- 24 Feb, 2016 25 commits
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Chris J Arges authored
Stacktool generates the following warning: stacktool: arch/x86/kvm/vmx.o: vmx_handle_external_intr()+0x67: call without frame pointer save/setup By adding the stackpointer as an output operand, this patch ensures that a stack frame is created when CONFIG_FRAME_POINTER is enabled for the inline assmebly statement. Signed-off-by:
Chris J Arges <chris.j.arges@canonical.com> Reviewed-by:
Josh Poimboeuf <jpoimboe@redhat.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: gleb@kernel.org Cc: kvm@vger.kernel.org Cc: live-patching@vger.kernel.org Cc: pbonzini@redhat.com Link: http://lkml.kernel.org/r/1453499078-9330-3-git-send-email-chris.j.arges@canonical.comSigned-off-by:
Ingo Molnar <mingo@kernel.org>
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Josh Poimboeuf authored
The assembly PV_UNLOCK function is a callable non-leaf function which doesn't honor CONFIG_FRAME_POINTER, which can result in bad stack traces. Create a stack frame when CONFIG_FRAME_POINTER is enabled. Signed-off-by:
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Josh Poimboeuf authored
asminline_call() is a callable non-leaf function which doesn't honor CONFIG_FRAME_POINTER, which can result in bad stack traces. Create a stack frame when CONFIG_FRAME_POINTER is enabled. Signed-off-by:
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Josh Poimboeuf authored
With some configs (including allyesconfig), gcc doesn't inline test_cc(). When that happens, test_cc() doesn't create a stack frame before inserting the inline asm call instruction. This breaks frame pointer convention if CONFIG_FRAME_POINTER is enabled and can result in a bad stack trace. Force it to always be inlined so that its containing function's stack frame can be used. Suggested-by:
Paolo Bonzini <pbonzini@redhat.com> Signed-off-by:
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Josh Poimboeuf authored
The callable functions created with the FOP* and FASTOP* macros are missing ELF function annotations, which confuses tools like stacktool. Properly annotate them. This adds some additional labels to the assembly, but the generated binary code is unchanged (with the exception of instructions which have embedded references to __LINE__). Signed-off-by:
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Josh Poimboeuf authored
The kretprobe_trampoline_holder() wrapper around kretprobe_trampoline() isn't used anywhere and adds some unnecessary frame pointer instructions which never execute. Instead, just make kretprobe_trampoline() a proper ELF function. Signed-off-by:
Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Andy Lutomirski <luto@amacapital.net> Cc: Andy Lutomirski <luto@kernel.org> Cc: Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com> Cc: Arnaldo Carvalho de Melo <acme@kernel.org> Cc: Bernd Petrovitsch <bernd@petrovitsch.priv.at> Cc: Borislav Petkov <bp@alien8.de> Cc: Brian Gerst <brgerst@gmail.com> Cc: Chris J Arges <chris.j.arges@canonical.com> Cc: David S. Miller <davem@davemloft.net> Cc: Denys Vlasenko <dvlasenk@redhat.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Jiri Slaby <jslaby@suse.cz> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Michal Marek <mmarek@suse.cz> Cc: Namhyung Kim <namhyung@gmail.com> Cc: Pedro Alves <palves@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: live-patching@vger.kernel.org Link: http://lkml.kernel.org/r/92d921b102fb865a7c254cfde9e4a0a72b9a781e.1453405861.git.jpoimboe@redhat.comSigned-off-by:
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Josh Poimboeuf authored
bpf_jit.S has several callable non-leaf functions which don't honor CONFIG_FRAME_POINTER, which can result in bad stack traces. Create a stack frame before the call instructions when CONFIG_FRAME_POINTER is enabled. Signed-off-by:
Alexei Starovoitov <ast@kernel.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Andy Lutomirski <luto@amacapital.net> Cc: Andy Lutomirski <luto@kernel.org> Cc: Arnaldo Carvalho de Melo <acme@kernel.org> Cc: Bernd Petrovitsch <bernd@petrovitsch.priv.at> Cc: Borislav Petkov <bp@alien8.de> Cc: Brian Gerst <brgerst@gmail.com> Cc: Chris J Arges <chris.j.arges@canonical.com> Cc: Denys Vlasenko <dvlasenk@redhat.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Jiri Slaby <jslaby@suse.cz> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Michal Marek <mmarek@suse.cz> Cc: Namhyung Kim <namhyung@gmail.com> Cc: Pedro Alves <palves@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: live-patching@vger.kernel.org Cc: netdev@vger.kernel.org Link: http://lkml.kernel.org/r/fa4c41976b438b51954cb8021f06bceb1d1d66cc.1453405861.git.jpoimboe@redhat.comSigned-off-by:
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Josh Poimboeuf authored
bpf_jit.S has several functions which can be called from C code. Give them proper ELF annotations. Signed-off-by:
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Chris J Arges authored
Numerous 'call without frame pointer save/setup' warnings are introduced by stacktool because of functions using the get_user() macro. Bad stack traces could occur due to lack of or misplacement of stack frame setup code. This patch forces a stack frame to be created before the inline asm code if CONFIG_FRAME_POINTER is enabled by listing the stack pointer as an output operand for the get_user() inline assembly statement. Signed-off-by:
Borislav Petkov <bp@suse.de> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Andy Lutomirski <luto@amacapital.net> Cc: Andy Lutomirski <luto@kernel.org> Cc: Arnaldo Carvalho de Melo <acme@kernel.org> Cc: Bernd Petrovitsch <bernd@petrovitsch.priv.at> Cc: Borislav Petkov <bp@alien8.de> Cc: Brian Gerst <brgerst@gmail.com> Cc: Denys Vlasenko <dvlasenk@redhat.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Jiri Slaby <jslaby@suse.cz> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Michal Marek <mmarek@suse.cz> Cc: Namhyung Kim <namhyung@gmail.com> Cc: Pedro Alves <palves@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: live-patching@vger.kernel.org Link: http://lkml.kernel.org/r/bc85501f221ee512670797c7f110022e64b12c81.1453405861.git.jpoimboe@redhat.comSigned-off-by:
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Josh Poimboeuf authored
swsusp_arch_suspend() and restore_registers() are callable non-leaf functions which don't honor CONFIG_FRAME_POINTER, which can result in bad stack traces. Also they aren't annotated as ELF callable functions which can confuse tooling. Create a stack frame for them when CONFIG_FRAME_POINTER is enabled and give them proper ELF function annotations. Signed-off-by:
Pavel Machek <pavel@ucw.cz> Acked-by:
Rafael J. Wysocki <rafael.j.wysocki@intel.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Andy Lutomirski <luto@amacapital.net> Cc: Andy Lutomirski <luto@kernel.org> Cc: Arnaldo Carvalho de Melo <acme@kernel.org> Cc: Bernd Petrovitsch <bernd@petrovitsch.priv.at> Cc: Borislav Petkov <bp@alien8.de> Cc: Brian Gerst <brgerst@gmail.com> Cc: Chris J Arges <chris.j.arges@canonical.com> Cc: Denys Vlasenko <dvlasenk@redhat.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Jiri Slaby <jslaby@suse.cz> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Michal Marek <mmarek@suse.cz> Cc: Namhyung Kim <namhyung@gmail.com> Cc: Pedro Alves <palves@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: live-patching@vger.kernel.org Link: http://lkml.kernel.org/r/bdad00205897dc707aebe9e9e39757085e2bf999.1453405861.git.jpoimboe@redhat.comSigned-off-by:
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Josh Poimboeuf authored
efi_call() is a callable non-leaf function which doesn't honor CONFIG_FRAME_POINTER, which can result in bad stack traces. Create a stack frame for it when CONFIG_FRAME_POINTER is enabled. Signed-off-by:
Matt Fleming <matt@codeblueprint.co.uk> Reviewed-by:
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Josh Poimboeuf authored
rwsem.S has several callable non-leaf functions which don't honor CONFIG_FRAME_POINTER, which can result in bad stack traces. Create stack frames for them when CONFIG_FRAME_POINTER is enabled. Signed-off-by:
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Josh Poimboeuf authored
do_suspend_lowlevel() is a callable non-leaf function which doesn't honor CONFIG_FRAME_POINTER, which can result in bad stack traces. Create a stack frame for it when CONFIG_FRAME_POINTER is enabled. Signed-off-by:
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Josh Poimboeuf authored
Thunk functions are callable non-leaf functions that don't honor CONFIG_FRAME_POINTER, which can result in bad stack traces. Also they aren't annotated as ELF callable functions which can confuse tooling. Create stack frames for them when CONFIG_FRAME_POINTER is enabled and add the ELF function type. Signed-off-by:
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Josh Poimboeuf authored
The crypto code has several callable non-leaf functions which don't honor CONFIG_FRAME_POINTER, which can result in bad stack traces. Create stack frames for them when CONFIG_FRAME_POINTER is enabled. Signed-off-by:
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Josh Poimboeuf authored
The frame pointer (RBP) is getting clobbered in sha1_mb_mgr_submit_avx2() before a function call, which can mess up stack traces. Use R12 instead. Signed-off-by:
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Josh Poimboeuf authored
sha1_mb_mgr_flush_avx2() and sha1_mb_mgr_submit_avx2() both allocate a lot of stack space which is never used. Also, many of the registers being saved aren't being clobbered so there's no need to save them. Signed-off-by:
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Josh Poimboeuf authored
stacktool reports the following warning: stacktool: arch/x86/crypto/crc32c-pcl-intel-asm_64.o: crc_pcl()+0x11dd: can't decode instruction It gets confused when trying to decode jump_table data. Move jump_table to the .rodata section which is a more appropriate home for read-only data. Signed-off-by:
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Josh Poimboeuf authored
stacktool reports the following warning: stacktool: arch/x86/crypto/aesni-intel_asm.o: _aesni_inc_init(): can't find starting instruction stacktool gets confused when it tries to disassemble the following data in the .text section: .Lbswap_mask: .byte 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0 Move it to .rodata which is a more appropriate section for read-only data. Signed-off-by: -
Josh Poimboeuf authored
vide() is a callable function, but is missing the ELF function type, which confuses tools like stacktool. Properly annotate it to be a callable function. The generated code is unchanged. Signed-off-by:
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Josh Poimboeuf authored
A function created with the PV_CALLEE_SAVE_REGS_THUNK macro doesn't set up a new stack frame before the call instruction, which breaks frame pointer convention if CONFIG_FRAME_POINTER is enabled and can result in a bad stack trace. Also, the thunk functions aren't annotated as ELF callable functions. Create a stack frame when CONFIG_FRAME_POINTER is enabled and add the ELF function type. Signed-off-by:
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Josh Poimboeuf authored
If a PVOP call macro is inlined at the beginning of a function, gcc can insert the call instruction before setting up a stack frame, which breaks frame pointer convention if CONFIG_FRAME_POINTER is enabled and can result in a bad stack trace. Force a stack frame to be created if CONFIG_FRAME_POINTER is enabled by listing the stack pointer as an output operand for the PVOP inline asm statements. Signed-off-by:
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Josh Poimboeuf authored
xen_irq_enable_direct(), xen_restore_fl_direct(), and check_events() are callable non-leaf functions which don't honor CONFIG_FRAME_POINTER, which can result in bad stack traces. Create stack frames for them when CONFIG_FRAME_POINTER is enabled. Signed-off-by:
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Josh Poimboeuf authored
xen_adjust_exception_frame() is a callable function, but is missing the ELF function type, which confuses tools like stacktool. Properly annotate it to be a callable function. The generated code is unchanged. Signed-off-by:
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Josh Poimboeuf authored
If a hypercall is inlined at the beginning of a function, gcc can insert the call instruction before setting up a stack frame, which breaks frame pointer convention if CONFIG_FRAME_POINTER is enabled and can result in a bad stack trace. Force a stack frame to be created if CONFIG_FRAME_POINTER is enabled by listing the stack pointer as an output operand for the hypercall inline asm statements. Signed-off-by:
David Vrabel <david.vrabel@citrix.com> Reviewed-by:
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- 18 Feb, 2016 3 commits
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Tony Luck authored
The Intel Software Developer Manual describes bit 24 in the MCG_CAP MSR: MCG_SER_P (software error recovery support present) flag, bit 24 — Indicates (when set) that the processor supports software error recovery But only some models with this capability bit set will actually generate recoverable machine checks. Check the model name and set a synthetic capability bit. Provide a command line option to set this bit anyway in case the kernel doesn't recognise the model name. Signed-off-by:
Tony Luck <tony.luck@intel.com> Reviewed-by:
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Ingo Molnar authored
Signed-off-by: -
Toshi Kani authored
A kernel page fault oops with the callstack below was observed when a read syscall was made to a pmem device after a huge amount (>512GB) of vmalloc ranges was allocated by ioremap() on a x86_64 system: BUG: unable to handle kernel paging request at ffff880840000ff8 IP: vmalloc_fault+0x1be/0x300 PGD c7f03a067 PUD 0 Oops: 0000 [#1] SM Call Trace: __do_page_fault+0x285/0x3e0 do_page_fault+0x2f/0x80 ? put_prev_entity+0x35/0x7a0 page_fault+0x28/0x30 ? memcpy_erms+0x6/0x10 ? schedule+0x35/0x80 ? pmem_rw_bytes+0x6a/0x190 [nd_pmem] ? schedule_timeout+0x183/0x240 btt_log_read+0x63/0x140 [nd_btt] : ? __symbol_put+0x60/0x60 ? kernel_read+0x50/0x80 SyS_finit_module+0xb9/0xf0 entry_SYSCALL_64_fastpath+0x1a/0xa4 Since v4.1, ioremap() supports large page (pud/pmd) mappings in x86_64 and PAE. vmalloc_fault() however assumes that the vmalloc range is limited to pte mappings. vmalloc faults do not normally happen in ioremap'd ranges since ioremap() sets up the kernel page tables, which are shared by user processes. pgd_ctor() sets the kernel's PGD entries to user's during fork(). When allocation of the vmalloc ranges crosses a 512GB boundary, ioremap() allocates a new pud table and updates the kernel PGD entry to point it. If user process's PGD entry does not have this update yet, a read/write syscall to the range will cause a vmalloc fault, which hits the Oops above as it does not handle a large page properly. Following changes are made to vmalloc_fault(). 64-bit: - No change for the PGD sync operation as it handles large pages already. - Add pud_huge() and pmd_huge() to the validation code to handle large pages. - Change pud_page_vaddr() to pud_pfn() since an ioremap range is not directly mapped (while the if-statement still works with a bogus addr). - Change pmd_page() to pmd_pfn() since an ioremap range is not backed by struct page (while the if-statement still works with a bogus addr). 32-bit: - No change for the sync operation since the index3 PGD entry covers the entire vmalloc range, which is always valid. (A separate change to sync PGD entry is necessary if this memory layout is changed regardless of the page size.) - Add pmd_huge() to the validation code to handle large pages. This is for completeness since vmalloc_fault() won't happen in ioremap'd ranges as its PGD entry is always valid. Reported-by:Henning Schild <henning.schild@siemens.com> Signed-off-by:
Toshi Kani <toshi.kani@hpe.com> Acked-by:
Borislav Petkov <bp@alien8.de> Cc: <stable@vger.kernel.org> # 4.1+ Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Andy Lutomirski <luto@amacapital.net> Cc: Brian Gerst <brgerst@gmail.com> Cc: Denys Vlasenko <dvlasenk@redhat.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Luis R. Rodriguez <mcgrof@suse.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Toshi Kani <toshi.kani@hp.com> Cc: linux-mm@kvack.org Cc: linux-nvdimm@lists.01.org Link: http://lkml.kernel.org/r/1455758214-24623-1-git-send-email-toshi.kani@hpe.comSigned-off-by:
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- 17 Feb, 2016 12 commits
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Andy Lutomirski authored
Signal delivery needs to know the sign of an interrupted syscall's return value in order to detect -ERESTART variants. Normally this works independently of bitness because syscalls internally return long. Under ptrace, however, this can break, and syscall_get_error is supposed to sign-extend regs->ax if needed. We were clearing TS_COMPAT too early, though, and this prevented sign extension, which subtly broke syscall restart under ptrace. Reported-by:
Robert O'Callahan <robert@ocallahan.org> Signed-off-by:
Andy Lutomirski <luto@kernel.org> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Andy Lutomirski <luto@amacapital.net> Cc: Borislav Petkov <bp@alien8.de> Cc: Brian Gerst <brgerst@gmail.com> Cc: Denys Vlasenko <dvlasenk@redhat.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Shuah Khan <shuahkh@osg.samsung.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: stable@vger.kernel.org # 4.3.x- Fixes: c5c46f59 ("x86/entry: Add new, comprehensible entry and exit handlers written in C") Link: http://lkml.kernel.org/r/cbce3cf545522f64eb37f5478cb59746230db3b5.1455142412.git.luto@kernel.orgSigned-off-by:
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Andy Lutomirski authored
This catches a regression from the compat syscall rework. The 32-bit variant of this test currently fails. The issue is that, for a 32-bit tracer and a 32-bit tracee, GETREGS+SETREGS with no changes should be a no-op. It currently isn't a no-op if RAX indicates signal restart, because the high bits get cleared and the kernel loses track of the restart state. Reported-by:
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Andy Lutomirski authored
I had some obvious typos. Signed-off-by:
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Michael S. Tsirkin authored
Looks like the HPET spec at intel.com got moved. It isn't hard to find so drop the link, just mention the revision assumed. Suggested-by:
Thomas Gleixner <tglx@linutronix.de> Signed-off-by:
Michael S. Tsirkin <mst@redhat.com> Acked-by:
Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: Arnd Bergmann <arnd@arndb.de> Cc: Clemens Ladisch <clemens@ladisch.de> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: linux-doc@vger.kernel.org Link: http://lkml.kernel.org/r/1455145462-3877-1-git-send-email-mst@redhat.comSigned-off-by:
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Toshi Kani authored
Data corruption issues were observed in tests which initiated a system crash/reset while accessing BTT devices. This problem is reproducible. The BTT driver calls pmem_rw_bytes() to update data in pmem devices. This interface calls __copy_user_nocache(), which uses non-temporal stores so that the stores to pmem are persistent. __copy_user_nocache() uses non-temporal stores when a request size is 8 bytes or larger (and is aligned by 8 bytes). The BTT driver updates the BTT map table, which entry size is 4 bytes. Therefore, updates to the map table entries remain cached, and are not written to pmem after a crash. Change __copy_user_nocache() to use non-temporal store when a request size is 4 bytes. The change extends the current byte-copy path for a less-than-8-bytes request, and does not add any overhead to the regular path. Reported-and-tested-by:
Micah Parrish <micah.parrish@hpe.com> Reported-and-tested-by:
Brian Boylston <brian.boylston@hpe.com> Signed-off-by:
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Toshi Kani authored
Add comments to __copy_user_nocache() to clarify its procedures and alignment requirements. Also change numeric branch target labels to named local labels. No code changed: arch/x86/lib/copy_user_64.o: text data bss dec hex filename 1239 0 0 1239 4d7 copy_user_64.o.before 1239 0 0 1239 4d7 copy_user_64.o.after md5: 58bed94c2db98c1ca9a2d46d0680aaae copy_user_64.o.before.asm 58bed94c2db98c1ca9a2d46d0680aaae copy_user_64.o.after.asm Signed-off-by: -
Borislav Petkov authored
In order to keep this file's size sensible and not cause too much unnecessary churn, make the rule explicit - similar to pci_ids.h - that only MSRs which are used in multiple compilation units, should get added to it. Signed-off-by:
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Borislav Petkov authored
One of ftrace_caller_end and ftrace_return is redundant so unify them. Rename ftrace_return to ftrace_epilogue to mean that everything after that label represents, like an afterword, work which happens *after* the ftrace call, e.g., the function graph tracer for one. Steve wants this to rather mean "[a]n event which reflects meaningfully on a recently ended conflict or struggle." I can imagine that ftrace can be a struggle sometimes. Anyway, beef up the comment about the code contents and layout before ftrace_epilogue label. Signed-off-by:
Steven Rostedt <rostedt@goodmis.org> Cc: Andy Lutomirski <luto@amacapital.net> Cc: Borislav Petkov <bp@alien8.de> Cc: Brian Gerst <brgerst@gmail.com> Cc: Denys Vlasenko <dvlasenk@redhat.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Link: http://lkml.kernel.org/r/1455612202-14414-4-git-send-email-bp@alien8.deSigned-off-by:
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Andy Lutomirski authored
This tests the two ABI-preserving cases that DOSEMU cares about, and it also explicitly tests the new UC_SIGCONTEXT_SS and UC_STRICT_RESTORE_SS flags. Signed-off-by:
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Andy Lutomirski authored
This is a second attempt to make the improvements from c6f20629 ("x86/signal/64: Fix SS handling for signals delivered to 64-bit programs"), which was reverted by 51adbfbba5c6 ("x86/signal/64: Add support for SS in the 64-bit signal context"). This adds two new uc_flags flags. UC_SIGCONTEXT_SS will be set for all 64-bit signals (including x32). It indicates that the saved SS field is valid and that the kernel supports the new behavior. The goal is to fix a problems with signal handling in 64-bit tasks: SS wasn't saved in the 64-bit signal context, making it awkward to determine what SS was at the time of signal delivery and making it impossible to return to a non-flat SS (as calling sigreturn clobbers SS). This also made it extremely difficult for 64-bit tasks to return to fully-defined 16-bit contexts, because only the kernel can easily do espfix64, but sigreturn was unable to set a non-flag SS:ESP. (DOSEMU has a monstrous hack to partially work around this limitation.) If we could go back in time, the correct fix would be to make 64-bit signals work just like 32-bit signals with respect to SS: save it in signal context, reset it when delivering a signal, and restore it in sigreturn. Unfortunately, doing that (as I tried originally) breaks DOSEMU: DOSEMU wouldn't reset the signal context's SS when clearing the LDT and changing the saved CS to 64-bit mode, since it predates the SS context field existing in the first place. This patch is a bit more complicated, and it tries to balance a bunch of goals. It makes most cases of changing ucontext->ss during signal handling work as expected. I do this by special-casing the interesting case. On sigreturn, ucontext->ss will be honored by default, unless the ucontext was created from scratch by an old program and had a 64-bit CS (unfortunately, CRIU can do this) or was the result of changing a 32-bit signal context to 64-bit without resetting SS (as DOSEMU does). For the benefit of new 64-bit software that uses segmentation (new versions of DOSEMU might), the new behavior can be detected with a new ucontext flag UC_SIGCONTEXT_SS. To avoid compilation issues, __pad0 is left as an alias for ss in ucontext. The nitty-gritty details are documented in the header file. This patch also re-enables the sigreturn_64 and ldt_gdt_64 selftests, as the kernel change allows both of them to pass. Tested-by:
Stas Sergeev <stsp@list.ru> Signed-off-by:
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Andy Lutomirski authored
Signals are always delivered to 64-bit tasks with CS set to a long mode segment. In long mode, SS doesn't matter as long as it's a present writable segment. If SS starts out invalid (this can happen if the signal was caused by an IRET fault or was delivered on the way out of set_thread_area or modify_ldt), then IRET to the signal handler can fail, eventually killing the task. The straightforward fix would be to simply reset SS when delivering a signal. That breaks DOSEMU, though: 64-bit builds of DOSEMU rely on SS being set to the faulting SS when signals are delivered. As a compromise, this patch leaves SS alone so long as it's valid. The net effect should be that the behavior of successfully delivered signals is unchanged. Some signals that would previously have failed to be delivered will now be delivered successfully. This has no effect for x32 or 32-bit tasks: their signal handlers were already called with SS == __USER_DS. (On Xen, there's a slight hole: if a task sets SS to a writable *kernel* data segment, then we will fail to identify it as invalid and we'll still kill the task. If anyone cares, this could be fixed with a new paravirt hook.) Signed-off-by:
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Andy Lutomirski authored
These fields have a strange history. This tries to document it. This borrows from 9a036b93 ("x86/signal/64: Remove 'fs' and 'gs' from sigcontext"), which was reverted by ed596cde ("Revert x86 sigcontext cleanups"). Signed-off-by:
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