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_restore_current_state -> ensure current's FPSIMD state is loaded
- fpsimd_update_current_state -> replace current's FPSIMD state
- fpsimd_flush_task_state -> invalidate live copies of a task's FPSIMD state
Where necessary, the ptrace, 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@xxxxxxxxxx>
---
arch/arm64/include/asm/fpsimd.h | 6 ++++++
arch/arm64/kernel/fpsimd.c | 33 +++++++++++++++++++++++++++++++++
arch/arm64/kernel/process.c | 2 +-
arch/arm64/kernel/ptrace.c | 2 ++
arch/arm64/kernel/signal.c | 9 +++------
arch/arm64/kernel/signal32.c | 9 +++------
6 files changed, 48 insertions(+), 13 deletions(-)
diff --git a/arch/arm64/include/asm/fpsimd.h b/arch/arm64/include/asm/fpsimd.h
index c43b4ac13008..9f9b8e438546 100644
--- a/arch/arm64/include/asm/fpsimd.h
+++ b/arch/arm64/include/asm/fpsimd.h
@@ -58,6 +58,12 @@ extern void fpsimd_load_state(struct fpsimd_state *state);
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_restore_current_state(void);
+extern void fpsimd_update_current_state(struct fpsimd_state *state);
+
+extern void fpsimd_flush_task_state(struct task_struct *target);
+
#endif
#endif
diff --git a/arch/arm64/kernel/fpsimd.c b/arch/arm64/kernel/fpsimd.c
index 4aef42a04bdc..86ac6a9bc86a 100644
--- a/arch/arm64/kernel/fpsimd.c
+++ b/arch/arm64/kernel/fpsimd.c
@@ -87,6 +87,39 @@ void fpsimd_flush_thread(void)
preempt_enable();
}
+/*
+ * Save the userland FPSIMD state of 'current' to memory
+ */
+void fpsimd_preserve_current_state(void)
+{
+ fpsimd_save_state(¤t->thread.fpsimd_state);
+}
+
+/*
+ * Load the userland FPSIMD state of 'current' from memory
+ */
+void fpsimd_restore_current_state(void)
+{
+ fpsimd_load_state(¤t->thread.fpsimd_state);
+}
+
+/*
+ * 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();
+}
+
+/*
+ * Invalidate live CPU copies of task t's FPSIMD state
+ */
+void fpsimd_flush_task_state(struct task_struct *t)
+{
+}
+
#ifdef CONFIG_KERNEL_MODE_NEON
/*
diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c
index 6391485f342d..c5693163408c 100644
--- a/arch/arm64/kernel/process.c
+++ b/arch/arm64/kernel/process.c
@@ -205,7 +205,7 @@ void release_thread(struct task_struct *dead_task)
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;
}
diff --git a/arch/arm64/kernel/ptrace.c b/arch/arm64/kernel/ptrace.c
index 6a8928bba03c..f8700eca24e7 100644
--- a/arch/arm64/kernel/ptrace.c
+++ b/arch/arm64/kernel/ptrace.c
@@ -517,6 +517,7 @@ static int fpr_set(struct task_struct *target, const struct user_regset *regset,
return ret;
target->thread.fpsimd_state.user_fpsimd = newstate;
+ fpsimd_flush_task_state(target);
return ret;
}
@@ -764,6 +765,7 @@ static int compat_vfp_set(struct task_struct *target,
uregs->fpcr = fpscr & VFP_FPSCR_CTRL_MASK;
}
+ fpsimd_flush_task_state(target);
return ret;
}
diff --git a/arch/arm64/kernel/signal.c b/arch/arm64/kernel/signal.c
index 890a591f75dd..06448a77ff53 100644
--- a/arch/arm64/kernel/signal.c
+++ b/arch/arm64/kernel/signal.c
@@ -51,7 +51,7 @@ static int preserve_fpsimd_context(struct fpsimd_context __user *ctx)
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));
@@ -86,11 +86,8 @@ static int restore_fpsimd_context(struct fpsimd_context __user *ctx)
__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;
}
diff --git a/arch/arm64/kernel/signal32.c b/arch/arm64/kernel/signal32.c
index b3fc9f5ec6d3..ac7e237d0bda 100644
--- a/arch/arm64/kernel/signal32.c
+++ b/arch/arm64/kernel/signal32.c
@@ -219,7 +219,7 @@ static int compat_preserve_vfp_context(struct compat_vfp_sigframe __user *frame)
* 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);
@@ -282,11 +282,8 @@ static int compat_restore_vfp_context(struct compat_vfp_sigframe __user *frame)
* 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;
}
--
1.8.3.2
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