[Ltrace-devel] 3 patches for ltrace - fixes "armhf" target

[Greg Alexander]

Hi -

Thanks, I got the git tree now.  I am surprised how far ahead of
debian-unstable it is.

The build problem and syscall tracing have both already been fixed. :)

The PTRACE_SINGLESTEP issue remains:
  26753 couldn't continue when handling __libc_start_main (0x9e88) at 0x9e88

This part of ltrace is much more sophisticated than it was at 0.5.3, so
it will take me a while to work around it.  With any luck, I'll have a
proposal soon.

Thanks,
- Greg

On Wed, Mar 06, 2013 at 06:38:11PM +0100, Sedat Dilek wrote:
> Did you try latest Git of ltrace on ARM arch?
> 
> - Sedat -
> 
> http://anonscm.debian.org/gitweb/?p=collab-maint/ltrace.git;a=summary
> 
> On Wed, Mar 6, 2013 at 4:47 PM, Greg Alexander <ltracedeb at galexander.org> wrote:
> > Hi all -
> >
> > Thanks for work on ltrace, it is fabulous.
> >
> > I am using Debian on armhf, and I built ltrace from
> > ltrace_0.5.3.orig.tar.gz that I downloaded from the Debian pool.
> > I found a few problems on this target, and corrected them.  The patches
> > aren't long so I'm just going to append them at the bottom of this email,
> > but let me know if I should have done something different.
> >
> > First patch corrects a build problem, header files were included in the
> > wrong order, so just use "common.h" instead.
> >
> > Second patch corrects syscall tracing.  For whatever reason, my EABI
> > syscalls calls are using the ARM-Thumb encoding of the SWI/SVC
> > instruction, so I just added a condition for that.
> >
> > Third patch provides fallback behavior if PTRACE_SINGLESTEP is
> > unavailable.  There is a #if to check for __sparc__ or __ia64__ to avoid
> > PTRACE_SINGLESTEP, and I left that alone, but probably it should go away
> > too.  My patch tries PTRACE_SINGLESTEP, but if -1 is returned then it
> > falls back to the same behavior as on sparc/ia64.  I think that is a
> > better solution than adding __arm__ to the #if, because if the kernel
> > does change to support PTRACE_SINGLESTEP here, it will not be any more
> > work for ltrace to support it.
> >
> > Thank you!
> > - Greg
> >
> >
> > --- ltrace-0.5.3.orig/sysdeps/linux-gnu/arm/breakpoint.c        2009-07-25 11:13:02.000000000 -0400
> > +++ ltrace-0.5.3/sysdeps/linux-gnu/arm/breakpoint.c     2013-03-06 09:21:41.803584766 -0500
> > @@ -25,9 +25,7 @@
> >  #include <sys/ptrace.h>
> >  #include "config.h"
> >  #include "arch.h"
> > -#include "options.h"
> > -#include "output.h"
> > -#include "debug.h"
> > +#include "common.h"
> >
> >  void
> >  arch_enable_breakpoint(pid_t pid, Breakpoint *sbp) {
> > --- ltrace-0.5.3.orig/sysdeps/linux-gnu/arm/trace.c     2009-07-25 11:13:02.000000000 -0400
> > +++ ltrace-0.5.3/sysdeps/linux-gnu/arm/trace.c  2013-03-06 09:41:38.078585339 -0500
> > @@ -52,6 +52,9 @@
> >                 if (insn == 0xef000000 || insn == 0x0f000000) {
> >                         /* EABI syscall */
> >                         *sysnum = ptrace(PTRACE_PEEKUSER, proc->pid, off_r7, 0);
> > +               } else if ((insn & 0xffff0000) == 0xdf000000) {
> > +                       /* EABI syscall "encoding T1" (thumb) */
> > +                       *sysnum = ptrace(PTRACE_PEEKUSER, proc->pid, off_r7, 0);
> >                 } else if ((insn & 0xfff00000) == 0xef900000) {
> >                         /* old ABI syscall */
> >                         *sysnum = insn & 0xfffff;
> > --- ltrace-0.5.3.orig/sysdeps/linux-gnu/trace.c 2009-07-25 11:13:02.000000000 -0400
> > +++ ltrace-0.5.3/sysdeps/linux-gnu/trace.c      2013-03-06 10:26:15.368586617 -0500
> > @@ -122,7 +122,10 @@
> >  #if defined __sparc__  || defined __ia64___
> >                 ptrace(PTRACE_SYSCALL, pid, 0, signum);
> >  #else
> > -               ptrace(PTRACE_SINGLESTEP, pid, 0, signum);
> > +               if (ptrace(PTRACE_SINGLESTEP, pid, 0, signum) == -1) {
> > +                       ptrace(PTRACE_SYSCALL, pid, 0, signum);
> > +               }
> > +
> >  #endif
> >         } else {
> >                 ptrace(PTRACE_SYSCALL, pid, 0, signum);
> > @@ -158,7 +161,9 @@
> >                 /* we don't want to singlestep here */
> >                 continue_process(proc->pid);
> >  #else
> > -               ptrace(PTRACE_SINGLESTEP, proc->pid, 0, 0);
> > +               if (ptrace(PTRACE_SINGLESTEP, proc->pid, 0, 0) == -1) {
> > +                       continue_process(proc->pid);
> > +               }
> >  #endif
> >         }
> >  }
> >
> > _______________________________________________
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