arm64: add abstractions for FPSIMD state manipulation
authorArd Biesheuvel <ard.biesheuvel@linaro.org>
Mon, 24 Feb 2014 14:26:27 +0000 (15:26 +0100)
committerArd Biesheuvel <ard.biesheuvel@linaro.org>
Thu, 8 May 2014 09:31:41 +0000 (11:31 +0200)
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>
arch/arm64/include/asm/fpsimd.h
arch/arm64/kernel/fpsimd.c
arch/arm64/kernel/process.c
arch/arm64/kernel/signal.c
arch/arm64/kernel/signal32.c

index c43b4ac13008ffec8f0b39101e5cfd77e43fd3b5..f4e524b67e912296ef7c539e535987b1f3405322 100644 (file)
@@ -58,6 +58,9 @@ 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_update_current_state(struct fpsimd_state *state);
+
 #endif
 
 #endif
index 4aef42a04bdcc38baa84c2090ffc537d67770854..8a97163debc77e9e9c0d7aaf7bfbda0ec6e392fe 100644 (file)
@@ -87,6 +87,26 @@ void fpsimd_flush_thread(void)
        preempt_enable();
 }
 
+/*
+ * Save the userland FPSIMD state of 'current' to memory
+ */
+void fpsimd_preserve_current_state(void)
+{
+       preempt_disable();
+       fpsimd_save_state(&current->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
 
 /*
index 6391485f342daaac57e207f129a62e28d169b114..c5693163408c3bb9ab967dc7819ee9ae14282c0d 100644 (file)
@@ -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(&current->thread.fpsimd_state);
+       fpsimd_preserve_current_state();
        *dst = *src;
        return 0;
 }
index 890a591f75dd1848e28e1ea62413775be5394c6d..06448a77ff5351a18ad98409311675144453462a 100644 (file)
@@ -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;
 }
index b3fc9f5ec6d34b423d70bc5f0fd75836fc307c95..ac7e237d0bda50aa9bb426509fc5689acbecfce0 100644 (file)
@@ -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;
 }