klibc - Oct 2024 - [klibc:master] syscalls: Clean up the fork() and clone() definitions

Commit-ID:  ccfcaca5bb151e8c2ddc3cd99172dea98429278a
Gitweb:    
http://git.kernel.org/?p=libs/klibc/klibc.git;a=commit;h=ccfcaca5bb151e8c2ddc3cd99172dea98429278a
Author:     Ben Hutchings <ben at decadent.org.uk>
AuthorDate: Tue, 1 Oct 2024 23:04:45 +0200
Committer:  Ben Hutchings <ben at decadent.org.uk>
CommitDate: Wed, 2 Oct 2024 02:07:27 +0200

[klibc] syscalls: Clean up the fork() and clone() definitions

Currently we're defining __clone() on all architectures, but it's only
needed where fork() is missing and it's broken on s390 and s390x where
the parameter order is incompatible.

We're also building a list of new architectures which don't implement
fork(), when we could automatically detect that.

To fix these problems:

- If __NR_fork is defined, generate a fork() system call wrapper, with
  only sparc and sparc64 as special cases.

- Otherwise, generate __clone() as a clone() system call wrapper.
  Comment why this works despite the architecture differences.

Signed-off-by: Ben Hutchings <ben at decadent.org.uk>

---
 usr/klibc/SYSCALLS.def | 12 ++++++++++--
 usr/klibc/fork.c       |  4 ++--
 2 files changed, 12 insertions(+), 4 deletions(-)

diff --git a/usr/klibc/SYSCALLS.def b/usr/klibc/SYSCALLS.def
index 65cf1c2e..e0f8895b 100644
--- a/usr/klibc/SYSCALLS.def
+++ b/usr/klibc/SYSCALLS.def
@@ -18,9 +18,17 @@
  * Process-related syscalls
  */
 void _exit,exit::_exit(int);
-<?> pid_t clone::__clone(unsigned long, void *);
-<!sparc,sparc64,arm64,riscv64,loongarch64> pid_t fork();
+#ifdef __NR_fork
+<!sparc,sparc64> pid_t fork();
 <sparc,sparc64> pid_t fork at forkish();
+#else
+/*
+ * The clone() parameter order varies between architectures.  However,
+ * the first 2 are always clone_flags and newsp, except on s390/s390x
+ * where we have fork() and do not use clone().
+ */
+pid_t clone::__clone(unsigned long, void *);
+#endif
 #if _KLIBC_REAL_VFORK
 /*
  * A lot of architectures need architecture-specific vfork
diff --git a/usr/klibc/fork.c b/usr/klibc/fork.c
index f5c5d753..bc0f3755 100644
--- a/usr/klibc/fork.c
+++ b/usr/klibc/fork.c
@@ -1,8 +1,8 @@
 /*
  * fork.c
  *
- * This is normally just a syscall stub, but at least one system
- * doesn't have sys_fork, only sys_clone...
+ * This is normally just a syscall stub, but new architectures only
+ * implement clone().
  */
 
 #include <sys/syscall.h>