Re: [Patch,ARM] Next pc of sigreturn/rt_sigreturn syscall

[Yao Qi <yao@codesourcery.com>]

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On Tue, Aug 24, 2010 at 10:12:57AM -0400, Daniel Jacobowitz wrote:
> On Tue, Aug 24, 2010 at 01:27:03PM +0200, Mark Kettenis wrote:
> > > Date: Mon, 23 Aug 2010 23:38:54 -0700
> > > From: Yao Qi <yao@codesourcery.com>
> > > 
> > > Hi,
> > > This patch is to calculate correct address of 'next pc' of syscall
> > > sigreturn and rt_sigreturn.
> > 
> > You're polluting the genric arm code with Linux-specific stuff.
> > Please don't do that.  If something like this is needed, it should be
> > added to code in arm-linux-tdep.c.
> 
> There's a couple of ways to do that; one example is
> mips_linux_syscall_next_pc.

Here is the updated patch, in which:
  1.  Add arm_linux_syscall_next_pc, similar to
mips_linux_syscall_next_pc.  Compute the return address of SWI in both
ARM mode and Thumb mode.
  2.  Extract some common code from arm_linux_copy_svc.

Tested on armv7l-unknown-linux-gnueabi again.  Result is the same as
my previous post.

-- 
Yao Qi
CodeSourcery
yao@codesourcery.com
(650) 331-3385 x739

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2010-08-25  Yao Qi  <yao@codesourcery.com>

	* arm-linux-tdep.c (arm_linux_sigreturn_return_addr): New.
	(arm_linux_syscall_next_pc): New.
	(arm_linux_copy_svc): Use arm_linux_sigreturn_return_addr instead. 
	(arm_linux_init_abi): Initialize syscall_next_pc.
	* arm-tdep.c (thumb_get_next_pc_raw):  Get next pc of SWI in Thumb mode.
	(arm_get_next_pc_raw): Get next pc of SWI in ARM mode.
	* arm-tdep.h (struct gdbarch_tdep): Add a function pointer syscall_next_pc. 
	Declare arm_frame_is_thumb.


diff --git a/gdb/arm-linux-tdep.c b/gdb/arm-linux-tdep.c
index 682054c..106cd85 100644
--- a/gdb/arm-linux-tdep.c
+++ b/gdb/arm-linux-tdep.c
@@ -630,6 +630,53 @@ arm_linux_regset_from_core_section (struct gdbarch *gdbarch,
   return NULL;
 }
 
+/* Get the value of next pc of sigreturn and rt_sigrturn.  Return 0 if it is 
+   not a rt_sigreturn/sigreturn syscall.  */
+static int
+arm_linux_sigreturn_return_addr(struct frame_info *frame,
+				unsigned long svc_number)
+{
+  /* Is this a sigreturn or rt_sigreturn syscall?  Note: these are only useful
+     for EABI.  */
+  if (svc_number == 119 || svc_number == 173)
+    {
+      if (get_frame_type (frame) == SIGTRAMP_FRAME)
+	{
+	  return frame_unwind_caller_pc (frame);
+	}
+    }
+  return 0;
+}
+
+/* When FRAME is at a syscall instruction, return the PC of the next
+   instruction to be executed.  */
+
+static CORE_ADDR
+arm_linux_syscall_next_pc (struct frame_info *frame)
+{
+  CORE_ADDR pc = get_frame_pc (frame);
+  CORE_ADDR return_addr = 0;
+  return_addr = arm_linux_sigreturn_return_addr(frame,
+						get_frame_register_unsigned (frame, 7));
+
+  if (return_addr)
+    return return_addr;
+  
+  if (arm_frame_is_thumb (frame))
+    {
+      return_addr = pc + 2;
+      /* Addresses for calling Thumb functions have the bit 0 set.  */
+      return_addr |= 1;
+    }
+  else
+    {
+      return_addr = pc + 4;
+    }
+
+  return return_addr;
+}
+
+
 /* Insert a single step breakpoint at the next executed instruction.  */
 
 static int
@@ -688,6 +735,8 @@ arm_linux_copy_svc (struct gdbarch *gdbarch, uint32_t insn, CORE_ADDR to,
 		    struct regcache *regs, struct displaced_step_closure *dsc)
 {
   CORE_ADDR from = dsc->insn_addr;
+  CORE_ADDR return_to = 0;
+
   struct frame_info *frame;
   unsigned int svc_number = displaced_read_reg (regs, from, 7);
 
@@ -697,13 +746,9 @@ arm_linux_copy_svc (struct gdbarch *gdbarch, uint32_t insn, CORE_ADDR to,
 
   frame = get_current_frame ();
 
-  /* Is this a sigreturn or rt_sigreturn syscall?  Note: these are only useful
-     for EABI.  */
-  if (svc_number == 119 || svc_number == 173)
-    {
-      if (get_frame_type (frame) == SIGTRAMP_FRAME)
+  return_to = arm_linux_sigreturn_return_addr(frame, svc_number);
+  if (return_to)
 	{
-	  CORE_ADDR return_to;
 	  struct symtab_and_line sal;
 
 	  if (debug_displaced)
@@ -711,7 +756,6 @@ arm_linux_copy_svc (struct gdbarch *gdbarch, uint32_t insn, CORE_ADDR to,
 	      "sigreturn/rt_sigreturn SVC call. PC in frame = %lx\n",
 	      (unsigned long) get_frame_pc (frame));
 
-	  return_to = frame_unwind_caller_pc (frame);
 	  if (debug_displaced)
 	    fprintf_unfiltered (gdb_stdlog, "displaced: unwind pc = %lx. "
 	      "Setting momentary breakpoint.\n", (unsigned long) return_to);
@@ -743,7 +787,7 @@ arm_linux_copy_svc (struct gdbarch *gdbarch, uint32_t insn, CORE_ADDR to,
       else if (debug_displaced)
 	fprintf_unfiltered (gdb_stdlog, "displaced: sigreturn/rt_sigreturn "
 			    "SVC call not in signal trampoline frame\n");
-    }
+    
 
   /* Preparation: If we detect sigreturn, set momentary breakpoint at resume
 		  location, else nothing.
@@ -946,6 +990,9 @@ arm_linux_init_abi (struct gdbarch_info info,
   set_gdbarch_displaced_step_free_closure (gdbarch,
 					   simple_displaced_step_free_closure);
   set_gdbarch_displaced_step_location (gdbarch, displaced_step_at_entry_point);
+
+
+  tdep->syscall_next_pc = arm_linux_syscall_next_pc;
 }
 
 /* Provide a prototype to silence -Wmissing-prototypes.  */
diff --git a/gdb/arm-tdep.c b/gdb/arm-tdep.c
index 1ac8817..518e4e8 100644
--- a/gdb/arm-tdep.c
+++ b/gdb/arm-tdep.c
@@ -257,7 +257,7 @@ int arm_apcs_32 = 1;
 
 /* Determine if FRAME is executing in Thumb mode.  */
 
-static int
+int
 arm_frame_is_thumb (struct frame_info *frame)
 {
   CORE_ADDR cpsr;
@@ -2808,7 +2808,16 @@ thumb_get_next_pc_raw (struct frame_info *frame, CORE_ADDR pc, int insert_bkpt)
   else if ((inst1 & 0xf000) == 0xd000)	/* conditional branch */
     {
       unsigned long cond = bits (inst1, 8, 11);
-      if (cond != 0x0f && condition_true (cond, status))    /* 0x0f = SWI */
+      if (cond == 0x0f)  /* 0x0f = SWI */
+	{
+	  struct gdbarch_tdep *tdep;
+	  tdep = gdbarch_tdep (get_frame_arch (frame));
+
+	  if (tdep->syscall_next_pc != NULL)
+	    nextpc = tdep->syscall_next_pc (frame);
+
+	}
+      else if (cond != 0x0f && condition_true (cond, status))
 	nextpc = pc_val + (sbits (inst1, 0, 7) << 1);
     }
   else if ((inst1 & 0xf800) == 0xe000)	/* unconditional branch */
@@ -3257,7 +3266,16 @@ arm_get_next_pc_raw (struct frame_info *frame, CORE_ADDR pc, int insert_bkpt)
 	case 0xc:
 	case 0xd:
 	case 0xe:		/* coproc ops */
+	  break;
 	case 0xf:		/* SWI */
+	  {
+	    struct gdbarch_tdep *tdep;
+	    tdep = gdbarch_tdep (get_frame_arch (frame));
+
+	    if (tdep->syscall_next_pc != NULL)
+	      nextpc = tdep->syscall_next_pc (frame);
+
+	  }
 	  break;
 
 	default:
diff --git a/gdb/arm-tdep.h b/gdb/arm-tdep.h
index b6283ef..2f4e99b 100644
--- a/gdb/arm-tdep.h
+++ b/gdb/arm-tdep.h
@@ -193,6 +193,10 @@ struct gdbarch_tdep
   struct type *arm_ext_type;
   struct type *neon_double_type;
   struct type *neon_quad_type;
+
+  /* Return the expected next PC if FRAME is stopped at a syscall
+     instruction.  */
+  CORE_ADDR (*syscall_next_pc) (struct frame_info *frame);
 };
 
 /* Structures used for displaced stepping.  */
@@ -294,6 +298,7 @@ extern void
 CORE_ADDR arm_skip_stub (struct frame_info *, CORE_ADDR);
 CORE_ADDR arm_get_next_pc (struct frame_info *, CORE_ADDR);
 int arm_software_single_step (struct frame_info *);
+int arm_frame_is_thumb (struct frame_info *frame);
 
 extern struct displaced_step_closure *
   arm_displaced_step_copy_insn (struct gdbarch *, CORE_ADDR, CORE_ADDR,