Commit bad94163 authored by Anton Blanchard's avatar Anton Blanchard Committed by Luis Henriques

powerpc: do_notify_resume can be called with bad thread_info flags argument

commit 808be314 upstream.

Back in 7230c564 ("powerpc: Rework lazy-interrupt handling") we
added a call out to restore_interrupts() (written in c) before calling
do_notify_resume:

        bl      restore_interrupts
        addi    r3,r1,STACK_FRAME_OVERHEAD
        bl      do_notify_resume

Unfortunately do_notify_resume takes two arguments, the second one
being the thread_info flags:

void do_notify_resume(struct pt_regs *regs, unsigned long thread_info_flags)

We do populate r4 (the second argument) earlier, but
restore_interrupts() is free to muck it up all it wants. My guess is
the gcc compiler gods shone down on us and its register allocator
never used r4. Sometimes, rarely, luck is on our side.

LLVM on the other hand did trample r4.
Signed-off-by: default avatarAnton Blanchard <anton@samba.org>
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
Signed-off-by: default avatarLuis Henriques <luis.henriques@canonical.com>
parent 90491745
...@@ -663,7 +663,13 @@ _GLOBAL(ret_from_except_lite) ...@@ -663,7 +663,13 @@ _GLOBAL(ret_from_except_lite)
3: 3:
#endif #endif
bl save_nvgprs bl save_nvgprs
/*
* Use a non volatile GPR to save and restore our thread_info flags
* across the call to restore_interrupts.
*/
mr r30,r4
bl restore_interrupts bl restore_interrupts
mr r4,r30
addi r3,r1,STACK_FRAME_OVERHEAD addi r3,r1,STACK_FRAME_OVERHEAD
bl do_notify_resume bl do_notify_resume
b ret_from_except b ret_from_except
......
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