diff mbox series

[v5,11/14] tools/nolibc: clean up mmap() support

Message ID f054cd45de26bccb330ad842bc2b3b708b2a429d.1687957589.git.falcon@tinylab.org
State Superseded
Headers show
Series [v5,01/14] tools/nolibc: sys.h: add a syscall return helper | expand

Commit Message

Zhangjin Wu June 28, 2023, 1:41 p.m. UTC
Do several cleanups together:

- Since all supported architectures have my_syscall6() now, remove the
  #ifdef check.

- Move the mmap() related macros to tools/include/nolibc/types.h and
  reuse most of them from <linux/mman.h>

- Apply the new __sysret() to convert the calling of sys_map() to
  oneline code

Signed-off-by: Zhangjin Wu <falcon@tinylab.org>
---
 tools/include/nolibc/sys.h   | 24 +-----------------------
 tools/include/nolibc/types.h |  6 ++++++
 2 files changed, 7 insertions(+), 23 deletions(-)

Comments

Willy Tarreau July 2, 2023, 7:23 p.m. UTC | #1
On Wed, Jun 28, 2023 at 09:41:13PM +0800, Zhangjin Wu wrote:
>  static __attribute__((unused))
>  void *mmap(void *addr, size_t length, int prot, int flags, int fd, off_t offset)
>  {
> -	void *ret = sys_mmap(addr, length, prot, flags, fd, offset);
> -
> -	if ((unsigned long)ret >= -4095UL) {
> -		SET_ERRNO(-(long)ret);
> -		ret = MAP_FAILED;
> -	}
> -	return ret;
> +	return (void *)__sysret((unsigned long)sys_mmap(addr, length, prot, flags, fd, offset));
>  }

One point regarding this one. By doing so, we're hard-coding the fact
that we consider that MAP_FAILED is always -1. I'm not necessarily
against it, but this implication can be confusing for those searching
where it's being set. I would suggest putting a comment before the
mmap() function saying:

 /* Note that on Linux MAP_FAILED is -1 so we can use the generic __sysret()
  * which returns -1 upon error and still satisfy user land that checks for
  * MAP_FAILED.
  */

Since it's an assumed choice that theoretically could affect portability,
it should be reflected in the commit message as well (and we all know it
does not have any impact).

Thanks!
Willy
Zhangjin Wu July 3, 2023, 6:51 a.m. UTC | #2
> On Wed, Jun 28, 2023 at 09:41:13PM +0800, Zhangjin Wu wrote:
> >  static __attribute__((unused))
> >  void *mmap(void *addr, size_t length, int prot, int flags, int fd, off_t offset)
> >  {
> > -	void *ret = sys_mmap(addr, length, prot, flags, fd, offset);
> > -
> > -	if ((unsigned long)ret >= -4095UL) {
> > -		SET_ERRNO(-(long)ret);
> > -		ret = MAP_FAILED;
> > -	}
> > -	return ret;
> > +	return (void *)__sysret((unsigned long)sys_mmap(addr, length, prot, flags, fd, offset));
> >  }
> 
> One point regarding this one. By doing so, we're hard-coding the fact
> that we consider that MAP_FAILED is always -1. I'm not necessarily
> against it, but this implication can be confusing for those searching
> where it's being set. I would suggest putting a comment before the
> mmap() function saying:
> 
>  /* Note that on Linux MAP_FAILED is -1 so we can use the generic __sysret()
>   * which returns -1 upon error and still satisfy user land that checks for
>   * MAP_FAILED.
>   */
> 
> Since it's an assumed choice that theoretically could affect portability,
> it should be reflected in the commit message as well (and we all know it
> does not have any impact).
>

Yeah, we do need such a comment and commit message note, thanks.

Best regards,
Zhangjin

> Thanks!
> Willy
diff mbox series

Patch

diff --git a/tools/include/nolibc/sys.h b/tools/include/nolibc/sys.h
index b6125e600dc2..e0ac95a4bfa1 100644
--- a/tools/include/nolibc/sys.h
+++ b/tools/include/nolibc/sys.h
@@ -632,26 +632,11 @@  int mknod(const char *path, mode_t mode, dev_t dev)
 	return __sysret(sys_mknod(path, mode, dev));
 }
 
-#ifndef MAP_SHARED
-#define MAP_SHARED		0x01	/* Share changes */
-#define MAP_PRIVATE		0x02	/* Changes are private */
-#define MAP_SHARED_VALIDATE	0x03	/* share + validate extension flags */
-#endif
-
-#ifndef MAP_FAILED
-#define MAP_FAILED ((void *)-1)
-#endif
-
 #ifndef sys_mmap
 static __attribute__((unused))
 void *sys_mmap(void *addr, size_t length, int prot, int flags, int fd,
 	       off_t offset)
 {
-#ifndef my_syscall6
-	/* Function not implemented. */
-	return (void *)-ENOSYS;
-#else
-
 	int n;
 
 #if defined(__NR_mmap2)
@@ -662,20 +647,13 @@  void *sys_mmap(void *addr, size_t length, int prot, int flags, int fd,
 #endif
 
 	return (void *)my_syscall6(n, addr, length, prot, flags, fd, offset);
-#endif
 }
 #endif
 
 static __attribute__((unused))
 void *mmap(void *addr, size_t length, int prot, int flags, int fd, off_t offset)
 {
-	void *ret = sys_mmap(addr, length, prot, flags, fd, offset);
-
-	if ((unsigned long)ret >= -4095UL) {
-		SET_ERRNO(-(long)ret);
-		ret = MAP_FAILED;
-	}
-	return ret;
+	return (void *)__sysret((unsigned long)sys_mmap(addr, length, prot, flags, fd, offset));
 }
 
 static __attribute__((unused))
diff --git a/tools/include/nolibc/types.h b/tools/include/nolibc/types.h
index f96e28bff4ba..bed62da7877c 100644
--- a/tools/include/nolibc/types.h
+++ b/tools/include/nolibc/types.h
@@ -10,6 +10,7 @@ 
 #include "std.h"
 #include <linux/time.h>
 #include <linux/stat.h>
+#include <linux/mman.h>
 
 
 /* Only the generic macros and types may be defined here. The arch-specific
@@ -81,6 +82,11 @@ 
 #define MAXPATHLEN     (PATH_MAX)
 #endif
 
+/* flags for mmap */
+#ifndef MAP_FAILED
+#define MAP_FAILED ((void *)-1)
+#endif
+
 /* whence values for lseek() */
 #define SEEK_SET       0
 #define SEEK_CUR       1