[PATCH liburing 1/3] arch/syscall-defs: Use `__NR_mmap2` instead of `__NR_mmap` for x86 32-bit

[Ammar Faizi <ammarfaizi2@gnuweeb.org>]

A preparation to add x86 32-bit native syscall support for the nolibc
build. On x86 32-bit, the __NR_mmap maps to sys_old_mmap:

  long sys_old_mmap(struct mmap_arg_struct __user *arg);

which only receives one argument and is not suitable with the canonical
mmap() definition we use. As such, use __NR_mmap2 that maps to
sys_mmap_pgoff:

  long sys_mmap_pgoff(unsigned long addr, unsigned long len,
                      unsigned long prot, unsigned long flags,
                      unsigned long fd, unsigned long pgoff);

Note: For __NR_mmap2, the offset must be shifted-right by 12-bit.

Co-authored-by: Alviro Iskandar Setiawan <alviro.iskandar@gnuweeb.org>
Signed-off-by: Alviro Iskandar Setiawan <alviro.iskandar@gnuweeb.org>
Signed-off-by: Ammar Faizi <ammarfaizi2@gnuweeb.org>
---
 src/arch/syscall-defs.h | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/src/arch/syscall-defs.h b/src/arch/syscall-defs.h
index f79f56a..1e8ae1b 100644
--- a/src/arch/syscall-defs.h
+++ b/src/arch/syscall-defs.h
@@ -6,8 +6,15 @@
 static inline void *__sys_mmap(void *addr, size_t length, int prot, int flags,
 			       int fd, off_t offset)
 {
-	return (void *) __do_syscall6(__NR_mmap, addr, length, prot, flags, fd,
-				      offset);
+	int nr;
+
+#if defined(__i386__)
+	nr = __NR_mmap2;
+	offset >>= 12;
+#else
+	nr = __NR_mmap;
+#endif
+	return (void *) __do_syscall6(nr, addr, length, prot, flags, fd, offset);
 }
 
 static inline int __sys_munmap(void *addr, size_t length)
-- 
Ammar Faizi