__hypercall_fast_ret1 trusts the contents of %o1 (too much)

[Jakub Jermář]

In the sun4v branch, there is:

  static inline uint64_t
__hypercall_fast_ret1(const uint64_t p1, const uint64_t p2, const uint64_t p3,
    const uint64_t p4, const uint64_t p5, const uint64_t function_number,
    uint64_t * const ret1)
{
	uint64_t errno = __hypercall_fast(p1, p2, p3, p4, p5, function_number);
	if (ret1 != NULL) {
		asm volatile ("mov %%o1, %0\n" : "=r" (*ret1));
	}
	return errno;
}

It seems like the asm statement is making unjustified assumptions about the register %o1. %o1 is a scratch register and the function can do pretty much anything with it between the call to __hypercall_fast() and the asm statement.

Noticed by Petr Tuma.

[Jakub Jermář]

Fixed in changeset:head,303.