Patchwork [v2,AArch64] Add more debugging output to aarch64_displaced_step_fixup

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Submitter Luis Machado
Date Jan. 13, 2020, 5:42 p.m.
Message ID <20200113174239.7819-1-luis.machado@linaro.org>
Download mbox | patch
Permalink /patch/37352/
State New
Headers show

Comments

Luis Machado - Jan. 13, 2020, 5:42 p.m.
New in v2:

- Fixed misc comments from review.

--

While debugging the step-over-syscall problem, i wanted to see a bit more
debugging output to try to determine the root cause.

This patch does this.

gdb/ChangeLog:

2020-01-13  Luis Machado  <luis.machado@linaro.org>

	* aarch64-tdep.c (aarch64_displaced_step_fixup): Add more debugging
	output.
---
 gdb/aarch64-tdep.c | 27 +++++++++++++++++++++++++--
 1 file changed, 25 insertions(+), 2 deletions(-)

Patch

diff --git a/gdb/aarch64-tdep.c b/gdb/aarch64-tdep.c
index 6a9d34dc67..29b712c155 100644
--- a/gdb/aarch64-tdep.c
+++ b/gdb/aarch64-tdep.c
@@ -3037,8 +3037,16 @@  aarch64_displaced_step_fixup (struct gdbarch *gdbarch,
 
   regcache_cooked_read_unsigned (regs, AARCH64_PC_REGNUM, &pc);
 
+  if (debug_displaced)
+    debug_printf ("Displaced: PC after stepping: %s (was %s).\n",
+		  paddress (gdbarch, pc), paddress (gdbarch, to));
+
   if (dsc->cond)
     {
+      if (debug_displaced)
+	debug_printf ("Displaced: [Conditional] pc_adjust before: %d\n",
+		      dsc->pc_adjust);
+
       if (pc - to == 8)
 	{
 	  /* Condition is true.  */
@@ -3050,8 +3058,18 @@  aarch64_displaced_step_fixup (struct gdbarch *gdbarch,
 	}
       else
 	gdb_assert_not_reached ("Unexpected PC value after displaced stepping");
+
+      if (debug_displaced)
+	debug_printf ("Displaced: [Conditional] pc_adjust after: %d\n",
+		      dsc->pc_adjust);
     }
 
+  if (debug_displaced)
+    debug_printf ("Displaced: %s PC by %d\n",
+		  dsc->pc_adjust? "adjusting" : "not adjusting",
+		  dsc->pc_adjust);
+
+
   if (dsc->pc_adjust != 0)
     {
       /* Make sure the previous instruction was executed (that is, the PC
@@ -3059,11 +3077,16 @@  aarch64_displaced_step_fixup (struct gdbarch *gdbarch,
 	 offset.  Otherwise we may skip an instruction before its execution
 	 took place.  */
       if ((pc - to) == 0)
-	dsc->pc_adjust = 0;
+	{
+	  if (debug_displaced)
+	    debug_printf ("Displaced: PC did not move. Discarding PC "
+			  "adjustment.\n");
+	  dsc->pc_adjust = 0;
+	}
 
       if (debug_displaced)
 	{
-	  debug_printf ("displaced: fixup: set PC to %s:%d\n",
+	  debug_printf ("Displaced: fixup: set PC to %s:%d\n",
 			paddress (gdbarch, from), dsc->pc_adjust);
 	}
       regcache_cooked_write_unsigned (regs, AARCH64_PC_REGNUM,