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Add backwards memory examination for the dereference command #942

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merged 5 commits into from
Apr 5, 2023

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tramasys
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@tramasys tramasys commented Apr 4, 2023

Description/Motivation/Screenshots

This commit extends the dereference command, allowing to examine memory backwards via a negative --length value, analogous to the behaviour of x.

Against which architecture was this tested ?

"Tested" indicates that the PR works and the unit test (see docs/testing.md) run passes without issue.

  • x86-32
  • x86-64
  • ARM
  • AARCH64
  • MIPS
  • POWERPC
  • SPARC
  • RISC-V

Checklist

  • My PR was done against the dev branch, not main.
  • My code follows the code style of this project.
  • My change includes a change to the documentation, if required.
  • If my change adds new code, adequate tests have been added.
  • I have read and agree to the CONTRIBUTING document.

gef.py Outdated
to_insnum = self.repeat_count * nb - 1
insnum_step = -1
else:
from_insnum = 0 + self.repeat_count * nb
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Why 0 +?

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The previous implementation had them, so I simply left them in place. I can't tell why they were placed, so I just left them there in case there's some obsure edge-case that I'm not aware of.

gef.py Outdated
if nb > 0:
from_insnum = nb * (self.repeat_count + 1) - 1
to_insnum = self.repeat_count * nb - 1
insnum_step = -1
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we don't have to repeat this line in both cases

gef.py Outdated
if nb > 0:
from_insnum = 0 + self.repeat_count * nb
to_insnum = nb * (self.repeat_count + 1)
insnum_step = 1
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we don't have to repeat this in both cases

gef.py Outdated
to_insnum = nb * (self.repeat_count + 1)
insnum_step = 1
if nb > 0:
from_insnum = 0 + self.repeat_count * nb
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why 0+

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Please add tests in tests/commands/dereference.py, other than that and graz remarks, it looks good to me

docs/commands/dereference.md Show resolved Hide resolved
"set {char[9]} ($sp+0x8) = { 0x41, 0x41, 0x41, 0x41, 0x41, 0x41, 0x41, 0x41, 0x00 }",
"set {char[9]} ($sp-0x8) = { 0x42, 0x42, 0x42, 0x42, 0x42, 0x42, 0x42, 0x42, 0x00 }"
]
res = gdb_start_silent_cmd(cmd=setup, after=cmd)
self.assertNoException(res)
print(res)
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remove

"set {char[9]} ($sp+0x8) = { 0x41, 0x41, 0x41, 0x41, 0x41, 0x41, 0x41, 0x41, 0x00 }",
"set {char[9]} ($sp-0x8) = { 0x42, 0x42, 0x42, 0x42, 0x42, 0x42, 0x42, 0x42, 0x00 }"
]
res = gdb_start_silent_cmd(cmd=setup, after=cmd)
self.assertNoException(res)
print(res)
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remove

gef.py Outdated
to_insnum = nb * (self.repeat_count + 1)
else:
from_insnum = nb * (self.repeat_count + 1) + 1
to_insnum = (0 + self.repeat_count * nb) + 1
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why 0+

"""
res = res.splitlines()[-2]
self.assertTrue("AAAAAAAA" not in res)
self.assertTrue("BBBBBBBB" in res)
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assertIn

Hence, we want to look at the second last line of the output
"""
res = res.splitlines()[-1]
self.assertTrue("AAAAAAAA" in res)
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assertIn

"""
res = res.splitlines()[-1]
self.assertTrue("AAAAAAAA" in res)
self.assertTrue("BBBBBBBB" not in res)
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assertNotIn

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Thanks for the PR!

@hugsy hugsy merged commit 0f477e7 into hugsy:dev Apr 5, 2023
@tramasys tramasys deleted the deref-extended branch April 5, 2023 17:01
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3 participants