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proper error handling for fcntl F_GETOWN on modern kernels

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on old kernels, there's no way to detect errors; we must assume
negative syscall return values are pgrp ids. but if the F_GETOWN_EX
fcntl works, we can get a reliable answer.
This commit is contained in:
Rich Felker
2012-06-20 22:16:47 -04:00
parent e5fb6820a4
commit 4e8b0938d9
5 changed files with 29 additions and 1 deletions
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10
src/fcntl/fcntl.c
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@@ -1,6 +1,8 @@
#define _GNU_SOURCE
#include <fcntl.h>
#include <unistd.h>
#include <stdarg.h>
#include <errno.h>
#include "syscall.h"
#include "libc.h"
@@ -13,6 +15,12 @@ int fcntl(int fd, int cmd, ...)
va_end(ap);
if (cmd == F_SETFL) arg |= O_LARGEFILE;
if (cmd == F_SETLKW) return syscall_cp(SYS_fcntl, fd, cmd, arg);
if (cmd == F_GETOWN) return __syscall(SYS_fcntl, fd, cmd, arg);
if (cmd == F_GETOWN) {
struct f_owner_ex ex;
int ret = __syscall(SYS_fcntl, fd, F_GETOWN_EX, &ex);
if (ret == -EINVAL) return __syscall(SYS_fcntl, fd, cmd, arg);
if (ret) return __syscall_ret(ret);
return ex.type == F_OWNER_PGRP ? -ex.pid : ex.pid;
}
return syscall(SYS_fcntl, fd, cmd, arg);
}