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Message-ID: <20150520144810.GA10374@gmail.com> Date: Wed, 20 May 2015 16:48:10 +0200 From: Ingo Molnar <mingo@...nel.org> To: Josh Poimboeuf <jpoimboe@...hat.com> Cc: Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, "H. Peter Anvin" <hpa@...or.com>, Michal Marek <mmarek@...e.cz>, Peter Zijlstra <peterz@...radead.org>, x86@...nel.org, live-patching@...r.kernel.org, linux-kernel@...r.kernel.org, Linus Torvalds <torvalds@...ux-foundation.org>, Andy Lutomirski <luto@...nel.org>, Denys Vlasenko <dvlasenk@...hat.com>, Brian Gerst <brgerst@...il.com>, Peter Zijlstra <a.p.zijlstra@...llo.nl>, Borislav Petkov <bp@...en8.de>, Andrew Morton <akpm@...ux-foundation.org> Subject: Re: [PATCH v4 0/3] Compile-time stack frame pointer validation * Josh Poimboeuf <jpoimboe@...hat.com> wrote: > On Wed, May 20, 2015 at 12:33:39PM +0200, Ingo Molnar wrote: > > > > * Josh Poimboeuf <jpoimboe@...hat.com> wrote: > > > > > In discussions around the live kernel patching consistency model RFC > > > [1], Peter and Ingo correctly pointed out that stack traces aren't > > > reliable. And as Ingo said, there's no "strong force" which ensures we > > > can rely on them. > > > > > > So I've been thinking about how to fix that. My goal is to eventually > > > make stack traces reliable. Or at the very least, to be able to detect > > > at runtime when a given stack trace *might* be unreliable. But improved > > > stack traces would broadly benefit the entire kernel, regardless of the > > > outcome of the live kernel patching consistency model discussions. > > > > > > This patch set is just the first in a series of proposed stack trace > > > reliability improvements. Future proposals will include runtime stack > > > reliability checking, as well as compile-time and runtime DWARF > > > validations. > > > > > > As far as I can tell, there are two main obstacles which prevent frame > > > pointer based stack traces from being reliable: > > > > > > 1) Missing frame pointer logic: currently, most assembly functions don't > > > set up the frame pointer. > > > > Could you please paste here the output of what the new checks print > > for x86/64 defconfig? > > Here are all 89 warnings from defconfig: > > arch/x86/ia32/ia32entry.o: ia32_sysenter_target() is missing frame pointer logic. Please use FUNC_ENTER. > arch/x86/ia32/ia32entry.o: return instruction outside of a function at .entry.text+0x52e. Please use FUNC_ENTER. > arch/x86/kernel/entry_64.o: return instruction outside of a function at .entry.text+0x359. Please use FUNC_ENTER. > arch/x86/kernel/entry_64.o: return instruction outside of a function at .entry.text+0x19be. Please use FUNC_ENTER. > arch/x86/kernel/entry_64.o: return instruction outside of a function at .entry.text+0x19e5. Please use FUNC_ENTER. > arch/x86/kernel/entry_64.o: return instruction outside of a function at .entry.text+0x1c21. Please use FUNC_ENTER. > arch/x86/kernel/entry_64.o: return instruction outside of a function at .entry.text+0x1ceb. Please use FUNC_ENTER. > arch/x86/kernel/acpi/wakeup_64.o: wakeup_long64() is missing frame pointer logic. Please use FUNC_ENTER. > arch/x86/kernel/acpi/wakeup_64.o: do_suspend_lowlevel() is missing frame pointer logic. Please use FUNC_ENTER. > arch/x86/platform/efi/efi_stub_64.o: efi_call() is missing frame pointer logic. Please use FUNC_ENTER. > arch/x86/kernel/relocate_kernel_64.o: return instruction outside of a function at .text+0x6b. Please use FUNC_ENTER. > arch/x86/kernel/relocate_kernel_64.o: return instruction outside of a function at .text+0xc7. Please use FUNC_ENTER. > arch/x86/kernel/relocate_kernel_64.o: return instruction outside of a function at .text+0x110. Please use FUNC_ENTER. > arch/x86/kernel/relocate_kernel_64.o: return instruction outside of a function at .text+0x145. Please use FUNC_ENTER. > arch/x86/kernel/relocate_kernel_64.o: return instruction outside of a function at .text+0x1c4. Please use FUNC_ENTER. > arch/x86/realmode/rm/trampoline_64.o: return instruction outside of a function at .text+0x170. Please use FUNC_ENTER. > arch/x86/realmode/rm/trampoline_64.o: return instruction outside of a function at .text+0x176. Please use FUNC_ENTER. > arch/x86/kernel/head_64.o: return instruction outside of a function at .head.text+0x1a2. Please use FUNC_ENTER. > arch/x86/kernel/head_64.o: start_cpu0() is missing frame pointer logic. Please use FUNC_ENTER. > arch/x86/kernel/head_64.o: early_idt_handler() is missing frame pointer logic. Please use FUNC_ENTER. > arch/x86/realmode/rm/reboot.o: return instruction outside of a function at .text+0x2a. Please use FUNC_ENTER. > arch/x86/realmode/rm/copy.o: memcpy() is missing frame pointer logic. Please use FUNC_ENTER. > arch/x86/realmode/rm/copy.o: memset() is missing frame pointer logic. Please use FUNC_ENTER. > arch/x86/realmode/rm/copy.o: copy_from_fs() is missing frame pointer logic. Please use FUNC_ENTER. > arch/x86/realmode/rm/copy.o: copy_to_fs() is missing frame pointer logic. Please use FUNC_ENTER. > arch/x86/realmode/rm/bioscall.o: intcall() is missing frame pointer logic. Please use FUNC_ENTER. > arch/x86/vdso/vdso32/int80.o: __kernel_sigreturn() is missing frame pointer logic. Please use FUNC_ENTER. > arch/x86/vdso/vdso32/int80.o: __kernel_rt_sigreturn() is missing frame pointer logic. Please use FUNC_ENTER. > arch/x86/vdso/vdso32/int80.o: __kernel_vsyscall() is missing frame pointer logic. Please use FUNC_ENTER. > arch/x86/vdso/vdso32/syscall.o: __kernel_sigreturn() is missing frame pointer logic. Please use FUNC_ENTER. > arch/x86/vdso/vdso32/syscall.o: __kernel_rt_sigreturn() is missing frame pointer logic. Please use FUNC_ENTER. > arch/x86/vdso/vdso32/syscall.o: __kernel_vsyscall() is missing frame pointer logic. Please use FUNC_ENTER. > arch/x86/vdso/vdso32/sysenter.o: __kernel_sigreturn() is missing frame pointer logic. Please use FUNC_ENTER. > arch/x86/vdso/vdso32/sysenter.o: __kernel_rt_sigreturn() is missing frame pointer logic. Please use FUNC_ENTER. > arch/x86/power/hibernate_asm_64.o: return instruction outside of a function at .text+0x69. Please use FUNC_ENTER. > arch/x86/power/hibernate_asm_64.o: return instruction outside of a function at .text+0x16d. Please use FUNC_ENTER. > arch/x86/lib/msr-reg.o: rdmsr_safe_regs() is missing frame pointer logic. Please use FUNC_ENTER. > arch/x86/lib/msr-reg.o: wrmsr_safe_regs() is missing frame pointer logic. Please use FUNC_ENTER. > arch/x86/lib/iomap_copy_64.o: __iowrite32_copy() is missing frame pointer logic. Please use FUNC_ENTER. > arch/x86/lib/clear_page_64.o: clear_page() is missing frame pointer logic. Please use FUNC_ENTER. > arch/x86/lib/clear_page_64.o: clear_page_orig() is missing frame pointer logic. Please use FUNC_ENTER. > arch/x86/lib/clear_page_64.o: clear_page_c_e() is missing frame pointer logic. Please use FUNC_ENTER. > arch/x86/lib/cmpxchg16b_emu.o: this_cpu_cmpxchg16b_emu() is missing frame pointer logic. Please use FUNC_ENTER. > arch/x86/lib/copy_page_64.o: copy_page() is missing frame pointer logic. Please use FUNC_ENTER. > arch/x86/lib/copy_page_64.o: copy_page_regs() is missing frame pointer logic. Please use FUNC_ENTER. > arch/x86/lib/copy_user_64.o: _copy_to_user() is missing frame pointer logic. Please use FUNC_ENTER. > arch/x86/lib/copy_user_64.o: _copy_from_user() is missing frame pointer logic. Please use FUNC_ENTER. > arch/x86/lib/copy_user_64.o: copy_user_generic_unrolled() is missing frame pointer logic. Please use FUNC_ENTER. > arch/x86/lib/copy_user_64.o: copy_user_generic_string() is missing frame pointer logic. Please use FUNC_ENTER. > arch/x86/lib/copy_user_64.o: copy_user_enhanced_fast_string() is missing frame pointer logic. Please use FUNC_ENTER. > arch/x86/lib/copy_user_64.o: __copy_user_nocache() is missing frame pointer logic. Please use FUNC_ENTER. > arch/x86/lib/copy_user_64.o: bad_from_user() is missing frame pointer logic. Please use FUNC_ENTER. > arch/x86/lib/csum-copy_64.o: csum_partial_copy_generic() is missing frame pointer logic. Please use FUNC_ENTER. > arch/x86/lib/getuser.o: __get_user_1() is missing frame pointer logic. Please use FUNC_ENTER. > arch/x86/lib/getuser.o: __get_user_2() is missing frame pointer logic. Please use FUNC_ENTER. > arch/x86/lib/getuser.o: __get_user_4() is missing frame pointer logic. Please use FUNC_ENTER. > arch/x86/lib/getuser.o: __get_user_8() is missing frame pointer logic. Please use FUNC_ENTER. > arch/x86/lib/getuser.o: return instruction outside of a function at .text+0xc5. Please use FUNC_ENTER. > arch/x86/lib/memcpy_64.o: memcpy() is missing frame pointer logic. Please use FUNC_ENTER. > arch/x86/lib/memcpy_64.o: __memcpy() is missing frame pointer logic. Please use FUNC_ENTER. > arch/x86/lib/memcpy_64.o: memcpy_erms() is missing frame pointer logic. Please use FUNC_ENTER. > arch/x86/lib/memcpy_64.o: memcpy_orig() is missing frame pointer logic. Please use FUNC_ENTER. > arch/x86/lib/memmove_64.o: memmove() is missing frame pointer logic. Please use FUNC_ENTER. > arch/x86/lib/memmove_64.o: __memmove() is missing frame pointer logic. Please use FUNC_ENTER. > arch/x86/lib/memmove_64.o: return instruction outside of a function at .altinstr_replacement+0x5. Please use FUNC_ENTER. > arch/x86/lib/memset_64.o: memset() is missing frame pointer logic. Please use FUNC_ENTER. > arch/x86/lib/memset_64.o: __memset() is missing frame pointer logic. Please use FUNC_ENTER. > arch/x86/lib/memset_64.o: memset_erms() is missing frame pointer logic. Please use FUNC_ENTER. > arch/x86/lib/memset_64.o: memset_orig() is missing frame pointer logic. Please use FUNC_ENTER. > arch/x86/lib/putuser.o: __put_user_1() is missing frame pointer logic. Please use FUNC_ENTER. > arch/x86/lib/putuser.o: __put_user_2() is missing frame pointer logic. Please use FUNC_ENTER. > arch/x86/lib/putuser.o: __put_user_4() is missing frame pointer logic. Please use FUNC_ENTER. > arch/x86/lib/putuser.o: __put_user_8() is missing frame pointer logic. Please use FUNC_ENTER. > arch/x86/lib/putuser.o: return instruction outside of a function at .text+0xc1. Please use FUNC_ENTER. > arch/x86/lib/rwsem.o: call_rwsem_down_read_failed() is missing frame pointer logic. Please use FUNC_ENTER. > arch/x86/lib/rwsem.o: call_rwsem_down_write_failed() is missing frame pointer logic. Please use FUNC_ENTER. > arch/x86/lib/rwsem.o: call_rwsem_wake() is missing frame pointer logic. Please use FUNC_ENTER. > arch/x86/lib/rwsem.o: call_rwsem_downgrade_wake() is missing frame pointer logic. Please use FUNC_ENTER. > arch/x86/boot/bioscall.o: intcall() is missing frame pointer logic. Please use FUNC_ENTER. > arch/x86/boot/copy.o: memcpy() is missing frame pointer logic. Please use FUNC_ENTER. > arch/x86/boot/copy.o: memset() is missing frame pointer logic. Please use FUNC_ENTER. > arch/x86/boot/copy.o: copy_from_fs() is missing frame pointer logic. Please use FUNC_ENTER. > arch/x86/boot/copy.o: copy_to_fs() is missing frame pointer logic. Please use FUNC_ENTER. > arch/x86/boot/pmjump.o: protected_mode_jump() is missing frame pointer logic. Please use FUNC_ENTER. > arch/x86/boot/pmjump.o: in_pm32() is missing frame pointer logic. Please use FUNC_ENTER. > arch/x86/boot/compressed/head_64.o: return instruction outside of a function at .text+0x16e. Please use FUNC_ENTER. > arch/x86/boot/compressed/head_64.o: return instruction outside of a function at .text+0x172. Please use FUNC_ENTER. > arch/x86/boot/compressed/head_64.o: startup_32() is missing frame pointer logic. Please use FUNC_ENTER. > arch/x86/boot/header.o: die() is missing frame pointer logic. Please use FUNC_ENTER. Yeah, so many of these seem to be 'leaf only' functions: functions that don't ever call functions themselves. So lets assume we always have CONFIG_FRAME_POINTERS=y. If they don't set up a frame pointer then they in essence won't show up in the call chain - but normally they wouldn't because they call nothing. If they trigger an exception/fault or if they get hit by an interrupt then I think we'll still correctly walk the stack - just those functions might be missing from the deterministic call chain, right? (it will still show up as a '?' entry.) If they crash then we'll see them because the crashing RIP will be printed. So I'm wondering what the x86 policy here should be: to create frame pointers in them or not. Cc:-ed a few more gents for thoughts. Thanks, Ingo -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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