From d00ff2950eacc375d57e44d65c7697f636c67625 Mon Sep 17 00:00:00 2001
From: Rich Felker <dalias@aerifal.cx>
Date: Sat, 19 Mar 2011 18:51:42 -0400
Subject: overhaul syscall interface

this commit shuffles around the location of syscall definitions so
that we can make a syscall() library function with both SYS_* and
__NR_* style syscall names available to user applications, provides
the syscall() library function, and optimizes the code that performs
the actual inline syscalls in the library itself.

previously on i386 when built as PIC (shared library), syscalls were
incurring bus lock (lock prefix) overhead at entry and exit, due to
the way the ebx register was being loaded (xchg instruction with a
memory operand). now the xchg takes place between two registers.

further cleanup to arch/$(ARCH)/syscall.h is planned.
---
 src/internal/i386/syscall.s   | 21 +++++++++++++++++++++
 src/internal/syscall.c        | 11 -----------
 src/internal/syscall_ret.c    | 11 +++++++++++
 src/internal/x86_64/syscall.s | 14 ++++++++++++++
 4 files changed, 46 insertions(+), 11 deletions(-)
 create mode 100644 src/internal/i386/syscall.s
 create mode 100644 src/internal/syscall_ret.c
 create mode 100644 src/internal/x86_64/syscall.s

(limited to 'src/internal')

diff --git a/src/internal/i386/syscall.s b/src/internal/i386/syscall.s
new file mode 100644
index 00000000..5b19a1b8
--- /dev/null
+++ b/src/internal/i386/syscall.s
@@ -0,0 +1,21 @@
+.global __syscall
+.type __syscall,%function
+__syscall:
+	pushl %ebx
+	pushl %esi
+	pushl %edi
+	pushl %ebp
+	movl 20(%esp),%eax
+	movl 24(%esp),%ebx
+	movl 28(%esp),%ecx
+	movl 32(%esp),%edx
+	movl 36(%esp),%esi
+	movl 40(%esp),%edi
+	movl 44(%esp),%ebp
+	int $128
+	popl %ebp
+	popl %edi
+	popl %esi
+	popl %ebx
+	ret
+.size __syscall,.-__syscall
diff --git a/src/internal/syscall.c b/src/internal/syscall.c
index 4f159e0b..e69de29b 100644
--- a/src/internal/syscall.c
+++ b/src/internal/syscall.c
@@ -1,11 +0,0 @@
-#include <errno.h>
-#include <unistd.h>
-
-long __syscall_ret(unsigned long r)
-{
-	if (r >= (unsigned long)-1 - 4096) {
-		errno = -(long)r;
-		return -1;
-	}
-	return (long)r;
-}
diff --git a/src/internal/syscall_ret.c b/src/internal/syscall_ret.c
new file mode 100644
index 00000000..4f159e0b
--- /dev/null
+++ b/src/internal/syscall_ret.c
@@ -0,0 +1,11 @@
+#include <errno.h>
+#include <unistd.h>
+
+long __syscall_ret(unsigned long r)
+{
+	if (r >= (unsigned long)-1 - 4096) {
+		errno = -(long)r;
+		return -1;
+	}
+	return (long)r;
+}
diff --git a/src/internal/x86_64/syscall.s b/src/internal/x86_64/syscall.s
new file mode 100644
index 00000000..7bec7291
--- /dev/null
+++ b/src/internal/x86_64/syscall.s
@@ -0,0 +1,14 @@
+.global __syscall
+.type __syscall,%function
+__syscall:
+di,si,dx,cx,r8,r9
+	movq %rdi,%rax
+	movq %rsi,%rdi
+	movq %rdx,%rsi
+	movq %rcx,%rdx
+	movq %r8,%r10
+	movq %r9,%r8
+	movq 8(%rsp),%r9
+	syscall
+	ret
+.size __syscall,.-__syscall
-- 
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