### Context
Over a year ago, I landed support for 64b Memory ranges in Minidump
(#95312). In this patch we added the Memory64 list stream, which is
effectively a Linked List on disk. The layout is a sixteen byte header
and then however many Memory descriptors.
### The Bug
This is a classic off-by one error, where I added 8 bytes instead of 16
for the header. This caused the first region to start 8 bytes before the
correct RVA, thus shifting all memory reads by 8 bytes. We are correctly
writing all the regions to disk correctly, with no physical corruption
but the RVA is defined wrong, meaning we were incorrectly reading memory
### Why wasn't this caught?
One problem we've had is forcing Minidump to actually use the 64b mode,
it would be a massive waste of resources to have a test that actually
wrote >4.2gb of IO to validate the 64b regions, and so almost all
validation has been manual. As a weakness of manual testing, this issue
is psuedo non-deterministic, as what regions end up in 64b or 32b is
handled greedily and iterated in the order it's laid out in
/proc/pid/maps. We often validated 64b was written correctly by
hexdumping the Minidump itself, which was not corrupted (other than the
BaseRVA)
### Why is this showing up now?
During internal usage, we had a bug report that the Minidump wasn't
displaying values. I was unable to repro the issue, but during my
investigation I saw the variables were in the 64b regions which resulted
in me identifying the bug.
### How do we prevent future regressions?
To prevent regressions, and honestly to save my sanity for figuring out
where 8 bytes magically came from, I've added a new API to
SBSaveCoreOptions.
```SBSaveCoreOptions::GetMemoryRegionsToSave()```
The ability to get the memory regions that we intend to include in the Coredump. I added this so we can compare what we intended to include versus what was actually included. Traditionally we've always had issues comparing regions because Minidump includes `/proc/pid/maps` and it can be difficult to know what memoryregion read failure was a genuine error or just a page that wasn't meant to be included.
We are also leveraging this API to choose the memory regions to be generated, as well as for testing what regions should be bytewise 1:1.
After much debate with @clayborg, I've moved all non-stack memory to the Memory64 List. This list doesn't incur us any meaningful overhead and Greg originally suggested doing this in the original 64b PR. This also means we're exercising the 64b path every single time we save a Minidump, preventing regressions on this feature from slipping through testing in the future.
Snippet produced by [minidump.py](https://github.com/clayborg/scripts)
```
MINIDUMP_MEMORY_LIST:
NumberOfMemoryRanges = 0x00000002
MemoryRanges[0] = [0x00007f61085ff9f0 - 0x00007f6108601000) @ 0x0003f655
MemoryRanges[1] = [0x00007ffe47e50910 - 0x00007ffe47e52000) @ 0x00040c65
MINIDUMP_MEMORY64_LIST:
NumberOfMemoryRanges = 0x000000000000002e
BaseRva = 0x0000000000042669
MemoryRanges[0] = [0x00005584162d8000 - 0x00005584162d9000)
MemoryRanges[1] = [0x00005584162d9000 - 0x00005584162db000)
MemoryRanges[2] = [0x00005584162db000 - 0x00005584162dd000)
MemoryRanges[3] = [0x00005584162dd000 - 0x00005584162ff000)
MemoryRanges[4] = [0x00007f6100000000 - 0x00007f6100021000)
MemoryRanges[5] = [0x00007f6108800000 - 0x00007f6108828000)
MemoryRanges[6] = [0x00007f6108828000 - 0x00007f610899d000)
MemoryRanges[7] = [0x00007f610899d000 - 0x00007f61089f9000)
MemoryRanges[8] = [0x00007f61089f9000 - 0x00007f6108a08000)
MemoryRanges[9] = [0x00007f6108bf5000 - 0x00007f6108bf7000)
```
### Misc
As a part of this fix I had to look at LLDB logs a lot, you'll notice I added `0x` to many of the PRIx64 `LLDB_LOGF`. This is so the user (or I) can directly copy paste the address in the logs instead of adding the hex prefix themselves.
Added some SBSaveCore tests for the new GetMemoryAPI, and Docstrings.
CC: @DavidSpickett, @da-viper @labath because we've been working together on save-core plugins, review it optional and I didn't tag you but figured you'd want to know
My current internal work requires some sensitivity to IO usage. I had a
work around to calculate the expected size of a Minidump, but I've added
this PR so an automated system could look at the expected size of an
LLDB generated Minidump and then choose if it has the space or wants to
generate it.
There are some prerequisites to calculating the correct size, so I have
the API take a reference for an SBError, I originally tried to return an
SBError and instead take a uint64_t reference, but this made the API
very difficult to use in python.
Added a test case as well.
This patch adds the ability to get a thread at a give index, based on
insertion order, for SBSaveCore Options. This is primarily to benefit
scripts using SBSaveCore, and remove the need to have both options and a
second collection if your script is tracking what threads need to be
saved. Such as if you want to collect the source of all the threads to
be saved after the Core is generated.
Recently in #107731 this change was revereted due to excess memory size
in `TestSkinnyCore`. This was due to a bug where a range's end was being
passed as size. Creating massive memory ranges.
Additionally, and requiring additional review, I added more unit tests
and more verbose logic to the merging of save core memory regions.
@jasonmolenda as an FYI.
Reapplies #106293, testing identified issue in the merging code. I used
this opportunity to strip CoreFileMemoryRanges to it's own file and then
add unit tests on it's behavior.
This patch adds the option to specify specific memory ranges to be
included in a given core file. The current implementation lets user
specified ranges either be in addition to a certain save style, or
independent of them via the newly added custom enum.
To achieve being inclusive of save style, I've moved from a std::vector
of ranges to a RangeDataVector, and to join overlapping ranges to
prevent duplication of memory ranges in the core file.
As a non function bonus, when SBSavecore was initially created, the
header was included in the lldb-private interfaces, and I've fixed that
and moved it the forward declare as an oversight. CC @bulbazord in case
we need to include that into swift.
Reapply #100443 and #101770. These were originally reverted due to a
test failure and an MSAN failure. I changed the test attribute to
restrict to x86 (following the other existing tests). I could not
reproduce the test or the MSAN failure and no repo steps were provided.
This class is technically not usable in its current state. When you use
it in a simple C++ project, your compiler will complain about an
incomplete definition of SaveCoreOptions. Normally this isn't a problem,
other classes in the SBAPI do this. The difference is that
SBSaveCoreOptions has a default destructor in the header, so the
compiler will attempt to generate the code for the destructor with an
incomplete definition of the impl type.
All methods for every class, including constructors and destructors,
must have a separate implementation not in a header.
In #98403 I enabled the SBSaveCoreOptions object, which allows users via
the scripting API to define what they want saved into their core file.
As the first option I've added a threadlist, so users can scan and
identify which threads and corresponding stacks they want to save.
In order to support this, I had to add a new method to `Process.h` on
how we identify which threads are to be saved, and I had to change the
book keeping in minidump to ensure we don't double save the stacks.
Important to @jasonmolenda I also changed the MachO coredump to accept
these new APIs.
This PR adds `SBSaveCoreOptions`, which is a container class for options
when LLDB is taking coredumps. For this first iteration this container
just keeps parity with the extant API of `file, style, plugin`. In the
future this options object can be extended to allow users to take a
subset of their core dumps.
