Re: [PATCH] elf: Get rid of alloca usage in _dl_start_profile

[Joe Simmons-Talbott <josimmon@redhat.com>]

Ping.

On Tue, Oct 03, 2023 at 03:33:16PM -0400, Joe Simmons-Talbott wrote:
> On Fri, Sep 29, 2023 at 09:52:19AM -0400, Joe Simmons-Talbott wrote:
> > Replace alloca usage with a scratch_buffer.
> 
> This was tested by enabling profiling in the build and running a test
> application with LD_PROFILE defined.  I also generated a directory with
> over 1024 characters and defined LD_PROFILE_OUTPUT pointing to that
> directory to test the malloc path.  In both cases the .profile file was
> created.  I wasn't able to process the .profile files with gprof though
> as it complained about the version.
> 
> Thanks,
> Joe
> > ---
> >  elf/dl-profile.c | 17 +++++++++++++++--
> >  1 file changed, 15 insertions(+), 2 deletions(-)
> > 
> > diff --git a/elf/dl-profile.c b/elf/dl-profile.c
> > index 8be0065fbd..8ae50020bb 100644
> > --- a/elf/dl-profile.c
> > +++ b/elf/dl-profile.c
> > @@ -22,6 +22,7 @@
> >  #include <fcntl.h>
> >  #include <inttypes.h>
> >  #include <limits.h>
> > +#include <scratch_buffer.h>
> >  #include <stdio.h>
> >  #include <stdlib.h>
> >  #include <string.h>
> > @@ -201,6 +202,8 @@ _dl_start_profile (void)
> >    int s_scale;
> >  #define SCALE_1_TO_1	0x10000L
> >    const char *errstr = NULL;
> > +  struct scratch_buffer sbuf;
> > +  scratch_buffer_init (&sbuf);
> >  
> >    /* Compute the size of the sections which contain program code.  */
> >    for (ph = GL(dl_profile_map)->l_phdr;
> > @@ -318,8 +321,14 @@ _dl_start_profile (void)
> >    /* First determine the output name.  We write in the directory
> >       OUTPUT_DIR and the name is composed from the shared objects
> >       soname (or the file name) and the ending ".profile".  */
> > -  filename = (char *) alloca (strlen (GLRO(dl_profile_output)) + 1
> > -			      + strlen (GLRO(dl_profile)) + sizeof ".profile");
> > +  size_t filename_len = (strlen (GLRO(dl_profile_output)) + 1
> > +	+ strlen (GLRO(dl_profile)) + sizeof ".profile");
> > +  if (!scratch_buffer_set_array_size (&sbuf, 1, filename_len))
> > +    {
> > +      _dl_error_printf ("failed to allocate memory");
> > +      return;
> > +    }
> > +  filename = sbuf.data;
> >    cp = __stpcpy (filename, GLRO(dl_profile_output));
> >    *cp++ = '/';
> >    __stpcpy (__stpcpy (cp, GLRO(dl_profile)), ".profile");
> > @@ -339,6 +348,7 @@ _dl_start_profile (void)
> >  	__close_nocancel (fd);
> >        _dl_error_printf (errstr, filename,
> >  			__strerror_r (errnum, buf, sizeof buf));
> > +      scratch_buffer_free (&sbuf);
> >        return;
> >      }
> >  
> > @@ -380,6 +390,7 @@ _dl_start_profile (void)
> >  
> >        _dl_error_printf ("%s: file is no correct profile data file for `%s'\n",
> >  			filename, GLRO(dl_profile));
> > +      scratch_buffer_free (&sbuf);
> >        return;
> >      }
> >  
> > @@ -483,6 +494,8 @@ _dl_start_profile (void)
> >  
> >    /* Turn on profiling.  */
> >    running = 1;
> > +
> > +  scratch_buffer_free (&sbuf);
> >  }
> >  
> >  
> > -- 
> > 2.39.2
> > 
>