commit 9ce09e423f24823d52f19ab8247e078977100132
author Mingwei Shi <mingwei.shi@intel.com> Thu Nov 12 07:02:14 2015 +0000
committer Elliott Hughes <enh@google.com> Tue Mar 29 08:46:32 2016 -0700
tree d8d4847e29e86e2fc33790c25ca0c0cab371dbe9
parent 79e92282240e9e09568f3138b5f8caa6b85cb1c6

libc: implement kernel vdso syscalls for i386

This patch uses __kernel_vsyscall instead of "int 0x80"
as the syscall entry point. AT_SYSINFO points to
an adapter to mask the arch specific difference and gives a
performance boost on i386 architecture.

Bug: http://b/27533895
Change-ID: Ib340c604d02c6c25714a95793737e3cfdc3fc5d7
Signed-off-by: Mingwei Shi <mingwei.shi@intel.com>

(cherry picked from commit be910529322b461148debefd50b9e0d67ae84f8e)

libc/arch-x86/syscalls/process_vm_writev.S

diff --git a/libc/arch-x86/syscalls/process_vm_writev.S b/libc/arch-x86/syscalls/process_vm_writev.S
index 555c822..de0d218 100644
--- a/libc/arch-x86/syscalls/process_vm_writev.S
+++ b/libc/arch-x86/syscalls/process_vm_writev.S
@@ -21,14 +21,22 @@
     pushl   %ebp
     .cfi_adjust_cfa_offset 4
     .cfi_rel_offset ebp, 0
-    mov     28(%esp), %ebx
-    mov     32(%esp), %ecx
-    mov     36(%esp), %edx
-    mov     40(%esp), %esi
-    mov     44(%esp), %edi
-    mov     48(%esp), %ebp
+
+    call    __kernel_syscall
+    pushl   %eax
+    .cfi_adjust_cfa_offset 4
+    .cfi_rel_offset eax, 0
+
+    mov     32(%esp), %ebx
+    mov     36(%esp), %ecx
+    mov     40(%esp), %edx
+    mov     44(%esp), %esi
+    mov     48(%esp), %edi
+    mov     52(%esp), %ebp
     movl    $__NR_process_vm_writev, %eax
-    int     $0x80
+    call    *(%esp)
+    addl    $4, %esp
+
     cmpl    $-MAX_ERRNO, %eax
     jb      1f
     negl    %eax