Message ID | aae854b2de881f9bc1c82ab9dda53b51d7330c9a.1687187451.git.falcon@tinylab.org |
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State | New |
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Series |
tools/nolibc: add a new syscall helper
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Commit Message
Zhangjin Wu
June 19, 2023, 3:48 p.m. UTC
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.aculab.com/
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; }