Content-Type: multipart/mixed; boundary="===============0645423908256765083==" MIME-Version: 1.0 From: Alexey Dobriyan 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 Message-ID: <20180515225845.GB21902@avx2> In-Reply-To: <20180515225028.GA21902@avx2> List-Id: --===============0645423908256765083== Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable 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 --- 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_STI= MER0_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 =20 --===============0645423908256765083==--