[PATCH 12/13] tools/nolibc: sys_wait4: riscv: use __NR_waitid for rv32

Zhangjin Wu
2023-05-24T18:02:40Z

rv32 uses the generic include/uapi/asm-generic/unistd.h and it has no
__NR_wait4 after kernel commit d4c08b9776b3 ("riscv: Use latest system
call ABI"), use __NR_waitid instead.

This code is based on sysdeps/unix/sysv/linux/wait4.c of glibc.

Notes: The kernel wait4 syscall has the 'pid == INT_MIN' path and
returns -ESRCH, but the kernel waitid syscall has no such path, to let
this __NR_waitid based sys_wait4 has the same return value and pass the
'waitpid_min' test, we emulate such path in our new nolibc __NR_waitid
branch.

Signed-off-by: Zhangjin Wu <falcon@tinylab.org>
---
tools/include/nolibc/sys.h | 54 ++++++++++++++++++++++++++++++++++++
tools/include/nolibc/types.h | 15 +++++++++-
2 files changed, 68 insertions(+), 1 deletion(-)

diff --git a/tools/include/nolibc/sys.h b/tools/include/nolibc/sys.h
index 00c7197dcd50..2642b380c6aa 100644
--- a/tools/include/nolibc/sys.h
+++ b/tools/include/nolibc/sys.h
@@ -12,6 +12,7 @@

/* system includes */
#include <asm/unistd.h>
+#include <asm/siginfo.h> /* for siginfo_t */
#include <asm/signal.h> /* for SIGCHLD */
#include <asm/ioctls.h>
#include <asm/mman.h>
@@ -1333,7 +1334,60 @@ int unlink(const char *path)
static __attribute__((unused))
pid_t sys_wait4(pid_t pid, int *status, int options, struct rusage *rusage)
{
+#ifdef __NR_wait4
return my_syscall4(__NR_wait4, pid, status, options, rusage);
+#elif defined(__NR_waitid)
+ siginfo_t infop;
+ int idtype = P_PID;
+ int ret;
+
+ /* emulate the 'pid == INT_MIN' path of wait4 */
+ if (pid == INT_MIN)
+ return -ESRCH;
+
+ if (pid < -1) {
+ idtype = P_PGID;
+ pid *= -1;
+ } else if (pid == -1) {
+ idtype = P_ALL;
+ } else if (pid == 0) {
+ idtype = P_PGID;
+ }
+
+ options |= WEXITED;
+
+ ret = my_syscall5(__NR_waitid, idtype, pid, &infop, options, rusage);
+ if (ret < 0)
+ return ret;
+
+ if (status) {
+ switch (infop.si_code) {
+ case CLD_EXITED:
+ *status = W_EXITCODE(infop.si_status, 0);
+ break;
+ case CLD_DUMPED:
+ *status = __WCOREFLAG | infop.si_status;
+ break;
+ case CLD_KILLED:
+ *status = infop.si_status;
+ break;
+ case CLD_TRAPPED:
+ case CLD_STOPPED:
+ *status = W_STOPCODE(infop.si_status);
+ break;
+ case CLD_CONTINUED:
+ *status = __W_CONTINUED;
+ break;
+ default:
+ *status = 0;
+ break;
+ }
+ }
+
+ return infop.si_pid;
+#else
+#error Neither __NR_wait4 nor __NR_waitid defined, cannot implement sys_wait4()
+#endif
}

static __attribute__((unused))
diff --git a/tools/include/nolibc/types.h b/tools/include/nolibc/types.h
index ee914391439c..c4f95c267607 100644
--- a/tools/include/nolibc/types.h
+++ b/tools/include/nolibc/types.h
@@ -92,8 +92,21 @@
#define WTERMSIG(status) ((status) & 0x7f)
#define WIFSIGNALED(status) ((status) - 1 < 0xff)

-/* waitpid() flags */
+/* waitpid() and waitid() flags */
#define WNOHANG 1
+#define WEXITED 0x00000004
+
+/* first argument for waitid() */
+#define P_ALL 0
+#define P_PID 1
+#define P_PGID 2
+#define P_PIDFD 3
+
+/* Macros used on waitid's status setting */
+#define W_EXITCODE(ret, sig) ((ret) << 8 | (sig))
+#define W_STOPCODE(sig) ((sig) << 8 | 0x7f)
+#define __W_CONTINUED 0xffff
+#define __WCOREFLAG 0x80

/* standard exit() codes */
#define EXIT_SUCCESS 0
--
2.25.1