[PATCH v3 7/7] amd64_analyze_prologue: use target_read_code instead of read_code

[Victor Collod <vcollod@nvidia.com>]

Using target_read_code enables gracefuly handling error cases.

2020-06-23  Victor Collod  <vcollod@nvidia.com>

	* amd64-tdep.c (amd64_analyze_prologue): Use target_read_code
	instead of read_code.
---
 gdb/amd64-tdep.c | 19 ++++++++++++++-----
 1 file changed, 14 insertions(+), 5 deletions(-)

diff --git a/gdb/amd64-tdep.c b/gdb/amd64-tdep.c
index 901733cf443..7f70c1d0d8d 100644
--- a/gdb/amd64-tdep.c
+++ b/gdb/amd64-tdep.c
@@ -2394,9 +2394,15 @@ amd64_analyze_prologue (struct gdbarch *gdbarch,
   else
     pc = amd64_analyze_stack_align (pc, current_pc, cache);
 
-  read_code (pc, buf, 4);
-  /* Check for the `endbr64' instruction and skip it if found.  */
-  if (memcmp (buf, endbr64, sizeof (endbr64)) == 0)
+  /* Try to read enough bytes to check for `endbr64'.  */
+  if (target_read_code (pc, buf, 4) != 0)
+    {
+      /* If it fails, read just enough data for `pushq %rbp'.  */
+      if (target_read_code (pc, buf, 1) != 0)
+	return pc;
+    }
+  /* If reading succeeded, check for the `endbr64' instruction and skip it if found.  */
+  else if (memcmp (buf, endbr64, sizeof (endbr64)) == 0)
     {
       pc += sizeof (endbr64);
       /* If we went past the allowed bound, stop.  */
@@ -2404,7 +2410,8 @@ amd64_analyze_prologue (struct gdbarch *gdbarch,
 	return current_pc;
 
       /* Update the code buffer, as pc changed.  */
-      read_code (pc, buf, 1);
+      if (target_read_code (pc, buf, 1) != 0)
+	return pc;
     }
 
   /* Stop right now if there's no `pushq %rbp'.  */
@@ -2422,7 +2429,9 @@ amd64_analyze_prologue (struct gdbarch *gdbarch,
   if (pc >= current_pc)
     return current_pc;
 
-  read_code (pc, buf, 3);
+  /* Try to read the code for the stack base move.  */
+  if (target_read_code (pc, buf, 3) != 0)
+    return pc;
 
   /* Check for `movq %rsp, %rbp'.  */
   if (memcmp (buf, mov_rsp_rbp_1, 3) == 0
-- 
2.20.1