d88a6165c4d62b513088dd0a7c7ea9d39d4c2bf0
16 Commits
| Author | SHA1 | Message | Date | |
|---|---|---|---|---|
Sami Tolvanen
|
a46cc20143 |
Merge 5.10.133 into android12-5.10-lts
Changes in 5.10.133
KVM/VMX: Use TEST %REG,%REG instead of CMP $0,%REG in vmenter.SKVM/nVMX: Use __vmx_vcpu_run in nested_vmx_check_vmentry_hw
objtool: Refactor ORC section generation
objtool: Add 'alt_group' struct
objtool: Support stack layout changes in alternatives
objtool: Support retpoline jump detection for vmlinux.o
objtool: Assume only ELF functions do sibling calls
objtool: Combine UNWIND_HINT_RET_OFFSET and UNWIND_HINT_FUNC
x86/xen: Support objtool validation in xen-asm.S
x86/xen: Support objtool vmlinux.o validation in xen-head.S
x86/alternative: Merge include files
x86/alternative: Support not-feature
x86/alternative: Support ALTERNATIVE_TERNARY
x86/alternative: Use ALTERNATIVE_TERNARY() in _static_cpu_has()
x86/insn: Rename insn_decode() to insn_decode_from_regs()
x86/insn: Add a __ignore_sync_check__ marker
x86/insn: Add an insn_decode() API
x86/insn-eval: Handle return values from the decoder
x86/alternative: Use insn_decode()
x86: Add insn_decode_kernel()
x86/alternatives: Optimize optimize_nops()
x86/retpoline: Simplify retpolines
objtool: Correctly handle retpoline thunk calls
objtool: Handle per arch retpoline naming
objtool: Rework the elf_rebuild_reloc_section() logic
objtool: Add elf_create_reloc() helper
objtool: Create reloc sections implicitly
objtool: Extract elf_strtab_concat()
objtool: Extract elf_symbol_add()
objtool: Add elf_create_undef_symbol()
objtool: Keep track of retpoline call sites
objtool: Cache instruction relocs
objtool: Skip magical retpoline .altinstr_replacement
objtool/x86: Rewrite retpoline thunk calls
objtool: Support asm jump tables
x86/alternative: Optimize single-byte NOPs at an arbitrary position
objtool: Fix .symtab_shndx handling for elf_create_undef_symbol()
objtool: Only rewrite unconditional retpoline thunk calls
objtool/x86: Ignore __x86_indirect_alt_* symbols
objtool: Don't make .altinstructions writable
objtool: Teach get_alt_entry() about more relocation types
objtool: print out the symbol type when complaining about it
objtool: Remove reloc symbol type checks in get_alt_entry()
objtool: Make .altinstructions section entry size consistent
objtool: Introduce CFI hash
objtool: Handle __sanitize_cov*() tail calls
objtool: Classify symbols
objtool: Explicitly avoid self modifying code in .altinstr_replacement
objtool,x86: Replace alternatives with .retpoline_sites
x86/retpoline: Remove unused replacement symbols
x86/asm: Fix register order
x86/asm: Fixup odd GEN-for-each-reg.h usage
x86/retpoline: Move the retpoline thunk declarations to nospec-branch.h
x86/retpoline: Create a retpoline thunk array
x86/alternative: Implement .retpoline_sites support
x86/alternative: Handle Jcc __x86_indirect_thunk_\reg
x86/alternative: Try inline spectre_v2=retpoline,amd
x86/alternative: Add debug prints to apply_retpolines()
bpf,x86: Simplify computing label offsets
bpf,x86: Respect X86_FEATURE_RETPOLINE*
x86/lib/atomic64_386_32: Rename things
x86: Prepare asm files for straight-line-speculation
x86: Prepare inline-asm for straight-line-speculation
x86/alternative: Relax text_poke_bp() constraint
objtool: Add straight-line-speculation validation
x86: Add straight-line-speculation mitigation
tools arch: Update arch/x86/lib/mem{cpy,set}_64.S copies used in 'perf bench mem memcpy'
kvm/emulate: Fix SETcc emulation function offsets with SLS
objtool: Default ignore INT3 for unreachable
crypto: x86/poly1305 - Fixup SLS
objtool: Fix SLS validation for kcov tail-call replacement
objtool: Fix code relocs vs weak symbols
objtool: Fix type of reloc::addend
objtool: Fix symbol creation
x86/entry: Remove skip_r11rcx
objtool: Fix objtool regression on x32 systems
x86/realmode: build with -D__DISABLE_EXPORTS
x86/kvm/vmx: Make noinstr clean
x86/cpufeatures: Move RETPOLINE flags to word 11
x86/retpoline: Cleanup some #ifdefery
x86/retpoline: Swizzle retpoline thunk
Makefile: Set retpoline cflags based on CONFIG_CC_IS_{CLANG,GCC}
x86/retpoline: Use -mfunction-return
x86: Undo return-thunk damage
x86,objtool: Create .return_sites
objtool: skip non-text sections when adding return-thunk sites
x86,static_call: Use alternative RET encoding
x86/ftrace: Use alternative RET encoding
x86/bpf: Use alternative RET encoding
x86/kvm: Fix SETcc emulation for return thunks
x86/vsyscall_emu/64: Don't use RET in vsyscall emulation
x86/sev: Avoid using __x86_return_thunk
x86: Use return-thunk in asm code
objtool: Treat .text.__x86.* as noinstr
x86: Add magic AMD return-thunk
x86/bugs: Report AMD retbleed vulnerability
x86/bugs: Add AMD retbleed= boot parameter
x86/bugs: Enable STIBP for JMP2RET
x86/bugs: Keep a per-CPU IA32_SPEC_CTRL value
x86/entry: Add kernel IBRS implementation
x86/bugs: Optimize SPEC_CTRL MSR writes
x86/speculation: Add spectre_v2=ibrs option to support Kernel IBRS
x86/bugs: Split spectre_v2_select_mitigation() and spectre_v2_user_select_mitigation()
x86/bugs: Report Intel retbleed vulnerability
intel_idle: Disable IBRS during long idle
objtool: Update Retpoline validation
x86/xen: Rename SYS* entry points
x86/bugs: Add retbleed=ibpb
x86/bugs: Do IBPB fallback check only once
objtool: Add entry UNRET validation
x86/cpu/amd: Add Spectral Chicken
x86/speculation: Fix RSB filling with CONFIG_RETPOLINE=n
x86/speculation: Fix firmware entry SPEC_CTRL handling
x86/speculation: Fix SPEC_CTRL write on SMT state change
x86/speculation: Use cached host SPEC_CTRL value for guest entry/exit
x86/speculation: Remove x86_spec_ctrl_mask
objtool: Re-add UNWIND_HINT_{SAVE_RESTORE}
KVM: VMX: Flatten __vmx_vcpu_run()
KVM: VMX: Convert launched argument to flags
KVM: VMX: Prevent guest RSB poisoning attacks with eIBRS
KVM: VMX: Fix IBRS handling after vmexit
x86/speculation: Fill RSB on vmexit for IBRS
x86/common: Stamp out the stepping madness
x86/cpu/amd: Enumerate BTC_NO
x86/retbleed: Add fine grained Kconfig knobs
x86/bugs: Add Cannon lake to RETBleed affected CPU list
x86/bugs: Do not enable IBPB-on-entry when IBPB is not supported
x86/kexec: Disable RET on kexec
x86/speculation: Disable RRSBA behavior
x86/static_call: Serialize __static_call_fixup() properly
tools/insn: Restore the relative include paths for cross building
x86, kvm: use proper ASM macros for kvm_vcpu_is_preempted
x86/xen: Fix initialisation in hypercall_page after rethunk
x86/ftrace: Add UNWIND_HINT_FUNC annotation for ftrace_stub
x86/asm/32: Fix ANNOTATE_UNRET_SAFE use on 32-bit
x86/speculation: Use DECLARE_PER_CPU for x86_spec_ctrl_current
efi/x86: use naked RET on mixed mode call wrapper
x86/kvm: fix FASTOP_SIZE when return thunks are enabled
KVM: emulate: do not adjust size of fastop and setcc subroutines
tools arch x86: Sync the msr-index.h copy with the kernel sources
tools headers cpufeatures: Sync with the kernel sources
x86/bugs: Remove apostrophe typo
um: Add missing apply_returns()
x86: Use -mindirect-branch-cs-prefix for RETPOLINE builds
kvm: fix objtool relocation warning
objtool: Fix elf_create_undef_symbol() endianness
tools arch: Update arch/x86/lib/mem{cpy,set}_64.S copies used in 'perf bench mem memcpy' - again
tools headers: Remove broken definition of __LITTLE_ENDIAN
Linux 5.10.133
Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Change-Id: I7e23843058c509562ae3f3a68e0710f31249a087
|
||
|
Peter Zijlstra
|
b24fdd0f1c |
x86/retbleed: Add fine grained Kconfig knobs
commit f43b9876e857c739d407bc56df288b0ebe1a9164 upstream. Do fine-grained Kconfig for all the various retbleed parts. NOTE: if your compiler doesn't support return thunks this will silently 'upgrade' your mitigation to IBPB, you might not like this. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Borislav Petkov <bp@suse.de> [cascardo: there is no CONFIG_OBJTOOL] [cascardo: objtool calling and option parsing has changed] Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com> [bwh: Backported to 5.10: - In scripts/Makefile.build, add the objtool option with an ifdef block, same as for other options - Adjust filename, context] Signed-off-by: Ben Hutchings <ben@decadent.org.uk> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
||
|
Peter Zijlstra
|
0d1a8a16e6 |
objtool: Add entry UNRET validation
commit a09a6e2399ba0595c3042b3164f3ca68a3cff33e upstream. Since entry asm is tricky, add a validation pass that ensures the retbleed mitigation has been done before the first actual RET instruction. Entry points are those that either have UNWIND_HINT_ENTRY, which acts as UNWIND_HINT_EMPTY but marks the instruction as an entry point, or those that have UWIND_HINT_IRET_REGS at +0. This is basically a variant of validate_branch() that is intra-function and it will simply follow all branches from marked entry points and ensures that all paths lead to ANNOTATE_UNRET_END. If a path hits RET or an indirection the path is a fail and will be reported. There are 3 ANNOTATE_UNRET_END instances: - UNTRAIN_RET itself - exception from-kernel; this path doesn't need UNTRAIN_RET - all early exceptions; these also don't need UNTRAIN_RET Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Borislav Petkov <bp@suse.de> Reviewed-by: Josh Poimboeuf <jpoimboe@kernel.org> Signed-off-by: Borislav Petkov <bp@suse.de> [cascardo: arch/x86/entry/entry_64.S no pt_regs return at .Lerror_entry_done_lfence] [cascardo: tools/objtool/builtin-check.c no link option validation] [cascardo: tools/objtool/check.c opts.ibt is ibt] [cascardo: tools/objtool/include/objtool/builtin.h leave unret option as bool, no struct opts] [cascardo: objtool is still called from scripts/link-vmlinux.sh] [cascardo: no IBT support] Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com> [bwh: Backported to 5.10: - In scripts/link-vmlinux.sh, use "test -n" instead of is_enabled - Adjust context] Signed-off-by: Ben Hutchings <ben@decadent.org.uk> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
||
|
Peter Zijlstra
|
0f8532c283 |
objtool: Add straight-line-speculation validation
commit 1cc1e4c8aab4213bd4e6353dec2620476a233d6d upstream. Teach objtool to validate the straight-line-speculation constraints: - speculation trap after indirect calls - speculation trap after RET Notable: when an instruction is annotated RETPOLINE_SAFE, indicating speculation isn't a problem, also don't care about sls for that instruction. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Borislav Petkov <bp@suse.de> Link: https://lore.kernel.org/r/20211204134908.023037659@infradead.org Signed-off-by: Sasha Levin <sashal@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> [bwh: Backported to 5.10: adjust filenames, context] Signed-off-by: Ben Hutchings <ben@decadent.org.uk> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
||
|
Sami Tolvanen
|
8fdc2dc3ca |
FROMLIST: objtool: Split noinstr validation from --vmlinux
This change adds a --noinstr flag to objtool to allow us to specify that we're processing vmlinux.o without also enabling noinstr validation. This is needed to avoid false positives with LTO when we run objtool on vmlinux.o without CONFIG_DEBUG_ENTRY. Bug: 145210207 Change-Id: I479c72d2733844d2059253035391a0c6e8ad7771 Link: https://lore.kernel.org/lkml/20201013003203.4168817-11-samitolvanen@google.com/ Signed-off-by: Sami Tolvanen <samitolvanen@google.com> |
||
|
Peter Zijlstra
|
7dcfcd46b9 |
FROMLIST: objtool: Add a pass for generating __mcount_loc
Add the --mcount option for generating __mcount_loc sections needed for dynamic ftrace. Using this pass requires the kernel to be compiled with -mfentry and CC_USING_NOP_MCOUNT to be defined in Makefile. Bug: 145210207 Change-Id: I34eeeb00c184bf265391549094fc15525536886b Link: https://lore.kernel.org/lkml/20200625200235.GQ4781@hirez.programming.kicks-ass.net/ Signed-off-by: Peter Zijlstra <peterz@infradead.org> [Sami: rebased, dropped config changes, fixed to actually use --mcount, and wrote a commit message.] Signed-off-by: Sami Tolvanen <samitolvanen@google.com> Reviewed-by: Kees Cook <keescook@chromium.org> |
||
|
Peter Zijlstra
|
c4a33939a7 |
objtool: Implement noinstr validation
Validate that any call out of .noinstr.text is in between instr_begin() and instr_end() annotations. This annotation is useful to ensure correct behaviour wrt tracing sensitive code like entry/exit and idle code. When we run code in a sensitive context we want a guarantee no unknown code is ran. Since this validation relies on knowing the section of call destination symbols, we must run it on vmlinux.o instead of on individual object files. Add two options: -d/--duplicate "duplicate validation for vmlinux" -l/--vmlinux "vmlinux.o validation" Where the latter auto-detects when objname ends with "vmlinux.o" and the former will force all validations, also those already done on !vmlinux object files. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Miroslav Benes <mbenes@suse.cz> Reviewed-by: Alexandre Chartre <alexandre.chartre@oracle.com> Acked-by: Josh Poimboeuf <jpoimboe@redhat.com> Link: https://lkml.kernel.org/r/20200416115119.106268040@infradead.org Signed-off-by: Ingo Molnar <mingo@kernel.org> |
||
|
Peter Zijlstra
|
1e11f3fdc3 |
objtool: Add a statistics mode
Have it print a few numbers which can be used to size the hashtables. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Miroslav Benes <mbenes@suse.cz> Acked-by: Josh Poimboeuf <jpoimboe@redhat.com> Link: https://lkml.kernel.org/r/20200324160924.321381240@infradead.org |
||
|
Thomas Gleixner
|
1ccea77e2a |
treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 13
Based on 2 normalized pattern(s): this program is free software you can redistribute it and or modify it under the terms of the gnu general public license as published by the free software foundation either version 2 of the license or at your option any later version this program is distributed in the hope that it will be useful but without any warranty without even the implied warranty of merchantability or fitness for a particular purpose see the gnu general public license for more details you should have received a copy of the gnu general public license along with this program if not see http www gnu org licenses this program is free software you can redistribute it and or modify it under the terms of the gnu general public license as published by the free software foundation either version 2 of the license or at your option any later version this program is distributed in the hope that it will be useful but without any warranty without even the implied warranty of merchantability or fitness for a particular purpose see the gnu general public license for more details [based] [from] [clk] [highbank] [c] you should have received a copy of the gnu general public license along with this program if not see http www gnu org licenses extracted by the scancode license scanner the SPDX license identifier GPL-2.0-or-later has been chosen to replace the boilerplate/reference in 355 file(s). Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Kate Stewart <kstewart@linuxfoundation.org> Reviewed-by: Jilayne Lovejoy <opensource@jilayne.com> Reviewed-by: Steve Winslow <swinslow@gmail.com> Reviewed-by: Allison Randal <allison@lohutok.net> Cc: linux-spdx@vger.kernel.org Link: https://lkml.kernel.org/r/20190519154041.837383322@linutronix.de Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
||
|
Peter Zijlstra
|
ea24213d80 |
objtool: Add UACCESS validation
It is important that UACCESS regions are as small as possible; furthermore the UACCESS state is not scheduled, so doing anything that might directly call into the scheduler will cause random code to be ran with UACCESS enabled. Teach objtool too track UACCESS state and warn about any CALL made while UACCESS is enabled. This very much includes the __fentry__() and __preempt_schedule() calls. Note that exceptions _do_ save/restore the UACCESS state, and therefore they can drive preemption. This also means that all exception handlers must have an otherwise redundant UACCESS disable instruction; therefore ignore this warning for !STT_FUNC code (exception handlers are not normal functions). Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Acked-by: Josh Poimboeuf <jpoimboe@redhat.com> Cc: Borislav Petkov <bp@alien8.de> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Ingo Molnar <mingo@kernel.org> |
||
|
Peter Zijlstra
|
7697eee3dd |
objtool: Add --backtrace support
For when you want to know the path that reached your fail state:
$ ./objtool check --no-fp --backtrace arch/x86/lib/usercopy_64.o
arch/x86/lib/usercopy_64.o: warning: objtool: .altinstr_replacement+0x3: UACCESS disable without MEMOPs: __clear_user()
arch/x86/lib/usercopy_64.o: warning: objtool: __clear_user()+0x3a: (alt)
arch/x86/lib/usercopy_64.o: warning: objtool: __clear_user()+0x2e: (branch)
arch/x86/lib/usercopy_64.o: warning: objtool: __clear_user()+0x18: (branch)
arch/x86/lib/usercopy_64.o: warning: objtool: .altinstr_replacement+0xffffffffffffffff: (branch)
arch/x86/lib/usercopy_64.o: warning: objtool: __clear_user()+0x5: (alt)
arch/x86/lib/usercopy_64.o: warning: objtool: __clear_user()+0x0: <=== (func)
0000000000000000 <__clear_user>:
0: e8 00 00 00 00 callq 5 <__clear_user+0x5>
1: R_X86_64_PLT32 __fentry__-0x4
5: 90 nop
6: 90 nop
7: 90 nop
8: 48 89 f0 mov %rsi,%rax
b: 48 c1 ee 03 shr $0x3,%rsi
f: 83 e0 07 and $0x7,%eax
12: 48 89 f1 mov %rsi,%rcx
15: 48 85 c9 test %rcx,%rcx
18: 74 0f je 29 <__clear_user+0x29>
1a: 48 c7 07 00 00 00 00 movq $0x0,(%rdi)
21: 48 83 c7 08 add $0x8,%rdi
25: ff c9 dec %ecx
27: 75 f1 jne 1a <__clear_user+0x1a>
29: 48 89 c1 mov %rax,%rcx
2c: 85 c9 test %ecx,%ecx
2e: 74 0a je 3a <__clear_user+0x3a>
30: c6 07 00 movb $0x0,(%rdi)
33: 48 ff c7 inc %rdi
36: ff c9 dec %ecx
38: 75 f6 jne 30 <__clear_user+0x30>
3a: 90 nop
3b: 90 nop
3c: 90 nop
3d: 48 89 c8 mov %rcx,%rax
40: c3 retq
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
|
||
|
Peter Zijlstra
|
ca41b97ed9 |
objtool: Add module specific retpoline rules
David allowed retpolines in .init.text, except for modules, which will trip up objtool retpoline validation, fix that. Requested-by: David Woodhouse <dwmw2@infradead.org> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Acked-by: Thomas Gleixner <tglx@linutronix.de> Acked-by: Josh Poimboeuf <jpoimboe@redhat.com> Cc: Andy Lutomirski <luto@kernel.org> Cc: Arjan van de Ven <arjan@linux.intel.com> Cc: Borislav Petkov <bp@alien8.de> Cc: Dan Williams <dan.j.williams@intel.com> Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: David Woodhouse <dwmw2@infradead.org> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Ingo Molnar <mingo@kernel.org> |
||
|
Peter Zijlstra
|
b5bc2231b8 |
objtool: Add retpoline validation
David requested a objtool validation pass for CONFIG_RETPOLINE=y enabled builds, where it validates no unannotated indirect jumps or calls are left. Add an additional .discard.retpoline_safe section to allow annotating the few indirect sites that are required and safe. Requested-by: David Woodhouse <dwmw2@infradead.org> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: David Woodhouse <dwmw@amazon.co.uk> Acked-by: Thomas Gleixner <tglx@linutronix.de> Acked-by: Josh Poimboeuf <jpoimboe@redhat.com> Cc: Andy Lutomirski <luto@kernel.org> Cc: Arjan van de Ven <arjan@linux.intel.com> Cc: Borislav Petkov <bp@alien8.de> Cc: Dan Williams <dan.j.williams@intel.com> Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Ingo Molnar <mingo@kernel.org> |
||
|
Peter Zijlstra
|
43a4525f80 |
objtool: Use existing global variables for options
Use the existing global variables instead of passing them around and creating duplicate global variables. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Acked-by: Thomas Gleixner <tglx@linutronix.de> Acked-by: Josh Poimboeuf <jpoimboe@redhat.com> Cc: Andy Lutomirski <luto@kernel.org> Cc: Arjan van de Ven <arjan@linux.intel.com> Cc: Borislav Petkov <bp@alien8.de> Cc: Dan Williams <dan.j.williams@intel.com> Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: David Woodhouse <dwmw2@infradead.org> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Ingo Molnar <mingo@kernel.org> |
||
|
Josh Poimboeuf
|
627fce1480 |
objtool: Add ORC unwind table generation
Now that objtool knows the states of all registers on the stack for each instruction, it's straightforward to generate debuginfo for an unwinder to use. Instead of generating DWARF, generate a new format called ORC, which is more suitable for an in-kernel unwinder. See Documentation/x86/orc-unwinder.txt for a more detailed description of this new debuginfo format and why it's preferable to DWARF. Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com> Cc: Andy Lutomirski <luto@kernel.org> 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: Mike Galbraith <efault@gmx.de> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: live-patching@vger.kernel.org Link: http://lkml.kernel.org/r/c9b9f01ba6c5ed2bdc9bb0957b78167fdbf9632e.1499786555.git.jpoimboe@redhat.com Signed-off-by: Ingo Molnar <mingo@kernel.org> |
||
|
Josh Poimboeuf
|
442f04c34a |
objtool: Add tool to perform compile-time stack metadata validation
This adds a host tool named objtool which has a "check" subcommand which
analyzes .o files to ensure the validity of stack metadata. It enforces
a set of rules on asm code and C inline assembly code so that stack
traces can be reliable.
For each function, it recursively follows all possible code paths and
validates the correct frame pointer state at each instruction.
It also follows code paths involving kernel special sections, like
.altinstructions, __jump_table, and __ex_table, which can add
alternative execution paths to a given instruction (or set of
instructions). Similarly, it knows how to follow switch statements, for
which gcc sometimes uses jump tables.
Here are some of the benefits of validating stack metadata:
a) More reliable stack traces for frame pointer enabled kernels
Frame pointers are used for debugging purposes. They allow runtime
code and debug tools to be able to walk the stack to determine the
chain of function call sites that led to the currently executing
code.
For some architectures, frame pointers are enabled by
CONFIG_FRAME_POINTER. For some other architectures they may be
required by the ABI (sometimes referred to as "backchain pointers").
For C code, gcc automatically generates instructions for setting up
frame pointers when the -fno-omit-frame-pointer option is used.
But for asm code, the frame setup instructions have to be written by
hand, which most people don't do. So the end result is that
CONFIG_FRAME_POINTER is honored for C code but not for most asm code.
For stack traces based on frame pointers to be reliable, all
functions which call other functions must first create a stack frame
and update the frame pointer. If a first function doesn't properly
create a stack frame before calling a second function, the *caller*
of the first function will be skipped on the stack trace.
For example, consider the following example backtrace with frame
pointers enabled:
[<ffffffff81812584>] dump_stack+0x4b/0x63
[<ffffffff812d6dc2>] cmdline_proc_show+0x12/0x30
[<ffffffff8127f568>] seq_read+0x108/0x3e0
[<ffffffff812cce62>] proc_reg_read+0x42/0x70
[<ffffffff81256197>] __vfs_read+0x37/0x100
[<ffffffff81256b16>] vfs_read+0x86/0x130
[<ffffffff81257898>] SyS_read+0x58/0xd0
[<ffffffff8181c1f2>] entry_SYSCALL_64_fastpath+0x12/0x76
It correctly shows that the caller of cmdline_proc_show() is
seq_read().
If we remove the frame pointer logic from cmdline_proc_show() by
replacing the frame pointer related instructions with nops, here's
what it looks like instead:
[<ffffffff81812584>] dump_stack+0x4b/0x63
[<ffffffff812d6dc2>] cmdline_proc_show+0x12/0x30
[<ffffffff812cce62>] proc_reg_read+0x42/0x70
[<ffffffff81256197>] __vfs_read+0x37/0x100
[<ffffffff81256b16>] vfs_read+0x86/0x130
[<ffffffff81257898>] SyS_read+0x58/0xd0
[<ffffffff8181c1f2>] entry_SYSCALL_64_fastpath+0x12/0x76
Notice that cmdline_proc_show()'s caller, seq_read(), has been
skipped. Instead the stack trace seems to show that
cmdline_proc_show() was called by proc_reg_read().
The benefit of "objtool check" here is that because it ensures that
*all* functions honor CONFIG_FRAME_POINTER, no functions will ever[*]
be skipped on a stack trace.
[*] unless an interrupt or exception has occurred at the very
beginning of a function before the stack frame has been created,
or at the very end of the function after the stack frame has been
destroyed. This is an inherent limitation of frame pointers.
b) 100% reliable stack traces for DWARF enabled kernels
This is not yet implemented. For more details about what is planned,
see tools/objtool/Documentation/stack-validation.txt.
c) Higher live patching compatibility rate
This is not yet implemented. For more details about what is planned,
see tools/objtool/Documentation/stack-validation.txt.
To achieve the validation, "objtool check" enforces the following rules:
1. Each callable function must be annotated as such with the ELF
function type. In asm code, this is typically done using the
ENTRY/ENDPROC macros. If objtool finds a return instruction
outside of a function, it flags an error since that usually indicates
callable code which should be annotated accordingly.
This rule is needed so that objtool can properly identify each
callable function in order to analyze its stack metadata.
2. Conversely, each section of code which is *not* callable should *not*
be annotated as an ELF function. The ENDPROC macro shouldn't be used
in this case.
This rule is needed so that objtool can ignore non-callable code.
Such code doesn't have to follow any of the other rules.
3. Each callable function which calls another function must have the
correct frame pointer logic, if required by CONFIG_FRAME_POINTER or
the architecture's back chain rules. This can by done in asm code
with the FRAME_BEGIN/FRAME_END macros.
This rule ensures that frame pointer based stack traces will work as
designed. If function A doesn't create a stack frame before calling
function B, the _caller_ of function A will be skipped on the stack
trace.
4. Dynamic jumps and jumps to undefined symbols are only allowed if:
a) the jump is part of a switch statement; or
b) the jump matches sibling call semantics and the frame pointer has
the same value it had on function entry.
This rule is needed so that objtool can reliably analyze all of a
function's code paths. If a function jumps to code in another file,
and it's not a sibling call, objtool has no way to follow the jump
because it only analyzes a single file at a time.
5. A callable function may not execute kernel entry/exit instructions.
The only code which needs such instructions is kernel entry code,
which shouldn't be be in callable functions anyway.
This rule is just a sanity check to ensure that callable functions
return normally.
It currently only supports x86_64. I tried to make the code generic so
that support for other architectures can hopefully be plugged in
relatively easily.
On my Lenovo laptop with a i7-4810MQ 4-core/8-thread CPU, building the
kernel with objtool checking every .o file adds about three seconds of
total build time. It hasn't been optimized for performance yet, so
there are probably some opportunities for better build performance.
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
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: Chris J Arges <chris.j.arges@canonical.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/f3efb173de43bd067b060de73f856567c0fa1174.1456719558.git.jpoimboe@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
|