debug/pe: enable parsing of variable length optional header in PE file
The debug/pe package assumes there are always 16 entries in
DataDirectory in OptionalHeader32/64
ref pe.go:
...
NumberOfRvaAndSizes uint32
DataDirectory [16]DataDirectory
}
...
But that is not always the case, there could be less no of
entries (PE signed linux kernel for example):
$ sudo pev /boot/vmlinuz-4.15.0-47-generic
....
Data-dictionary entries: 6
....
In such case, the parsing gives incorrect results.
This changes aims to fix that by:
1. Determining type of optional header by looking at header
magic instead of size
2. Parsing optional header in 2 steps:
a. Fixed part
b. Variable data directories part
Testing:
1. Fixed existing test cases to reflect the change
2. Added new file (modified linux kernel image)
which has smaller number of data directories
Fixes #32126
Change-Id: Iee56ecc4369a0e75a4be805e7cb8555c7d81ae2f
Reviewed-on: https://go-review.googlesource.com/c/go/+/177959
Run-TryBot: Alex Brainman <alex.brainman@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Alex Brainman <alex.brainman@gmail.com>