To support syscalls (e.g. mmap()) who return a pointer and to allow the pointer as big as possible, we should convert the negated errno value to unsigned long (uintptr_t), otherwise, in signed long, a potential big pointer (whose highest bit is 1) will be treated as a failure.
tools/include/nolibc/errno.h defines the MAX_ERRNO, let's use it directly. after converting to unsigned long, the negative errno value from -1 to -MAX_ERRNO becomes something like '~1 + 1' (every bit is 1) to '~MAX_ERRNO + 1', '~1 + 1' is the biggest, '~MAX_ERRNO + 1' is the smallest, so, the check becomes:
if (ret <= (unsigned long)-1 && ret >= (unsigned long)-MAX_ERRNO) { ... }
Since (unsigned long)-1 is the biggest unsigned long value, it is always true if bigger than (unsigned long)-MAX_ERRNO, so, just reserve the following check is enough:
if (ret >= (unsigned long)-MAX_ERRNO) { ... }
Suggested-by: David Laight David.Laight@ACULAB.COM Link: https://lore.kernel.org/linux-riscv/94dd5170929f454fbc0a10a2eb3b108d@AcuMS.a... Signed-off-by: Zhangjin Wu falcon@tinylab.org --- tools/include/nolibc/sys.h | 13 ++++++++----- 1 file changed, 8 insertions(+), 5 deletions(-)
diff --git a/tools/include/nolibc/sys.h b/tools/include/nolibc/sys.h index 4fbefe5adf93..8a6e16472d54 100644 --- a/tools/include/nolibc/sys.h +++ b/tools/include/nolibc/sys.h @@ -28,13 +28,16 @@ #include "errno.h" #include "types.h"
-/* Syscall return helper, set errno as -ret when ret < 0 */ + +/* Syscall return helper for library routines + * set errno as -ret when ret in [-MAX_ERRNO, -1] + */ static __inline__ __attribute__((unused, always_inline)) -long __sysret(long ret) +long __sysret(unsigned long ret) { - if (ret < 0) { - SET_ERRNO(-ret); - ret = -1; + if (ret >= (unsigned long)-MAX_ERRNO) { + SET_ERRNO(-(long)ret); + return -1; } return ret; }