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Subject[tip:x86/asm] x86/asm/entry/32: Open-code LOAD_ARGS32
Commit-ID:  73cbf687914fd5f4ef88a42a55784fd28b7450cf
Gitweb: http://git.kernel.org/tip/73cbf687914fd5f4ef88a42a55784fd28b7450cf
Author: Denys Vlasenko <dvlasenk@redhat.com>
AuthorDate: Tue, 2 Jun 2015 21:04:02 +0200
Committer: Ingo Molnar <mingo@kernel.org>
CommitDate: Fri, 5 Jun 2015 13:22:22 +0200

x86/asm/entry/32: Open-code LOAD_ARGS32

This macro is small, has only three 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>
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/1433271842-9139-2-git-send-email-dvlasenk@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
arch/x86/entry/ia32entry.S | 54 +++++++++++++++++++++++++---------------------
1 file changed, 29 insertions(+), 25 deletions(-)

diff --git a/arch/x86/entry/ia32entry.S b/arch/x86/entry/ia32entry.S
index 8a45d2c..56f819e 100644
--- a/arch/x86/entry/ia32entry.S
+++ b/arch/x86/entry/ia32entry.S
@@ -29,28 +29,6 @@

.section .entry.text, "ax"

- /*
- * Reload arg registers from stack in case ptrace changed them.
- * We don't reload %eax because syscall_trace_enter() returned
- * the %rax value we should see. Instead, we just truncate that
- * value to 32 bits again as we did on entry from user mode.
- * If it's a new value set by user_regset during entry tracing,
- * this matches the normal truncation of the user-mode value.
- * If it's -1 to make us punt the syscall, then (u32)-1 is still
- * an appropriately invalid value.
- */
- .macro LOAD_ARGS32 _r9=0
- .if \_r9
- movl R9(%rsp),%r9d
- .endif
- movl RCX(%rsp),%ecx
- movl RDX(%rsp),%edx
- movl RSI(%rsp),%esi
- movl RDI(%rsp),%edi
- movl %eax,%eax /* zero extension */
- .endm
-
-
#ifdef CONFIG_PARAVIRT
ENTRY(native_usergs_sysret32)
swapgs
@@ -269,7 +247,14 @@ sysenter_tracesys:
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 */
+
+ /* Reload arg registers from stack. (see sysenter_tracesys) */
+ movl RCX(%rsp), %ecx
+ movl RDX(%rsp), %edx
+ movl RSI(%rsp), %esi
+ movl RDI(%rsp), %edi
+ movl %eax, %eax /* zero extension */
+
RESTORE_EXTRA_REGS
jmp sysenter_do_call
ENDPROC(ia32_sysenter_target)
@@ -413,7 +398,15 @@ cstar_tracesys:
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 */
+ movl R9(%rsp),%r9d
+
+ /* Reload arg registers from stack. (see sysenter_tracesys) */
+ movl RCX(%rsp), %ecx
+ movl RDX(%rsp), %edx
+ movl RSI(%rsp), %esi
+ movl RDI(%rsp), %edi
+ movl %eax, %eax /* zero extension */
+
RESTORE_EXTRA_REGS
xchgl %ebp,%r9d
jmp cstar_do_call
@@ -502,7 +495,18 @@ ia32_tracesys:
SAVE_EXTRA_REGS
movq %rsp,%rdi /* &pt_regs -> arg1 */
call syscall_trace_enter
- LOAD_ARGS32 /* reload args from stack in case ptrace changed it */
+ /*
+ * Reload arg registers from stack in case ptrace changed them.
+ * Don't reload %eax because syscall_trace_enter() returned
+ * the %rax value we should see. But do truncate it to 32 bits.
+ * If it's -1 to make us punt the syscall, then (u32)-1 is still
+ * an appropriately invalid value.
+ */
+ movl RCX(%rsp), %ecx
+ movl RDX(%rsp), %edx
+ movl RSI(%rsp), %esi
+ movl RDI(%rsp), %edi
+ movl %eax, %eax /* zero extension */
RESTORE_EXTRA_REGS
jmp ia32_do_call
END(ia32_syscall)

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