diff mbox series

[PATCHv2,4/5] gdbserver: cleanup in handle_v_run

Message ID 101de2688bc146244f0ae89477cfd4adf3606551.1695835626.git.aburgess@redhat.com
State New
Headers
Series Fixes for passing arguments to gdbserver |

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Commit Message

Andrew Burgess Sept. 27, 2023, 5:27 p.m. UTC 
  After the previous commit there is now a redundant string copy in
handle_v_run, this commit cleans that up.

There should be no functional change after this commit.
---
 gdbserver/server.cc | 24 +++++-------------------
 1 file changed, 5 insertions(+), 19 deletions(-)

Comments

Tom Tromey Oct. 3, 2023, 7:13 p.m. UTC | #1 
>>>>> "Andrew" == Andrew Burgess via Gdb-patches <gdb-patches@sourceware.org> writes:

Andrew> After the previous commit there is now a redundant string copy in
Andrew> handle_v_run, this commit cleans that up.

Andrew> +	  /* Buffer to decode the argument into.  */
Andrew>  	  char *arg = (char *) xmalloc (len + 1);
... 
Andrew>  	  hex2bin (p, (gdb_byte *) arg, len);
Andrew>  	  arg[len] = '\0';
 
Not really your problem, but since you're changing it anyway, using the
byte_vector form of hex2bin would remove some manual memory management
here.

Tom
Andrew Burgess Oct. 4, 2023, 2:40 p.m. UTC | #2 
Tom Tromey <tom@tromey.com> writes:

>>>>>> "Andrew" == Andrew Burgess via Gdb-patches <gdb-patches@sourceware.org> writes:
>
> Andrew> After the previous commit there is now a redundant string copy in
> Andrew> handle_v_run, this commit cleans that up.
>
> Andrew> +	  /* Buffer to decode the argument into.  */
> Andrew>  	  char *arg = (char *) xmalloc (len + 1);
> ... 
> Andrew>  	  hex2bin (p, (gdb_byte *) arg, len);
> Andrew>  	  arg[len] = '\0';
>  
> Not really your problem, but since you're changing it anyway, using the
> byte_vector form of hex2bin would remove some manual memory management
> here.

I see two problems with that plan.  First, we currently run hex2bin on a
slice of a larger string buffer, the slice is not null-terminated.  The
current hex2bin that returns a gdb::byte_vector expects a
null-terminated string (it uses strlen internally).  We can easily solve
this by adding an overload of hex2bin that takes a gdb::string_view,
except...

... for the second problem, which is the result of calling hex2bin is
passed off to either new_program_name or the new_argv vector.  There's
no way to "release" the memory from a gdb::byte_vector, so we'd end up
copying the contents into a malloc'd buffer anyway, like:

  gdb::byte_vector vec = hex2bin (gdb::string_view (p, (next_p - p)));
  const char *arg = xstrdup ((const char *) vec.data ());

Which I'm not sure is really any better than we have right now?

Did you have something else in mind?  Let me know and I'm happy to have
a look at an alternative approach.

Thanks,
Andrew
Tom Tromey Oct. 4, 2023, 7:35 p.m. UTC | #3 
>>>>> "Andrew" == Andrew Burgess via Gdb-patches <gdb-patches@sourceware.org> writes:

Andrew> Which I'm not sure is really any better than we have right now?

Andrew> Did you have something else in mind?  Let me know and I'm happy to have
Andrew> a look at an alternative approach.

Thanks, I agree your current approach is the better of the two.

Tom
diff mbox series

Patch

diff --git a/gdbserver/server.cc b/gdbserver/server.cc
index 84b8712e668..e02cdb83b51 100644
--- a/gdbserver/server.cc
+++ b/gdbserver/server.cc
@@ -2989,33 +2989,19 @@  handle_v_run (char *own_buf)
 	}
       else
 	{
+	  /* The length of the decoded argument.  */
 	  size_t len = (next_p - p) / 2;
-	  /* ARG is the unquoted argument received via the RSP.  */
+
+	  /* Buffer to decode the argument into.  */
 	  char *arg = (char *) xmalloc (len + 1);
-	  /* FULL_ARGS will contain the quoted version of ARG.  */
-	  char *full_arg = (char *) xmalloc ((len + 1) * 2);
-	  /* These are pointers used to navigate the strings above.  */
-	  char *tmp_arg = arg;
-	  char *tmp_full_arg = full_arg;
 
 	  hex2bin (p, (gdb_byte *) arg, len);
 	  arg[len] = '\0';
 
-	  while (*tmp_arg != '\0')
-	    {
-	      *tmp_full_arg = *tmp_arg;
-	      ++tmp_full_arg;
-	      ++tmp_arg;
-	    }
-
-	  /* Finish FULL_ARG and push it into the vector containing
-	     the argv.  */
-	  *tmp_full_arg = '\0';
 	  if (i == 0)
-	    new_program_name = full_arg;
+	    new_program_name = arg;
 	  else
-	    new_argv.push_back (full_arg);
-	  xfree (arg);
+	    new_argv.push_back (arg);
 	}
       if (*next_p == '\0')
 	break;