From: Alexey Dobriyan <adobriyan@gmail.com> To: mingo@kernel.org, tglx@linutronix.de Cc: Peter Anvin <h.peter.anvin@intel.com>, kernel test robot <xiaolong.ye@intel.com>, Andrew Lutomirski <luto@kernel.org>, Borislav Petkov <bp@alien8.de>, Brian Gerst <brgerst@gmail.com>, Denys Vlasenko <dvlasenk@redhat.com>, Josh Poimboeuf <jpoimboe@redhat.com>, Peter Zijlstra <peterz@infradead.org>, Linux Kernel Mailing List <linux-kernel@vger.kernel.org>, Peter Anvin <hpa@zytor.com>, tipbuild@zytor.com, LKP <lkp@01.org>, torvalds@linux-foundation.org, x86@kernel.org Subject: [PATCH v2] x86/asm: Pad assembly functions with INT3 instructions Date: Wed, 16 May 2018 01:58:45 +0300 [thread overview] Message-ID: <20180515225845.GB21902@avx2> (raw) In-Reply-To: <20180515225028.GA21902@avx2> Use INT3 instead of NOP. All that padding between functions is an illegal area, no legitimate code should jump into it. I've checked x86_64 allyesconfig disassembly, all changes looks sane: INT3 is only used after RET or unconditional JMP. On i386: * promote ret_from_exception into ENTRY as it has corresponding END, * demote "resume_userspace" -- unused, * delete ALIGN directive in page_fault. It is leftover from x86 assembly cleanups. commit d211af055d0c12dc3416c2886e6fbdc6eb74a381 i386: get rid of the use of KPROBE_ENTRY / KPROBE_END has ALIGN directive before branch target which makes sense. All the code after ALIGN disappeared later. Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com> --- arch/x86/entry/entry_32.S | 6 +----- arch/x86/include/asm/linkage.h | 2 +- 2 files changed, 2 insertions(+), 6 deletions(-) --- a/arch/x86/entry/entry_32.S +++ b/arch/x86/entry/entry_32.S @@ -320,8 +320,7 @@ END(ret_from_fork) */ # userspace resumption stub bypassing syscall exit tracing - ALIGN -ret_from_exception: +ENTRY(ret_from_exception) preempt_stop(CLBR_ANY) ret_from_intr: #ifdef CONFIG_VM86 @@ -337,8 +336,6 @@ ret_from_intr: #endif cmpl $USER_RPL, %eax jb resume_kernel # not returning to v8086 or userspace - -ENTRY(resume_userspace) DISABLE_INTERRUPTS(CLBR_ANY) TRACE_IRQS_OFF movl %esp, %eax @@ -910,7 +907,6 @@ BUILD_INTERRUPT3(hv_stimer0_callback_vector, HYPERV_STIMER0_VECTOR, ENTRY(page_fault) ASM_CLAC pushl $do_page_fault - ALIGN jmp common_exception END(page_fault) --- a/arch/x86/include/asm/linkage.h +++ b/arch/x86/include/asm/linkage.h @@ -18,7 +18,7 @@ name: #if defined(CONFIG_X86_64) || defined(CONFIG_X86_ALIGNMENT_16) -#define __ALIGN .p2align 4, 0x90 +#define __ALIGN .p2align 4, 0xCC #define __ALIGN_STR __stringify(__ALIGN) #endif
WARNING: multiple messages have this Message-ID (diff)
From: Alexey Dobriyan <adobriyan@gmail.com> To: lkp@lists.01.org Subject: [PATCH v2] x86/asm: Pad assembly functions with INT3 instructions Date: Wed, 16 May 2018 01:58:45 +0300 [thread overview] Message-ID: <20180515225845.GB21902@avx2> (raw) In-Reply-To: <20180515225028.GA21902@avx2> [-- Attachment #1: Type: text/plain, Size: 1912 bytes --] Use INT3 instead of NOP. All that padding between functions is an illegal area, no legitimate code should jump into it. I've checked x86_64 allyesconfig disassembly, all changes looks sane: INT3 is only used after RET or unconditional JMP. On i386: * promote ret_from_exception into ENTRY as it has corresponding END, * demote "resume_userspace" -- unused, * delete ALIGN directive in page_fault. It is leftover from x86 assembly cleanups. commit d211af055d0c12dc3416c2886e6fbdc6eb74a381 i386: get rid of the use of KPROBE_ENTRY / KPROBE_END has ALIGN directive before branch target which makes sense. All the code after ALIGN disappeared later. Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com> --- arch/x86/entry/entry_32.S | 6 +----- arch/x86/include/asm/linkage.h | 2 +- 2 files changed, 2 insertions(+), 6 deletions(-) --- a/arch/x86/entry/entry_32.S +++ b/arch/x86/entry/entry_32.S @@ -320,8 +320,7 @@ END(ret_from_fork) */ # userspace resumption stub bypassing syscall exit tracing - ALIGN -ret_from_exception: +ENTRY(ret_from_exception) preempt_stop(CLBR_ANY) ret_from_intr: #ifdef CONFIG_VM86 @@ -337,8 +336,6 @@ ret_from_intr: #endif cmpl $USER_RPL, %eax jb resume_kernel # not returning to v8086 or userspace - -ENTRY(resume_userspace) DISABLE_INTERRUPTS(CLBR_ANY) TRACE_IRQS_OFF movl %esp, %eax @@ -910,7 +907,6 @@ BUILD_INTERRUPT3(hv_stimer0_callback_vector, HYPERV_STIMER0_VECTOR, ENTRY(page_fault) ASM_CLAC pushl $do_page_fault - ALIGN jmp common_exception END(page_fault) --- a/arch/x86/include/asm/linkage.h +++ b/arch/x86/include/asm/linkage.h @@ -18,7 +18,7 @@ name: #if defined(CONFIG_X86_64) || defined(CONFIG_X86_ALIGNMENT_16) -#define __ALIGN .p2align 4, 0x90 +#define __ALIGN .p2align 4, 0xCC #define __ALIGN_STR __stringify(__ALIGN) #endif
next prev parent reply other threads:[~2018-05-15 22:58 UTC|newest] Thread overview: 61+ messages / expand[flat|nested] mbox.gz Atom feed top 2018-05-15 8:00 [lkp-robot] [x86/asm] 51bad67ffb: int3:#[##] kernel test robot 2018-05-15 8:00 ` kernel test robot 2018-05-15 21:07 ` Alexey Dobriyan 2018-05-15 21:07 ` Alexey Dobriyan 2018-05-15 21:25 ` Anvin, H Peter 2018-05-15 21:43 ` Alexey Dobriyan 2018-05-15 21:43 ` Alexey Dobriyan 2018-05-15 22:22 ` Josh Poimboeuf 2018-05-15 22:22 ` Josh Poimboeuf 2018-05-15 22:26 ` Thomas Gleixner 2018-05-15 22:26 ` Thomas Gleixner 2018-05-15 22:28 ` Linus Torvalds 2018-05-15 22:28 ` Linus Torvalds 2018-05-15 22:43 ` Josh Poimboeuf 2018-05-15 22:43 ` Josh Poimboeuf 2018-05-15 22:52 ` Linus Torvalds 2018-05-15 22:52 ` Linus Torvalds 2018-05-15 23:05 ` Linus Torvalds 2018-05-15 23:05 ` Linus Torvalds 2018-05-16 3:30 ` Josh Poimboeuf 2018-05-16 3:30 ` Josh Poimboeuf 2018-05-17 13:49 ` [PATCH] objtool: Detect assembly code falling through to INT3 padding Josh Poimboeuf 2018-05-17 13:49 ` Josh Poimboeuf 2018-05-17 14:01 ` Peter Zijlstra 2018-05-17 14:01 ` Peter Zijlstra 2018-05-18 7:24 ` Ingo Molnar 2018-05-18 7:24 ` Ingo Molnar 2018-05-18 7:18 ` Ingo Molnar 2018-05-18 7:18 ` Ingo Molnar 2018-05-18 7:27 ` H. Peter Anvin 2018-05-18 16:06 ` Borislav Petkov 2018-05-18 16:06 ` Borislav Petkov 2018-05-18 7:27 ` Ingo Molnar 2018-05-18 7:27 ` Ingo Molnar 2018-05-18 17:51 ` Alexey Dobriyan 2018-05-18 17:51 ` Alexey Dobriyan 2018-05-19 8:18 ` hpa 2018-05-19 7:00 ` "interesting" entry in hibernation code was Re: [lkp-robot] [x86/asm] 51bad67ffb: int3:#[##] Pavel Machek 2018-05-19 7:00 ` Pavel Machek 2018-05-19 8:35 ` Rafael J. Wysocki 2018-05-19 8:35 ` Rafael J. Wysocki 2018-05-18 7:15 ` Ingo Molnar 2018-05-18 7:15 ` Ingo Molnar 2018-05-15 22:25 ` Thomas Gleixner 2018-05-15 22:25 ` Thomas Gleixner 2018-05-15 22:29 ` Andy Lutomirski 2018-05-15 22:29 ` Andy Lutomirski 2018-05-15 22:27 ` Linus Torvalds 2018-05-15 22:27 ` Linus Torvalds 2018-05-15 22:50 ` Alexey Dobriyan 2018-05-15 22:50 ` Alexey Dobriyan 2018-05-15 22:58 ` Alexey Dobriyan [this message] 2018-05-15 22:58 ` [PATCH v2] x86/asm: Pad assembly functions with INT3 instructions Alexey Dobriyan 2018-05-15 23:28 ` Linus Torvalds 2018-05-15 23:28 ` Linus Torvalds 2018-05-18 7:36 ` Ingo Molnar 2018-05-18 7:36 ` Ingo Molnar 2018-05-18 13:02 ` Josh Poimboeuf 2018-05-18 13:02 ` Josh Poimboeuf 2018-05-18 17:34 ` Alexey Dobriyan 2018-05-18 17:34 ` Alexey Dobriyan
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