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[PATCH v2] ARM: Add pointer guard support.


Add support for pointer mangling in glibc internal structures in C
and assembler code.

ports/ChangeLog.arm:

2013-09-27  Will Newton  <will.newton@linaro.org>

	* sysdeps/arm/__longjmp.S (__longjmp): Demangle fp, sp
	and lr when restoring register values.
	* sysdeps/arm/include/bits/setjmp.h (JMP_BUF_REGLIST): Remove
	sp and lr from list and replace fp with a4.
	* sysdeps/arm/jmpbuf-unwind.h (_jmpbuf_sp): New function.
	(_JMPBUF_UNWINDS_ADJ): Call _jmpbuf_sp.
	* sysdeps/arm/setjmp.S (__sigsetjmp): Mangle fp, sp and lr
	before storing register values.
	* sysdeps/arm/sysdep.h (LDST_GLOBAL): New macro.
	* sysdeps/unix/sysv/linux/arm/sysdep.h (PTR_MANGLE): New macro.
	(PTR_DEMANGLE): Likewise. (PTR_MANGLE2): Likewise.
	(PTR_DEMANGLE2): Likewise.
---
 ports/sysdeps/arm/__longjmp.S              | 14 +++++++++++
 ports/sysdeps/arm/include/bits/setjmp.h    |  5 ++--
 ports/sysdeps/arm/jmpbuf-unwind.h          | 13 +++++++++-
 ports/sysdeps/arm/setjmp.S                 | 14 +++++++++++
 ports/sysdeps/arm/sysdep.h                 | 11 +++++++++
 ports/sysdeps/unix/sysv/linux/arm/sysdep.h | 39 +++++++++++++++++++++++++++---
 6 files changed, 90 insertions(+), 6 deletions(-)

Changes in v2:
 - Use a global instead of a thread local variable to store the guard value
 - The bit I don't like in this version of the patch is the test for !IS_IN_nscd,
   but without it I get undefined references to __pointer_chk_guard_local.

diff --git a/ports/sysdeps/arm/__longjmp.S b/ports/sysdeps/arm/__longjmp.S
index a5edede..2b1f7f4 100644
--- a/ports/sysdeps/arm/__longjmp.S
+++ b/ports/sysdeps/arm/__longjmp.S
@@ -34,10 +34,24 @@ ENTRY (__longjmp)
 	sfi_breg ip, \
 	ldr	r4, [\B, #32]	/* jmpbuf's sp */
 	cfi_undefined (r4)
+#ifdef PTR_DEMANGLE
+	PTR_DEMANGLE (r4, r4, a3, a4)
+#endif
 	CHECK_SP (r4)
 #endif
 	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 (sp, a4, a3)
+	ldr	a4, [ip], #4
+	PTR_DEMANGLE2 (lr, a4, a3)
+#else
+	mov	fp, a4
+	ldr	sp, [ip], #4
+	ldr	lr, [ip], #4
+#endif
 	cfi_restore (v1)
 	cfi_restore (v2)
 	cfi_restore (v3)
diff --git a/ports/sysdeps/arm/include/bits/setjmp.h b/ports/sysdeps/arm/include/bits/setjmp.h
index 1559d7b..64505dc 100644
--- a/ports/sysdeps/arm/include/bits/setjmp.h
+++ b/ports/sysdeps/arm/include/bits/setjmp.h
@@ -26,8 +26,9 @@

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

 /* Index of __jmp_buf where the sp register resides.  */
 # define __JMP_BUF_SP		8
diff --git a/ports/sysdeps/arm/jmpbuf-unwind.h b/ports/sysdeps/arm/jmpbuf-unwind.h
index 0863540..1b0d020 100644
--- a/ports/sysdeps/arm/jmpbuf-unwind.h
+++ b/ports/sysdeps/arm/jmpbuf-unwind.h
@@ -17,6 +17,7 @@

 #include <setjmp.h>
 #include <stdint.h>
+#include <sysdep.h>
 #include <unwind.h>

 /* Test if longjmp to JMPBUF would unwind the frame
@@ -27,8 +28,18 @@
 #define _JMPBUF_CFA_UNWINDS_ADJ(_jmpbuf, _context, _adj) \
   _JMPBUF_UNWINDS_ADJ (_jmpbuf, (void *) _Unwind_GetCFA (_context), _adj)

+static inline uintptr_t __attribute__ ((unused))
+_jmpbuf_sp (__jmp_buf regs)
+{
+  uintptr_t sp = regs[__JMP_BUF_SP];
+#ifdef PTR_DEMANGLE
+  PTR_DEMANGLE (sp);
+#endif
+  return sp;
+}
+
 #define _JMPBUF_UNWINDS_ADJ(_jmpbuf, _address, _adj) \
-  ((uintptr_t) (_address) - (_adj) < (uintptr_t) (_jmpbuf)[__JMP_BUF_SP] - (_adj))
+  ((uintptr_t) (_address) - (_adj) < _jmpbuf_sp (_jmpbuf) - (_adj))

 /* We use the normal longjmp for unwinding.  */
 #define __libc_unwind_longjmp(buf, val) __libc_longjmp (buf, val)
diff --git a/ports/sysdeps/arm/setjmp.S b/ports/sysdeps/arm/setjmp.S
index a6c161d..b38b919 100644
--- a/ports/sysdeps/arm/setjmp.S
+++ b/ports/sysdeps/arm/setjmp.S
@@ -24,11 +24,25 @@
 #include <arm-features.h>

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

 	/* Save registers */
 	sfi_breg ip, \
 	stmia	\B!, JMP_BUF_REGLIST
+#ifdef PTR_MANGLE
+	PTR_MANGLE2 (a4, sp, a3)
+	str	a4, [ip], #4
+	PTR_MANGLE2 (a4, lr, a3)
+	str	a4, [ip], #4
+#else
+	str	sp, [ip], #4
+	str	lr, [ip], #4
+#endif

 #if !defined ARM_ASSUME_NO_IWMMXT || defined __SOFTFP__
 # define NEED_HWCAP 1
diff --git a/ports/sysdeps/arm/sysdep.h b/ports/sysdeps/arm/sysdep.h
index 5501597..60d26fd 100644
--- a/ports/sysdeps/arm/sysdep.h
+++ b/ports/sysdeps/arm/sysdep.h
@@ -171,6 +171,17 @@
 99:	OP	R, [pc, T]
 # endif

+# define LDST_GLOBAL(OP, R, T, EXPR)			\
+	ldr	T, 99f;					\
+	ldr	R, 100f;				\
+98:	add	T, T, pc;				\
+	ldr	T, [T, R];				\
+	.subsection 2;					\
+99:	.word	_GLOBAL_OFFSET_TABLE_ - 98b - PC_OFS;	\
+100:	.word	EXPR##(GOT);				\
+	.previous;					\
+	OP	R, [T]
+
 /* Cope with negative memory offsets, which thumb can't encode.
    Use NEGOFF_ADJ_BASE to (conditionally) alter the base register,
    and then NEGOFF_OFF1 to use 0 for thumb and the offset for arm,
diff --git a/ports/sysdeps/unix/sysv/linux/arm/sysdep.h b/ports/sysdeps/unix/sysv/linux/arm/sysdep.h
index b195d8e..7ef8374 100644
--- a/ports/sysdeps/unix/sysv/linux/arm/sysdep.h
+++ b/ports/sysdeps/unix/sysv/linux/arm/sysdep.h
@@ -435,8 +435,41 @@ __local_syscall_error:						\

 #endif	/* __ASSEMBLER__ */

-/* Pointer mangling is not yet supported for ARM.  */
-#define PTR_MANGLE(var) (void) (var)
-#define PTR_DEMANGLE(var) (void) (var)
+/* Pointer mangling support.  */
+#if (defined NOT_IN_libc && defined IS_IN_rtld) || (!defined SHARED && !defined IS_IN_nscd)
+# ifdef __ASSEMBLER__
+#  define PTR_MANGLE(dst, src, guard, tmp)				\
+  LDST_PCREL(ldr, guard, tmp, C_SYMBOL_NAME(__pointer_chk_guard_local)); \
+  PTR_MANGLE2(dst, src, guard)
+#  define PTR_MANGLE2(dst, src, guard)		\
+  eor dst, src, guard
+#  define PTR_DEMANGLE(dst, src, guard, tmp)	\
+  PTR_MANGLE (dst, src, guard, tmp)
+#  define PTR_DEMANGLE2(dst, src, guard)	\
+  PTR_MANGLE2 (dst, src, guard)
+# else
+extern uintptr_t __pointer_chk_guard_local attribute_relro attribute_hidden;
+#  define PTR_MANGLE(var) \
+  (var) = (__typeof (var)) ((uintptr_t) (var) ^ __pointer_chk_guard_local)
+#  define PTR_DEMANGLE(var)     PTR_MANGLE (var)
+# endif
+#else
+# ifdef __ASSEMBLER__
+#  define PTR_MANGLE(dst, src, guard, tmp)				\
+  LDST_GLOBAL(ldr, guard, tmp, C_SYMBOL_NAME(__pointer_chk_guard));	\
+  PTR_MANGLE2(dst, src, guard)
+#  define PTR_MANGLE2(dst, src, guard)		\
+  eor dst, src, guard
+#  define PTR_DEMANGLE(dst, src, guard, tmp)	\
+  PTR_MANGLE (dst, src, guard, tmp)
+#  define PTR_DEMANGLE2(dst, src, guard)	\
+  PTR_MANGLE2 (dst, src, guard)
+# else
+extern uintptr_t __pointer_chk_guard attribute_relro;
+#  define PTR_MANGLE(var) \
+  (var) = (__typeof (var)) ((uintptr_t) (var) ^ __pointer_chk_guard)
+#  define PTR_DEMANGLE(var)     PTR_MANGLE (var)
+# endif
+#endif

 #endif /* linux/arm/sysdep.h */
-- 
1.8.1.4


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