ARM: Add pointer encryption support.

Add support for pointer encryption in glibc internal structures in C
and assembler code. Pointer encryption is a glibc security feature
described here:

https://sourceware.org/glibc/wiki/PointerEncryption

The ARM implementation uses global variables instead of thread pointer
relative accesses to get the value of the pointer encryption guard
because accessing the thread pointer can be very expensive on older
ARM cores.

ports/ChangeLog.arm:

2013-10-03  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.

6 files changed, 94 insertions, 6 deletions

diff --git a/ports/sysdeps/arm/__longjmp.S b/ports/sysdeps/arm/__longjmp.S
index a5edede16d..2b1f7f41c1 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 1559d7b8e6..64505dcb94 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 0863540ce0..1b0d0202e3 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 a6c161db54..b38b919af0 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 550159740b..3823617f13 100644
--- a/ports/sysdeps/arm/sysdep.h
+++ b/ports/sysdeps/arm/sysdep.h
@@ -171,6 +171,18 @@
 99:	OP	R, [pc, T]
 # endif
 
+/* Load or store to/from a global EXPR into/from R, using T.  */
+# 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 b195d8ea1d..6cfe4e08a7 100644
--- a/ports/sysdeps/unix/sysv/linux/arm/sysdep.h
+++ b/ports/sysdeps/unix/sysv/linux/arm/sysdep.h
@@ -435,8 +435,44 @@ __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 NOT_IN_libc || defined IS_IN_libpthread))
+# 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)
+/* Use PTR_MANGLE2 for efficiency if guard is already loaded.  */
+#  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)
+/* Use PTR_MANGLE2 for efficiency if guard is already loaded.  */
+#  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 */