RFC: Annotate immediates in x86 disassembly

[H.J. Lu]

On Wed, Apr 22, 2026 at 5:02 PM Nick Clifton <nickc@redhat.com> wrote:
>
> Hi Guys,
>
>    Attached is a small potential patch that adds a new target specific
>    option to the x86 and x86_64 disassemblers: "-M annotate-immediates".
>    If enabled immediate operands which match a symbol's value will have
>    the name of that symbol displayed alongside them.
>
>    For example, without the new option a line of disassembly might look
>    like this:
>
>       400419:   bf 18 30 40 00          mov    $0x403018,%edi
>
>    whereas with the option enabled it could look like this:
>
>       400419:   bf 18 30 40 00          mov    $0x403018 [func1],%edi
>
>    I find this helpful when looking at code that loads function
>    addresses into registers for example.
>
>    What do you think ?  Would this be a useful addition to the assembler?
>
>    Notes:
>      * The feature is only enabled when disassembling executables as
>        the symbolic addresses in object files too often match small
>        ordinary constants.
>
>      * The option parser will accept "-M annotate" or "-M
>        annotate-immediates" or "-M annotate<anything>".  I could make it
>        more strict, but I was not sure if it was worth it.
>
>    I did try to make this a generic option, rather than specific to the
>    x86/x86_64 architecture, but I quickly ran into problems with how
>    different ISAs handle the loading of constant values.  Still if this
>    kind of feature is considered useful it could be added to more
>    backends or a per-architecture basis.
>
> Cheers
>   Nick
>

  /* Determine if we can display some more information about this immediate.  */
+  if (! annotate_immediates
+      /* Don't bother with xero, even if there is symbol associated
with it.  */
                                       zero.
+      /* For the next tests we need a BFD.  If we do not have one
then do not proceed.  */
+      || ins->info->section == NULL
+      || ins->info->section->owner == NULL
+      /* Save time by avoiding immediates that cannot reference part
of the address space.  */
+      || imm < ins->info->section->owner->start_address
+      /* Also skip object files as their symbols have not been resolved.  */
+      || (ins->info->section->owner->flags & EXEC_P) == 0)

Should it also handle shared libraries?

+    return;

-- 
H.J.