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Date: Sun, 7 Jun 2015 01:31:54 -0700 From: tip-bot for Denys Vlasenko <tipbot@...or.com> To: linux-tip-commits@...r.kernel.org Cc: akpm@...ux-foundation.org, rostedt@...dmis.org, mingo@...nel.org, ast@...mgrid.com, hpa@...or.com, peterz@...radead.org, tglx@...utronix.de, wad@...omium.org, linux-kernel@...r.kernel.org, dvlasenk@...hat.com, fweisbec@...il.com, bp@...en8.de, brgerst@...il.com, keescook@...omium.org, torvalds@...ux-foundation.org, oleg@...hat.com, luto@...capital.net Subject: [tip:x86/asm] x86/asm/entry/32: Do not use R9 in SYSCALL32 entry point Commit-ID: 53e9accf0f7682d717c7b578b6e01fd297ba6630 Gitweb: http://git.kernel.org/tip/53e9accf0f7682d717c7b578b6e01fd297ba6630 Author: Denys Vlasenko <dvlasenk@...hat.com> AuthorDate: Wed, 3 Jun 2015 14:56:09 +0200 Committer: Ingo Molnar <mingo@...nel.org> CommitDate: Fri, 5 Jun 2015 13:22:22 +0200 x86/asm/entry/32: Do not use R9 in SYSCALL32 entry point SYSENTER and SYSCALL 32-bit entry points differ in handling of arg2 and arg6. SYSENTER: * ecx arg2 * ebp user stack * 0(%ebp) arg6 SYSCALL: * ebp arg2 * esp user stack * 0(%esp) arg6 Sysenter code loads 0(%ebp) to %ebp right away. (This destroys %ebp. It means we do not preserve it on return. It's not causing problems since userspace VDSO code does not depend on it, and SYSENTER insn can't be sanely used outside of VDSO). Syscall code loads 0(%ebp) to %r9. This allows to eliminate one MOV insn (r9 is a register where arg6 should be for 64-bit ABI), but on audit/ptrace code paths this requires juggling of r9 and ebp: (1) ptrace expects arg6 to be in pt_regs->bp; (2) r9 is callee-clobbered register and needs to be saved/restored around calls to C functions. This patch changes syscall code to load 0(%ebp) to %ebp, making it more similar to sysenter code. It's a bit smaller: text data bss dec hex filename 1407 0 0 1407 57f ia32entry.o.before 1391 0 0 1391 56f ia32entry.o To preserve ABI compat, we restore ebp on exit. Run-tested. Signed-off-by: Denys Vlasenko <dvlasenk@...hat.com> Cc: Alexei Starovoitov <ast@...mgrid.com> Cc: Andrew Morton <akpm@...ux-foundation.org> Cc: Andy Lutomirski <luto@...capital.net> Cc: Borislav Petkov <bp@...en8.de> Cc: Brian Gerst <brgerst@...il.com> Cc: Frederic Weisbecker <fweisbec@...il.com> Cc: H. Peter Anvin <hpa@...or.com> Cc: Kees Cook <keescook@...omium.org> Cc: Linus Torvalds <torvalds@...ux-foundation.org> Cc: Oleg Nesterov <oleg@...hat.com> Cc: Peter Zijlstra <peterz@...radead.org> Cc: Steven Rostedt <rostedt@...dmis.org> Cc: Thomas Gleixner <tglx@...utronix.de> Cc: Will Drewry <wad@...omium.org> Link: http://lkml.kernel.org/r/1433336169-18964-1-git-send-email-dvlasenk@redhat.com Signed-off-by: Ingo Molnar <mingo@...nel.org> --- arch/x86/entry/ia32entry.S | 19 ++++++++----------- 1 file changed, 8 insertions(+), 11 deletions(-) diff --git a/arch/x86/entry/ia32entry.S b/arch/x86/entry/ia32entry.S index 56f819e..6321915 100644 --- a/arch/x86/entry/ia32entry.S +++ b/arch/x86/entry/ia32entry.S @@ -323,7 +323,7 @@ ENTRY(ia32_cstar_target) * 32bit zero extended */ ASM_STAC -1: movl (%r8),%r9d +1: movl (%r8),%ebp _ASM_EXTABLE(1b,ia32_badarg) ASM_CLAC orl $TS_COMPAT, ASM_THREAD_INFO(TI_status, %rsp, SIZEOF_PTREGS) @@ -333,7 +333,7 @@ ENTRY(ia32_cstar_target) cstar_do_call: /* 32bit syscall -> 64bit C ABI argument conversion */ movl %edi,%r8d /* arg5 */ - /* r9 already loaded */ /* arg6 */ + movl %ebp,%r9d /* arg6 */ xchg %ecx,%esi /* rsi:arg2, rcx:arg4 */ movl %ebx,%edi /* arg1 */ movl %edx,%edx /* arg3 (zero extension) */ @@ -349,6 +349,7 @@ cstar_dispatch: jnz sysretl_audit sysretl_from_sys_call: andl $~TS_COMPAT, ASM_THREAD_INFO(TI_status, %rsp, SIZEOF_PTREGS) + movl RCX(%rsp), %ebp RESTORE_RSI_RDI_RDX movl RIP(%rsp),%ecx movl EFLAGS(%rsp),%r11d @@ -375,9 +376,8 @@ sysretl_from_sys_call: #ifdef CONFIG_AUDITSYSCALL cstar_auditsys: - movl %r9d,R9(%rsp) /* register to be clobbered by call */ auditsys_entry_common - movl R9(%rsp),%r9d /* reload 6th syscall arg */ + movl %ebp, %r9d /* reload 6th syscall arg */ jmp cstar_dispatch sysretl_audit: @@ -389,16 +389,14 @@ cstar_tracesys: testl $(_TIF_WORK_SYSCALL_ENTRY & ~_TIF_SYSCALL_AUDIT), ASM_THREAD_INFO(TI_flags, %rsp, SIZEOF_PTREGS) jz cstar_auditsys #endif - xchgl %r9d,%ebp SAVE_EXTRA_REGS xorl %eax, %eax /* do not leak kernel information */ movq %rax, R11(%rsp) movq %rax, R10(%rsp) - movq %r9, R9(%rsp) + movq %rax, R9(%rsp) movq %rax, R8(%rsp) - movq %rsp,%rdi /* &pt_regs -> arg1 */ - call syscall_trace_enter - movl R9(%rsp),%r9d + movq %rsp, %rdi /* &pt_regs -> arg1 */ + call syscall_trace_enter /* Reload arg registers from stack. (see sysenter_tracesys) */ movl RCX(%rsp), %ecx @@ -408,8 +406,7 @@ cstar_tracesys: movl %eax, %eax /* zero extension */ RESTORE_EXTRA_REGS - xchgl %ebp,%r9d - jmp cstar_do_call + jmp cstar_do_call END(ia32_cstar_target) ia32_badarg: -- 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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