[ARM] 5387/1: Add ptrace VFP support on ARM

This patch adds ptrace support for setting and getting the VFP registers
using PTRACE_SETVFPREGS and PTRACE_GETVFPREGS. The user_vfp structure
defined in asm/user.h contains 32 double registers (to cover VFPv3 and
Neon hardware) and the FPSCR register.

Cc: Paul Brook <paul@codesourcery.com>
Cc: Daniel Jacobowitz <dan@codesourcery.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

3 files changed, 49 insertions, 4 deletions

diff --git a/arch/arm/vfp/vfp.h b/arch/arm/vfp/vfp.h
index 8de86e4fead..c8c98dd44ad 100644
--- a/arch/arm/vfp/vfp.h
+++ b/arch/arm/vfp/vfp.h
@@ -377,6 +377,4 @@ struct op {
         u32 flags;
 };
 
-#if defined(CONFIG_SMP) || defined(CONFIG_PM)
 extern void vfp_save_state(void *location, u32 fpexc);
-#endif
diff --git a/arch/arm/vfp/vfphw.S b/arch/arm/vfp/vfphw.S
index c92a08bd6a8..a5a4e57763c 100644
--- a/arch/arm/vfp/vfphw.S
+++ b/arch/arm/vfp/vfphw.S
@@ -172,7 +172,6 @@ process_exception:
                                         @ retry the faulted instruction
 ENDPROC(vfp_support_entry)
 
-#if defined(CONFIG_SMP) || defined(CONFIG_PM)
 ENTRY(vfp_save_state)
         @ Save the current VFP state
         @ r0 - save location
@@ -190,7 +189,6 @@ ENTRY(vfp_save_state)
         stmia   r0, {r1, r2, r3, r12}   @ save FPEXC, FPSCR, FPINST, FPINST2
         mov     pc, lr
 ENDPROC(vfp_save_state)
-#endif
 
 last_VFP_context_address:
         .word   last_VFP_context
diff --git a/arch/arm/vfp/vfpmodule.c b/arch/arm/vfp/vfpmodule.c
index 9f476a1be2c..7e1239041b3 100644
--- a/arch/arm/vfp/vfpmodule.c
+++ b/arch/arm/vfp/vfpmodule.c
@@ -377,6 +377,55 @@ static void vfp_pm_init(void)
 static inline void vfp_pm_init(void) { }
 #endif /* CONFIG_PM */
 
+/*
+ * Synchronise the hardware VFP state of a thread other than current with the
+ * saved one. This function is used by the ptrace mechanism.
+ */
+#ifdef CONFIG_SMP
+void vfp_sync_state(struct thread_info *thread)
+{
+        /*
+         * On SMP systems, the VFP state is automatically saved at every
+         * context switch. We mark the thread VFP state as belonging to a
+         * non-existent CPU so that the saved one will be reloaded when
+         * needed.
+         */
+        thread->vfpstate.hard.cpu = NR_CPUS;
+}
+#else
+void vfp_sync_state(struct thread_info *thread)
+{
+        unsigned int cpu = get_cpu();
+        u32 fpexc = fmrx(FPEXC);
+
+        /*
+         * If VFP is enabled, the previous state was already saved and
+         * last_VFP_context updated.
+         */
+        if (fpexc & FPEXC_EN)
+                goto out;
+
+        if (!last_VFP_context[cpu])
+                goto out;
+
+        /*
+         * Save the last VFP state on this CPU.
+         */
+        fmxr(FPEXC, fpexc | FPEXC_EN);
+        vfp_save_state(last_VFP_context[cpu], fpexc);
+        fmxr(FPEXC, fpexc);
+
+        /*
+         * Set the context to NULL to force a reload the next time the thread
+         * uses the VFP.
+         */
+        last_VFP_context[cpu] = NULL;
+
+out:
+        put_cpu();
+}
+#endif
+
 #include <linux/smp.h>
 
 /*