: [ 3.138368] vdso: 2 pages (1 code @ ffffffc0006de000, 1 data @ ffffffc000a74000) ---[ Kernel Mapping ]--- 0xffffffc000000000-0xffffffc000082000 520K RW NX SHD AF UXN MEM/NORMAL 0xffffffc000082000-0xffffffc000200000 1528K ro x SHD AF UXN MEM/NORMAL 0xffffffc000200000-0xffffffc000800000 6M ro x SHD AF BLK UXN MEM/NORMAL 0xffffffc000800000-0xffffffc0009b8000 1760K ro x SHD AF UXN MEM/NORMAL 0xffffffc0009b8000-0xffffffc000c00000 2336K RW NX SHD AF UXN MEM/NORMAL 0xffffffc000c00000-0xffffffc008000000 116M RW NX SHD AF BLK UXN MEM/NORMAL 0xffffffc00c000000-0xffffffc07f000000 1840M RW NX SHD AF BLK UXN MEM/NORMAL 0xffffffc800000000-0xffffffc840000000 1G RW NX SHD AF BLK UXN MEM/NORMAL 0xffffffc840000000-0xffffffc87ae00000 942M RW NX SHD AF BLK UXN MEM/NORMAL 0xffffffc87ae00000-0xffffffc87ae70000 448K RW NX SHD AF UXN MEM/NORMAL 0xffffffc87af80000-0xffffffc87af8a000 40K RW NX SHD AF UXN MEM/NORMAL 0xffffffc87af8b000-0xffffffc87b000000 468K RW NX SHD AF UXN MEM/NORMAL 0xffffffc87b000000-0xffffffc87fe00000 78M RW NX SHD AF BLK UXN MEM/NORMAL 0xffffffc87fe00000-0xffffffc87ff50000 1344K RW NX SHD AF UXN MEM/NORMAL 0xffffffc87ff90000-0xffffffc87ffa0000 64K RW NX SHD AF UXN MEM/NORMAL 0xffffffc87fff0000-0xffffffc880000000 64K RW NX SHD AF UXN MEM/NORMAL Inspired by https://lkml.org/lkml/2016/1/19/494 based on work by the PaX Team, Brad Spengler, and Kees Cook. Signed-off-by:
David Brown <david.brown@linaro.org> Acked-by:
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Yang Shi authored
To enable UBSAN on arm64, ARCH_HAS_UBSAN_SANITIZE_ALL need to be selected. Basic kernel bootup test is passed on arm64 with CONFIG_UBSAN_SANITIZE_ALL enabled. Signed-off-by:
Yang Shi <yang.shi@linaro.org> Acked-by:
Andrey Ryabinin <aryabinin@virtuozzo.com> Tested-by:
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Yang Shi authored
BUG: sleeping function called from invalid context at kernel/locking/rtmutex.c:917 in_atomic(): 1, irqs_disabled(): 128, pid: 383, name: sh Preemption disabled at:[<ffff800000124c18>] kgdb_cpu_enter+0x158/0x6b8 CPU: 3 PID: 383 Comm: sh Tainted: G W 4.1.13-rt13 #2 Hardware name: Freescale Layerscape 2085a RDB Board (DT) Call trace: [<ffff8000000885e8>] dump_backtrace+0x0/0x128 [<ffff800000088734>] show_stack+0x24/0x30 [<ffff80000079a7c4>] dump_stack+0x80/0xa0 [<ffff8000000bd324>] ___might_sleep+0x18c/0x1a0 [<ffff8000007a20ac>] __rt_spin_lock+0x2c/0x40 [<ffff8000007a2268>] rt_read_lock+0x40/0x58 [<ffff800000085328>] single_step_handler+0x38/0xd8 [<ffff800000082368>] do_debug_exception+0x58/0xb8 Exception stack(0xffff80834a1e7c80 to 0xffff80834a1e7da0) 7c80: ffffff9c ffffffff 92c23ba0 0000ffff 4a1e7e40 ffff8083 001bfcc4 ffff8000 7ca0: f2000400 00000000 00000000 00000000 4a1e7d80 ffff8083 0049501c ffff8000 7cc0: 00005402 00000000 00aaa210 ffff8000 4a1e7ea0 ffff8083 000833f4 ffff8000 7ce0: ffffff9c ffffffff 92c23ba0 0000ffff 4a1e7ea0 ffff8083 001bfcc0 ffff8000 7d00: 4a0fc400 ffff8083 00005402 00000000 4a1e7d40 ffff8083 00490324 ffff8000 7d20: ffffff9c 00000000 92c23ba0 0000ffff 000a0000 00000000 00000000 00000000 7d40: 00000008 00000000 00080000 00000000 92c23b8b 0000ffff 92c23b8e 0000ffff 7d60: 00000038 00000000 00001cb2 00000000 00000005 00000000 92d7b498 0000ffff 7d80: 01010101 01010101 92be9000 0000ffff 00000000 00000000 00000030 00000000 [<ffff8000000833f4>] el1_dbg+0x18/0x6c This issue is similar with 62c6c61a("arm64: replace read_lock to rcu lock in call_break_hook"), but comes to single_step_handler. This also solves kgdbts boot test silent hang issue on 4.4 -rt kernel. Signed-off-by:
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Laura Abbott authored
With CONFIG_DEBUG_PAGEALLOC, pages do not have the valid bit set when free in the buddy allocator. Add an indiciation to the page table dumping code that the valid bit is not set, 'F' for fault, to make this easier to understand. Reviewed-by:
Laura Abbott <labbott@fedoraproject.org> Signed-off-by:
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Laura Abbott authored
ARCH_SUPPORTS_DEBUG_PAGEALLOC provides a hook to map and unmap pages for debugging purposes. This requires memory be mapped with PAGE_SIZE mappings since breaking down larger mappings at runtime will lead to TLB conflicts. Check if debug_pagealloc is enabled at runtime and if so, map everyting with PAGE_SIZE pages. Implement the functions to actually map/unmap the pages at runtime. Reviewed-by:
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Laura Abbott authored
create_mapping is only used in fixmap_remap_fdt. All the create_mapping calls need to happen on existing translation table pages without additional allocations. Rather than have an alloc function be called and fail, just set it to NULL and catch its use. Also change the name to create_mapping_noalloc to better capture what exactly is going on. Reviewed-by:
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Will Deacon authored
As of 52e662326e1e ("arm64: prefetch: don't provide spin_lock_prefetch with LSE"), spin_lock_prefetch is patched at runtime when the LSE atomics are in use. This relies on the ARM64_LSE_ATOMIC_INSN macro to drive the alternatives framework, but that macro is only available via asm/lse.h, which isn't explicitly included in processor.h. Consequently, drivers can run into build failures such as: In file included from include/linux/prefetch.h:14:0, from drivers/net/ethernet/intel/i40e/i40e_txrx.c:27: arch/arm64/include/asm/processor.h: In function 'spin_lock_prefetch': arch/arm64/include/asm/processor.h:183:15: error: expected string literal before 'ARM64_LSE_ATOMIC_INSN' asm volatile(ARM64_LSE_ATOMIC_INSN( This patch add the missing include and gets things building again. Reported-by:kbuild test robot <fengguang.wu@intel.com> Signed-off-by:
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Andrew Pinski authored
On ThunderX T88 pass 1 and pass 2, there is no hardware prefetching so we need to patch in explicit software prefetching instructions Prefetching improves this code by 60% over the original code and 2x over the code without prefetching for the affected hardware using the benchmark code at https://github.com/apinski-cavium/copy_page_benchmarkSigned-off-by:
Andrew Pinski <apinski@cavium.com> Signed-off-by:
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Will Deacon authored
We want to avoid lots of different copy_page implementations, settling for something that is "good enough" everywhere and hopefully easy to understand and maintain whilst we're at it. This patch reworks our copy_page implementation based on discussions with Cavium on the list and benchmarking on Cortex-A processors so that: - The loop is unrolled to copy 128 bytes per iteration - The reads are offset so that we read from the next 128-byte block in the same iteration that we store the previous block - Explicit prefetch instructions are removed for now, since they hurt performance on CPUs with hardware prefetching - The loop exit condition is calculated at the start of the loop Signed-off-by: -
Will Deacon authored
Most CPUs have a hardware prefetcher which generally performs better without explicit prefetch instructions issued by software, however some CPUs (e.g. Cavium ThunderX) rely solely on explicit prefetch instructions. This patch adds an alternative pattern (ARM64_HAS_NO_HW_PREFETCH) to allow our library code to make use of explicit prefetch instructions during things like copy routines only when the CPU does not have the capability to perform the prefetching itself. Signed-off-by:
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Will Deacon authored
The LSE atomics rely on us not dirtying data at L1 if we can avoid it, otherwise many of the potential scalability benefits are lost. This patch replaces spin_lock_prefetch with a nop when the LSE atomics are in use, so that users don't shoot themselves in the foot by causing needless coherence traffic at L1. Signed-off-by:
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Lorenzo Pieralisi authored
The SBBR and ACPI specifications allow ACPI based systems that do not implement PSCI (eg systems with no EL3) to boot through the ACPI parking protocol specification[1]. This patch implements the ACPI parking protocol CPU operations, and adds code that eases parsing the parking protocol data structures to the ARM64 SMP initializion carried out at the same time as cpus enumeration. To wake-up the CPUs from the parked state, this patch implements a wakeup IPI for ARM64 (ie arch_send_wakeup_ipi_mask()) that mirrors the ARM one, so that a specific IPI is sent for wake-up purpose in order to distinguish it from other IPI sources. Given the current ACPI MADT parsing API, the patch implements a glue layer that helps passing MADT GICC data structure from SMP initialization code to the parking protocol implementation somewhat overriding the CPU operations interfaces. This to avoid creating a completely trasparent DT/ACPI CPU operations layer that would require creating opaque structure handling for CPUs data (DT represents CPU through DT nodes, ACPI through static MADT table entries), which seems overkill given that ACPI on ARM64 mandates only two booting protocols (PSCI and parking protocol), so there is no need for further protocol additions. Based on the original work by Mark Salter <msalter@redhat.com> [1] https://acpica.org/sites/acpica/files/MP%20Startup%20for%20ARM%20platforms.docxSigned-off-by:
Lorenzo Pieralisi <lorenzo.pieralisi@arm.com> Tested-by:
Loc Ho <lho@apm.com> Cc: Will Deacon <will.deacon@arm.com> Cc: Hanjun Guo <hanjun.guo@linaro.org> Cc: Sudeep Holla <sudeep.holla@arm.com> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Mark Salter <msalter@redhat.com> Cc: Al Stone <ahs3@redhat.com> [catalin.marinas@arm.com: Added WARN_ONCE(!acpi_parking_protocol_valid() on the IPI] Signed-off-by:
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Mark Rutland authored
At boot we may change the granularity of the tables mapping the kernel (by splitting or making sections). This may happen when we create the linear mapping (in __map_memblock), or at any point we try to apply fine-grained permissions to the kernel (e.g. fixup_executable, mark_rodata_ro, fixup_init). Changing the active page tables in this manner may result in multiple entries for the same address being allocated into TLBs, risking problems such as TLB conflict aborts or issues derived from the amalgamation of TLB entries. Generally, a break-before-make (BBM) approach is necessary to avoid conflicts, but we cannot do this for the kernel tables as it risks unmapping text or data being used to do so. Instead, we can create a new set of tables from scratch in the safety of the existing mappings, and subsequently migrate over to these using the new cpu_replace_ttbr1 helper, which avoids the two sets of tables being active simultaneously. To avoid issues when we later modify permissions of the page tables (e.g. in fixup_init), we must create the page tables at a granularity such that later modification does not result in splitting of tables. This patch applies this strategy, creating a new set of fine-grained page tables from scratch, and safely migrating to them. The existing fixmap and kasan shadow page tables are reused in the new fine-grained tables. Signed-off-by:
Jeremy Linton <jeremy.linton@arm.com> Cc: Laura Abbott <labbott@fedoraproject.org> Cc: Will Deacon <will.deacon@arm.com> Signed-off-by:
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Mark Rutland authored
Currently we have separate ALIGN_DEBUG_RO{,_MIN} directives to align _etext and __init_begin. While we ensure that __init_begin is page-aligned, we do not provide the same guarantee for _etext. This is not problematic currently as the alignment of __init_begin is sufficient to prevent issues when we modify permissions. Subsequent patches will assume page alignment of segments of the kernel we wish to map with different permissions. To ensure this, move _etext after the ALIGN_DEBUG_RO_MIN for the init section. This renders the prior ALIGN_DEBUG_RO irrelevant, and hence it is removed. Likewise, upgrade to ALIGN_DEBUG_RO_MIN(PAGE_SIZE) for _stext. Signed-off-by: -
Mark Rutland authored
To allow us to initialise pgdirs which are fixmapped, allow explicitly passing a pgdir rather than an mm. A new __create_pgd_mapping function is added for this, with existing __create_mapping callers migrated to this. The mm argument was previously only used at the top level. Now that it is redundant at all levels, it is removed. To indicate its new found similarity to alloc_init_{pud,pmd,pte}, __create_mapping is renamed to init_pgd. Signed-off-by: -
Mark Rutland authored
Now that create_mapping uses fixmap slots to modify pte, pmd, and pud entries, we can access page tables anywhere in physical memory, regardless of the extent of the linear mapping. Given that, we no longer need to limit memblock allocations during page table creation, and can leave the limit as its default MEMBLOCK_ALLOC_ANYWHERE. We never add memory which will fall outside of the linear map range given phys_offset and MAX_MEMBLOCK_ADDR are configured appropriately, so any tables we create will fall in the linear map of the final tables. Signed-off-by:
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Mark Rutland authored
As a preparatory step to allow us to allocate early page tables from unmapped memory using memblock_alloc, modify the __create_mapping callees to map and unmap the tables they modify using fixmap entries. All but the top-level pgd initialisation is performed via the fixmap. Subsequent patches will inject the pgd physical address, and migrate to using the FIX_PGD slot. Signed-off-by:
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Mark Rutland authored
As a preparatory step to allow us to allocate early page tables from unmapped memory using memblock_alloc, add new p??_{set,clear}_fixmap* functions which can be used to walk page tables outside of the linear mapping by using fixmap slots. Signed-off-by: -
Mark Rutland authored
We currently have __pmd_populate for creating a pmd table entry given the physical address of a pte, but don't have equivalents for the pud or pgd levels of table. To enable us to manipulate tables which are mapped outside of the linear mapping (where we have a PA, but not a linear map VA), it is useful to have these functions. This patch adds __{pud,pgd}_populate. As these should not be called when the kernel uses folded {pmd,pud}s, in these cases they expand to BUILD_BUG(). So long as the appropriate checks are made on the {pud,pgd} entry prior to attempting population, these should be optimized out at compile time. Signed-off-by: -
Mark Rutland authored
When we "upgrade" to a section mapping, we free any table we made redundant by giving it back to memblock. To get the PA, we acquire the physical address and convert this to a VA, then subsequently convert this back to a PA. This works currently, but will not work if the tables are not accessed via linear map VAs (e.g. is we use fixmap slots). This patch uses {pmd,pud}_page_paddr to acquire the PA. This avoids the __pa(__va()) round trip, saving some work and avoiding reliance on the linear mapping. Signed-off-by: -
Mark Rutland authored
To allow us to walk tables allocated into the fixmap, we need to acquire the physical address of a page, rather than the virtual address in the linear map. This patch adds new p??_page_paddr and p??_offset_phys functions to acquire the physical address of a next-level table, and changes p??_offset* into macros which simply convert this to a linear map VA. This renders p??_page_vaddr unused, and hence they are removed. At the pgd level, a new pgd_offset_raw function is added to find the relevant PGD entry given the base of a PGD and a virtual address. Signed-off-by:
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Mark Rutland authored
For pmd, pud, and pgd levels of table, functions including p?d_index and p?d_offset are defined after the p?d_page_vaddr function for the immediately higher level of table. The pte functions however are defined much earlier, even though several rely on the later definition of pmd_page_vaddr. While this isn't currently a problem as these are macros, it prevents the logical grouping of later C functions (which cannot rely on prototypes for functions not yet defined). Move these definitions after pmd_page_vaddr, for consistency with the placement of these functions for other levels of table. Signed-off-by:
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Mark Rutland authored
The page table modification performed during the KASAN init risks the allocation of conflicting TLB entries, as it swaps a set of valid global entries for another without suitable TLB maintenance. The presence of conflicting TLB entries can result in the delivery of synchronous TLB conflict aborts, or may result in the use of erroneous data being returned in response to a TLB lookup. This can affect explicit data accesses from software as well as translations performed asynchronously (e.g. as part of page table walks or speculative I-cache fetches), and can therefore result in a wide variety of problems. To avoid this, use cpu_replace_ttbr1 to swap the page tables. This ensures that when the new tables are installed there are no stale entries from the old tables which may conflict. As all updates are made to the tables while they are not active, the updates themselves are safe. At the same time, add the missing barrier to ensure that the tmp_pg_dir entries updated via memcpy are visible to the page table walkers at the point the tmp_pg_dir is installed. All other page table updates made as part of KASAN initialisation have the requisite barriers due to the use of the standard page table accessors. Signed-off-by:
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Mark Rutland authored
If page tables are modified without suitable TLB maintenance, the ARM architecture permits multiple TLB entries to be allocated for the same VA. When this occurs, it is permitted that TLB conflict aborts are raised in response to synchronous data/instruction accesses, and/or and amalgamation of the TLB entries may be used as a result of a TLB lookup. The presence of conflicting TLB entries may result in a variety of behaviours detrimental to the system (e.g. erroneous physical addresses may be used by I-cache fetches and/or page table walks). Some of these cases may result in unexpected changes of hardware state, and/or result in the (asynchronous) delivery of SError. To avoid these issues, we must avoid situations where conflicting entries may be allocated into TLBs. For user and module mappings we can follow a strict break-before-make approach, but this cannot work for modifications to the swapper page tables that cover the kernel text and data. Instead, this patch adds code which is intended to be executed from the idmap, which can safely unmap the swapper page tables as it only requires the idmap to be active. This enables us to uninstall the active TTBR1_EL1 entry, invalidate TLBs, then install a new TTBR1_EL1 entry without potentially unmapping code or data required for the sequence. This avoids the risk of conflict, but requires that updates are staged in a copy of the swapper page tables prior to being installed. Signed-off-by:
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Mark Rutland authored
In some cases (e.g. when making invasive changes to the kernel page tables) we will need to execute code from the idmap. Add a new helper which may be used to install the idmap, complementing the existing cpu_uninstall_idmap. Signed-off-by:
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Mark Rutland authored
During boot we leave the idmap in place until paging_init, as we previously had to wait for the zero page to become allocated and accessible. Now that we have a statically-allocated zero page, we can uninstall the idmap much earlier in the boot process, making it far easier to spot accidental use of physical addresses. This also brings the cold boot path in line with the secondary boot path. Signed-off-by:
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Mark Rutland authored
We currently open-code the removal of the idmap and restoration of the current task's MMU state in a few places. Before introducing yet more copies of this sequence, unify these to call a new helper, cpu_uninstall_idmap. Signed-off-by:
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Mark Rutland authored
Currently the zero page is set up in paging_init, and thus we cannot use the zero page earlier. We use the zero page as a reserved TTBR value from which no TLB entries may be allocated (e.g. when uninstalling the idmap). To enable such usage earlier (as may be required for invasive changes to the kernel page tables), and to minimise the time that the idmap is active, we need to be able to use the zero page before paging_init. This patch follows the example set by x86, by allocating the zero page at compile time, in .bss. This means that the zero page itself is available immediately upon entry to start_kernel (as we zero .bss before this), and also means that the zero page takes up no space in the raw Image binary. The associated struct page is allocated in bootmem_init, and remains unavailable until this time. Outside of arch code, the only users of empty_zero_page assume that the empty_zero_page symbol refers to the zeroed memory itself, and that ZERO_PAGE(x) must be used to acquire the associated struct page, following the example of x86. This patch also brings arm64 inline with these assumptions. Signed-off-by:
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