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>

diff --git a/arch/x86/ia32/ia32entry.S b/arch/x86/ia32/ia32entry.S
index ffc1bb4fed7d1ade2ed385597fd05464fea55528..eb4314768bf7ad7f14e8589fe66876a99dc52b8c 100644 (file)
--- 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