[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>

7 files changed, 120 insertions, 4 deletions

diff --git a/arch/arm/include/asm/ptrace.h b/arch/arm/include/asm/ptrace.h
index 73192618f1c2..236a06b9b7ce 100644
--- a/arch/arm/include/asm/ptrace.h
+++ b/arch/arm/include/asm/ptrace.h
@@ -27,6 +27,8 @@
 /* PTRACE_SYSCALL is 24 */
 #define PTRACE_GETCRUNCHREGS    25
 #define PTRACE_SETCRUNCHREGS    26
+#define PTRACE_GETVFPREGS       27
+#define PTRACE_SETVFPREGS       28
 
 /*
  * PSR bits
diff --git a/arch/arm/include/asm/thread_info.h b/arch/arm/include/asm/thread_info.h
index 68b9ec82a37f..b9dc8a842573 100644
--- a/arch/arm/include/asm/thread_info.h
+++ b/arch/arm/include/asm/thread_info.h
@@ -113,6 +113,8 @@ extern void iwmmxt_task_restore(struct thread_info *, void *);
 extern void iwmmxt_task_release(struct thread_info *);
 extern void iwmmxt_task_switch(struct thread_info *);
 
+extern void vfp_sync_state(struct thread_info *thread);
+
 #endif
 
 /*
diff --git a/arch/arm/include/asm/user.h b/arch/arm/include/asm/user.h
index 825c1e7c582d..df95e050f9dd 100644
--- a/arch/arm/include/asm/user.h
+++ b/arch/arm/include/asm/user.h
@@ -81,4 +81,13 @@ struct user{
 #define HOST_TEXT_START_ADDR (u.start_code)
 #define HOST_STACK_END_ADDR (u.start_stack + u.u_ssize * NBPG)
 
+/*
+ * User specific VFP registers. If only VFPv2 is present, registers 16 to 31
+ * are ignored by the ptrace system call.
+ */
+struct user_vfp {
+        unsigned long long fpregs[32];
+        unsigned long fpscr;
+};
+
 #endif /* _ARM_USER_H */
diff --git a/arch/arm/kernel/ptrace.c b/arch/arm/kernel/ptrace.c
index df653ea59250..89882a1d0187 100644
--- a/arch/arm/kernel/ptrace.c
+++ b/arch/arm/kernel/ptrace.c
@@ -653,6 +653,54 @@ static int ptrace_setcrunchregs(struct task_struct *tsk, void __user *ufp)
 }
 #endif
 
+#ifdef CONFIG_VFP
+/*
+ * Get the child VFP state.
+ */
+static int ptrace_getvfpregs(struct task_struct *tsk, void __user *data)
+{
+        struct thread_info *thread = task_thread_info(tsk);
+        union vfp_state *vfp = &thread->vfpstate;
+        struct user_vfp __user *ufp = data;
+
+        vfp_sync_state(thread);
+
+        /* copy the floating point registers */
+        if (copy_to_user(&ufp->fpregs, &vfp->hard.fpregs,
+                         sizeof(vfp->hard.fpregs)))
+                return -EFAULT;
+
+        /* copy the status and control register */
+        if (put_user(vfp->hard.fpscr, &ufp->fpscr))
+                return -EFAULT;
+
+        return 0;
+}
+
+/*
+ * Set the child VFP state.
+ */
+static int ptrace_setvfpregs(struct task_struct *tsk, void __user *data)
+{
+        struct thread_info *thread = task_thread_info(tsk);
+        union vfp_state *vfp = &thread->vfpstate;
+        struct user_vfp __user *ufp = data;
+
+        vfp_sync_state(thread);
+
+        /* copy the floating point registers */
+        if (copy_from_user(&vfp->hard.fpregs, &ufp->fpregs,
+                           sizeof(vfp->hard.fpregs)))
+                return -EFAULT;
+
+        /* copy the status and control register */
+        if (get_user(vfp->hard.fpscr, &ufp->fpscr))
+                return -EFAULT;
+
+        return 0;
+}
+#endif
+
 long arch_ptrace(struct task_struct *child, long request, long addr, long data)
 {
         int ret;
@@ -775,6 +823,16 @@ long arch_ptrace(struct task_struct *child, long request, long addr, long data)
                         break;
 #endif
 
+#ifdef CONFIG_VFP
+                case PTRACE_GETVFPREGS:
+                        ret = ptrace_getvfpregs(child, (void __user *)data);
+                        break;
+
+                case PTRACE_SETVFPREGS:
+                        ret = ptrace_setvfpregs(child, (void __user *)data);
+                        break;
+#endif
+
                 default:
                         ret = ptrace_request(child, request, addr, data);
                         break;
diff --git a/arch/arm/vfp/vfp.h b/arch/arm/vfp/vfp.h
index 8de86e4feada..c8c98dd44ad4 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 c92a08bd6a86..a5a4e57763c3 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 9f476a1be2ca..7e1239041b39 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>
 
 /*