OpenE2K/qemu-e2k
13
4
Fork 0
Code Issues 4 Pull Requests Projects 2 Releases Activity

tests/avocado: reverse-debugging cope with re-executing breakpoints

Browse Source 
The reverse-debugging test creates a trace, then replays it and:

1. Steps the first 10 instructions and records their addresses.
2. Steps backward and verifies their addresses match.
3. Runs to (near) the end of the trace.
4. Sets breakpoints on the first 10 instructions.
5. Continues backward and verifies execution stops at the last
   breakpoint.

Step 5 breaks if any of the other 9 breakpoints are re-executed in the
trace after the 10th instruction is run, because those will be
unexpectedly hit when reverse continuing. This situation does arise
with the ppc pseries machine, the SLOF bios branches to its own entry
point.

Deal with this by switching steps 3 and 4, so the trace will be run to
the end *or* one of the breakpoints being re-executed. Step 5 then
reverses from there to the 10th instruction will not hit a breakpoint in
between, by definition.

Another step is added between steps 2 and 3, which steps forward over
the first 10 instructions and verifies their addresses, to support this.

Reviewed-by: Pavel Dovgalyuk <Pavel.Dovgalyuk@ispras.ru>
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Cédric Le Goater <clg@kaod.org>
This commit is contained in:
Nicholas Piggin 2023-08-08 14:20:00 +10:00 committed by Cédric Le Goater
parent d08c825c80
commit 76e9c1dfb9
1 changed files with 21 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

25
tests/avocado/reverse_debugging.py
View File

@ -150,16 +150,33 @@ class ReverseDebugging(LinuxKernelTest):
self.check_pc(g, addr)
logger.info('found position %x' % addr)
logger.info('seeking to the end (icount %s)' % (last_icount - 1))
vm.qmp('replay-break', icount=last_icount - 1)
# continue - will return after pausing
g.cmd(b'c', b'T02thread:01;')
# visit the recorded instruction in forward order
logger.info('stepping forward')
for addr in steps:
self.check_pc(g, addr)
self.gdb_step(g)
logger.info('found position %x' % addr)
# set breakpoints for the instructions just stepped over
logger.info('setting breakpoints')
for addr in steps:
# hardware breakpoint at addr with len=1
g.cmd(b'Z1,%x,1' % addr, b'OK')
# this may hit a breakpoint if first instructions are executed
# again
logger.info('continuing execution')
vm.qmp('replay-break', icount=last_icount - 1)
# continue - will return after pausing
# This could stop at the end and get a T02 return, or by
# re-executing one of the breakpoints and get a T05 return.
g.cmd(b'c')
if self.vm_get_icount(vm) == last_icount - 1:
logger.info('reached the end (icount %s)' % (last_icount - 1))
else:
logger.info('hit a breakpoint again at %x (icount %s)' %
(self.get_pc(g), self.vm_get_icount(vm)))
logger.info('running reverse continue to reach %x' % steps[-1])
# reverse continue - will return after stopping at the breakpoint
g.cmd(b'bc', b'T05thread:01;')