On Linux/MIPS (O32 ABI) for system call we have two result registers - v0 and a3. v0 contains actual syscall result on success or error number on fail, a3 set to 0/1 for indicating syscall success/fail. (if a3 == 1, v0 contains errno). Now as we can see from definition of handle_sys (arch/mips/kernel/scall32-o32.S), handler treats returned by syscall function (let's call "original") values in range [-EMAXERRNO; 0[ as -errno, a3 is set to 1 and final returned (to userspace) value is (-original).

INLINE_SYSCALL_NOERR_NCS defined in mips/bits/syscalls.h will handle this behaviour.

Signed-off-by: Volodymyr Boyko boyko.cxx@gmail.com --- libc/sysdeps/linux/mips/bits/syscalls.h | 10 ++++++++++ 1 file changed, 10 insertions(+)

diff --git a/libc/sysdeps/linux/mips/bits/syscalls.h b/libc/sysdeps/linux/mips/bits/syscalls.h index 787bb7d..b8f8059 100644 --- a/libc/sysdeps/linux/mips/bits/syscalls.h +++ b/libc/sysdeps/linux/mips/bits/syscalls.h @@ -29,6 +29,16 @@ } \ result_var; })

+#define INLINE_SYSCALL_NOERR_NCS(name, nr, args...) \ +({ \ + INTERNAL_SYSCALL_DECL(err); \ + long res = INTERNAL_SYSCALL_NCS(name, err, nr, args); \ + if (unlikely(INTERNAL_SYSCALL_ERROR_P(res, err))) { \ + res = -res; \ + } \ + res; \ +}) + #define INTERNAL_SYSCALL_DECL(err) long err attribute_unused

#define INTERNAL_SYSCALL_ERROR_P(val, err) ((long) (err))