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x86/fpu: Fix fpu__activate_fpstate_read() and update comments

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fpu__activate_fpstate_read() can be called for the current task
when coredumping - or for stopped tasks when ptrace-ing.

Implement this properly in the code and update the comments.

This also fixes an incorrect (but harmless) warning introduced by
one of the earlier patches.

Cc: Andrew Morton <[email protected]>
Cc: Andy Lutomirski <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: Dave Hansen <[email protected]>
Cc: Eric Biggers <[email protected]>
Cc: Fenghua Yu <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Oleg Nesterov <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Rik van Riel <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Yu-cheng Yu <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Ingo Molnar <[email protected]>
This commit is contained in:
Ingo Molnar 2017-09-23 15:00:10 +02:00
commit 4618e90965
1 changed files with 10 additions and 7 deletions
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17
arch/x86/kernel/fpu/core.c
View file

@ -254,18 +254,21 @@ EXPORT_SYMBOL_GPL(fpu__activate_curr);
/*
* This function must be called before we read a task's fpstate.
*
* If the task has not used the FPU before then initialize its
* fpstate.
* There's two cases where this gets called:
*
* - for the current task (when coredumping), in which case we have
* to save the latest FPU registers into the fpstate,
*
* - or it's called for stopped tasks (ptrace), in which case the
* registers were already saved by the context-switch code when
* the task scheduled out - we only have to initialize the registers
* if they've never been initialized.
*
* If the task has used the FPU before then save it.
*/
void fpu__activate_fpstate_read(struct fpu *fpu)
{
/*
* If fpregs are active (in the current CPU), then
* copy them to the fpstate:
*/
if (fpu->fpstate_active) {
if (fpu == &current->thread.fpu) {
fpu__save(fpu);
} else {
if (!fpu->fpstate_active) {