Re: [PATCH] Return real errno from execve in ____call_usermodehelper

From: Björn Steinbrink
Date: Sun Aug 20 2006 - 09:45:23 EST

On 2006.08.20 15:01:28 +0200, Arnd Bergmann wrote:
> On Saturday 19 August 2006 10:42, Russell King wrote:
> > Maybe what we should be thinking of doing is changing execve() calls
> > to kernel_execve() which returns the error code.
> >
> > This way, architectures are free to implement execve() whatever way
> > they wish - and if they're concerned about using errno, that's their
> > own implementation specific detail.
> Sounds good, it means we could finally kill __KERNEL_SYSCALLS__ along
> with lib/errno.c.
> I guess a fallback for those that haven't yet done kernel_execve could be
> extern int kernel_execve(const char *filename,
> char *const argv[], char *const envp[]);
> #else
> static inline int kernel_execve(const char *filename,
> char *const argv[], char *const envp[]);
> {
> int errno;
> mm_segment_t old_fs = get_fs();
> set_fs(KERNEL_DS);
> /* the kernel syscall macro modifies errno */
> execve(filename, argv, envp);
> set_fs(old_fs);
> return errno;
> }
> #endif
> With that in place, we can remove the global errno right away, and the
> kernel syscalls for any architecture that implements its own kernel_execve.

How is execve() supposed to use the local errno? The kernel syscall
macro only "creates" a function, so you still need a global errno for
that code, don't you?

And I (because I'm clueless ;) wonder about the calls to set_fs(), why
do we need them? The current code does not seem to do them. Or is there
something special about kernel_execve that I'm missing? cscope and grep
didn't tell anything and Google had only a few useless results for

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