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Subject[tip:x86/asm] x86/asm/entry/32: Open-code CLEAR_RREGS
Commit-ID:  ef0cd5dc25404594f832dad9133abae52e3b2fa3
Gitweb: http://git.kernel.org/tip/ef0cd5dc25404594f832dad9133abae52e3b2fa3
Author: Denys Vlasenko <dvlasenk@redhat.com>
AuthorDate: Tue, 2 Jun 2015 21:04:01 +0200
Committer: Ingo Molnar <mingo@kernel.org>
CommitDate: Fri, 5 Jun 2015 13:22:22 +0200

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 <dvlasenk@redhat.com>
[ Added comments. ]
Cc: Alexei Starovoitov <ast@plumgrid.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Drewry <wad@chromium.org>
Link: http://lkml.kernel.org/r/1433271842-9139-1-git-send-email-dvlasenk@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
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 f00a409..8a45d2c 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

/*

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