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

[Zhangjin Wu]

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@xxxxxxxxxxx>
---
 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