[commit] Eliminate current_regcache from ia64-tdep.c libunwind accessor routines

["Ulrich Weigand" <uweigand at de dot ibm dot com>]

Hello,

ia64-tdep.c contains callback routines providing register access to
the libunwind library.  There are two flavours of these accessors:
one uses the actual thread registers (from current_regcache), the
other unwinds the register values from a given next frame.

However, there are two problems with this: in the next_frame versions
of the accessor functions, the "write" methods still modify the
current_regcache directly; and in the regcache versions, there is
no way to actually specify which regcache to use.

Now, as to the "write" problem: since we only ever call into libunwind
to query state and do not use any of the operations that would modify
state, libunwind in turn never has the need to call the accessor
functions to perform a write operation.  So this problem doesn't
actually exist.

As to the second problem: the libunwind routines do receive a callback
argument that can be set by the caller.  For the next_frame versions,
this is indeed being used to pass in the frame.  The patch uses that
same method now to also pass in the regcache into the regcache versions
of the accessor routines.

This eliminates all references to global state from the libunwind
accessor routines.

Tested on ia64-linux.
Committed to mainline.

Bye,
Ulrich


ChangeLog:

	* libunwind-frame.h (struct regcache): Add forward declaration.
	(libunwind_get_reg_special): Add REGCACHE argument.
	* libunwind-frame.c (libunwind_get_reg_special): Add REGCACHE
	argument.  Pass it to unw_init_remote_p.

	* ia64-tdep.c (ia64_pseudo_register_read): Pass regcache to
	libunwind_get_reg_special.
	(ia64_access_reg): Remove "write" case.
	(ia64_access_fpreg): Likewise.  Read from next_frame passed
	as callback argument instead of from current_regcache.
	(ia64_access_rse_reg): Remove "write" case.  Read from regcache
	passed as callback argument instead of from current_regcache.
	(ia64_access_rse_fpreg): New function.
	(ia64_unw_rse_acce): Use it instead of ia64_access_fpreg.

diff -urNp gdb-orig/gdb/ia64-tdep.c gdb-head/gdb/ia64-tdep.c
--- gdb-orig/gdb/ia64-tdep.c	2007-05-12 00:01:46.000000000 +0200
+++ gdb-head/gdb/ia64-tdep.c	2007-05-12 00:04:51.000000000 +0200
@@ -692,7 +692,7 @@ ia64_pseudo_register_read (struct gdbarc
       /* First try and use the libunwind special reg accessor, otherwise fallback to
 	 standard logic.  */
       if (!libunwind_is_initialized ()
-	  || libunwind_get_reg_special (gdbarch, regnum, buf) != 0)
+	  || libunwind_get_reg_special (gdbarch, regcache, regnum, buf) != 0)
 #endif
 	{
 	  /* The fallback position is to assume that r32-r127 are found sequentially
@@ -2218,106 +2218,53 @@ ia64_access_reg (unw_addr_space_t as, un
   long new_sof, old_sof;
   char buf[MAX_REGISTER_SIZE];
   
-  if (write)
-    {
-      if (regnum < 0)
-	/* ignore writes to pseudo-registers such as UNW_IA64_PROC_STARTI.  */
-	return 0;
-  
-      switch (uw_regnum)
-	{
-	case UNW_REG_IP:
-	  ia64_write_pc (*val, inferior_ptid);
-	  break;
+  /* We never call any libunwind routines that need to write registers.  */
+  gdb_assert (!write);
 
-	case UNW_IA64_AR_BSPSTORE:
-	  write_register (IA64_BSP_REGNUM, *val);
-	  break;
-	  
-	case UNW_IA64_AR_BSP:
-	case UNW_IA64_BSP:
-	  /* Account for the fact that ptrace() expects bsp to point
-	     after the current register frame.  */
-	  cfm = read_register (IA64_CFM_REGNUM);
-	  sof = (cfm & 0x7f);
-	  bsp = ia64_rse_skip_regs (*val, sof);
-	  write_register (IA64_BSP_REGNUM, bsp);
-	  break;
-	  
-	case UNW_IA64_CFM:
-	  /* If we change CFM, we need to adjust ptrace's notion of
-	     bsp accordingly, so that the real bsp remains
-	     unchanged.  */
-	  bsp = read_register (IA64_BSP_REGNUM);
-	  cfm = read_register (IA64_CFM_REGNUM);
-	  old_sof = (cfm & 0x7f);
-	  new_sof = (*val & 0x7f);
-	  if (old_sof != new_sof)
-	    {
-	      bsp = ia64_rse_skip_regs (bsp, -old_sof + new_sof);
-	      write_register (IA64_BSP_REGNUM, bsp);
-	    }
-	  write_register (IA64_CFM_REGNUM, *val);
-	  break;
-	  
-	default:
-	  write_register (regnum, *val);
-	  break;
-	}
-      if (gdbarch_debug >= 1)
-	fprintf_unfiltered (gdb_stdlog, 
-			    "  access_reg: to cache: %4s=0x%s\n",
-			    (((unsigned) regnum <= IA64_NAT127_REGNUM)
-			     ? ia64_register_names[regnum] : "r??"), 
-			    paddr_nz (*val));
-    }
-  else
+  switch (uw_regnum)
     {
-      switch (uw_regnum)
-	{
-	case UNW_REG_IP:
-	  /* Libunwind expects to see the pc value which means the slot number
-	     from the psr must be merged with the ip word address.  */
-	  frame_unwind_register (next_frame, IA64_IP_REGNUM, buf);
-	  ip = extract_unsigned_integer (buf, 8); 
-	  frame_unwind_register (next_frame, IA64_PSR_REGNUM, buf);
-	  psr = extract_unsigned_integer (buf, 8); 
-	  *val = ip | ((psr >> 41) & 0x3);
-	  break;
-	  
-	case UNW_IA64_AR_BSP:
-	  /* Libunwind expects to see the beginning of the current register
-	     frame so we must account for the fact that ptrace() will return a value
-	     for bsp that points *after* the current register frame.  */
-	  frame_unwind_register (next_frame, IA64_BSP_REGNUM, buf);
-	  bsp = extract_unsigned_integer (buf, 8);
-	  frame_unwind_register (next_frame, IA64_CFM_REGNUM, buf);
-	  cfm = extract_unsigned_integer (buf, 8); 
-	  sof = (cfm & 0x7f);
-	  *val = ia64_rse_skip_regs (bsp, -sof);
-	  break;
-	  
-	case UNW_IA64_AR_BSPSTORE:
-	  /* Libunwind wants bspstore to be after the current register frame.
-	     This is what ptrace() and gdb treats as the regular bsp value.  */
-	  frame_unwind_register (next_frame, IA64_BSP_REGNUM, buf);
-	  *val = extract_unsigned_integer (buf, 8);
-	  break;
+      case UNW_REG_IP:
+	/* Libunwind expects to see the pc value which means the slot number
+	   from the psr must be merged with the ip word address.  */
+	frame_unwind_register (next_frame, IA64_IP_REGNUM, buf);
+	ip = extract_unsigned_integer (buf, 8); 
+	frame_unwind_register (next_frame, IA64_PSR_REGNUM, buf);
+	psr = extract_unsigned_integer (buf, 8); 
+	*val = ip | ((psr >> 41) & 0x3);
+	break;
+ 
+      case UNW_IA64_AR_BSP:
+	/* Libunwind expects to see the beginning of the current register
+	   frame so we must account for the fact that ptrace() will return a value
+	   for bsp that points *after* the current register frame.  */
+	frame_unwind_register (next_frame, IA64_BSP_REGNUM, buf);
+	bsp = extract_unsigned_integer (buf, 8);
+	frame_unwind_register (next_frame, IA64_CFM_REGNUM, buf);
+	cfm = extract_unsigned_integer (buf, 8); 
+	sof = (cfm & 0x7f);
+	*val = ia64_rse_skip_regs (bsp, -sof);
+	break;
 
-	default:
-	  /* For all other registers, just unwind the value directly.  */
-	  frame_unwind_register (next_frame, regnum, buf);
-	  *val = extract_unsigned_integer (buf, 8); 
-	  break;
-	}
-      
-      if (gdbarch_debug >= 1)
-	fprintf_unfiltered (gdb_stdlog, 
-			    "  access_reg: from cache: %4s=0x%s\n",
-			    (((unsigned) regnum <= IA64_NAT127_REGNUM)
-			     ? ia64_register_names[regnum] : "r??"), 
-			    paddr_nz (*val));
+      case UNW_IA64_AR_BSPSTORE:
+	/* Libunwind wants bspstore to be after the current register frame.
+	   This is what ptrace() and gdb treats as the regular bsp value.  */
+	frame_unwind_register (next_frame, IA64_BSP_REGNUM, buf);
+	*val = extract_unsigned_integer (buf, 8);
+	break;
+
+      default:
+	/* For all other registers, just unwind the value directly.  */
+	frame_unwind_register (next_frame, regnum, buf);
+	*val = extract_unsigned_integer (buf, 8); 
+	break;
     }
+      
+  if (gdbarch_debug >= 1)
+    fprintf_unfiltered (gdb_stdlog, 
+			"  access_reg: from cache: %4s=0x%s\n",
+			(((unsigned) regnum <= IA64_NAT127_REGNUM)
+			? ia64_register_names[regnum] : "r??"), 
+			paddr_nz (*val));
   return 0;
 }
 
@@ -2327,11 +2274,13 @@ ia64_access_fpreg (unw_addr_space_t as, 
 		   int write, void *arg)
 {
   int regnum = ia64_uw2gdb_regnum (uw_regnum);
+  struct frame_info *next_frame = arg;
   
-  if (write)
-    regcache_cooked_write (current_regcache, regnum, (char *) val);
-  else
-    regcache_cooked_read (current_regcache, regnum, (char *) val);
+  /* We never call any libunwind routines that need to write registers.  */
+  gdb_assert (!write);
+
+  frame_unwind_register (next_frame, regnum, (char *) val);
+
   return 0;
 }
 
@@ -2342,94 +2291,49 @@ ia64_access_rse_reg (unw_addr_space_t as
 {
   int regnum = ia64_uw2gdb_regnum (uw_regnum);
   unw_word_t bsp, sof, sol, cfm, psr, ip;
+  struct regcache *regcache = arg;
   long new_sof, old_sof;
+  char buf[MAX_REGISTER_SIZE];
   
-  if (write)
-    {
-      if (regnum < 0)
-	/* ignore writes to pseudo-registers such as UNW_IA64_PROC_STARTI.  */
-	return 0;
-  
-      switch (uw_regnum)
-	{
-	case UNW_REG_IP:
-	  ia64_write_pc (*val, inferior_ptid);
-	  break;
+  /* We never call any libunwind routines that need to write registers.  */
+  gdb_assert (!write);
 
-	case UNW_IA64_AR_BSPSTORE:
-	  write_register (IA64_BSP_REGNUM, *val);
-	  break;
-	  
-	case UNW_IA64_AR_BSP:
-	case UNW_IA64_BSP:
-	  /* Account for the fact that ptrace() expects bsp to point
-	     after the current register frame.  */
-	  cfm = read_register (IA64_CFM_REGNUM);
-	  sof = (cfm & 0x7f);
-	  bsp = ia64_rse_skip_regs (*val, sof);
-	  write_register (IA64_BSP_REGNUM, bsp);
-	  break;
-	  
-	case UNW_IA64_CFM:
-	  /* If we change CFM, we need to adjust ptrace's notion of
-	     bsp accordingly, so that the real bsp remains
-	     unchanged.  */
-	  bsp = read_register (IA64_BSP_REGNUM);
-	  cfm = read_register (IA64_CFM_REGNUM);
-	  old_sof = (cfm & 0x7f);
-	  new_sof = (*val & 0x7f);
-	  if (old_sof != new_sof)
-	    {
-	      bsp = ia64_rse_skip_regs (bsp, -old_sof + new_sof);
-	      write_register (IA64_BSP_REGNUM, bsp);
-	    }
-	  write_register (IA64_CFM_REGNUM, *val);
-	  break;
-	  
-	default:
-	  write_register (regnum, *val);
-	  break;
-	}
-      if (gdbarch_debug >= 1)
-	fprintf_unfiltered (gdb_stdlog, 
-			    "  access_rse_reg: to cache: %4s=0x%s\n",
-			    (((unsigned) regnum <= IA64_NAT127_REGNUM)
-			     ? ia64_register_names[regnum] : "r??"), 
-			    paddr_nz (*val));
-    }
-  else
+  switch (uw_regnum)
     {
-      switch (uw_regnum)
-	{
-	case UNW_REG_IP:
-	  /* Libunwind expects to see the pc value which means the slot number
-	     from the psr must be merged with the ip word address.  */
-	  ip = read_register (IA64_IP_REGNUM); 
-	  psr = read_register (IA64_PSR_REGNUM);
-	  *val = ip | ((psr >> 41) & 0x3);
-	  break;
+      case UNW_REG_IP:
+	/* Libunwind expects to see the pc value which means the slot number
+	   from the psr must be merged with the ip word address.  */
+	regcache_cooked_read (regcache, IA64_IP_REGNUM, buf);
+	ip = extract_unsigned_integer (buf, 8); 
+	regcache_cooked_read (regcache, IA64_PSR_REGNUM, buf);
+	psr = extract_unsigned_integer (buf, 8); 
+	*val = ip | ((psr >> 41) & 0x3);
+	break;
 	  
-	case UNW_IA64_AR_BSP:
-	  /* Libunwind expects to see the beginning of the current register
-	     frame so we must account for the fact that ptrace() will return a value
-	     for bsp that points *after* the current register frame.  */
-	  bsp = read_register (IA64_BSP_REGNUM);
-	  cfm = read_register (IA64_CFM_REGNUM);
-	  sof = (cfm & 0x7f);
-	  *val = ia64_rse_skip_regs (bsp, -sof);
-	  break;
+      case UNW_IA64_AR_BSP:
+	/* Libunwind expects to see the beginning of the current register
+	   frame so we must account for the fact that ptrace() will return a value
+	   for bsp that points *after* the current register frame.  */
+	regcache_cooked_read (regcache, IA64_BSP_REGNUM, buf);
+	bsp = extract_unsigned_integer (buf, 8);
+	regcache_cooked_read (regcache, IA64_CFM_REGNUM, buf);
+	cfm = extract_unsigned_integer (buf, 8); 
+	sof = (cfm & 0x7f);
+	*val = ia64_rse_skip_regs (bsp, -sof);
+	break;
 	  
-	case UNW_IA64_AR_BSPSTORE:
-	  /* Libunwind wants bspstore to be after the current register frame.
-	     This is what ptrace() and gdb treats as the regular bsp value.  */
-	  *val = read_register (IA64_BSP_REGNUM);
-	  break;
+      case UNW_IA64_AR_BSPSTORE:
+	/* Libunwind wants bspstore to be after the current register frame.
+	   This is what ptrace() and gdb treats as the regular bsp value.  */
+	regcache_cooked_read (regcache, IA64_BSP_REGNUM, buf);
+	*val = extract_unsigned_integer (buf, 8);
+	break;
 
-	default:
-	  /* For all other registers, just read the value directly.  */
-	  *val = read_register (regnum);
-	  break;
-	}
+      default:
+        /* For all other registers, just unwind the value directly.  */
+	regcache_cooked_read (regcache, regnum, buf);
+	*val = extract_unsigned_integer (buf, 8); 
+	break;
     }
       
   if (gdbarch_debug >= 1)
@@ -2442,6 +2346,22 @@ ia64_access_rse_reg (unw_addr_space_t as
   return 0;
 }
 
+/* Libunwind callback accessor function for top-level fp registers.  */
+static int
+ia64_access_rse_fpreg (unw_addr_space_t as, unw_regnum_t uw_regnum,
+		       unw_fpreg_t *val, int write, void *arg)
+{
+  int regnum = ia64_uw2gdb_regnum (uw_regnum);
+  struct regcache *regcache = arg;
+  
+  /* We never call any libunwind routines that need to write registers.  */
+  gdb_assert (!write);
+
+  regcache_cooked_read (regcache, regnum, (char *) val);
+
+  return 0;
+}
+
 /* Libunwind callback accessor function for accessing memory.  */
 static int
 ia64_access_mem (unw_addr_space_t as,
@@ -2976,7 +2896,7 @@ static unw_accessors_t ia64_unw_rse_acce
   ia64_get_dyn_info_list,
   ia64_access_mem,
   ia64_access_rse_reg,
-  ia64_access_fpreg,
+  ia64_access_rse_fpreg,
   /* resume */
   /* get_proc_name */
 };
diff -urNp gdb-orig/gdb/libunwind-frame.c gdb-head/gdb/libunwind-frame.c
--- gdb-orig/gdb/libunwind-frame.c	2007-05-12 00:01:46.000000000 +0200
+++ gdb-head/gdb/libunwind-frame.c	2007-05-12 00:03:45.000000000 +0200
@@ -395,7 +395,8 @@ libunwind_sigtramp_frame_sniffer (struct
    are usually located at BOF, this is not always true and only the libunwind
    info can decipher where they actually are.  */
 int
-libunwind_get_reg_special (struct gdbarch *gdbarch, int regnum, void *buf)
+libunwind_get_reg_special (struct gdbarch *gdbarch, struct regcache *regcache,
+			   int regnum, void *buf)
 {
   unw_cursor_t cursor;
   unw_accessors_t *acc;
@@ -415,7 +416,7 @@ libunwind_get_reg_special (struct gdbarc
 				 ? __BIG_ENDIAN
 				 : __LITTLE_ENDIAN);
 
-  ret = unw_init_remote_p (&cursor, as, NULL);
+  ret = unw_init_remote_p (&cursor, as, regcache);
   if (ret < 0)
     return -1;
 
diff -urNp gdb-orig/gdb/libunwind-frame.h gdb-head/gdb/libunwind-frame.h
--- gdb-orig/gdb/libunwind-frame.h	2007-05-12 00:01:46.000000000 +0200
+++ gdb-head/gdb/libunwind-frame.h	2007-05-12 00:03:45.000000000 +0200
@@ -25,6 +25,7 @@
 
 struct frame_info;
 struct frame_id;
+struct regcache;
 struct gdbarch;
 
 #ifndef LIBUNWIND_FRAME_H
@@ -62,7 +63,9 @@ int libunwind_search_unwind_table (void 
 unw_word_t libunwind_find_dyn_list (unw_addr_space_t, unw_dyn_info_t *,
 				    void *);
 
-int libunwind_get_reg_special (struct gdbarch *gdbarch, int regnum, void *buf);
+int libunwind_get_reg_special (struct gdbarch *gdbarch,
+			       struct regcache *regcache,
+			       int regnum, void *buf);
 
 #endif /* libunwind-frame.h */
 
-- 
  Dr. Ulrich Weigand
  GNU Toolchain for Linux on System z and Cell BE
  Ulrich.Weigand@de.ibm.com