diff options
| author | Felipe Rechia <felipe.rechia@datacom.com.br> | 2018-10-24 16:57:22 +0300 |
|---|---|---|
| committer | Michael Ellerman <mpe@ellerman.id.au> | 2018-10-26 13:58:58 +0300 |
| commit | e901378578c62202594cba0f6c076f3df365ec91 (patch) | |
| tree | 1b16ca7e9f1075a5cc6104c3650e93e87d844c83 /arch/powerpc | |
| parent | 8dce6b2215eaa91dbf04463e11098a48748da5ab (diff) | |
| download | linux-e901378578c62202594cba0f6c076f3df365ec91.tar.xz | |
powerpc/process: Fix flush_all_to_thread for SPE
Fix a bug introduced by the creation of flush_all_to_thread() for
processors that have SPE (Signal Processing Engine) and use it to
compute floating-point operations.
>From userspace perspective, the problem was seen in attempts of
computing floating-point operations which should generate exceptions.
For example:
fork();
float x = 0.0 / 0.0;
isnan(x); // forked process returns False (should be True)
The operation above also should always cause the SPEFSCR FINV bit to
be set. However, the SPE floating-point exceptions were turned off
after a fork().
Kernel versions prior to the bug used flush_spe_to_thread(), which
first saves SPEFSCR register values in tsk->thread and then calls
giveup_spe(tsk).
After commit 579e633e764e, the save_all() function was called first
to giveup_spe(), and then the SPEFSCR register values were saved in
tsk->thread. This would save the SPEFSCR register values after
disabling SPE for that thread, causing the bug described above.
Fixes 579e633e764e ("powerpc: create flush_all_to_thread()")
Signed-off-by: Felipe Rechia <felipe.rechia@datacom.com.br>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Diffstat (limited to 'arch/powerpc')
| -rw-r--r-- | arch/powerpc/kernel/process.c | 3 |
1 files changed, 1 insertions, 2 deletions
diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c index 7ad304a3cc7d..bcb36229d4fd 100644 --- a/arch/powerpc/kernel/process.c +++ b/arch/powerpc/kernel/process.c @@ -590,12 +590,11 @@ void flush_all_to_thread(struct task_struct *tsk) if (tsk->thread.regs) { preempt_disable(); BUG_ON(tsk != current); - save_all(tsk); - #ifdef CONFIG_SPE if (tsk->thread.regs->msr & MSR_SPE) tsk->thread.spefscr = mfspr(SPRN_SPEFSCR); #endif + save_all(tsk); preempt_enable(); } |