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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.
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@ -177,12 +177,15 @@
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/* Registers clobbered by syscall. */
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# define REGISTERS_CLOBBERED_BY_SYSCALL "cc", "r11", "cx"
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/* Create a variable 'name' based on type 'X' to avoid explicit types.
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This is mainly used set use 64-bits arguments in x32. */
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#define TYPEFY(X, name) __typeof__ ((X) - (X)) name
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/* Explicit cast the argument to avoid integer from pointer warning on
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x32. */
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#define ARGIFY(X) ((__typeof__ ((X) - (X))) (X))
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/* NB: This also works when X is an array. For an array X, type of
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(X) - (X) is ptrdiff_t, which is signed, since size of ptrdiff_t
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== size of pointer, cast is a NOP. */
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#define TYPEFY1(X) __typeof__ ((X) - (X))
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/* Explicit cast the argument. */
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#define ARGIFY(X) ((TYPEFY1 (X)) (X))
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/* Create a variable 'name' based on type of variable 'X' to avoid
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explicit types. */
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#define TYPEFY(X, name) __typeof__ (ARGIFY (X)) name
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#undef INTERNAL_SYSCALL
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#define INTERNAL_SYSCALL(name, nr, args...) \
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@ -26,4 +26,20 @@
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#undef LO_HI_LONG
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#define LO_HI_LONG(val) (val)
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#ifndef __ASSEMBLER__
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# undef ARGIFY
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/* Enforce zero-extension for pointers and array system call arguments.
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For integer types, extend to int64_t (the full register) using a
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regular cast, resulting in zero or sign extension based on the
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signedness of the original type. */
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# define ARGIFY(X) \
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({ \
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_Pragma ("GCC diagnostic push"); \
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_Pragma ("GCC diagnostic ignored \"-Wpointer-to-int-cast\""); \
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(__builtin_classify_type (X) == 5 \
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? (uintptr_t) (X) : (int64_t) (X)); \
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_Pragma ("GCC diagnostic pop"); \
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})
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#endif /* __ASSEMBLER__ */
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#endif /* linux/x86_64/x32/sysdep.h */
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