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[PATCH] ARM: Don't apply pointer encryption to the frame pointer


The frame pointer register is rarely used for that purpose on ARM and
applications that look at the contents of the jmp_buf may be relying
on reading the value. Ruby uses the contents of jmp_buf to find the
root set for garbage collection so relies on this pointer value being
unencrypted.

ports/ChangeLog.arm:

2013-12-10  Will Newton  <will.newton@linaro.org>

	* sysdeps/arm/__longjmp.S: Don't apply pointer encryption
	to fp register.
	* sysdeps/arm/setjmp.S: Likewise.
 	* sysdeps/arm/include/bits/setjmp.h (JMP_BUF_REGLIST): Add
	fp to register list, remove a4.
	* sysdeps/unix/sysv/linux/arm/sysdep.h: (PTR_MANGLE_LOAD):
	New macro.
---
 ports/sysdeps/arm/__longjmp.S              | 4 +---
 ports/sysdeps/arm/include/bits/setjmp.h    | 5 ++---
 ports/sysdeps/arm/setjmp.S                 | 4 +---
 ports/sysdeps/unix/sysv/linux/arm/sysdep.h | 8 ++++++--
 4 files changed, 10 insertions(+), 11 deletions(-)

diff --git a/ports/sysdeps/arm/__longjmp.S b/ports/sysdeps/arm/__longjmp.S
index 894c121..aaa2d3d 100644
--- a/ports/sysdeps/arm/__longjmp.S
+++ b/ports/sysdeps/arm/__longjmp.S
@@ -41,14 +41,12 @@ ENTRY (__longjmp)
 	sfi_sp sfi_breg ip, \
 	ldmia	\B!, JMP_BUF_REGLIST
 #ifdef PTR_DEMANGLE
-	PTR_DEMANGLE (fp, a4, a3, a2)
 	ldr	a4, [ip], #4
-	PTR_DEMANGLE2 (a4, a4, a3)
+	PTR_DEMANGLE (a4, a4, a3, a2)
 	mov	sp, a4
 	ldr	a4, [ip], #4
 	PTR_DEMANGLE2 (lr, a4, a3)
 #else
-	mov	fp, a4
 	ldr	sp, [ip], #4
 	ldr	lr, [ip], #4
 #endif
diff --git a/ports/sysdeps/arm/include/bits/setjmp.h b/ports/sysdeps/arm/include/bits/setjmp.h
index 64505dc..7bb4f00 100644
--- a/ports/sysdeps/arm/include/bits/setjmp.h
+++ b/ports/sysdeps/arm/include/bits/setjmp.h
@@ -26,9 +26,8 @@

 #ifndef _ISOMAC
 /* Register list for a ldm/stm instruction to load/store
-   the general registers from a __jmp_buf. The a4 register
-   contains fp at this point.  */
-# define JMP_BUF_REGLIST	{a4, v1-v6, sl}
+   the general registers from a __jmp_buf.  */
+# define JMP_BUF_REGLIST	{v1-v6, sl, fp}

 /* Index of __jmp_buf where the sp register resides.  */
 # define __JMP_BUF_SP		8
diff --git a/ports/sysdeps/arm/setjmp.S b/ports/sysdeps/arm/setjmp.S
index fedd994..803591e 100644
--- a/ports/sysdeps/arm/setjmp.S
+++ b/ports/sysdeps/arm/setjmp.S
@@ -23,9 +23,7 @@

 ENTRY (__sigsetjmp)
 #ifdef PTR_MANGLE
-	PTR_MANGLE (a4, fp, a3, ip)
-#else
-	mov	a4, fp
+	PTR_MANGLE_LOAD (a3, ip)
 #endif
 	mov	ip, r0

diff --git a/ports/sysdeps/unix/sysv/linux/arm/sysdep.h b/ports/sysdeps/unix/sysv/linux/arm/sysdep.h
index 6cfe4e0..ccab57e 100644
--- a/ports/sysdeps/unix/sysv/linux/arm/sysdep.h
+++ b/ports/sysdeps/unix/sysv/linux/arm/sysdep.h
@@ -439,8 +439,10 @@ __local_syscall_error:						\
 #if (defined NOT_IN_libc && defined IS_IN_rtld) || \
   (!defined SHARED && (!defined NOT_IN_libc || defined IS_IN_libpthread))
 # ifdef __ASSEMBLER__
+#  define PTR_MANGLE_LOAD(guard, tmp)					\
+  LDST_PCREL(ldr, guard, tmp, C_SYMBOL_NAME(__pointer_chk_guard_local));
 #  define PTR_MANGLE(dst, src, guard, tmp)				\
-  LDST_PCREL(ldr, guard, tmp, C_SYMBOL_NAME(__pointer_chk_guard_local)); \
+  PTR_MANGLE_LOAD(guard, tmp);						\
   PTR_MANGLE2(dst, src, guard)
 /* Use PTR_MANGLE2 for efficiency if guard is already loaded.  */
 #  define PTR_MANGLE2(dst, src, guard)		\
@@ -457,8 +459,10 @@ extern uintptr_t __pointer_chk_guard_local attribute_relro attribute_hidden;
 # endif
 #else
 # ifdef __ASSEMBLER__
+#  define PTR_MANGLE_LOAD(guard, tmp)					\
+  LDST_GLOBAL(ldr, guard, tmp, C_SYMBOL_NAME(__pointer_chk_guard));
 #  define PTR_MANGLE(dst, src, guard, tmp)				\
-  LDST_GLOBAL(ldr, guard, tmp, C_SYMBOL_NAME(__pointer_chk_guard));	\
+  PTR_MANGLE_LOAD(guard, tmp);						\
   PTR_MANGLE2(dst, src, guard)
 /* Use PTR_MANGLE2 for efficiency if guard is already loaded.  */
 #  define PTR_MANGLE2(dst, src, guard)		\
-- 
1.8.1.4


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