We can automatically detect if pselect6 is needed or not from the kernel
headers. This removes the need to manually specify it.

Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
---
 tools/include/nolibc/arch-aarch64.h   |  3 ---
 tools/include/nolibc/arch-loongarch.h |  4 +---
 tools/include/nolibc/arch-riscv.h     |  3 ---
 tools/include/nolibc/sys.h            | 10 +++++-----
 4 files changed, 6 insertions(+), 14 deletions(-)

diff --git a/tools/include/nolibc/arch-aarch64.h b/tools/include/nolibc/arch-aarch64.h
index 6c33c46848e3..b23ac1f04035 100644
--- a/tools/include/nolibc/arch-aarch64.h
+++ b/tools/include/nolibc/arch-aarch64.h
@@ -20,10 +20,7 @@
  *   - the arguments are cast to long and assigned into the target registers
  *     which are then simply passed as registers to the asm code, so that we
  *     don't have to experience issues with register constraints.
- *
- * On aarch64, select() is not implemented so we have to use pselect6().
  */
-#define __ARCH_WANT_SYS_PSELECT6
 
 #define my_syscall0(num)                                                      \
 ({                                                                            \
diff --git a/tools/include/nolibc/arch-loongarch.h b/tools/include/nolibc/arch-loongarch.h
index bf98f6220195..3f8ef8f86c0f 100644
--- a/tools/include/nolibc/arch-loongarch.h
+++ b/tools/include/nolibc/arch-loongarch.h
@@ -19,10 +19,8 @@
  *   - the arguments are cast to long and assigned into the target
  *     registers which are then simply passed as registers to the asm code,
  *     so that we don't have to experience issues with register constraints.
- *
- * On LoongArch, select() is not implemented so we have to use pselect6().
  */
-#define __ARCH_WANT_SYS_PSELECT6
+
 #define _NOLIBC_SYSCALL_CLOBBERLIST \
 	"memory", "$t0", "$t1", "$t2", "$t3", "$t4", "$t5", "$t6", "$t7", "$t8"
 
diff --git a/tools/include/nolibc/arch-riscv.h b/tools/include/nolibc/arch-riscv.h
index 950cc2283fd7..1927c643c739 100644
--- a/tools/include/nolibc/arch-riscv.h
+++ b/tools/include/nolibc/arch-riscv.h
@@ -19,10 +19,7 @@
  *   - the arguments are cast to long and assigned into the target
  *     registers which are then simply passed as registers to the asm code,
  *     so that we don't have to experience issues with register constraints.
- *
- * On riscv, select() is not implemented so we have to use pselect6().
  */
-#define __ARCH_WANT_SYS_PSELECT6
 
 #define my_syscall0(num)                                                      \
 ({                                                                            \
diff --git a/tools/include/nolibc/sys.h b/tools/include/nolibc/sys.h
index d96f2aa7d987..dbf5cc92181b 100644
--- a/tools/include/nolibc/sys.h
+++ b/tools/include/nolibc/sys.h
@@ -946,7 +946,11 @@ int sys_select(int nfds, fd_set *rfds, fd_set *wfds, fd_set *efds, struct timeva
 		struct timeval *t;
 	} arg = { .n = nfds, .r = rfds, .w = wfds, .e = efds, .t = timeout };
 	return my_syscall1(__NR_select, &arg);
-#elif defined(__ARCH_WANT_SYS_PSELECT6) && defined(__NR_pselect6)
+#elif defined(__NR__newselect)
+	return my_syscall5(__NR__newselect, nfds, rfds, wfds, efds, timeout);
+#elif defined(__NR_select)
+	return my_syscall5(__NR_select, nfds, rfds, wfds, efds, timeout);
+#elif defined(__NR_pselect6)
 	struct timespec t;
 
 	if (timeout) {
@@ -954,10 +958,6 @@ int sys_select(int nfds, fd_set *rfds, fd_set *wfds, fd_set *efds, struct timeva
 		t.tv_nsec = timeout->tv_usec * 1000;
 	}
 	return my_syscall6(__NR_pselect6, nfds, rfds, wfds, efds, timeout ? &t : NULL, NULL);
-#elif defined(__NR__newselect)
-	return my_syscall5(__NR__newselect, nfds, rfds, wfds, efds, timeout);
-#elif defined(__NR_select)
-	return my_syscall5(__NR_select, nfds, rfds, wfds, efds, timeout);
 #else
 	(void)nfds;
 	(void)rfds;

-- 
2.42.0

On Thu, Sep 14, 2023 at 06:01:20PM +0200, Thomas Weißschuh wrote:
> We can automatically detect if pselect6 is needed or not from the kernel
> headers. This removes the need to manually specify it.
> 
> Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>

That's indeed cleaner, I can't find the reason why we didn't do it
like this initially, I suspect that maybe we were having __NR_select
defined but not usable, I don't know. I've found it first introduced with
nolibc commit 28a7178 ("nolibc: fall back to pselect6() on aarch64"), and
the test was made before __NR_newselect, so maybe I wanted to be sure not
to use pselect6() in case another arch would define it.

Let's do as you propose, it's much cleaner and simpler. If we ever find
any breakage at least we'll know how to deal with it so I'm not worried.

Acked-by: Willy Tarreau <w@1wt.eu>

Thanks!
Willy