[v3,2/2] aarch64: Set the syscall register right before doing the syscall.
Checks
| Context |
Check |
Description |
| dj/TryBot-apply_patch |
success
|
Patch applied to master at the time it was sent
|
| dj/TryBot-32bit |
success
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Build for i686
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Commit Message
To make identifying syscalls easier during call tree analysis load the
syscall number just before performing the syscall.
Compiler optimizations can place quite a few instructions between the
setting of the syscall number and the syscall instruction. During call
tree analysis the number of instructions between the two can lead to
more difficulty for both tools and humans in properly identifying the
syscall number. Having the syscall number set in the prior instruction
to the syscall instruction makes this task easier and less error prone.
Being able to reliably identify syscalls made by a given API will make
it easier to understand and verify the safety and security of glibc.
---
sysdeps/unix/sysv/linux/aarch64/sysdep.h | 20 +++++++++++++++++---
1 file changed, 17 insertions(+), 3 deletions(-)
@@ -167,14 +167,28 @@
# define HAVE_CLONE3_WRAPPER 1
+# define MSTR_HELPER(x) # x
+# define MSTR(x) MSTR_HELPER(x)
+
# undef INTERNAL_SYSCALL_RAW
# define INTERNAL_SYSCALL_RAW(name, nr, args...) \
({ long _sys_result; \
{ \
LOAD_ARGS_##nr (args) \
- register long _x8 asm ("x8") = (name); \
- asm volatile ("svc 0 // syscall " # name \
- : "=r" (_x0) : "r"(_x8) ASM_ARGS_##nr : "memory"); \
+ if (__builtin_constant_p(name)) \
+ asm volatile ("mov x8, %1\n" \
+ "svc 0 // syscall " # name \
+ : "=r" (_x0) \
+ : "i" (name) ASM_ARGS_##nr \
+ : "x8", "memory"); \
+ else \
+ { \
+ register long _x8 asm ("x8") = (name); \
+ asm volatile ("svc 0 // syscall " # name \
+ : "=r" (_x0) \
+ : "r"(_x8) ASM_ARGS_##nr \
+ : "memory"); \
+ } \
_sys_result = _x0; \
} \
_sys_result; })