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* [glibc/release/2.30/master] x32: Properly pass long to syscall [BZ #25810]
@ 2020-05-07 12:24 H.J. Lu
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From: H.J. Lu @ 2020-05-07 12:24 UTC (permalink / raw)
To: glibc-cvs
https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=7378e9c520558af769ced2d8e2cd64ca31c337a0
commit 7378e9c520558af769ced2d8e2cd64ca31c337a0
Author: H.J. Lu <hjl.tools@gmail.com>
Date: Mon Apr 13 10:31:26 2020 -0700
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.
(cherry picked from commit df76ff3a446a787a95cf74cb15c285464d73a93d)
Diff:
---
sysdeps/unix/sysv/linux/x86_64/sysdep.h | 15 +++++++++------
sysdeps/unix/sysv/linux/x86_64/x32/sysdep.h | 16 ++++++++++++++++
2 files changed, 25 insertions(+), 6 deletions(-)
diff --git a/sysdeps/unix/sysv/linux/x86_64/sysdep.h b/sysdeps/unix/sysv/linux/x86_64/sysdep.h
index b88c46b589..4636d9dddd 100644
--- a/sysdeps/unix/sysv/linux/x86_64/sysdep.h
+++ b/sysdeps/unix/sysv/linux/x86_64/sysdep.h
@@ -223,12 +223,15 @@
/* Registers clobbered by syscall. */
# define REGISTERS_CLOBBERED_BY_SYSCALL "cc", "r11", "cx"
-/* Create a variable 'name' based on type 'X' to avoid explicit types.
- This is mainly used set use 64-bits arguments in x32. */
-#define TYPEFY(X, name) __typeof__ ((X) - (X)) name
-/* Explicit cast the argument to avoid integer from pointer warning on
- x32. */
-#define ARGIFY(X) ((__typeof__ ((X) - (X))) (X))
+/* NB: This also works when X is an array. For an array X, type of
+ (X) - (X) is ptrdiff_t, which is signed, since size of ptrdiff_t
+ == size of pointer, cast is a NOP. */
+#define TYPEFY1(X) __typeof__ ((X) - (X))
+/* Explicit cast the argument. */
+#define ARGIFY(X) ((TYPEFY1 (X)) (X))
+/* Create a variable 'name' based on type of variable 'X' to avoid
+ explicit types. */
+#define TYPEFY(X, name) __typeof__ (ARGIFY (X)) name
#undef INTERNAL_SYSCALL
#define INTERNAL_SYSCALL(name, err, nr, args...) \
diff --git a/sysdeps/unix/sysv/linux/x86_64/x32/sysdep.h b/sysdeps/unix/sysv/linux/x86_64/x32/sysdep.h
index 1401f2ddec..8a771d9694 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 */
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