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[rfa] alpha sjlj vs pointer mangling


For Alpha, it's faster to access through got than through thread pointer.
So I'd rather rely on __pointer_chk_guard{,_local} than have to manage 
setting up a local thread base pointer.

This does cause one complication -- the iconvdata libraries use one of
the objects that does a pointer check, and thus must be linked against
ld.so to get that resolved.  This isn't strictly needed for other targets,
so I wonder what the best way to avoid this is?  Unless of course we
already default to --as-needed?



r~


2006-01-09  Richard Henderson  <rth@redhat.com>

	* iconvdata/extra-module.mk ($(objpfx)$(mod).so): Depend on ld.so.
	* sysdeps/alpha/__longjmp.S: Use PTR_DEMANGLE.
	* sysdeps/alpha/setjmp.S: Likewise.  Avoid __sigjmp_save for rtld;
	tailcall in libc.so.
	* sysdeps/unix/sysv/linux/alpha/sysdep.h (PTR_MANGLE): New.
	(PTR_MANGLE2): New.

Index: iconvdata/extra-module.mk
===================================================================
RCS file: /cvs/glibc/libc/iconvdata/extra-module.mk,v
retrieving revision 1.4
diff -u -p -d -r1.4 extra-module.mk
--- iconvdata/extra-module.mk	26 Apr 2003 23:38:36 -0000	1.4
+++ iconvdata/extra-module.mk	9 Jan 2006 23:05:58 -0000
@@ -10,7 +10,9 @@ $(objpfx)$(mod).so: $(addprefix $(objpfx
 # Depend on libc.so so a DT_NEEDED is generated in the shared objects.
 # This ensures they will load libc.so for needed symbols if loaded by
 # a statically-linked program that hasn't already loaded it.
-$(objpfx)$(mod).so: $(common-objpfx)libc.so $(common-objpfx)libc_nonshared.a
+$(objpfx)$(mod).so: $(common-objpfx)libc.so \
+	$(common-objpfx)/elf/ld.so \
+	$(common-objpfx)libc_nonshared.a
 
 ifneq (,$(extra-modules-left))
 include extra-module.mk
Index: sysdeps/alpha/__longjmp.S
===================================================================
RCS file: /cvs/glibc/libc/sysdeps/alpha/__longjmp.S,v
retrieving revision 1.3
diff -u -p -d -r1.3 __longjmp.S
--- sysdeps/alpha/__longjmp.S	6 Jul 2001 04:55:44 -0000	1.3
+++ sysdeps/alpha/__longjmp.S	9 Jan 2006 23:06:01 -0000
@@ -54,6 +54,11 @@ ENTRY(__longjmp)
 	ldt     $f7, JB_F7*8(a0)
 	ldt     $f8, JB_F8*8(a0)
 	ldt     $f9, JB_F9*8(a0)
+#ifdef PTR_DEMANGLE
+	PTR_DEMANGLE(ra, t1)
+	PTR_DEMANGLE2(t0, t1)
+	PTR_DEMANGLE2(fp, t1)
+#endif
 	cmoveq  v0, 1, v0
 	mov     t0, sp
 	ret
Index: sysdeps/alpha/setjmp.S
===================================================================
RCS file: /cvs/glibc/libc/sysdeps/alpha/setjmp.S,v
retrieving revision 1.19
diff -u -p -d -r1.19 setjmp.S
--- sysdeps/alpha/setjmp.S	24 Jun 2003 16:29:21 -0000	1.19
+++ sysdeps/alpha/setjmp.S	9 Jan 2006 23:06:01 -0000
@@ -23,16 +23,22 @@
 #define _SETJMP_H
 #include <bits/setjmp.h>
 
-       .ent __sigsetjmp
-       .global __sigsetjmp
+	.ent __sigsetjmp
+	.global __sigsetjmp
 __sigsetjmp:
-       ldgp    gp, 0(pv)
+	ldgp    gp, 0(pv)
 
 $sigsetjmp_local:
-       subq    sp, 16, sp
-       .frame  sp, 16, ra, 0
-       stq     ra, 0(sp)
-       .mask   0x04000000, -16
+#ifndef PIC
+#define FRAME	16	
+	subq    sp, FRAME, sp
+	.frame  sp, FRAME, ra, 0
+	stq     ra, 0(sp)
+	.mask   0x04000000, -FRAME
+#else
+#define FRAME	0
+	.frame	sp, FRAME, ra, 0
+#endif
 #ifdef PROF
 	.set noat
 	lda	AT, _mcount
@@ -47,10 +53,27 @@ $sigsetjmp_local:
 	stq	s3, JB_S3*8(a0)
 	stq	s4, JB_S4*8(a0)
 	stq	s5, JB_S5*8(a0)
+#ifdef PTR_MANGLE
+	PTR_MANGLE(t1, ra, t0)
+	stq	t1, JB_PC*8(a0)
+#else
 	stq	ra, JB_PC*8(a0)
-	addq	sp, 16, t0
+#endif
+#if defined(PTR_MANGLE) && FRAME == 0
+	PTR_MANGLE2(t1, sp, t0)
+#else
+	addq	sp, FRAME, t1
+# ifdef PTR_MANGLE
+	PTR_MANGLE2(t1, t1, t0)
+# endif
+#endif
+	stq	t1, JB_SP*8(a0)
+#ifdef PTR_MANGLE
+	PTR_MANGLE2(t1, fp, t0)
+	stq	t1, JB_FP*8(a0)
+#else
 	stq	fp, JB_FP*8(a0)
-	stq	t0, JB_SP*8(a0)
+#endif
 	stt	$f2, JB_F2*8(a0)
 	stt	$f3, JB_F3*8(a0)
 	stt	$f4, JB_F4*8(a0)
@@ -60,12 +83,20 @@ $sigsetjmp_local:
 	stt	$f8, JB_F8*8(a0)
 	stt	$f9, JB_F9*8(a0)
 
+#ifndef PIC
 	/* Call to C to (potentially) save our signal mask.  */
 	jsr	ra, __sigjmp_save
-
 	ldq	ra, 0(sp)
 	addq	sp, 16, sp
 	ret
+#elif defined NOT_IN_libc && defined IS_IN_rtld
+	/* In ld.so we never save the signal mask.  */
+	mov	0, v0
+	ret
+#else
+	/* Tailcall to save the signal mask.  */
+	br	$31, __sigjmp_save	!samegp
+#endif
 
 END(__sigsetjmp)
 
Index: sysdeps/unix/sysv/linux/alpha/sysdep.h
===================================================================
RCS file: /cvs/glibc/libc/sysdeps/unix/sysv/linux/alpha/sysdep.h,v
retrieving revision 1.17
diff -u -p -d -r1.17 sysdep.h
--- sysdeps/unix/sysv/linux/alpha/sysdep.h	23 Mar 2004 23:31:47 -0000	1.17
+++ sysdeps/unix/sysv/linux/alpha/sysdep.h	9 Jan 2006 23:06:03 -0000
@@ -22,10 +22,10 @@
 #define _LINUX_ALPHA_SYSDEP_H 1
 
 #ifdef __ASSEMBLER__
-
 #include <asm/pal.h>
 #include <alpha/regdef.h>
-
+#else
+#include <stdint.h>
 #endif
 
 /* There is some commonality.  */
@@ -98,4 +98,39 @@
 	INTERNAL_SYSCALL1(name, err_out, nr, args);			\
 })
 
+/* Pointer mangling support.  Note that tls access is slow enough that
+   we don't deoptimize things by placing the pointer check value there.  */
+#if defined NOT_IN_libc && defined IS_IN_rtld
+# ifdef __ASSEMBLER__
+#  define PTR_MANGLE(dst, src, tmp)				\
+	ldah	tmp, __pointer_chk_guard_local($29) !gprelhigh;	\
+	ldq	tmp, __pointer_chk_guard_local(tmp) !gprellow;	\
+	xor	src, tmp, dst
+#  define PTR_MANGLE2(dst, src, tmp)				\
+	xor	src, tmp, dst
+#  define PTR_DEMANGLE(dst, tmp)   PTR_MANGLE(dst, dst, tmp)
+#  define PTR_DEMANGLE2(dst, tmp)  PTR_MANGLE2(dst, dst, tmp)
+# else
+extern uintptr_t __pointer_chk_guard_local attribute_relro attribute_hidden;
+#  define PTR_MANGLE(var)	\
+	(var) = (void *) ((uintptr_t) (var) ^ __pointer_chk_guard_local)
+#  define PTR_DEMANGLE(var)  PTR_MANGLE(var)
+# endif
+#elif defined PIC
+# ifdef __ASSEMBLER__
+#  define PTR_MANGLE(dst, src, tmp)		\
+	ldq	tmp, __pointer_chk_guard;	\
+	xor	src, tmp, dst
+#  define PTR_MANGLE2(dst, src, tmp)		\
+	xor	src, tmp, dst
+#  define PTR_DEMANGLE(dst, tmp)   PTR_MANGLE(dst, dst, tmp)
+#  define PTR_DEMANGLE2(dst, tmp)  PTR_MANGLE2(dst, dst, tmp)
+# else
+extern uintptr_t __pointer_chk_guard attribute_relro;
+#  define PTR_MANGLE(var)	\
+	(var) = (void *) ((uintptr_t) (var) ^ __pointer_chk_guard)
+#  define PTR_DEMANGLE(var)  PTR_MANGLE(var)
+# endif
+#endif
+
 #endif /* _LINUX_ALPHA_SYSDEP_H */


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