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Fix PR gdb/19676: Disable displaced stepping if /proc not mounted

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On GNU/Linux archs that support displaced stepping, if /proc is not
mounted, GDB gets stuck not able to step past breakpoints:

 (gdb) c
 Continuing.
 dl_main (phdr=<optimized out>, phnum=<optimized out>, user_entry=<optimized out>, auxv=<optimized out>) at rtld.c:2163
 2163      LIBC_PROBE (init_complete, 2, LM_ID_BASE, r);
 Cannot find AT_ENTRY auxiliary vector entry.
 (gdb) c
 Continuing.
 dl_main (phdr=<optimized out>, phnum=<optimized out>, user_entry=<optimized out>, auxv=<optimized out>) at rtld.c:2163
 2163      LIBC_PROBE (init_complete, 2, LM_ID_BASE, r);
 Cannot find AT_ENTRY auxiliary vector entry.
 (gdb)

That's because GDB can't figure out where the scratch pad is.

This is a regression introduced by the earlier changes to make the
Linux native target always work in non-stop mode.

This commit makes GDB detect the case and fallback to stepping over
breakpoints in-line.

gdb/ChangeLog:
2016-03-15  Pedro Alves  <palves@redhat.com>

	PR gdb/19676
	* infrun.c (displaced_step_prepare): Also disable displaced
	stepping on NOT_SUPPORTED_ERROR.
	* linux-tdep.c (linux_displaced_step_location): If reading auxv
	fails, throw NOT_SUPPORTED_ERROR instead of generic error.
This commit is contained in:
Pedro Alves 2016-03-15 16:33:04 +00:00
parent 2a60e18f8f
commit 16b4184277
3 changed files with 12 additions and 2 deletions
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8
gdb/ChangeLog
View file

@ -1,3 +1,11 @@
2016-03-15 Pedro Alves <palves@redhat.com>
PR gdb/19676
* infrun.c (displaced_step_prepare): Also disable displaced
stepping on NOT_SUPPORTED_ERROR.
* linux-tdep.c (linux_displaced_step_location): If reading auxv
fails, throw NOT_SUPPORTED_ERROR instead of generic error.
2016-03-13 Marcin Kościelnicki <koriakin@0x04.net>
* s390-linux-tdep.c (s390_gen_return_address): New function.

3
gdb/infrun.c
View file

@ -1894,7 +1894,8 @@ displaced_step_prepare (ptid_t ptid)
{
struct displaced_step_inferior_state *displaced_state;
if (ex.error != MEMORY_ERROR)
if (ex.error != MEMORY_ERROR
&& ex.error != NOT_SUPPORTED_ERROR)
throw_exception (ex);
if (debug_infrun)

3
gdb/linux-tdep.c
View file

@ -2426,7 +2426,8 @@ linux_displaced_step_location (struct gdbarch *gdbarch)
location. The auxiliary vector gets us the PowerPC-side entry
point address instead. */
if (target_auxv_search (&current_target, AT_ENTRY, &addr) <= 0)
error (_("Cannot find AT_ENTRY auxiliary vector entry."));
throw_error (NOT_SUPPORTED_ERROR,
_("Cannot find AT_ENTRY auxiliary vector entry."));
/* Make certain that the address points at real code, and not a
function descriptor. */