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authorMike Frysinger <vapier@gentoo.org>2006-01-31 00:33:26 +0000
committerMike Frysinger <vapier@gentoo.org>2006-01-31 00:33:26 +0000
commitfa30ad140d5f298befc3c59524a4640c8022c705 (patch)
tree06571101de8cb1ce03e67ba24dfb5c2f86e19be0
parent8504c3b4d833a77dc3384a0af36a85aeb36d9dcc (diff)
John Bowler writes in Bug 385:
This is a work round for a fairly serious GCC compiler bug - when the syscall assembler overwrites r7 (required on thumb) the compiler fails to protect the register when it is using it as a frame pointer.
-rw-r--r--libc/sysdeps/linux/arm/bits/syscalls.h27
1 files changed, 27 insertions, 0 deletions
diff --git a/libc/sysdeps/linux/arm/bits/syscalls.h b/libc/sysdeps/linux/arm/bits/syscalls.h
index c6ab3ecf7..d25d1824e 100644
--- a/libc/sysdeps/linux/arm/bits/syscalls.h
+++ b/libc/sysdeps/linux/arm/bits/syscalls.h
@@ -141,6 +141,11 @@ return (type) (INLINE_SYSCALL(name, 7, arg1, arg2, arg3, arg4, arg5, arg6, arg7)
} \
(int) _sys_result; })
#else
+#if 0
+/* This doesn't work because GCC uses r7 as a frame pointer in
+ * some cases and doesn't notice that the _r7 value changes
+ * it, resulting in mysterious crashes after the SWI.
+ */
#define INTERNAL_SYSCALL(name, err, nr, args...) \
({ unsigned int _sys_result; \
{ \
@@ -154,6 +159,28 @@ return (type) (INLINE_SYSCALL(name, 7, arg1, arg2, arg3, arg4, arg5, arg6, arg7)
_sys_result = _a1; \
} \
(int) _sys_result; })
+#else
+/* So hide the use of r7 from the compiler, this would be a lot
+ * easier but for the fact that the syscalls can exceed 255.
+ * For the moment the LOAD_ARG_7 is sacrificed.
+ */
+#define INTERNAL_SYSCALL(name, err, nr, args...) \
+ ({ unsigned int _sys_result; \
+ { \
+ register int _a1 asm ("a1"); \
+ LOAD_ARGS_##nr (args) \
+ register int _v3 asm ("v3") = (int) (SYS_ify(name)); \
+ asm volatile ("push {r7}\n" \
+ "\tmov r7, v3\n" \
+ "\tswi 0 @ syscall " #name "\n" \
+ "\tpop {r7}" \
+ : "=r" (_a1) \
+ : "r" (_v3) ASM_ARGS_##nr \
+ : "memory"); \
+ _sys_result = _a1; \
+ } \
+ (int) _sys_result; })
+#endif
#endif
#endif /* !defined(__ARM_EABI__) */