[PATCH v7 1/3] disass: Add /x modifier to print offsets in hex

[fam@euphon.net]

From: Fam Zheng <famzheng@amazon.com>

Backtrace messages printed by Linux kernel and Xen have hex offsets,
e.g.:

(XEN) Xen call trace:
(XEN)    [<ffff82d0402eefbb>] R guest_walk_tables_2_levels+0x189/0x66d
(XEN)    [<ffff82d0402edbbd>] F hap_p2m_ga_to_gfn_2_levels+0x112/0x25b
(XEN)    [<ffff82d0402edd22>] F hap_gva_to_gfn_2_levels+0x1c/0x1e
(XEN)    [<ffff82d0402f832e>] F paging_gva_to_gfn+0x14a/0x167

Having this modifier saves converting between hex values from the
backtrace log and offsets in gdb disass output.

gdb/ChangeLog:

2020-09-25  Fam Zheng  <famzheng@amazon.com>

	* NEWS: Mention the /x modifier of disass.
	* cli/cli-cmds.c (disassemble_current_function): Add usage text
	for /x modifier.
	(disassemble_command): Parse /x modifier for disass.
	* disasm.c (gdb_pretty_print_disassembler::pretty_print_insn):
	Handle /x modifier.
	* disasm.h (enum gdb_disassembly_flag): Add a new flag for /x
	modifier.
	* record.c (get_insn_history_modifiers): Parse /x modifier.
---
 gdb/NEWS           |  3 +++
 gdb/cli/cli-cmds.c | 17 ++++++++++++-----
 gdb/disasm.c       |  5 ++++-
 gdb/disasm.h       |  1 +
 gdb/record.c       |  3 +++
 5 files changed, 23 insertions(+), 6 deletions(-)

diff --git a/gdb/NEWS b/gdb/NEWS
index f30d718331..ba1cf76b36 100644
--- a/gdb/NEWS
+++ b/gdb/NEWS
@@ -3,6 +3,9 @@
 
 *** Changes since GDB 10
 
+* A new modifier '/x' is added to disassemble command, to print instruction
+  offsets in hex.
+
 * MI changes
 
  ** '-break-insert --qualified' and '-dprintf-insert --qualified'
diff --git a/gdb/cli/cli-cmds.c b/gdb/cli/cli-cmds.c
index e3965fea07..e10544a734 100644
--- a/gdb/cli/cli-cmds.c
+++ b/gdb/cli/cli-cmds.c
@@ -1456,12 +1456,12 @@ disassemble_current_function (gdb_disassembly_flags flags)
 /* Dump a specified section of assembly code.
 
    Usage:
-     disassemble [/mrs]
+     disassemble [/mrsx]
        - dump the assembly code for the function of the current pc
-     disassemble [/mrs] addr
+     disassemble [/mrsx] addr
        - dump the assembly code for the function at ADDR
-     disassemble [/mrs] low,high
-     disassemble [/mrs] low,+length
+     disassemble [/mrsx] low,high
+     disassemble [/mrsx] low,+length
        - dump the assembly code in the range [LOW,HIGH), or [LOW,LOW+length)
 
    A /m modifier will include source code with the assembly in a
@@ -1472,6 +1472,8 @@ disassemble_current_function (gdb_disassembly_flags flags)
 
    A /r modifier will include raw instructions in hex with the assembly.
 
+   A /x modifier will print offsets in hex.
+
    A /s modifier will include source code with the assembly, like /m, with
    two important differences:
    1) The output is still in pc address order.
@@ -1510,6 +1512,9 @@ disassemble_command (const char *arg, int from_tty)
 	    case 'r':
 	      flags |= DISASSEMBLY_RAW_INSN;
 	      break;
+	    case 'x':
+	      flags |= DISASSEMBLY_HEX_OFFSET;
+	      break;
 	    case 's':
 	      flags |= DISASSEMBLY_SOURCE;
 	      break;
@@ -2535,7 +2540,7 @@ can be shown using \"show listsize\"."));
 
   c = add_com ("disassemble", class_vars, disassemble_command, _("\
 Disassemble a specified section of memory.\n\
-Usage: disassemble[/m|/r|/s] START [, END]\n\
+Usage: disassemble[/m|/r|/s|/x] START [, END]\n\
 Default is the function surrounding the pc of the selected frame.\n\
 \n\
 With a /s modifier, source lines are included (if available).\n\
@@ -2551,6 +2556,8 @@ in favor of /s.\n\
 \n\
 With a /r modifier, raw instructions in hex are included.\n\
 \n\
+With a /x modifier, offsets are printed in hex.\n\
+\n\
 With a single argument, the function surrounding that address is dumped.\n\
 Two arguments (separated by a comma) are taken as a range of memory to dump,\n\
   in the form of \"start,end\", or \"start,+length\".\n\
diff --git a/gdb/disasm.c b/gdb/disasm.c
index e45c840068..c681d8b1e9 100644
--- a/gdb/disasm.c
+++ b/gdb/disasm.c
@@ -250,7 +250,10 @@ gdb_pretty_print_disassembler::pretty_print_insn (const struct disasm_insn *insn
 	   the offset takes the place of the "+" here.  */
 	if (offset >= 0)
 	  m_uiout->text ("+");
-	m_uiout->field_signed ("offset", offset);
+	m_uiout->field_fmt ("offset",
+			    ((flags & DISASSEMBLY_HEX_OFFSET) != 0
+			     ? "0x%x" : "%d"),
+			    offset);
 	m_uiout->text (">:\t");
       }
     else
diff --git a/gdb/disasm.h b/gdb/disasm.h
index b0f535eaa2..fb293650de 100644
--- a/gdb/disasm.h
+++ b/gdb/disasm.h
@@ -31,6 +31,7 @@ enum gdb_disassembly_flag
     DISASSEMBLY_OMIT_PC = (0x1 << 4),
     DISASSEMBLY_SOURCE = (0x1 << 5),
     DISASSEMBLY_SPECULATIVE = (0x1 << 6),
+    DISASSEMBLY_HEX_OFFSET = (0x1 << 7),
   };
 DEF_ENUM_FLAGS_TYPE (enum gdb_disassembly_flag, gdb_disassembly_flags);
 
diff --git a/gdb/record.c b/gdb/record.c
index 759395d5bc..44591e8cf0 100644
--- a/gdb/record.c
+++ b/gdb/record.c
@@ -494,6 +494,9 @@ get_insn_history_modifiers (const char **arg)
 	    case 'r':
 	      modifiers |= DISASSEMBLY_RAW_INSN;
 	      break;
+	    case 'x':
+	      modifiers |= DISASSEMBLY_HEX_OFFSET;
+	      break;
 	    case 'f':
 	      modifiers |= DISASSEMBLY_OMIT_FNAME;
 	      break;
-- 
2.25.1