ARM: 6051/1: VFP: preserve the HW context when calling signal handlers

From: Imre Deak <imre.deak@nokia.com>

Signal handlers can use floating point, so prevent them to corrupt
the main thread's VFP context. So far there were two signal stack
frame formats defined based on the VFP implementation, but the user
struct used for ptrace covers all posibilities, so use it for the
signal stack too.

Introduce also a new user struct for VFP exception registers. In
this too fields not relevant to the current VFP architecture are
ignored.

Support to save / restore the exception registers was added by
Will Deacon.

Signed-off-by: Imre Deak <imre.deak@nokia.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

diff --git a/arch/arm/include/asm/ucontext.h b/arch/arm/include/asm/ucontext.h
index bf65e9f4525d04f78dacff51b229ee7f767b0432..47f023aa849587d89dc194f1aed5365cf7d81a92 100644 (file)
--- a/arch/arm/include/asm/ucontext.h
+++ b/arch/arm/include/asm/ucontext.h
@@ -59,23 +59,22 @@ struct iwmmxt_sigframe {
 #endif /* CONFIG_IWMMXT */
 
 #ifdef CONFIG_VFP
-#if __LINUX_ARM_ARCH__ < 6
-/* For ARM pre-v6, we use fstmiax and fldmiax.  This adds one extra
- * word after the registers, and a word of padding at the end for
- * alignment.  */
 #define VFP_MAGIC              0x56465001
-#define VFP_STORAGE_SIZE       152
-#else
-#define VFP_MAGIC              0x56465002
-#define VFP_STORAGE_SIZE       144
-#endif
 
 struct vfp_sigframe
 {
        unsigned long           magic;
        unsigned long           size;
-       union vfp_state         storage;
-};
+       struct user_vfp         ufp;
+       struct user_vfp_exc     ufp_exc;
+} __attribute__((__aligned__(8)));
+
+/*
+ *  8 byte for magic and size, 264 byte for ufp, 12 bytes for ufp_exc,
+ *  4 bytes padding.
+ */
+#define VFP_STORAGE_SIZE       sizeof(struct vfp_sigframe)
+
 #endif /* CONFIG_VFP */
 
 /*
@@ -91,7 +90,7 @@ struct aux_sigframe {
 #ifdef CONFIG_IWMMXT
        struct iwmmxt_sigframe  iwmmxt;
 #endif
-#if 0 && defined CONFIG_VFP /* Not yet saved.  */
+#ifdef CONFIG_VFP
        struct vfp_sigframe     vfp;
 #endif
        /* Something that isn't a valid magic number for any coprocessor.  */

diff --git a/arch/arm/include/asm/user.h b/arch/arm/include/asm/user.h
index df95e050f9dd75ea6305417e221574e55993bd9c..05ac4b06876a0c30b3f49dc2ad9652f20a63f9e5 100644 (file)
--- a/arch/arm/include/asm/user.h
+++ b/arch/arm/include/asm/user.h
@@ -83,11 +83,21 @@ struct user{
 
 /*
  * User specific VFP registers. If only VFPv2 is present, registers 16 to 31
- * are ignored by the ptrace system call.
+ * are ignored by the ptrace system call and the signal handler.
  */
 struct user_vfp {
        unsigned long long fpregs[32];
        unsigned long fpscr;
 };
 
+/*
+ * VFP exception registers exposed to user space during signal delivery.
+ * Fields not relavant to the current VFP architecture are ignored.
+ */
+struct user_vfp_exc {
+       unsigned long   fpexc;
+       unsigned long   fpinst;
+       unsigned long   fpinst2;
+};
+
 #endif /* _ARM_USER_H */

diff --git a/arch/arm/kernel/signal.c b/arch/arm/kernel/signal.c
index e7714f367eb83aa0a4b0224e5129ec94c87c3391..907d5a620bca2655a68a29fa004bc9445ae78543 100644 (file)
--- a/arch/arm/kernel/signal.c
+++ b/arch/arm/kernel/signal.c
@@ -18,6 +18,7 @@
 #include <asm/cacheflush.h>
 #include <asm/ucontext.h>
 #include <asm/unistd.h>
+#include <asm/vfp.h>
 
 #include "ptrace.h"
 #include "signal.h"
@@ -175,6 +176,90 @@ static int restore_iwmmxt_context(struct iwmmxt_sigframe *frame)
 
 #endif
 
+#ifdef CONFIG_VFP
+
+static int preserve_vfp_context(struct vfp_sigframe __user *frame)
+{
+       struct thread_info *thread = current_thread_info();
+       struct vfp_hard_struct *h = &thread->vfpstate.hard;
+       const unsigned long magic = VFP_MAGIC;
+       const unsigned long size = VFP_STORAGE_SIZE;
+       int err = 0;
+
+       vfp_sync_hwstate(thread);
+       __put_user_error(magic, &frame->magic, err);
+       __put_user_error(size, &frame->size, err);
+
+       /*
+        * Copy the floating point registers. There can be unused
+        * registers see asm/hwcap.h for details.
+        */
+       err |= __copy_to_user(&frame->ufp.fpregs, &h->fpregs,
+                             sizeof(h->fpregs));
+       /*
+        * Copy the status and control register.
+        */
+       __put_user_error(h->fpscr, &frame->ufp.fpscr, err);
+
+       /*
+        * Copy the exception registers.
+        */
+       __put_user_error(h->fpexc, &frame->ufp_exc.fpexc, err);
+       __put_user_error(h->fpinst, &frame->ufp_exc.fpinst, err);
+       __put_user_error(h->fpinst2, &frame->ufp_exc.fpinst2, err);
+
+       return err ? -EFAULT : 0;
+}
+
+static int restore_vfp_context(struct vfp_sigframe __user *frame)
+{
+       struct thread_info *thread = current_thread_info();
+       struct vfp_hard_struct *h = &thread->vfpstate.hard;
+       unsigned long magic;
+       unsigned long size;
+       unsigned long fpexc;
+       int err = 0;
+
+       __get_user_error(magic, &frame->magic, err);
+       __get_user_error(size, &frame->size, err);
+
+       if (err)
+               return -EFAULT;
+       if (magic != VFP_MAGIC || size != VFP_STORAGE_SIZE)
+               return -EINVAL;
+
+       /*
+        * Copy the floating point registers. There can be unused
+        * registers see asm/hwcap.h for details.
+        */
+       err |= __copy_from_user(&h->fpregs, &frame->ufp.fpregs,
+                               sizeof(h->fpregs));
+       /*
+        * Copy the status and control register.
+        */
+       __get_user_error(h->fpscr, &frame->ufp.fpscr, err);
+
+       /*
+        * Sanitise and restore the exception registers.
+        */
+       __get_user_error(fpexc, &frame->ufp_exc.fpexc, err);
+       /* Ensure the VFP is enabled. */
+       fpexc |= FPEXC_EN;
+       /* Ensure FPINST2 is invalid and the exception flag is cleared. */
+       fpexc &= ~(FPEXC_EX | FPEXC_FP2V);
+       h->fpexc = fpexc;
+
+       __get_user_error(h->fpinst, &frame->ufp_exc.fpinst, err);
+       __get_user_error(h->fpinst2, &frame->ufp_exc.fpinst2, err);
+
+       if (!err)
+               vfp_flush_hwstate(thread);
+
+       return err ? -EFAULT : 0;
+}
+
+#endif
+
 /*
  * Do a signal return; undo the signal stack.  These are aligned to 64-bit.
  */
@@ -233,8 +318,8 @@ static int restore_sigframe(struct pt_regs *regs, struct sigframe __user *sf)
                err |= restore_iwmmxt_context(&aux->iwmmxt);
 #endif
 #ifdef CONFIG_VFP
-//     if (err == 0)
-//             err |= vfp_restore_state(&sf->aux.vfp);
+       if (err == 0)
+               err |= restore_vfp_context(&aux->vfp);
 #endif
 
        return err;
@@ -348,8 +433,8 @@ setup_sigframe(struct sigframe __user *sf, struct pt_regs *regs, sigset_t *set)
                err |= preserve_iwmmxt_context(&aux->iwmmxt);
 #endif
 #ifdef CONFIG_VFP
-//     if (err == 0)
-//             err |= vfp_save_state(&sf->aux.vfp);
+       if (err == 0)
+               err |= preserve_vfp_context(&aux->vfp);
 #endif
        __put_user_error(0, &aux->end_magic, err);