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From: Ammar Faizi <[email protected]>
To: Jens Axboe <[email protected]>
Cc: Ammar Faizi <[email protected]>,
	io-uring Mailing List <[email protected]>,
	GNU/Weeb Mailing List <[email protected]>,
	Pavel Begunkov <[email protected]>,
	Alviro Iskandar Setiawan <[email protected]>
Subject: [PATCH liburing 1/3] arch/syscall-defs: Use `__NR_mmap2` instead of `__NR_mmap` for x86 32-bit
Date: Fri, 15 Apr 2022 05:41:38 +0700	[thread overview]
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>

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 <[email protected]>
Signed-off-by: Alviro Iskandar Setiawan <[email protected]>
Signed-off-by: Ammar Faizi <[email protected]>
---
 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


  reply	other threads:[~2022-04-14 22:42 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-04-14 22:41 [PATCH liburing 0/3] Add x86 32-bit support for the nolibc build Ammar Faizi
2022-04-14 22:41 ` Ammar Faizi [this message]
2022-04-14 22:41 ` [PATCH liburing 2/3] arch/x86/lib: Provide `get_page_size()` function for x86 32-bit Ammar Faizi
2022-04-14 22:41 ` [PATCH liburing 3/3] arch/x86/syscall: Add x86 32-bit native syscall support Ammar Faizi
2022-04-18  2:01 ` [PATCH liburing 0/3] Add x86 32-bit support for the nolibc build Jens Axboe
2022-04-18 14:14   ` Ammar Faizi
2022-04-18 15:23     ` Jens Axboe
2022-04-18 15:24 ` Jens Axboe

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