[BZ,#19490] Add unwind descriptors to pthread_spin_init, etc. on i386
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Message ID CALoOobPJLwc+iSG+w-2YqqiL6=iAL-ZPiS5iKtmdDmJTR9Fp6g@mail.gmail.com
State New
Headers show

Commit Message

Paul Pluzhnikov Jan. 24, 2016, 12:18 a.m. UTC
Greetings,

This is similar to
  https://www.sourceware.org/ml/libc-alpha/2016-01/msg00605.html
  https://www.sourceware.org/ml/libc-alpha/2016-01/msg00456.html
but for i386.

Tested on Linux/i686.

Assuming this is OK, should I wait for lifting of the freeze?



2016-01-23  Paul Pluzhnikov  <ppluzhnikov@google.com>

        [BZ #19490]
        * sysdeps/i386/i386-mcount.S (_mcount): Add unwind descriptor
        (__fentry__): Likewise
        * sysdeps/unix/sysv/linux/i386/_exit.S (_exit): Use ENTRY/END
        * sysdeps/i386/nptl/pthread_spin_lock.S (pthread_spin_lock):
        Likewise
        * sysdeps/i386/pthread_spin_trylock.S (pthread_spin_trylock):
        Likewise
        * sysdeps/i386/nptl/pthread_spin_unlock.S (pthread_spin_unlock):
        Likewise

Comments

Torvald Riegel Jan. 25, 2016, 1:06 p.m. UTC | #1
On Sat, 2016-01-23 at 16:18 -0800, Paul Pluzhnikov wrote:
> 2016-01-23  Paul Pluzhnikov  <ppluzhnikov@google.com>
> 
>         [BZ #19490]
>         * sysdeps/i386/i386-mcount.S (_mcount): Add unwind descriptor
>         (__fentry__): Likewise
>         * sysdeps/unix/sysv/linux/i386/_exit.S (_exit): Use ENTRY/END
>         * sysdeps/i386/nptl/pthread_spin_lock.S (pthread_spin_lock):
>         Likewise
>         * sysdeps/i386/pthread_spin_trylock.S (pthread_spin_trylock):
>         Likewise
>         * sysdeps/i386/nptl/pthread_spin_unlock.S (pthread_spin_unlock):
>         Likewise

For the spinlocks, I'd really prefer if we could just remove the asm
files.  The generic implementation should basically produce the same
code; if not, we should try to fix that instead of keeping the asm
files.
Paul Pluzhnikov Jan. 31, 2016, 11:09 p.m. UTC | #2
On Mon, Jan 25, 2016 at 5:06 AM, Torvald Riegel <triegel@redhat.com> wrote:

> For the spinlocks, I'd really prefer if we could just remove the asm
> files.  The generic implementation should basically produce the same
> code; if not, we should try to fix that instead of keeping the asm
> files.

Using gcc-4.8.4 (4.8.4-2ubuntu1~14.04):

$ objdump -d nptl/pthread_spin_unlock.o

nptl/pthread_spin_unlock.o:     file format elf32-i386


Disassembly of section .text:

00000000 <pthread_spin_unlock>:
   0: f0 83 0c 24 00       lock orl $0x0,(%esp)
   5: 8b 44 24 04           mov    0x4(%esp),%eax
   9: c7 00 00 00 00 00     movl   $0x0,(%eax)
   f: 31 c0                 xor    %eax,%eax
  11: c3                   ret

This isn't quite the same as sysdeps/i386/nptl/pthread_spin_unlock.S
For pthread_spin_lock it's much worse:

$ objdump -d nptl/pthread_spin_lock.o

nptl/pthread_spin_lock.o:     file format elf32-i386


Disassembly of section .text:

00000000 <pthread_spin_lock>:
   0: 57                   push   %edi
   1: b8 01 00 00 00       mov    $0x1,%eax
   6: 56                   push   %esi
   7: 53                   push   %ebx
   8: 83 ec 10             sub    $0x10,%esp
   b: 8b 5c 24 20           mov    0x20(%esp),%ebx
   f: 87 03                 xchg   %eax,(%ebx)
  11: 89 44 24 0c           mov    %eax,0xc(%esp)
  15: 8b 44 24 0c           mov    0xc(%esp),%eax
  19: 31 ff                 xor    %edi,%edi
  1b: be 01 00 00 00       mov    $0x1,%esi
  20: 85 c0                 test   %eax,%eax
  22: 74 29                 je     4d <pthread_spin_lock+0x4d>
  24: 8d 74 26 00           lea    0x0(%esi,%eiz,1),%esi
  28: 8b 03                 mov    (%ebx),%eax
  2a: 85 c0                 test   %eax,%eax
  2c: 74 15                 je     43 <pthread_spin_lock+0x43>
  2e: ba e8 03 00 00       mov    $0x3e8,%edx
  33: eb 08                 jmp    3d <pthread_spin_lock+0x3d>
  35: 8d 76 00             lea    0x0(%esi),%esi
  38: 83 ea 01             sub    $0x1,%edx
  3b: 74 06                 je     43 <pthread_spin_lock+0x43>
  3d: 8b 0b                 mov    (%ebx),%ecx
  3f: 85 c9                 test   %ecx,%ecx
  41: 75 f5                 jne    38 <pthread_spin_lock+0x38>
  43: 89 f8                 mov    %edi,%eax
  45: f0 0f b1 33           lock cmpxchg %esi,(%ebx)
  49: 85 c0                 test   %eax,%eax
  4b: 75 db                 jne    28 <pthread_spin_lock+0x28>
  4d: 83 c4 10             add    $0x10,%esp
  50: 31 c0                 xor    %eax,%eax
  52: 5b                   pop    %ebx
  53: 5e                   pop    %esi
  54: 5f                   pop    %edi
  55: c3                   ret

So I am not sure we should be throwing ASM out just yet.

Patch
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diff --git a/sysdeps/i386/i386-mcount.S b/sysdeps/i386/i386-mcount.S
index 94fb95e..f92f3ff 100644
--- a/sysdeps/i386/i386-mcount.S
+++ b/sysdeps/i386/i386-mcount.S
@@ -30,10 +30,17 @@ 
 	.type C_SYMBOL_NAME(_mcount), @function
 	.align ALIGNARG(4)
 C_LABEL(_mcount)
+	cfi_startproc
 	/* Save the caller-clobbered registers.  */
 	pushl %eax
+	cfi_adjust_cfa_offset (4)
 	pushl %ecx
+	cfi_adjust_cfa_offset (4)
 	pushl %edx
+	cfi_adjust_cfa_offset (4)
+	cfi_rel_offset (eax, 8)
+	cfi_rel_offset (ecx, 4)
+	cfi_rel_offset (edx, 0)
 
 	movl 12(%esp), %edx
 	movl 4(%ebp), %eax
@@ -45,9 +52,16 @@  C_LABEL(_mcount)
 	/* Pop the saved registers.  Please note that `mcount' has no
 	   return value.  */
 	popl %edx
+	cfi_adjust_cfa_offset (-4)
+	cfi_restore (edx)
 	popl %ecx
+	cfi_adjust_cfa_offset (-4)
+	cfi_restore (ecx)
 	popl %eax
+	cfi_adjust_cfa_offset (-4)
+	cfi_restore (eax)
 	ret
+	cfi_endproc
 	ASM_SIZE_DIRECTIVE(C_SYMBOL_NAME(_mcount))
 
 #undef mcount
@@ -58,10 +72,17 @@  weak_alias (_mcount, mcount)
 	.type C_SYMBOL_NAME(__fentry__), @function
 	.align ALIGNARG(4)
 C_LABEL(__fentry__)
+	cfi_startproc
 	/* Save the caller-clobbered registers.  */
 	pushl %eax
+	cfi_adjust_cfa_offset (4)
 	pushl %ecx
+	cfi_adjust_cfa_offset (4)
 	pushl %edx
+	cfi_adjust_cfa_offset (4)
+	cfi_rel_offset (eax, 8)
+	cfi_rel_offset (ecx, 4)
+	cfi_rel_offset (edx, 0)
 
 	movl 12(%esp), %edx
 	movl 16(%esp), %eax
@@ -73,7 +94,14 @@  C_LABEL(__fentry__)
 	/* Pop the saved registers.  Please note that `__fentry__' has no
 	   return value.  */
 	popl %edx
+	cfi_adjust_cfa_offset (-4)
+	cfi_restore (edx)
 	popl %ecx
+	cfi_adjust_cfa_offset (-4)
+	cfi_restore (ecx)
 	popl %eax
+	cfi_adjust_cfa_offset (-4)
+	cfi_restore (eax)
 	ret
+	cfi_endproc
 	ASM_SIZE_DIRECTIVE(C_SYMBOL_NAME(__fentry__))
diff --git a/sysdeps/i386/nptl/pthread_spin_lock.S b/sysdeps/i386/nptl/pthread_spin_lock.S
index e311d95..ea552da 100644
--- a/sysdeps/i386/nptl/pthread_spin_lock.S
+++ b/sysdeps/i386/nptl/pthread_spin_lock.S
@@ -16,11 +16,9 @@ 
    <http://www.gnu.org/licenses/>.  */
 
 #include <lowlevellock.h>
+#include <sysdep.h>
 
-	.globl	pthread_spin_lock
-	.type	pthread_spin_lock,@function
-	.align	16
-pthread_spin_lock:
+ENTRY(pthread_spin_lock)
 	mov	4(%esp), %eax
 1:	LOCK
 	decl	0(%eax)
@@ -34,4 +32,4 @@  pthread_spin_lock:
 	cmpl	$0, 0(%eax)
 	jg	1b
 	jmp	2b
-	.size	pthread_spin_lock,.-pthread_spin_lock
+END(pthread_spin_lock)
diff --git a/sysdeps/i386/nptl/pthread_spin_unlock.S b/sysdeps/i386/nptl/pthread_spin_unlock.S
index a552cf9..ef75a50 100644
--- a/sysdeps/i386/nptl/pthread_spin_unlock.S
+++ b/sysdeps/i386/nptl/pthread_spin_unlock.S
@@ -16,15 +16,14 @@ 
    License along with the GNU C Library; if not, see
    <http://www.gnu.org/licenses/>.  */
 
-	.globl	pthread_spin_unlock
-	.type	pthread_spin_unlock,@function
-	.align	16
-pthread_spin_unlock:
+#include <sysdep.h>
+
+ENTRY(pthread_spin_unlock)
 	movl	4(%esp), %eax
 	movl	$1, (%eax)
 	xorl	%eax, %eax
 	ret
-	.size	pthread_spin_unlock,.-pthread_spin_unlock
+END(pthread_spin_unlock)
 
 	/* The implementation of pthread_spin_init is identical.  */
 	.globl	pthread_spin_init
diff --git a/sysdeps/i386/pthread_spin_trylock.S b/sysdeps/i386/pthread_spin_trylock.S
index 36979bd..7d3dabb 100644
--- a/sysdeps/i386/pthread_spin_trylock.S
+++ b/sysdeps/i386/pthread_spin_trylock.S
@@ -17,7 +17,7 @@ 
    <http://www.gnu.org/licenses/>.  */
 
 #include <pthread-errnos.h>
-
+#include <sysdep.h>
 
 #ifdef UP
 # define LOCK
@@ -25,10 +25,7 @@ 
 # define LOCK lock
 #endif
 
-	.globl	pthread_spin_trylock
-	.type	pthread_spin_trylock,@function
-	.align	16
-pthread_spin_trylock:
+ENTRY(pthread_spin_trylock)
 	movl	4(%esp), %edx
 	movl	$1, %eax
 	xorl	%ecx, %ecx
@@ -43,4 +40,4 @@  pthread_spin_trylock:
 0:
 #endif
 	ret
-	.size	pthread_spin_trylock,.-pthread_spin_trylock
+END(pthread_spin_trylock)
diff --git a/sysdeps/unix/sysv/linux/i386/_exit.S b/sysdeps/unix/sysv/linux/i386/_exit.S
index e1550e6..6193ff2 100644
--- a/sysdeps/unix/sysv/linux/i386/_exit.S
+++ b/sysdeps/unix/sysv/linux/i386/_exit.S
@@ -17,10 +17,7 @@ 
 
 #include <sysdep.h>
 
-	.text
-	.type	_exit,@function
-	.global	_exit
-_exit:
+ENTRY(_exit)
 	movl	4(%esp), %ebx
 
 	/* Try the new syscall first.  */
@@ -37,7 +34,7 @@  _exit:
 
 	/* This must not fail.  Be sure we don't return.  */
 	hlt
-	.size	_exit,.-_exit
+END(_exit)
 
 libc_hidden_def (_exit)
 rtld_hidden_def (_exit)