[PATCH v6 0/3] disass: Add /x modifier

[PATCH v6 0/3] disass: Add /x modifier

[fam]

From: Fam Zheng <famzheng@amazon.com>

v6: Add texinfo section name in ChangeLog. [Eli]

v5: Add function names in ChangeLog. [Eli]

v4: Add ChangeLog entries. [Eli]

v3: Add a test, more doc, and drop tmp buffer. [Andreas, Simon, Pedro]

This is a new modifier for disass command, to print offsets in hex. This
reduces pain for low level debugging (Linux kernel, Xen, etc.) when the
backtraces from dmesg are in hex - no manual converting needed to do a cross
matching when looking at both sides at the same time.

Fam Zheng (3):
  disass: Add /x modifier to print offsets in hex
  disass: Add test for /x mode
  disass: Add texinfo doc for the /x modifier

 gdb/NEWS                                |  3 ++
 gdb/cli/cli-cmds.c                      | 17 +++++++----
 gdb/disasm.c                            |  5 +++-
 gdb/disasm.h                            |  1 +
 gdb/doc/gdb.texinfo                     | 38 +++++++++++++++++++------
 gdb/record.c                            |  3 ++
 gdb/testsuite/gdb.base/disasm-optim.exp |  7 +++++
 7 files changed, 59 insertions(+), 15 deletions(-)

-- 
2.25.1

[PATCH v6 1/3] disass: Add /x modifier to print offsets in hex

[fam]

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

[PATCH v6 2/3] disass: Add test for /x mode

[fam]

From: Fam Zheng <famzheng@amazon.com>

gdb/testsuite/ChangeLog:

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

	* gdb.base/disasm-optim.exp: Add test for /x.
---
 gdb/testsuite/gdb.base/disasm-optim.exp | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/gdb/testsuite/gdb.base/disasm-optim.exp b/gdb/testsuite/gdb.base/disasm-optim.exp
index 179e76ad0e..8c28fe10de 100644
--- a/gdb/testsuite/gdb.base/disasm-optim.exp
+++ b/gdb/testsuite/gdb.base/disasm-optim.exp
@@ -38,3 +38,10 @@ gdb_test_sequence "disassemble /s main" \
 	"disasm-optim\\.h:\r\n22"
 	"End of assembler dump\\."
     }
+
+gdb_test_sequence "disassemble /x main" \
+    "Disassemble main with source" {
+	"Dump of assembler code for function main:"
+	"=> 0x[0-9a-f]* \\<\\+0x0>:"
+	"End of assembler dump\\."
+    }
-- 
2.25.1

[PATCH v6 3/3] disass: Add texinfo doc for the /x modifier

[fam]

From: Fam Zheng <famzheng@amazon.com>

gdb/doc/ChangeLog:

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

	* gdb.texinfo (disassemble): Document /x modifier of disass
	command.
---
 gdb/doc/gdb.texinfo | 38 +++++++++++++++++++++++++++++---------
 1 file changed, 29 insertions(+), 9 deletions(-)

diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo
index 8bff27c940..4dad72a34f 100644
--- a/gdb/doc/gdb.texinfo
+++ b/gdb/doc/gdb.texinfo
@@ -9514,16 +9514,20 @@ line.
 @itemx disassemble /m
 @itemx disassemble /s
 @itemx disassemble /r
-This specialized command dumps a range of memory as machine
-instructions.  It can also print mixed source+disassembly by specifying
-the @code{/m} or @code{/s} modifier and print the raw instructions in hex
-as well as in symbolic form by specifying the @code{/r} modifier.
-The default memory range is the function surrounding the
-program counter of the selected frame.  A single argument to this
+@itemx disassemble /x
+This specialized command dumps a range of memory as machine instructions.
+If the address of an instruction resolves to a symbol, such as a function
+name, the symbol name and the offset are printed following the instruction
+address.  The offset is in decimal by default and in hex if @code{/x} is
+modifier is used.  It can also print mixed source+disassembly by
+specifying the @code{/m} or @code{/s} modifier and print the raw
+instructions in hex as well as in symbolic form by specifying the
+@code{/r} modifier.  The default memory range is the function surrounding
+the program counter of the selected frame.  A single argument to this
 command is a program counter value; @value{GDBN} dumps the function
-surrounding this value.  When two arguments are given, they should
-be separated by a comma, possibly surrounded by whitespace.  The
-arguments specify a range of addresses to dump, in one of two forms:
+surrounding this value.  When two arguments are given, they should be
+separated by a comma, possibly surrounded by whitespace.  The arguments
+specify a range of addresses to dump, in one of two forms:
 
 @table @code
 @item @var{start},@var{end}
@@ -9561,6 +9565,22 @@ Dump of assembler code from 0x32c4 to 0x32e4:
 End of assembler dump.
 @end smallexample
 
+@code{/x} could be used to show offsets in hex:
+
+@smallexample
+(@value{GDBP}) disas /x 0x32c4, 0x32e4
+Dump of assembler code from 0x32c4 to 0x32e4:
+   0x32c4 <main+0xcc>:      addil 0,dp
+   0x32c8 <main+0xd0>:      ldw 0x22c(sr0,r1),r26
+   0x32cc <main+0xd4>:      ldil 0x3000,r31
+   0x32d0 <main+0xd8>:      ble 0x3f8(sr4,r31)
+   0x32d4 <main+0xdc>:      ldo 0(r31),rp
+   0x32d8 <main+0xe0>:      addil -0x800,dp
+   0x32dc <main+0xe4>:      ldo 0x588(r1),r26
+   0x32e0 <main+0xe8>:      ldil 0x3000,r31
+End of assembler dump.
+@end smallexample
+
 Here is an example showing mixed source+assembly for Intel x86
 with @code{/m} or @code{/s}, when the program is stopped just after
 function prologue in a non-optimized function with no inline code.
-- 
2.25.1

Re: [PATCH v6 3/3] disass: Add texinfo doc for the /x modifier

[Eli Zaretskii]

> From: fam@euphon.net
> Cc: Simon Marchi <simark@simark.ca>,
> 	Pedro Alves <pedro@palves.net>,
> 	Andrew Burgess <andrew.burgess@embecosm.com>,
> 	Andreas Schwab <schwab@linux-m68k.org>,
> 	fam@euphon.net,
> 	Eli Zaretskii <eliz@gnu.org>
> Date: Sat, 26 Sep 2020 08:35:39 +0100
> 
> From: Fam Zheng <famzheng@amazon.com>
> 
> gdb/doc/ChangeLog:
> 
> 2020-09-25  Fam Zheng  <famzheng@amazon.com>
> 
> 	* gdb.texinfo (disassemble): Document /x modifier of disass
> 	command.

The name of that node is "Machine Code", not "disassemble".  You can
see the name by looking backward for a @node directive.  Or just use
Emacs's add-change-log-entry-* commands, they will do that for you.

Thanks.

Re: [PATCH v6 3/3] disass: Add texinfo doc for the /x modifier

[Fam Zheng]

On Sat, Sep 26, 2020 at 8:18 AM Eli Zaretskii <eliz@gnu.org> wrote:
>
> > From: fam@euphon.net
> > Cc: Simon Marchi <simark@simark.ca>,
> >       Pedro Alves <pedro@palves.net>,
> >       Andrew Burgess <andrew.burgess@embecosm.com>,
> >       Andreas Schwab <schwab@linux-m68k.org>,
> >       fam@euphon.net,
> >       Eli Zaretskii <eliz@gnu.org>
> > Date: Sat, 26 Sep 2020 08:35:39 +0100
> >
> > From: Fam Zheng <famzheng@amazon.com>
> >
> > gdb/doc/ChangeLog:
> >
> > 2020-09-25  Fam Zheng  <famzheng@amazon.com>
> >
> >       * gdb.texinfo (disassemble): Document /x modifier of disass
> >       command.
>
> The name of that node is "Machine Code", not "disassemble".  You can
> see the name by looking backward for a @node directive.  Or just use
> Emacs's add-change-log-entry-* commands, they will do that for you.

OK, no problem, it should be easy to fix. I just looked at git blame
in the context and copied 9b117ef31f which did the same. But I think
you're right.

I don't use Emacs, so I cannot take that benefit. :(

Thanks for the review and quick response!

Fam