From df76ff3a446a787a95cf74cb15c285464d73a93d Mon Sep 17 00:00:00 2001 From: "H.J. Lu" Date: Mon, 13 Apr 2020 10:31:26 -0700 Subject: 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. --- 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(-) (limited to 'sysdeps') diff --git a/sysdeps/unix/sysv/linux/x86_64/sysdep.h b/sysdeps/unix/sysv/linux/x86_64/sysdep.h index 24d8b8e..85f8f94 100644 --- a/sysdeps/unix/sysv/linux/x86_64/sysdep.h +++ b/sysdeps/unix/sysv/linux/x86_64/sysdep.h @@ -177,12 +177,15 @@ /* 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, 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 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 */ -- cgit v1.1