[PATCH v2 0/4] tools/nolibc: cleanups for syscall fallbacks

[PATCH v2 0/4] tools/nolibc: cleanups for syscall fallbacks

[Thomas Weißschuh]

Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
---
Changes in v2:
- Replace manual casts to (void) with __nolibc_enosys helpers
- Link to v1: https://lore.kernel.org/r/20230914-nolibc-syscall-nr-v1-0-e50df410da11@weissschuh.net

---
Thomas Weißschuh (4):
      selftests/nolibc: allow building i386 with multiarch compiler
      tools/nolibc: avoid unused parameter warnings for ENOSYS fallbacks
      tools/nolibc: don't define new syscall number
      tools/nolibc: automatically detect necessity to use pselect6

 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              | 55 +++++++++++++++++++--------------
 tools/testing/selftests/nolibc/Makefile |  1 +
 5 files changed, 34 insertions(+), 32 deletions(-)
---
base-commit: 3f79a57865b33f49fdae6655510bd27c8e6610e0
change-id: 20230914-nolibc-syscall-nr-9a5f544c8494

Best regards,
-- 
Thomas Weißschuh <linux@weissschuh.net>


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[PATCH v2 1/4] selftests/nolibc: allow building i386 with multiarch compiler

[Thomas Weißschuh]

When building with a multiarch-capable compiler, like those provided by
common distributions the -m32 argument is required to build 32bit code.

Wrap it in cc-option in case the compiler is not multiarch-capable.

Acked-by: Willy Tarreau <w@1wt.eu>
Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
---
 tools/testing/selftests/nolibc/Makefile | 1 +
 1 file changed, 1 insertion(+)

diff --git a/tools/testing/selftests/nolibc/Makefile b/tools/testing/selftests/nolibc/Makefile
index 689658f81a19..19096a9ded55 100644
--- a/tools/testing/selftests/nolibc/Makefile
+++ b/tools/testing/selftests/nolibc/Makefile
@@ -113,6 +113,7 @@ else
 Q=@
 endif
 
+CFLAGS_i386 = $(call cc-option,-m32)
 CFLAGS_ppc = -m32 -mbig-endian -mno-vsx $(call cc-option,-mmultiple)
 CFLAGS_ppc64 = -m64 -mbig-endian -mno-vsx $(call cc-option,-mmultiple)
 CFLAGS_ppc64le = -m64 -mlittle-endian -mno-vsx $(call cc-option,-mabi=elfv2)

-- 
2.42.0


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[PATCH v2 2/4] tools/nolibc: avoid unused parameter warnings for ENOSYS fallbacks

[Thomas Weißschuh]

The ENOSYS fallback code does not use its functions parameters.
This can lead to compiler warnings about unused parameters.

Explicitly avoid these warnings.

Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
---
 tools/include/nolibc/sys.h | 44 +++++++++++++++++++++++++++-----------------
 1 file changed, 27 insertions(+), 17 deletions(-)

diff --git a/tools/include/nolibc/sys.h b/tools/include/nolibc/sys.h
index b478750c9004..8389820e1928 100644
--- a/tools/include/nolibc/sys.h
+++ b/tools/include/nolibc/sys.h
@@ -43,6 +43,16 @@
 		: __sysret_arg;                         /* return original value */ \
 })
 
+/* Syscall ENOSYS helper: Avoids unused-parameter warnings and provides a
+ * debugging hook.
+ */
+
+static __inline__ int __nolibc_enosys(const char *syscall, ...)
+{
+	(void)syscall;
+	return -ENOSYS;
+}
+
 
 /* Functions in this file only describe syscalls. They're declared static so
  * that the compiler usually decides to inline them while still being allowed
@@ -133,7 +143,7 @@ int sys_chmod(const char *path, mode_t mode)
 #elif defined(__NR_chmod)
 	return my_syscall2(__NR_chmod, path, mode);
 #else
-	return -ENOSYS;
+	return __nolibc_enosys(__func__, path, mode);
 #endif
 }
 
@@ -156,7 +166,7 @@ int sys_chown(const char *path, uid_t owner, gid_t group)
 #elif defined(__NR_chown)
 	return my_syscall3(__NR_chown, path, owner, group);
 #else
-	return -ENOSYS;
+	return __nolibc_enosys(__func__, path, owner, group);
 #endif
 }
 
@@ -230,7 +240,7 @@ int sys_dup2(int old, int new)
 #elif defined(__NR_dup2)
 	return my_syscall2(__NR_dup2, old, new);
 #else
-	return -ENOSYS;
+	return __nolibc_enosys(__func__, old, new);
 #endif
 }
 
@@ -312,7 +322,7 @@ pid_t sys_fork(void)
 #elif defined(__NR_fork)
 	return my_syscall0(__NR_fork);
 #else
-	return -ENOSYS;
+	return __nolibc_enosys(__func__);
 #endif
 }
 #endif
@@ -486,7 +496,7 @@ int sys_gettimeofday(struct timeval *tv, struct timezone *tz)
 #ifdef __NR_gettimeofday
 	return my_syscall2(__NR_gettimeofday, tv, tz);
 #else
-	return -ENOSYS;
+	return __nolibc_enosys(__func__, tv, tz);
 #endif
 }
 
@@ -563,7 +573,7 @@ int sys_link(const char *old, const char *new)
 #elif defined(__NR_link)
 	return my_syscall2(__NR_link, old, new);
 #else
-	return -ENOSYS;
+	return __nolibc_enosys(__func__, old, new);
 #endif
 }
 
@@ -584,7 +594,7 @@ off_t sys_lseek(int fd, off_t offset, int whence)
 #ifdef __NR_lseek
 	return my_syscall3(__NR_lseek, fd, offset, whence);
 #else
-	return -ENOSYS;
+	return __nolibc_enosys(__func__, fd, offset, whence);
 #endif
 }
 
@@ -607,7 +617,7 @@ int sys_mkdir(const char *path, mode_t mode)
 #elif defined(__NR_mkdir)
 	return my_syscall2(__NR_mkdir, path, mode);
 #else
-	return -ENOSYS;
+	return __nolibc_enosys(__func__, path, mode);
 #endif
 }
 
@@ -629,7 +639,7 @@ int sys_rmdir(const char *path)
 #elif defined(__NR_unlinkat)
 	return my_syscall3(__NR_unlinkat, AT_FDCWD, path, AT_REMOVEDIR);
 #else
-	return -ENOSYS;
+	return __nolibc_enosys(__func__, path);
 #endif
 }
 
@@ -652,7 +662,7 @@ long sys_mknod(const char *path, mode_t mode, dev_t dev)
 #elif defined(__NR_mknod)
 	return my_syscall3(__NR_mknod, path, mode, dev);
 #else
-	return -ENOSYS;
+	return __nolibc_enosys(__func__, path, mode, dev);
 #endif
 }
 
@@ -742,7 +752,7 @@ int sys_open(const char *path, int flags, mode_t mode)
 #elif defined(__NR_open)
 	return my_syscall3(__NR_open, path, flags, mode);
 #else
-	return -ENOSYS;
+	return __nolibc_enosys(__func__, path, flags, mode);
 #endif
 }
 
@@ -842,7 +852,7 @@ int sys_poll(struct pollfd *fds, int nfds, int timeout)
 #elif defined(__NR_poll)
 	return my_syscall3(__NR_poll, fds, nfds, timeout);
 #else
-	return -ENOSYS;
+	return __nolibc_enosys(__func__, fds, nfds, timeout);
 #endif
 }
 
@@ -934,7 +944,7 @@ int sys_select(int nfds, fd_set *rfds, fd_set *wfds, fd_set *efds, struct timeva
 #endif
 	return my_syscall5(__NR__newselect, nfds, rfds, wfds, efds, timeout);
 #else
-	return -ENOSYS;
+	return __nolibc_enosys(__func__, nfds, rfds, wfds, efds, timeout);
 #endif
 }
 
@@ -989,7 +999,7 @@ int sys_statx(int fd, const char *path, int flags, unsigned int mask, struct sta
 #ifdef __NR_statx
 	return my_syscall5(__NR_statx, fd, path, flags, mask, buf);
 #else
-	return -ENOSYS;
+	return __nolibc_enosys(__func__, fd, path, flags, mask, buf);
 #endif
 }
 
@@ -1047,7 +1057,7 @@ int sys_symlink(const char *old, const char *new)
 #elif defined(__NR_symlink)
 	return my_syscall2(__NR_symlink, old, new);
 #else
-	return -ENOSYS;
+	return __nolibc_enosys(__func__, old, new);
 #endif
 }
 
@@ -1104,7 +1114,7 @@ int sys_unlink(const char *path)
 #elif defined(__NR_unlink)
 	return my_syscall1(__NR_unlink, path);
 #else
-	return -ENOSYS;
+	return __nolibc_enosys(__func__, path);
 #endif
 }
 
@@ -1127,7 +1137,7 @@ 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);
 #else
-	return -ENOSYS;
+	return __nolibc_enosys(__func__, pid, status, options, rusage);
 #endif
 }
 

-- 
2.42.0


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[PATCH v2 3/4] tools/nolibc: don't define new syscall number

[Thomas Weißschuh]

All symbols created by nolibc are also visible to user code.
Syscall constants are expected to come from the kernel headers and
should not be made up by nolibc.

Refactor the logic to avoid defining syscall numbers.
Also the new code is easier to understand.

Acked-by: Willy Tarreau <w@1wt.eu>
Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
---
 tools/include/nolibc/sys.h | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/tools/include/nolibc/sys.h b/tools/include/nolibc/sys.h
index 8389820e1928..f05144e46b67 100644
--- a/tools/include/nolibc/sys.h
+++ b/tools/include/nolibc/sys.h
@@ -938,11 +938,10 @@ 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) || defined(__NR_select)
-#ifndef __NR__newselect
-#define __NR__newselect __NR_select
-#endif
+#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
 	return __nolibc_enosys(__func__, nfds, rfds, wfds, efds, timeout);
 #endif

-- 
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[PATCH v2 4/4] tools/nolibc: automatically detect necessity to use pselect6

[Thomas Weißschuh]

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

Acked-by: Willy Tarreau <w@1wt.eu>
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 f05144e46b67..2f359cb03d10 100644
--- a/tools/include/nolibc/sys.h
+++ b/tools/include/nolibc/sys.h
@@ -930,7 +930,11 @@ 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) {
@@ -938,10 +942,6 @@ 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
 	return __nolibc_enosys(__func__, nfds, rfds, wfds, efds, timeout);
 #endif

-- 
2.42.0


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Re: [PATCH v2 2/4] tools/nolibc: avoid unused parameter warnings for ENOSYS fallbacks

[Willy Tarreau]

Hi Thomas,

On Sun, Sep 17, 2023 at 05:36:17PM +0200, Thomas Weißschuh wrote:
> The ENOSYS fallback code does not use its functions parameters.
> This can lead to compiler warnings about unused parameters.
> 
> Explicitly avoid these warnings.
> 
> Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
> ---
>  tools/include/nolibc/sys.h | 44 +++++++++++++++++++++++++++-----------------
>  1 file changed, 27 insertions(+), 17 deletions(-)
> 
> diff --git a/tools/include/nolibc/sys.h b/tools/include/nolibc/sys.h
> index b478750c9004..8389820e1928 100644
> --- a/tools/include/nolibc/sys.h
> +++ b/tools/include/nolibc/sys.h
> @@ -43,6 +43,16 @@
>  		: __sysret_arg;                         /* return original value */ \
>  })
>  
> +/* Syscall ENOSYS helper: Avoids unused-parameter warnings and provides a
> + * debugging hook.
> + */
> +
> +static __inline__ int __nolibc_enosys(const char *syscall, ...)
> +{
> +	(void)syscall;
> +	return -ENOSYS;
> +}
> +
>  
>  /* Functions in this file only describe syscalls. They're declared static so
>   * that the compiler usually decides to inline them while still being allowed
> @@ -133,7 +143,7 @@ int sys_chmod(const char *path, mode_t mode)
>  #elif defined(__NR_chmod)
>  	return my_syscall2(__NR_chmod, path, mode);
>  #else
> -	return -ENOSYS;
> +	return __nolibc_enosys(__func__, path, mode);
>  #endif
>  }
(...)

It's much cleaner like this.

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

Feel free to push the whole series to the next branch.

Thank you!
Willy

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Re: [PATCH v2 2/4] tools/nolibc: avoid unused parameter warnings for ENOSYS fallbacks

[Thomas Weißschuh]

On 2023-09-18 18:19:15+0200, Willy Tarreau wrote:
> Hi Thomas,
> 
> On Sun, Sep 17, 2023 at 05:36:17PM +0200, Thomas Weißschuh wrote:
> > The ENOSYS fallback code does not use its functions parameters.
> > This can lead to compiler warnings about unused parameters.
> > 
> > Explicitly avoid these warnings.
> > 
> > Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>

> [..]

> It's much cleaner like this.
> 
> Acked-by: Willy Tarreau <w@1wt.eu>
> 
> Feel free to push the whole series to the next branch.

I pushed all three recent series' to the next branch.

Thomas

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