[patch V4 19/65] x86/fpu/regset: Move fpu__read_begin() into regset

From: Thomas Gleixner
Date: Wed Jun 23 2021 - 08:24:36 EST


The function can only be used from the regset get() callbacks safely. So
there is no reason to have it globaly exposed.

Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Reviewed-by: Borislav Petkov <bp@xxxxxxx>
---
arch/x86/include/asm/fpu/internal.h | 1 -
arch/x86/kernel/fpu/core.c | 20 --------------------
arch/x86/kernel/fpu/regset.c | 22 +++++++++++++++++++---
3 files changed, 19 insertions(+), 24 deletions(-)

--- a/arch/x86/include/asm/fpu/internal.h
+++ b/arch/x86/include/asm/fpu/internal.h
@@ -26,7 +26,6 @@
/*
* High level FPU state handling functions:
*/
-extern void fpu__prepare_read(struct fpu *fpu);
extern void fpu__prepare_write(struct fpu *fpu);
extern void fpu__save(struct fpu *fpu);
extern int fpu__restore_sig(void __user *buf, int ia32_frame);
--- a/arch/x86/kernel/fpu/core.c
+++ b/arch/x86/kernel/fpu/core.c
@@ -282,26 +282,6 @@ static void fpu__initialize(struct fpu *
}

/*
- * This function must be called before we read a task's 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.
- *
- * If the task has used the FPU before then save it.
- */
-void fpu__prepare_read(struct fpu *fpu)
-{
- if (fpu == &current->thread.fpu)
- fpu__save(fpu);
-}
-
-/*
* This function must be called before we write a task's fpstate.
*
* Invalidate any cached FPU registers.
--- a/arch/x86/kernel/fpu/regset.c
+++ b/arch/x86/kernel/fpu/regset.c
@@ -28,6 +28,22 @@ int regset_xregset_fpregs_active(struct
return 0;
}

+/*
+ * The regset get() functions are invoked from:
+ *
+ * - coredump to dump the current task's fpstate. If the current task
+ * owns the FPU then the memory state has to be synchronized and the
+ * FPU register state preserved. Otherwise fpstate is already in sync.
+ *
+ * - ptrace to dump fpstate of a stopped task, in which case the registers
+ * have already been saved to fpstate on context switch.
+ */
+static void sync_fpstate(struct fpu *fpu)
+{
+ if (fpu == &current->thread.fpu)
+ fpu__save(fpu);
+}
+
int xfpregs_get(struct task_struct *target, const struct user_regset *regset,
struct membuf to)
{
@@ -36,7 +52,7 @@ int xfpregs_get(struct task_struct *targ
if (!cpu_feature_enabled(X86_FEATURE_FXSR))
return -ENODEV;

- fpu__prepare_read(fpu);
+ sync_fpstate(fpu);

if (!use_xsave()) {
return membuf_write(&to, &fpu->state.fxsave,
@@ -96,7 +112,7 @@ int xstateregs_get(struct task_struct *t
if (!cpu_feature_enabled(X86_FEATURE_XSAVE))
return -ENODEV;

- fpu__prepare_read(fpu);
+ sync_fpstate(fpu);

copy_xstate_to_uabi_buf(to, &fpu->state.xsave, XSTATE_COPY_XSAVE);
return 0;
@@ -287,7 +303,7 @@ int fpregs_get(struct task_struct *targe
struct user_i387_ia32_struct env;
struct fxregs_state fxsave, *fx;

- fpu__prepare_read(fpu);
+ sync_fpstate(fpu);

if (!cpu_feature_enabled(X86_FEATURE_FPU))
return fpregs_soft_get(target, regset, to);