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authorFelipe Rechia <felipe.rechia@datacom.com.br>2018-10-24 10:57:22 -0300
committerMichael Ellerman <mpe@ellerman.id.au>2018-10-26 21:58:58 +1100
commite901378578c62202594cba0f6c076f3df365ec91 (patch)
tree1b16ca7e9f1075a5cc6104c3650e93e87d844c83 /arch
parent8dce6b2215eaa91dbf04463e11098a48748da5ab (diff)
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')
-rw-r--r--arch/powerpc/kernel/process.c3
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();
}