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[Ping] [PATCH] Add support for accessing VFP registers to ARM native Linux


Hi,

Has anybody had a chance to look at this patch which I submitted last
week yet?  I am not concerned if it is just taking a while to review - I
just want to make sure it does not get missed by accident.

Thanks,

Matt

On Mon, 2010-03-01 at 11:50 +0000, Matthew Gretton-Dann wrote:
> All,
> 
> The attached patch adds support for VFP registers to GDB running
> natively under ARM Linux.  The patch is based in large part on the
> equivalent functionality in gdbserver for remote debugging of ARM Linux.
> 
> I have tested it with arm-unknown-linux-gnueabi on a target with Neon,
> one with VFPv3-D16, one with VFPv2, and a target without VFP.  I have
> also tested it on arm-none-linux on a target without VFP.  The patch has
> not been tested on an XScale as I do not have access to an appropriate
> device.
> 
> Can someone please review the patch, comment, and if appropriate commit
> it?
> 
> Proposed ChangeLog: 
> 
> 2010-03-01  Matthew Gretton-Dann  <matthew.gretton-dann@arm.com>
> 
> 	* arm-tdep.h (gdb_regnum): Add ARM_FPSCR_REGNUM
> 	* arm-linux-nat.c (arm_linux_vfp_register_count): Add new
> 	variable.
> 	(fetch_vfp_registers): New function to fetch VFP registers.
> 	(store_vfp_registers): New function to store VFP registers.
> 	(arm_linux_fetch_inferior_registers): Add support for VFP
> 	registers.
> 	(arm_linux_store_inferior_registers): Likewise.
> 	(arm_linux_read_description): Likewise.
> 	(arm_read_auxv, arm_get_hwcap): New function.
> 	(_initialize_arm_linux_nat): Delay initialising iWMMX tdesc
> 	until we need it.
> 
> Thanks,
> 
> Matt

-- 
Matthew Gretton-Dann
Principal Engineer - Tools, PD Software
ARM Limited
Index: gdb/arm-linux-nat.c
===================================================================
RCS file: /cvs/src/src/gdb/arm-linux-nat.c,v
retrieving revision 1.42
diff -u -p -r1.42 arm-linux-nat.c
--- gdb/arm-linux-nat.c	1 Jan 2010 07:31:29 -0000	1.42
+++ gdb/arm-linux-nat.c	1 Mar 2010 11:33:32 -0000
@@ -29,6 +29,7 @@
 #include "arm-tdep.h"
 #include "arm-linux-tdep.h"
 
+#include <elf/common.h>
 #include <sys/user.h>
 #include <sys/ptrace.h>
 #include <sys/utsname.h>
@@ -41,6 +42,9 @@
 #include "gdb_proc_service.h"
 
 #include "features/arm-with-iwmmxt.c"
+#include "features/arm-with-vfpv2.c"
+#include "features/arm-with-vfpv3.c"
+#include "features/arm-with-neon.c"
 
 #ifndef PTRACE_GET_THREAD_AREA
 #define PTRACE_GET_THREAD_AREA 22
@@ -51,9 +55,25 @@
 #define PTRACE_SETWMMXREGS 19
 #endif
 
+#ifndef PTRACE_GETVFPREGS
+#define PTRACE_GETVFPREGS 27
+#define PTRACE_SETVFPREGS 28
+#endif
+
+/* These are in <asm/elf.h> in current kernels.  */
+#define HWCAP_VFP       64
+#define HWCAP_IWMMXT    512
+#define HWCAP_NEON      4096
+#define HWCAP_VFPv3     8192
+#define HWCAP_VFPv3D16  16384
+
 /* A flag for whether the WMMX registers are available.  */
 static int arm_linux_has_wmmx_registers;
 
+/* The number of 64-bit VFP registers we have (expect this to be 0, 16, or
+   32). */
+static int arm_linux_vfp_register_count;
+
 extern int arm_apcs_32;
 
 /* The following variables are used to determine the version of the
@@ -447,6 +467,67 @@ store_wmmx_regs (const struct regcache *
     }
 }
 
+/* Fetch and store VFP Registers.  The kernel object has space for 32
+   64-bit registers, and the FPSCR.  This is even when on a VFPv2 or
+   VFPv3D16 target.  */
+#define VFP_REGS_SIZE (32 * 8 + 4)
+
+static void
+fetch_vfp_regs (struct regcache *regcache)
+{
+  char regbuf[VFP_REGS_SIZE];
+  int ret, regno, tid;
+
+  /* Get the thread id for the ptrace call.  */
+  tid = GET_THREAD_ID (inferior_ptid);
+
+  ret = ptrace (PTRACE_GETVFPREGS, tid, 0, regbuf);
+  if (ret < 0)
+    {
+      warning (_("Unable to fetch VFPv3 registers."));
+      return;
+    }
+
+  for (regno = 0; regno < arm_linux_vfp_register_count; regno++)
+    regcache_raw_supply (regcache, regno + ARM_D0_REGNUM,
+			 (char *) regbuf + regno * 8);
+
+  regcache_raw_supply (regcache, ARM_FPSCR_REGNUM,
+		       (char *) regbuf + 32 * 8);
+}
+
+static void
+store_vfp_regs (const struct regcache *regcache)
+{
+  char regbuf[VFP_REGS_SIZE];
+  int ret, regno, tid;
+
+  /* Get the thread id for the ptrace call.  */
+  tid = GET_THREAD_ID (inferior_ptid);
+
+  ret = ptrace (PTRACE_GETVFPREGS, tid, 0, regbuf);
+  if (ret < 0)
+    {
+      warning (_("Unable to fetch VFPv3 registers."));
+      return;
+    }
+
+  for (regno = 0; regno < arm_linux_vfp_register_count; regno++)
+    regcache_raw_collect (regcache, regno + ARM_D0_REGNUM,
+			  (char *) regbuf + regno * 8);
+
+  regcache_raw_collect (regcache, ARM_FPSCR_REGNUM,
+			(char *) regbuf + 32 * 8);
+
+  ret = ptrace (PTRACE_SETVFPREGS, tid, 0, regbuf);
+
+  if (ret < 0)
+    {
+      warning (_("Unable to store VFPv3 registers."));
+      return;
+    }
+}
+
 /* Fetch registers from the child process.  Fetch all registers if
    regno == -1, otherwise fetch all general registers or all floating
    point registers depending upon the value of regno.  */
@@ -461,6 +542,8 @@ arm_linux_fetch_inferior_registers (stru
       fetch_fpregs (regcache);
       if (arm_linux_has_wmmx_registers)
 	fetch_wmmx_regs (regcache);
+      if (arm_linux_vfp_register_count > 0)
+	fetch_vfp_regs (regcache);
     }
   else 
     {
@@ -471,6 +554,10 @@ arm_linux_fetch_inferior_registers (stru
       else if (arm_linux_has_wmmx_registers
 	       && regno >= ARM_WR0_REGNUM && regno <= ARM_WCGR7_REGNUM)
 	fetch_wmmx_regs (regcache);
+      else if (arm_linux_vfp_register_count > 0
+	       && regno >= ARM_D0_REGNUM
+	       && regno <= ARM_D0_REGNUM + arm_linux_vfp_register_count)
+	fetch_vfp_regs (regcache);
     }
 }
 
@@ -488,6 +575,8 @@ arm_linux_store_inferior_registers (stru
       store_fpregs (regcache);
       if (arm_linux_has_wmmx_registers)
 	store_wmmx_regs (regcache);
+      if (arm_linux_vfp_register_count > 0)
+	store_vfp_regs (regcache);
     }
   else
     {
@@ -498,6 +587,10 @@ arm_linux_store_inferior_registers (stru
       else if (arm_linux_has_wmmx_registers
 	       && regno >= ARM_WR0_REGNUM && regno <= ARM_WCGR7_REGNUM)
 	store_wmmx_regs (regcache);
+      else if (arm_linux_vfp_register_count > 0
+	       && regno >= ARM_D0_REGNUM
+	       && regno <= ARM_D0_REGNUM + arm_linux_vfp_register_count)
+	store_vfp_regs (regcache);
     }
 }
 
@@ -575,23 +668,118 @@ get_linux_version (unsigned int *vmajor,
   return ((*vmajor << 16) | (*vminor << 8) | *vrelease);
 }
 
+/* Copy LEN bytes from inferior's auxiliary vector starting at OFFSET
+   to debugger memory starting at MYADDR.  */
+
+static int
+arm_read_auxv(int offset, unsigned char *myaddr, unsigned int len)
+{
+  char filename[PATH_MAX];
+  int fd, n;
+  int pid = GET_LWP (inferior_ptid);
+
+  snprintf (filename, sizeof filename, "/proc/%d/auxv", pid);
+
+  fd = open (filename, O_RDONLY);
+  if (fd < 0)
+    return -1;
+
+  if (offset != (CORE_ADDR) 0
+      && lseek (fd, (off_t) offset, SEEK_SET) != (off_t) offset)
+    n = -1;
+  else
+    n = read (fd, myaddr, len);
+
+  close (fd);
+
+  return n;
+}
+
+static int
+arm_get_hwcap (unsigned long *valp)
+{
+  unsigned char *data = alloca (8);
+  int offset = 0;
+
+  while (arm_read_auxv (offset, data, 8) == 8)
+    {
+      unsigned int *data_p = (unsigned int *)data;
+      if (data_p[0] == AT_HWCAP)
+	{
+	  *valp = data_p[1];
+	  return 1;
+	}
+
+      offset += 8;
+    }
+
+  *valp = 0;
+  return 0;
+}
+
 static const struct target_desc *
 arm_linux_read_description (struct target_ops *ops)
 {
-  int ret;
-  char regbuf[IWMMXT_REGS_SIZE];
+  unsigned long arm_hwcap = 0;
+  arm_linux_has_wmmx_registers = 0;
+  arm_linux_vfp_register_count = 0;
+
+  if (arm_get_hwcap (&arm_hwcap) == 0)
+    {
+      return NULL;
+    }
+
+  if (arm_hwcap & HWCAP_IWMMXT)
+    {
+      arm_linux_has_wmmx_registers = 1;
+      if (tdesc_arm_with_iwmmxt == NULL)
+	initialize_tdesc_arm_with_iwmmxt ();
+      return tdesc_arm_with_iwmmxt;
+    }
+
+  if (arm_hwcap & HWCAP_VFP)
+    {
+      int pid;
+      char *buf;
+      const struct target_desc * result = NULL;
+
+      /* NEON implies VFPv3-D32 or no-VFP unit.  Say that we only support
+	 Neon with VFPv3-D32.  */
+      if (arm_hwcap & HWCAP_NEON)
+	{
+	  arm_linux_vfp_register_count = 32;
+	  if (tdesc_arm_with_neon == NULL)
+	    initialize_tdesc_arm_with_neon ();
+	  result = tdesc_arm_with_neon;
+	}
+      else if ((arm_hwcap & (HWCAP_VFPv3 | HWCAP_VFPv3D16)) == HWCAP_VFPv3)
+	{
+	  arm_linux_vfp_register_count = 32;
+	  if (tdesc_arm_with_vfpv3 == NULL)
+	    initialize_tdesc_arm_with_vfpv3 ();
+	  result = tdesc_arm_with_vfpv3;
+	}
+      else
+	{
+	  arm_linux_vfp_register_count = 16;
+	  if (tdesc_arm_with_vfpv2 == NULL)
+	    initialize_tdesc_arm_with_vfpv2 ();
+	  result = tdesc_arm_with_vfpv2;
+	}
+
+      /* Now make sure that the kernel supports reading these
+	 registers.  Support was added in 2.6.30.  */
+      pid = GET_LWP (inferior_ptid);
+      errno = 0;
+      buf = alloca (VFP_REGS_SIZE);
+      if (ptrace (PTRACE_GETVFPREGS, pid, 0, buf) < 0
+	  && errno == EIO)
+	result = NULL;
 
-  ret = ptrace (PTRACE_GETWMMXREGS, GET_THREAD_ID (inferior_ptid),
-		0, regbuf);
-  if (ret < 0)
-    arm_linux_has_wmmx_registers = 0;
-  else
-    arm_linux_has_wmmx_registers = 1;
+      return result;
+    }
 
-  if (arm_linux_has_wmmx_registers)
-    return tdesc_arm_with_iwmmxt;
-  else
-    return NULL;
+  return NULL;
 }
 
 void _initialize_arm_linux_nat (void);
@@ -614,7 +802,4 @@ _initialize_arm_linux_nat (void)
 
   /* Register the target.  */
   linux_nat_add_target (t);
-
-  /* Initialize the standard target descriptions.  */
-  initialize_tdesc_arm_with_iwmmxt ();
 }
Index: gdb/arm-tdep.h
===================================================================
RCS file: /cvs/src/src/gdb/arm-tdep.h,v
retrieving revision 1.39
diff -u -p -r1.39 arm-tdep.h
--- gdb/arm-tdep.h	1 Feb 2010 16:13:15 -0000	1.39
+++ gdb/arm-tdep.h	1 Mar 2010 11:33:32 -0000
@@ -50,6 +50,7 @@ enum gdb_regnum {
   ARM_WCGR7_REGNUM = ARM_WCGR0_REGNUM + 7,
   ARM_D0_REGNUM,		/* VFP double-precision registers.  */
   ARM_D31_REGNUM = ARM_D0_REGNUM + 31,
+  ARM_FPSCR_REGNUM,
 
   ARM_NUM_REGS,
 

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