[PATCH v2] disass: Add /x modifier to print offsets in hex

[Andrew Burgess]

* fam@euphon.net <fam@euphon.net> [2020-09-23 10:19:06 +0000]:

> 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.
> 
> ---
> 
> v2: Drop a overlooked change on file header.
> ---
>  gdb/cli/cli-cmds.c | 17 ++++++++++++-----
>  gdb/disasm.c       |  6 +++++-
>  gdb/disasm.h       |  1 +
>  gdb/record.c       |  3 +++
>  4 files changed, 21 insertions(+), 6 deletions(-)
> 
> diff --git a/gdb/cli/cli-cmds.c b/gdb/cli/cli-cmds.c
> index e3965fea07..2266f67695 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.

Shouldn't this be 'An /x modified ...' ? Saying it out loud it
certainly seems that way.

> +
>     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|/r] 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 as hex.\n\

Same I think.

Thanks, Andrew

> +\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..47936e54f1 100644
> --- a/gdb/disasm.c
> +++ b/gdb/disasm.c
> @@ -201,6 +201,7 @@ gdb_pretty_print_disassembler::pretty_print_insn (const struct disasm_insn *insn
>    int size;
>    CORE_ADDR pc;
>    struct gdbarch *gdbarch = arch ();
> +  char offset_buf[32];
>  
>    {
>      ui_out_emit_tuple tuple_emitter (m_uiout, NULL);
> @@ -250,7 +251,10 @@ 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);
> +	snprintf(offset_buf, sizeof(offset_buf),
> +                 flags & DISASSEMBLY_HEX_OFFSET ? "0x%x" : "%d",
> +                 offset);
> +	m_uiout->field_string("offset", offset_buf);
>  	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
> 
>