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Diffstat (limited to 'arch/x86/include/asm/fpu/internal.h')
-rw-r--r--arch/x86/include/asm/fpu/internal.h133
1 files changed, 100 insertions, 33 deletions
diff --git a/arch/x86/include/asm/fpu/internal.h b/arch/x86/include/asm/fpu/internal.h
index 745a19d34f23..9e27fa05a7ae 100644
--- a/arch/x86/include/asm/fpu/internal.h
+++ b/arch/x86/include/asm/fpu/internal.h
@@ -14,6 +14,7 @@
#include <linux/compat.h>
#include <linux/sched.h>
#include <linux/slab.h>
+#include <linux/mm.h>
#include <asm/user.h>
#include <asm/fpu/api.h>
@@ -24,14 +25,12 @@
/*
* High level FPU state handling functions:
*/
-extern void fpu__initialize(struct fpu *fpu);
extern void fpu__prepare_read(struct fpu *fpu);
extern void fpu__prepare_write(struct fpu *fpu);
extern void fpu__save(struct fpu *fpu);
-extern void fpu__restore(struct fpu *fpu);
extern int fpu__restore_sig(void __user *buf, int ia32_frame);
extern void fpu__drop(struct fpu *fpu);
-extern int fpu__copy(struct fpu *dst_fpu, struct fpu *src_fpu);
+extern int fpu__copy(struct task_struct *dst, struct task_struct *src);
extern void fpu__clear(struct fpu *fpu);
extern int fpu__exception_code(struct fpu *fpu, int trap_nr);
extern int dump_fpu(struct pt_regs *ptregs, struct user_i387_struct *fpstate);
@@ -122,6 +121,21 @@ extern void fpstate_sanitize_xstate(struct fpu *fpu);
err; \
})
+#define kernel_insn_err(insn, output, input...) \
+({ \
+ int err; \
+ asm volatile("1:" #insn "\n\t" \
+ "2:\n" \
+ ".section .fixup,\"ax\"\n" \
+ "3: movl $-1,%[err]\n" \
+ " jmp 2b\n" \
+ ".previous\n" \
+ _ASM_EXTABLE(1b, 3b) \
+ : [err] "=r" (err), output \
+ : "0"(0), input); \
+ err; \
+})
+
#define kernel_insn(insn, output, input...) \
asm volatile("1:" #insn "\n\t" \
"2:\n" \
@@ -150,6 +164,14 @@ static inline void copy_kernel_to_fxregs(struct fxregs_state *fx)
kernel_insn(fxrstorq %[fx], "=m" (*fx), [fx] "m" (*fx));
}
+static inline int copy_kernel_to_fxregs_err(struct fxregs_state *fx)
+{
+ if (IS_ENABLED(CONFIG_X86_32))
+ return kernel_insn_err(fxrstor %[fx], "=m" (*fx), [fx] "m" (*fx));
+ else
+ return kernel_insn_err(fxrstorq %[fx], "=m" (*fx), [fx] "m" (*fx));
+}
+
static inline int copy_user_to_fxregs(struct fxregs_state __user *fx)
{
if (IS_ENABLED(CONFIG_X86_32))
@@ -163,6 +185,11 @@ static inline void copy_kernel_to_fregs(struct fregs_state *fx)
kernel_insn(frstor %[fx], "=m" (*fx), [fx] "m" (*fx));
}
+static inline int copy_kernel_to_fregs_err(struct fregs_state *fx)
+{
+ return kernel_insn_err(frstor %[fx], "=m" (*fx), [fx] "m" (*fx));
+}
+
static inline int copy_user_to_fregs(struct fregs_state __user *fx)
{
return user_insn(frstor %[fx], "=m" (*fx), [fx] "m" (*fx));
@@ -363,6 +390,21 @@ static inline int copy_user_to_xregs(struct xregs_state __user *buf, u64 mask)
}
/*
+ * Restore xstate from kernel space xsave area, return an error code instead of
+ * an exception.
+ */
+static inline int copy_kernel_to_xregs_err(struct xregs_state *xstate, u64 mask)
+{
+ u32 lmask = mask;
+ u32 hmask = mask >> 32;
+ int err;
+
+ XSTATE_OP(XRSTOR, xstate, lmask, hmask, err);
+
+ return err;
+}
+
+/*
* These must be called with preempt disabled. Returns
* 'true' if the FPU state is still intact and we can
* keep registers active.
@@ -487,6 +529,25 @@ static inline void fpregs_activate(struct fpu *fpu)
}
/*
+ * Internal helper, do not use directly. Use switch_fpu_return() instead.
+ */
+static inline void __fpregs_load_activate(void)
+{
+ struct fpu *fpu = &current->thread.fpu;
+ int cpu = smp_processor_id();
+
+ if (WARN_ON_ONCE(current->mm == NULL))
+ return;
+
+ if (!fpregs_state_valid(fpu, cpu)) {
+ copy_kernel_to_fpregs(&fpu->state);
+ fpregs_activate(fpu);
+ fpu->last_cpu = cpu;
+ }
+ clear_thread_flag(TIF_NEED_FPU_LOAD);
+}
+
+/*
* FPU state switching for scheduling.
*
* This is a two-stage process:
@@ -494,12 +555,23 @@ static inline void fpregs_activate(struct fpu *fpu)
* - switch_fpu_prepare() saves the old state.
* This is done within the context of the old process.
*
- * - switch_fpu_finish() restores the new state as
- * necessary.
+ * - switch_fpu_finish() sets TIF_NEED_FPU_LOAD; the floating point state
+ * will get loaded on return to userspace, or when the kernel needs it.
+ *
+ * If TIF_NEED_FPU_LOAD is cleared then the CPU's FPU registers
+ * are saved in the current thread's FPU register state.
+ *
+ * If TIF_NEED_FPU_LOAD is set then CPU's FPU registers may not
+ * hold current()'s FPU registers. It is required to load the
+ * registers before returning to userland or using the content
+ * otherwise.
+ *
+ * The FPU context is only stored/restored for a user task and
+ * ->mm is used to distinguish between kernel and user threads.
*/
static inline void switch_fpu_prepare(struct fpu *old_fpu, int cpu)
{
- if (static_cpu_has(X86_FEATURE_FPU) && old_fpu->initialized) {
+ if (static_cpu_has(X86_FEATURE_FPU) && current->mm) {
if (!copy_fpregs_to_fpstate(old_fpu))
old_fpu->last_cpu = -1;
else
@@ -507,8 +579,7 @@ static inline void switch_fpu_prepare(struct fpu *old_fpu, int cpu)
/* But leave fpu_fpregs_owner_ctx! */
trace_x86_fpu_regs_deactivated(old_fpu);
- } else
- old_fpu->last_cpu = -1;
+ }
}
/*
@@ -516,36 +587,32 @@ static inline void switch_fpu_prepare(struct fpu *old_fpu, int cpu)
*/
/*
- * Set up the userspace FPU context for the new task, if the task
- * has used the FPU.
+ * Load PKRU from the FPU context if available. Delay loading of the
+ * complete FPU state until the return to userland.
*/
-static inline void switch_fpu_finish(struct fpu *new_fpu, int cpu)
+static inline void switch_fpu_finish(struct fpu *new_fpu)
{
- bool preload = static_cpu_has(X86_FEATURE_FPU) &&
- new_fpu->initialized;
+ u32 pkru_val = init_pkru_value;
+ struct pkru_state *pk;
- if (preload) {
- if (!fpregs_state_valid(new_fpu, cpu))
- copy_kernel_to_fpregs(&new_fpu->state);
- fpregs_activate(new_fpu);
- }
-}
+ if (!static_cpu_has(X86_FEATURE_FPU))
+ return;
-/*
- * Needs to be preemption-safe.
- *
- * NOTE! user_fpu_begin() must be used only immediately before restoring
- * the save state. It does not do any saving/restoring on its own. In
- * lazy FPU mode, it is just an optimization to avoid a #NM exception,
- * the task can lose the FPU right after preempt_enable().
- */
-static inline void user_fpu_begin(void)
-{
- struct fpu *fpu = &current->thread.fpu;
+ set_thread_flag(TIF_NEED_FPU_LOAD);
+
+ if (!cpu_feature_enabled(X86_FEATURE_OSPKE))
+ return;
- preempt_disable();
- fpregs_activate(fpu);
- preempt_enable();
+ /*
+ * PKRU state is switched eagerly because it needs to be valid before we
+ * return to userland e.g. for a copy_to_user() operation.
+ */
+ if (current->mm) {
+ pk = get_xsave_addr(&new_fpu->state.xsave, XFEATURE_PKRU);
+ if (pk)
+ pkru_val = pk->pkru;
+ }
+ __write_pkru(pkru_val);
}
/*
generated by cgit v1.2.3 (git 2.39.0) at 2025-01-09 10:39:10 +0300