ltp_clone

Hello,

The definition of ltp_clone looks like this:

int
ltp_clone(unsigned long clone_flags, int (*fn)(void *arg), void *arg,
size_t stack_size, void *stack)

{
	int ret;

#if defined(__hppa__)
	ret = clone(fn, stack, clone_flags, arg);
#elif defined(__ia64__)
	ret = clone2(fn, stack, stack_size, clone_flags, arg, NULL, NULL, NULL);
#elif defined(__arm__)
	/*
	 * Stack size should be a multiple of 32 bit words
	 * & stack limit must be aligned to a 32 bit boundary
	 */
	ret = clone(fn, (stack ? stack + stack_size : NULL),
			clone_flags, arg);
#else
	ret = clone(fn, (stack ? stack + stack_size - 1 : NULL),
			clone_flags, arg);

#endif

	return ret;
}

I believe the __arm__ case is to ensure that we pass an aligned stack pointer to the syscall (as required by the architecture). What I don't understand, is why we pass an unaligned address in the #else case? Given that a stack push decrements the sp before writing on every architecture I know of, it seems that the __arm__ case should be used as the default rather than forcing a misaligned stack on other architectures.

Will

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Hi,

have you fetched the latest from the git tree:
git://ltp.git.sourceforge.net/gitroot/ltp/ltp ?

Lines are:

int
ltp_clone(unsigned long clone_flags, int (*fn)(void *arg), void *arg,
size_t stack_size, void *stack)

{
        int ret;

#if defined(__hppa__)
        ret = clone(fn, stack, clone_flags, arg);

#elif defined(__ia64__)
ret = clone2(fn, stack, stack_size, clone_flags, arg, NULL, NULL,
NULL);
#else
/*
* For archs where stack grows downwards, stack points to the topmost
* address of the memory space set up for the child stack. */
ret = clone(fn, (stack ? stack + stack_size : NULL),
clone_flags, arg);
#endif

        return ret;
}

br,
Hannu

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Hi Hannu,

Wahey - that's much better! I was accidently looking in my checkout of the October stable release, where ARM is special-cased.

Thanks for pointing this out.

Will

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