Re: [PATCH v2 17/31] arm64: System calls handling

On Wed, Aug 15, 2012 at 03:22:16PM +0100, Arnd Bergmann wrote:

On Tuesday 14 August 2012, Catalin Marinas wrote:

quoted

+
+/* This matches struct stat64 in glibc2.1, hence the absolutely
+ * insane amounts of padding around dev_t's.
+ * Note: The kernel zero's the padded region because glibc might read them
+ * in the hope that the kernel has stretched to using larger sizes.
+ */
+struct stat64 {
+	compat_u64	st_dev;
+	unsigned char   __pad0[4];

The comment above struct stat64 is completely irrelevant here. I would instead
explain why you need your own stat64 in the first place.

OK, I added a comment. It's only needed for compat.

quoted

+int kernel_execve(const char *filename,
+		  const char *const argv[],
+		  const char *const envp[])

Al Viro was recently talking about a generic implementation of execve.
I can't find that now, but I think you should use that.

I've seen these but I'm waiting for the generic sys_execve and
kernel_execve to get into mainline before switch arch/arm64 to them.

quoted

+asmlinkage long sys_mmap(unsigned long addr, unsigned long len,
+			 unsigned long prot, unsigned long flags,
+			 unsigned long fd, off_t off)
+{
+	if (offset_in_page(off) != 0)
+		return -EINVAL;
+
+	return sys_mmap_pgoff(addr, len, prot, flags, fd, off >> PAGE_SHIFT);
+}

I think

#define sys_mmap sys_mmap_pgoff 

There are slightly different semantics with the last argument of
sys_mmap() which takes a byte offset. The sys_mmap_pgoff() function
takes the offset shifted by PAGE_SHIFT (which is the same as sys_mmap2).

Looking at the other architectures, it makes sense to use a generic
sys_mmap() implementation similar to the one above (or the ia-64, seems
to be the most complete).

-- 
Catalin