From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753183AbbETOsR (ORCPT ); Wed, 20 May 2015 10:48:17 -0400 Received: from mail-wg0-f42.google.com ([74.125.82.42]:33753 "EHLO mail-wg0-f42.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751117AbbETOsP (ORCPT ); Wed, 20 May 2015 10:48:15 -0400 Date: Wed, 20 May 2015 16:48:10 +0200 From: Ingo Molnar To: Josh Poimboeuf Cc: Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , Michal Marek , Peter Zijlstra , x86@kernel.org, live-patching@vger.kernel.org, linux-kernel@vger.kernel.org, Linus Torvalds , Andy Lutomirski , Denys Vlasenko , Brian Gerst , Peter Zijlstra , Borislav Petkov , Andrew Morton Subject: Re: [PATCH v4 0/3] Compile-time stack frame pointer validation Message-ID: <20150520144810.GA10374@gmail.com> References: <20150520103339.GA22205@gmail.com> <20150520141331.GA16995@treble.redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20150520141331.GA16995@treble.redhat.com> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Josh Poimboeuf wrote: > On Wed, May 20, 2015 at 12:33:39PM +0200, Ingo Molnar wrote: > > > > * Josh Poimboeuf 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