From ef0cd5dc25404594f832dad9133abae52e3b2fa3 Mon Sep 17 00:00:00 2001 From: Denys Vlasenko Date: Tue, 2 Jun 2015 21:04:01 +0200 Subject: [PATCH] x86/asm/entry/32: Open-code CLEAR_RREGS This macro is small, has only four callsites, and one of them is slightly different using a conditional parameter. A few saved lines aren't worth the resulting obfuscation. Generated machine code is identical. Signed-off-by: Denys Vlasenko [ Added comments. ] Cc: Alexei Starovoitov Cc: Andrew Morton Cc: Andy Lutomirski Cc: Borislav Petkov Cc: Brian Gerst Cc: Frederic Weisbecker Cc: H. Peter Anvin Cc: Kees Cook Cc: Linus Torvalds Cc: Oleg Nesterov Cc: Peter Zijlstra Cc: Steven Rostedt Cc: Thomas Gleixner Cc: Will Drewry Link: http://lkml.kernel.org/r/1433271842-9139-1-git-send-email-dvlasenk@redhat.com Signed-off-by: Ingo Molnar --- arch/x86/entry/ia32entry.S | 33 ++++++++++++++++++++------------- 1 file changed, 20 insertions(+), 13 deletions(-) diff --git a/arch/x86/entry/ia32entry.S b/arch/x86/entry/ia32entry.S index f00a409dc403..8a45d2cd2bef 100644 --- a/arch/x86/entry/ia32entry.S +++ b/arch/x86/entry/ia32entry.S @@ -29,15 +29,6 @@ .section .entry.text, "ax" - /* clobbers %rax */ - .macro CLEAR_RREGS _r9=rax - xorl %eax,%eax - movq %rax,R11(%rsp) - movq %rax,R10(%rsp) - movq %\_r9,R9(%rsp) - movq %rax,R8(%rsp) - .endm - /* * Reload arg registers from stack in case ptrace changed them. * We don't reload %eax because syscall_trace_enter() returned @@ -243,7 +234,11 @@ sysexit_from_sys_call: TRACE_IRQS_OFF testl %edi, ASM_THREAD_INFO(TI_flags, %rsp, SIZEOF_PTREGS) jz \exit - CLEAR_RREGS + xorl %eax, %eax /* do not leak kernel information */ + movq %rax, R11(%rsp) + movq %rax, R10(%rsp) + movq %rax, R9(%rsp) + movq %rax, R8(%rsp) jmp int_with_check .endm @@ -267,7 +262,11 @@ sysenter_tracesys: jz sysenter_auditsys #endif SAVE_EXTRA_REGS - CLEAR_RREGS + xorl %eax, %eax /* do not leak kernel information */ + movq %rax, R11(%rsp) + movq %rax, R10(%rsp) + movq %rax, R9(%rsp) + movq %rax, R8(%rsp) movq %rsp,%rdi /* &pt_regs -> arg1 */ call syscall_trace_enter LOAD_ARGS32 /* reload args from stack in case ptrace changed it */ @@ -407,7 +406,11 @@ cstar_tracesys: #endif xchgl %r9d,%ebp SAVE_EXTRA_REGS - CLEAR_RREGS r9 + xorl %eax, %eax /* do not leak kernel information */ + movq %rax, R11(%rsp) + movq %rax, R10(%rsp) + movq %r9, R9(%rsp) + movq %rax, R8(%rsp) movq %rsp,%rdi /* &pt_regs -> arg1 */ call syscall_trace_enter LOAD_ARGS32 1 /* reload args from stack in case ptrace changed it */ @@ -422,7 +425,11 @@ ia32_badarg: jmp ia32_sysret ia32_ret_from_sys_call: - CLEAR_RREGS + xorl %eax, %eax /* do not leak kernel information */ + movq %rax, R11(%rsp) + movq %rax, R10(%rsp) + movq %rax, R9(%rsp) + movq %rax, R8(%rsp) jmp int_ret_from_sys_call /* -- 2.34.1