Messages in this thread | | | Date | Thu, 9 Mar 2006 19:22:32 -0800 | From | Andrew Morton <> | Subject | Re: [PATCH 1/1] x86: Make _syscallX() macros compile in PIC mode on i386 |
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Markus Gutschke <markus@google.com> wrote: > > Andrew Morton wrote: > > But we don't compile the kernel with -fpic... We might want to, for kdump > > convenience at some stage, perhaps. > > Unless I am really confused, there should be no place in the kernel that > uses any of the _syscallX() macros. These macros are for the benefit of > userspace, and they get picked up by and distributed with glibc. They > just happen to be shipped and maintained with the kernel.
Nope, there's an int-80-based execve() implemented in include/asm-i386/unistd.h. It's called from init/do_mounts_initrd.c and kernel/kmod.c (at least).
> > If we do, it'd be better to simply replace those _syscallX functions with > > versions which work in either mode, rather than having two versions. > > That is certainly possible. The new macros work in both modes, but they > are slightly less efficient than the old macros, if you have access to > %ebx (i.e. in non-PIC code). If you prefer, we could just remove the old > macros and unconditionally replace them with the new ones.
I'd be OK with that - the kernel doesn't (shouldn't) care about the performance of __KERNEL_SYSCALLS__ stuff. I doubt if glibc is borrowing the kernel's macros.
> > The syscallX() macros are almost obsolete - it's preferred that code simply > > include syscalls.h and call sys_foo() directly. But there are a few > > hard-to-convert places, iirc. > > Are you thinking of the code that jumps through the vdso entry point? > That is not always an easy option for user-space applications which need > to remain backwards compatible to older versions of the kernel and of libc. >
afaik, execve() is the only reason for retaining __KERNEL_SYSCALLS__ support on x86. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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