There are two tacit assumptions in the FPSIMD handling code that will no longer
hold after the next patch that optimizes away some FPSIMD state restores:
. the FPSIMD registers of this CPU contain the userland FPSIMD state of
task 'current';
. when switching to a task, its FPSIMD state will always be restored from
memory.
This patch adds the following functions to abstract away from straight FPSIMD
register file saves and restores:
- fpsimd_preserve_current_state -> ensure current's FPSIMD state is saved
- fpsimd_update_current_state -> replace current's FPSIMD state
Where necessary, the signal handling and fork code are updated to use the above
wrappers instead of poking into the FPSIMD registers directly.
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
(cherry picked from commit
c51f92693c35c141cf7d9b7e2fcbb81128324eb4)
Signed-off-by: Mark Brown <broonie@linaro.org>
extern void fpsimd_thread_switch(struct task_struct *next);
extern void fpsimd_flush_thread(void);
+extern void fpsimd_preserve_current_state(void);
+extern void fpsimd_update_current_state(struct fpsimd_state *state);
+
#endif
#endif
preempt_enable();
}
+/*
+ * Save the userland FPSIMD state of 'current' to memory
+ */
+void fpsimd_preserve_current_state(void)
+{
+ preempt_disable();
+ fpsimd_save_state(¤t->thread.fpsimd_state);
+ preempt_enable();
+}
+
+/*
+ * Load an updated userland FPSIMD state for 'current' from memory
+ */
+void fpsimd_update_current_state(struct fpsimd_state *state)
+{
+ preempt_disable();
+ fpsimd_load_state(state);
+ preempt_enable();
+}
+
#ifdef CONFIG_KERNEL_MODE_NEON
/*
int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src)
{
- fpsimd_save_state(¤t->thread.fpsimd_state);
+ fpsimd_preserve_current_state();
*dst = *src;
return 0;
}
int err;
/* dump the hardware registers to the fpsimd_state structure */
- fpsimd_save_state(fpsimd);
+ fpsimd_preserve_current_state();
/* copy the FP and status/control registers */
err = __copy_to_user(ctx->vregs, fpsimd->vregs, sizeof(fpsimd->vregs));
__get_user_error(fpsimd.fpcr, &ctx->fpcr, err);
/* load the hardware registers from the fpsimd_state structure */
- if (!err) {
- preempt_disable();
- fpsimd_load_state(&fpsimd);
- preempt_enable();
- }
+ if (!err)
+ fpsimd_update_current_state(&fpsimd);
return err ? -EFAULT : 0;
}
* Note that this also saves V16-31, which aren't visible
* in AArch32.
*/
- fpsimd_save_state(fpsimd);
+ fpsimd_preserve_current_state();
/* Place structure header on the stack */
__put_user_error(magic, &frame->magic, err);
* We don't need to touch the exception register, so
* reload the hardware state.
*/
- if (!err) {
- preempt_disable();
- fpsimd_load_state(&fpsimd);
- preempt_enable();
- }
+ if (!err)
+ fpsimd_update_current_state(&fpsimd);
return err ? -EFAULT : 0;
}