diff mbox series

[13/23] linux: Use generic __syscall_error for x86_64

Message ID 20201109201826.120534-14-adhemerval.zanella@linaro.org
State Superseded
Headers show
Series Simplify internal Linux syscall | expand

Commit Message

Adhemerval Zanella Nov. 9, 2020, 8:18 p.m. UTC
The auto-generated syscalls issue the __syscall_error only for
static objects, so a arch specific syscall_error is added.  The
size of using extern __syscall_error is just slight better for
static case:
diff mbox series

Patch

--- size-fstatat64.o.inline
+++ size-fstatat64.o.outline
@@ -1,2 +1,2 @@ 
    text           data     bss     dec     hex filename
-    100              0       0     100      64 io/fstatat64.o
+     94              0       0      94      5e io/fstatat64.o

For shared objects the inline __syscall_error does generate more
compact code:

--- sizes-x86_64-linux-gnu.inline
+++ sizes-x86_64-linux-gnu.outline
@@ -1,5 +1,5 @@ 
    text           data     bss     dec     hex filename
-1774028          20520   15896 1810444  1ba00c libc.so
- 167499           7280     392  175171   2ac43 elf/ld.so
-  99261           1640   16728  117629   1cb7d nptl/libpthread.so
-  24751           1188    2400   28339    6eb3 rt/librt.so
+1776260          20520   15896 1812676  1ba8c4 libc.so
+ 167758           7280     392  175430   2ad46 elf/ld.so
+ 100221           1640   16728  118589   1cf3d nptl/libpthread.so
+  24927           1188    2400   28515    6f63 rt/librt.so

A possible option might be to use the same strategy for both static
and PIC code, which allow to remove the arch-specific syscall_error.c
with a slight increase of code size in static library.

Checked on x86_64-linux-gnu.
---
 sysdeps/unix/sysv/linux/sysdep.h              |  8 +++
 .../unix/sysv/linux/x86_64/syscall_error.c    |  5 ++
 sysdeps/unix/sysv/linux/x86_64/sysdep.S       | 40 ---------------
 sysdeps/unix/x86_64/sysdep.S                  | 49 -------------------
 4 files changed, 13 insertions(+), 89 deletions(-)
 create mode 100644 sysdeps/unix/sysv/linux/x86_64/syscall_error.c
 delete mode 100644 sysdeps/unix/sysv/linux/x86_64/sysdep.S
 delete mode 100644 sysdeps/unix/x86_64/sysdep.S

diff --git a/sysdeps/unix/sysv/linux/sysdep.h b/sysdeps/unix/sysv/linux/sysdep.h
index 6c0d1f9f6f..4f5b978838 100644
--- a/sysdeps/unix/sysv/linux/sysdep.h
+++ b/sysdeps/unix/sysv/linux/sysdep.h
@@ -24,6 +24,14 @@ 
 #include <errno.h>
 
 #ifndef __ASSEMBLER__
+/* The errno setting might be set either inline or with a help function.  For
+   some ABIs (x86_64), setting inline might generate less code; while for
+   others (i686) function call is preferable.
+
+   To use the helper function an ABI might define SYSCALL_ERROR_FUNC, it will
+   build a hidden function on each shared object that issues direct syscall
+   with {INLINE,INTERNAL}_SYSCALL_CALL.  */
+
 static inline _Bool
 syscall_error (unsigned long int val)
 {
diff --git a/sysdeps/unix/sysv/linux/x86_64/syscall_error.c b/sysdeps/unix/sysv/linux/x86_64/syscall_error.c
new file mode 100644
index 0000000000..40528f8ae9
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/x86_64/syscall_error.c
@@ -0,0 +1,5 @@ 
+/* The auto-generated syscalls calls __syscall_error for static objects.  */
+#ifndef SHARED
+# define SYSCALL_ERROR_FUNC
+#endif
+#include <sysdeps/unix/sysv/linux/syscall_error.c>
diff --git a/sysdeps/unix/sysv/linux/x86_64/sysdep.S b/sysdeps/unix/sysv/linux/x86_64/sysdep.S
deleted file mode 100644
index 2d3592296d..0000000000
--- a/sysdeps/unix/sysv/linux/x86_64/sysdep.S
+++ /dev/null
@@ -1,40 +0,0 @@ 
-/* Copyright (C) 2001-2020 Free Software Foundation, Inc.
-   This file is part of the GNU C Library.
-
-   The GNU C Library is free software; you can redistribute it and/or
-   modify it under the terms of the GNU Lesser General Public
-   License as published by the Free Software Foundation; either
-   version 2.1 of the License, or (at your option) any later version.
-
-   The GNU C Library is distributed in the hope that it will be useful,
-   but WITHOUT ANY WARRANTY; without even the implied warranty of
-   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-   Lesser General Public License for more details.
-
-   You should have received a copy of the GNU Lesser General Public
-   License along with the GNU C Library; if not, see
-   <https://www.gnu.org/licenses/>.  */
-
-#include <sysdep.h>
-
-/* The following code is only used in the shared library when we
-   compile the reentrant version.  Otherwise each system call defines
-   each own version.  */
-
-#ifndef PIC
-
-/* The syscall stubs jump here when they detect an error.
-   The code for Linux is almost identical to the canonical Unix
-   code, except that the error number in %rax is negated.  */
-
-#undef CALL_MCOUNT
-#define CALL_MCOUNT /* Don't insert the profiling call, it clobbers %rax.  */
-
-	.text
-ENTRY (__syscall_error)
-	neg %RAX_LP
-
-#define __syscall_error __syscall_error_1
-#include <sysdeps/unix/x86_64/sysdep.S>
-
-#endif	/* !PIC */
diff --git a/sysdeps/unix/x86_64/sysdep.S b/sysdeps/unix/x86_64/sysdep.S
deleted file mode 100644
index 2278fce9e4..0000000000
--- a/sysdeps/unix/x86_64/sysdep.S
+++ /dev/null
@@ -1,49 +0,0 @@ 
-/* Copyright (C) 2001-2020 Free Software Foundation, Inc.
-   This file is part of the GNU C Library.
-
-   The GNU C Library is free software; you can redistribute it and/or
-   modify it under the terms of the GNU Lesser General Public
-   License as published by the Free Software Foundation; either
-   version 2.1 of the License, or (at your option) any later version.
-
-   The GNU C Library is distributed in the hope that it will be useful,
-   but WITHOUT ANY WARRANTY; without even the implied warranty of
-   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-   Lesser General Public License for more details.
-
-   You should have received a copy of the GNU Lesser General Public
-   License along with the GNU C Library; if not, see
-   <https://www.gnu.org/licenses/>.  */
-
-#include <sysdep.h>
-#include <errno.h>
-#include <tls.h>
-
-#if IS_IN (rtld)
-# include <dl-sysdep.h>		/* Defines RTLD_PRIVATE_ERRNO.  */
-#endif
-
-.globl C_SYMBOL_NAME(errno)
-.globl syscall_error
-
-__syscall_error:
-#if defined (EWOULDBLOCK_sys) && EWOULDBLOCK_sys != EAGAIN
-	/* We translate the system's EWOULDBLOCK error into EAGAIN.
-	   The GNU C library always defines EWOULDBLOCK==EAGAIN.
-	   EWOULDBLOCK_sys is the original number.  */
-	cmp $EWOULDBLOCK_sys, %RAX_LP /* Is it the old EWOULDBLOCK?  */
-	jne notb		/* Branch if not.  */
-	movl $EAGAIN, %eax	/* Yes; translate it to EAGAIN.  */
-notb:
-#endif
-#ifdef PIC
-	movq C_SYMBOL_NAME(errno@GOTTPOFF)(%rip), %rcx
-	movl %eax, %fs:0(%rcx)
-#else
-	movl %eax, %fs:C_SYMBOL_NAME(errno@TPOFF)
-#endif
-	or $-1, %RAX_LP
-	ret
-
-#undef	__syscall_error
-END (__syscall_error)