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author | H.J. Lu <hjl.tools@gmail.com> | 2020-04-13 10:31:26 -0700 |
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committer | H.J. Lu <hjl.tools@gmail.com> | 2020-04-13 10:31:26 -0700 |
commit | df76ff3a446a787a95cf74cb15c285464d73a93d (patch) | |
tree | fb802ff931d65d7ee81b2425c7d26a4372cd81b6 /sysdeps/unix/sysv/linux/x86_64/x32/sysdep.h | |
parent | 319d2a7b60cc0d06bb5c29684c23475d41a7f8b7 (diff) | |
download | glibc-df76ff3a446a787a95cf74cb15c285464d73a93d.zip glibc-df76ff3a446a787a95cf74cb15c285464d73a93d.tar.gz glibc-df76ff3a446a787a95cf74cb15c285464d73a93d.tar.bz2 |
x32: Properly pass long to syscall [BZ #25810]
X32 has 32-bit long and pointer with 64-bit off_t. Since x32 psABI
requires that pointers passed in registers must be zero-extended to
64bit, x32 can share many syscall interfaces with LP64. When a LP64
syscall with long and unsigned long arguments is used for x32, these
arguments must be properly extended to 64-bit. Otherwise if the upper
32 bits of the register have undefined value, such a syscall will be
rejected by kernel.
Enforce zero-extension for pointers and array system call arguments.
For integer types, extend to int64_t (the full register) using a
regular cast, resulting in zero or sign extension based on the
signedness of the original type.
For
void *mmap(void *addr, size_t length, int prot, int flags,
int fd, off_t offset);
we now generate
0: 41 f7 c1 ff 0f 00 00 test $0xfff,%r9d
7: 75 1f jne 28 <__mmap64+0x28>
9: 48 63 d2 movslq %edx,%rdx
c: 89 f6 mov %esi,%esi
e: 4d 63 c0 movslq %r8d,%r8
11: 4c 63 d1 movslq %ecx,%r10
14: b8 09 00 00 40 mov $0x40000009,%eax
19: 0f 05 syscall
That is
1. addr is unchanged.
2. length is zero-extend to 64 bits.
3. prot is sign-extend to 64 bits.
4. flags is sign-extend to 64 bits.
5. fd is sign-extend to 64 bits.
6. offset is unchanged.
For int arguments, since kernel uses only the lower 32 bits and ignores
the upper 32 bits in 64-bit registers, these work correctly.
Tested on x86-64 and x32. There are no code changes on x86-64.
Diffstat (limited to 'sysdeps/unix/sysv/linux/x86_64/x32/sysdep.h')
-rw-r--r-- | sysdeps/unix/sysv/linux/x86_64/x32/sysdep.h | 16 |
1 files changed, 16 insertions, 0 deletions
diff --git a/sysdeps/unix/sysv/linux/x86_64/x32/sysdep.h b/sysdeps/unix/sysv/linux/x86_64/x32/sysdep.h index 5bf9eed..a37d520 100644 --- a/sysdeps/unix/sysv/linux/x86_64/x32/sysdep.h +++ b/sysdeps/unix/sysv/linux/x86_64/x32/sysdep.h @@ -26,4 +26,20 @@ #undef LO_HI_LONG #define LO_HI_LONG(val) (val) +#ifndef __ASSEMBLER__ +# undef ARGIFY +/* Enforce zero-extension for pointers and array system call arguments. + For integer types, extend to int64_t (the full register) using a + regular cast, resulting in zero or sign extension based on the + signedness of the original type. */ +# define ARGIFY(X) \ + ({ \ + _Pragma ("GCC diagnostic push"); \ + _Pragma ("GCC diagnostic ignored \"-Wpointer-to-int-cast\""); \ + (__builtin_classify_type (X) == 5 \ + ? (uintptr_t) (X) : (int64_t) (X)); \ + _Pragma ("GCC diagnostic pop"); \ + }) +#endif /* __ASSEMBLER__ */ + #endif /* linux/x86_64/x32/sysdep.h */ |