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authorIngo Molnar <[email protected]>2017-09-23 15:00:10 +0200
committerIngo Molnar <[email protected]>2017-09-26 09:41:09 +0200
commit4618e90965f272fe522f2af2523a60d0d4bc78f3 (patch)
tree22ca3f235053f90f117ff401f9622c4896ce08b6
parentd5c8028b4788f62b31fb79a331b3ad3e041fa366 (diff)
x86/fpu: Fix fpu__activate_fpstate_read() and update comments
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]>
-rw-r--r--arch/x86/kernel/fpu/core.c17
1 files changed, 10 insertions, 7 deletions
diff --git a/arch/x86/kernel/fpu/core.c b/arch/x86/kernel/fpu/core.c
index 93103a909c47..afd3f2a5c64e 100644
--- a/arch/x86/kernel/fpu/core.c
+++ b/arch/x86/kernel/fpu/core.c
@@ -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) {