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tools/nolibc/unistd: add syscall() 

syscall() is used by "normal" libcs to allow users to directly call
syscalls.
By having the same syntax inside nolibc users can more easily write code
that works with different libcs.

The macro logic is adapted from systemtaps STAP_PROBEV() macro that is
released in the public domain / CC0.

Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
Signed-off-by: Willy Tarreau <w@1wt.eu>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
This commit is contained in:
Thomas Weißschuh 2023-05-20 09:58:57 +02:00 committed by Paul E. McKenney
parent c22c7c81af
commit 53fcfafa8c
2 changed files with 17 additions and 0 deletions
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15
tools/include/nolibc/unistd.h
View File

@ -56,6 +56,21 @@ int tcsetpgrp(int fd, pid_t pid)
return ioctl(fd, TIOCSPGRP, &pid);
}
#define _syscall(N, ...) \
({ \
long _ret = my_syscall##N(__VA_ARGS__); \
if (_ret < 0) { \
SET_ERRNO(-_ret); \
_ret = -1; \
} \
_ret; \
})
#define _syscall_narg(...) __syscall_narg(__VA_ARGS__, 6, 5, 4, 3, 2, 1, 0)
#define __syscall_narg(_0, _1, _2, _3, _4, _5, _6, N, ...) N
#define _syscall_n(N, ...) _syscall(N, __VA_ARGS__)
#define syscall(...) _syscall_n(_syscall_narg(__VA_ARGS__), ##__VA_ARGS__)
/* make sure to include all global symbols */
#include "nolibc.h"

2
tools/testing/selftests/nolibc/nolibc-test.c
View File

@ -588,6 +588,8 @@ int run_syscall(int min, int max)
CASE_TEST(waitpid_child); EXPECT_SYSER(1, waitpid(getpid(), &tmp, WNOHANG), -1, ECHILD); break;
CASE_TEST(write_badf); EXPECT_SYSER(1, write(-1, &tmp, 1), -1, EBADF); break;
CASE_TEST(write_zero); EXPECT_SYSZR(1, write(1, &tmp, 0)); break;
CASE_TEST(syscall_noargs); EXPECT_SYSEQ(1, syscall(__NR_getpid), getpid()); break;
CASE_TEST(syscall_args); EXPECT_SYSER(1, syscall(__NR_fstat, 0, NULL), -1, EFAULT); break;
case __LINE__:
return ret; /* must be last */
/* note: do not set any defaults so as to permit holes above */