x86-64: slightly stream-line 32-bit syscall entry code

Avoid updating registers or memory twice as well as needlessly loading
or copying registers.

Signed-off-by: Jan Beulich <jbeulich@novell.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 10 insertions, 16 deletions

diff --git a/arch/x86/ia32/ia32entry.S b/arch/x86/ia32/ia32entry.S
index ffc1bb4fed7d..eb4314768bf7 100644
--- a/arch/x86/ia32/ia32entry.S
+++ b/arch/x86/ia32/ia32entry.S
@@ -39,11 +39,11 @@
         .endm 
 
         /* clobbers %eax */     
-        .macro  CLEAR_RREGS
+        .macro  CLEAR_RREGS _r9=rax
         xorl    %eax,%eax
         movq    %rax,R11(%rsp)
         movq    %rax,R10(%rsp)
-        movq    %rax,R9(%rsp)
+        movq    %\_r9,R9(%rsp)
         movq    %rax,R8(%rsp)
         .endm
 
@@ -52,11 +52,10 @@
          * We don't reload %eax because syscall_trace_enter() returned
          * the value it wants us to use in the table lookup.
          */
-        .macro LOAD_ARGS32 offset
-        movl \offset(%rsp),%r11d
-        movl \offset+8(%rsp),%r10d
+        .macro LOAD_ARGS32 offset, _r9=0
+        .if \_r9
         movl \offset+16(%rsp),%r9d
-        movl \offset+24(%rsp),%r8d
+        .endif
         movl \offset+40(%rsp),%ecx
         movl \offset+48(%rsp),%edx
         movl \offset+56(%rsp),%esi
@@ -145,7 +144,7 @@ ENTRY(ia32_sysenter_target)
         SAVE_ARGS 0,0,1
         /* no need to do an access_ok check here because rbp has been
            32bit zero extended */ 
-1:      movl    (%rbp),%r9d
+1:      movl    (%rbp),%ebp
         .section __ex_table,"a"
         .quad 1b,ia32_badarg
         .previous       
@@ -157,7 +156,7 @@ ENTRY(ia32_sysenter_target)
         cmpl    $(IA32_NR_syscalls-1),%eax
         ja      ia32_badsys
 sysenter_do_call:
-        IA32_ARG_FIXUP 1
+        IA32_ARG_FIXUP
 sysenter_dispatch:
         call    *ia32_sys_call_table(,%rax,8)
         movq    %rax,RAX-ARGOFFSET(%rsp)
@@ -234,20 +233,17 @@ sysexit_audit:
 #endif
 
 sysenter_tracesys:
-        xchgl   %r9d,%ebp
 #ifdef CONFIG_AUDITSYSCALL
         testl   $(_TIF_WORK_SYSCALL_ENTRY & ~_TIF_SYSCALL_AUDIT),TI_flags(%r10)
         jz      sysenter_auditsys
 #endif
         SAVE_REST
         CLEAR_RREGS
-        movq    %r9,R9(%rsp)
         movq    $-ENOSYS,RAX(%rsp)/* ptrace can change this for a bad syscall */
         movq    %rsp,%rdi        /* &pt_regs -> arg1 */
         call    syscall_trace_enter
         LOAD_ARGS32 ARGOFFSET  /* reload args from stack in case ptrace changed it */
         RESTORE_REST
-        xchgl   %ebp,%r9d
         cmpl    $(IA32_NR_syscalls-1),%eax
         ja      int_ret_from_sys_call /* sysenter_tracesys has set RAX(%rsp) */
         jmp     sysenter_do_call
@@ -314,9 +310,9 @@ ENTRY(ia32_cstar_target)
         testl $_TIF_WORK_SYSCALL_ENTRY,TI_flags(%r10)
         CFI_REMEMBER_STATE
         jnz   cstar_tracesys
-cstar_do_call:  
         cmpl $IA32_NR_syscalls-1,%eax
         ja  ia32_badsys
+cstar_do_call:
         IA32_ARG_FIXUP 1
 cstar_dispatch:
         call *ia32_sys_call_table(,%rax,8)
@@ -357,15 +353,13 @@ cstar_tracesys:
 #endif
         xchgl %r9d,%ebp
         SAVE_REST
-        CLEAR_RREGS
-        movq %r9,R9(%rsp)
+        CLEAR_RREGS r9
         movq $-ENOSYS,RAX(%rsp) /* ptrace can change this for a bad syscall */
         movq %rsp,%rdi        /* &pt_regs -> arg1 */
         call syscall_trace_enter
-        LOAD_ARGS32 ARGOFFSET  /* reload args from stack in case ptrace changed it */
+        LOAD_ARGS32 ARGOFFSET, 1  /* reload args from stack in case ptrace changed it */
         RESTORE_REST
         xchgl %ebp,%r9d
-        movl RSP-ARGOFFSET(%rsp), %r8d
         cmpl $(IA32_NR_syscalls-1),%eax
         ja int_ret_from_sys_call /* cstar_tracesys has set RAX(%rsp) */
         jmp cstar_do_call