Commit Graph

210 Commits

Author SHA1 Message Date
Felipe de Azevedo Piovezan 9749587498 [lldb] Reset breakpoint hit count before new runs
A common debugging pattern is to set a breakpoint that only stops after
a number of hits is recorded. The current implementation never resets
the hit count of breakpoints; as such, if a user re-`run`s their
program, the debugger will never stop on such a breakpoint again.

This behavior is arguably undesirable, as it renders such breakpoints
ineffective on all but the first run. This commit changes the
implementation of the `Will{Launch, Attach}` methods so that they reset
the _target's_ breakpoint hitcounts.

Differential Revision: https://reviews.llvm.org/D133858
2022-09-19 12:56:12 -04:00
Michał Górny 9ba71d03b0 [lldb] [gdb-remote] Remove unimplemented ProcessIDIsValid() (NFC)
This method is not implemented and not referenced anywhere in the code.

Sponsored by: The FreeBSD Foundation
2022-08-12 11:17:15 +02:00
Michał Górny 9b031d5e3a [lldb] Make Process and subclass constructors protected
Make constructors of the Process and its subclasses class protected,
to prevent accidentally constructing Process on stack when it could be
afterwards accessed via a shared_ptr (since it uses
std::enable_shared_from_this<>).

The only place where a stack allocation was used were unittests,
and fixing them via declaring an explicit public constructor
in the respective mock classes is trivial.

Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.llvm.org/D131275
2022-08-08 17:34:27 +02:00
Adrian Prantl 12606d16bc Revert "Expose GetAddressingBits() in the Process API."
This reverts commit 7504dd5e00.

In newer review feedback it was pointed out that there is a better API for this in Process::GetCodeAddressMask().
2022-03-23 15:28:34 -07:00
Adrian Prantl 7504dd5e00 Expose GetAddressingBits() in the Process API.
This is needed by the Swift Plugin.

See also  https://github.com/apple/llvm-project/pull/4110.

Differential Revision: https://reviews.llvm.org/D122347
2022-03-23 14:22:26 -07:00
Jonas Devlieghere 68099b1d5c
[lldb] Add a getter for the process' system architecture
This patch adds a getter for the process' system architecture. I went
with Process::GetSystemArchitecture to match
Platform::GetSystemArchitecture.

Differential revision: https://reviews.llvm.org/D121443
2022-03-11 10:58:04 -08:00
Pavel Labath ed1a83befe [lldb/gdb-remote] Remove ancient debugserver workaround
This workaround is the source of an awkwared Process->Platform
dependency. While this could be solved in various ways (the only thing
we really use is the plugin name), it may be better to just remove it --
the workaround was added 10 years ago (43c555dfc), and the affected
debugservers were "old" even then, so hopefully they are not in use
anymore.

Differential Revision: https://reviews.llvm.org/D121305
2022-03-10 20:26:54 +01:00
Pavel Labath 12c9c4a885 [lldb/host] Remove monitor_signals argument from process monitoring functions
All current callers set the argument to false. monitor_signals=true used
to be used in the Process plugins (which needed to know when the
debugged process gets a signal), but this implementation has several
serious issues, which means that individual process plugins now
orchestrate the monitoring of debugged processes themselves.

This allows us to simplify the implementation (no need to play with
process groups), and the interface (we only catch fatal events, so the
callback is always called just once).

Differential Revision: https://reviews.llvm.org/D120425
2022-02-24 11:12:59 +01:00
Pavel Labath d0810779b1 [lldb] Modernize ThreadLauncher
Accept a function object instead of a raw pointer. This avoids a bunch
of boilerplate typically needed to pass arguments to the thread
functions.

Differential Revision: https://reviews.llvm.org/D120321
2022-02-23 14:25:59 +01:00
David Spickett 2937b28218 Reland "[lldb] Remove non address bits when looking up memory regions"
This reverts commit 0df522969a.

Additional checks are added to fix the detection of the last memory region
in GetMemoryRegions or repeating the "memory region" command when the
target has non-address bits.

Normally you keep reading from address 0, looking up each region's end
address until you get LLDB_INVALID_ADDR as the region end address.
(0xffffffffffffffff)

This is what the remote will return once you go beyond the last mapped region:
[0x0000fffffffdf000-0x0001000000000000) rw- [stack]
[0x0001000000000000-0xffffffffffffffff) ---

Problem is that when we "fix" the lookup address, we remove some bits
from it. On an AArch64 system we have 48 bit virtual addresses, so when
we fix the end address of the [stack] region the result is 0.
So we loop back to the start.

[0x0000fffffffdf000-0x0001000000000000) rw- [stack]
[0x0000000000000000-0x0000000000400000) ---

To fix this I added an additional check for the last range.
If the end address of the region is different once you apply
FixDataAddress, we are at the last region.

Since the end of the last region will be the last valid mappable
address, plus 1. That 1 will be removed by the ABI plugin.

The only side effect is that on systems with non-address bits, you
won't get that last catch all unmapped region from the max virtual
address up to 0xf...f.

[0x0000fffff8000000-0x0000fffffffdf000) ---
[0x0000fffffffdf000-0x0001000000000000) rw- [stack]
<ends here>

Though in some way this is more correct because that region is not
just unmapped, it's not mappable at all.

No extra testing is needed because this is already covered by
TestMemoryRegion.py, I simply forgot to run it on system that had
both top byte ignore and pointer authentication.

This change has been tested on a qemu VM with top byte ignore,
memory tagging and pointer authentication enabled.

Reviewed By: omjavaid

Differential Revision: https://reviews.llvm.org/D115508
2022-02-10 10:42:49 +00:00
Pavel Labath a8ae6828a9 [lldb] Delete GDBRemoteCommunicationReplayServer
This survived the reproducer deletion.
2022-01-03 16:13:57 +01:00
David Spickett 0df522969a Revert "Reland "[lldb] Remove non address bits when looking up memory regions""
This reverts commit fac3f20de5.

I found this has broken how we detect the last memory region in
GetMemoryRegions/"memory region" command.

When you're debugging an AArch64 system with pointer authentication,
the ABI plugin will remove the top bit from the end address of the last
user mapped area.

(lldb)
[0x0000fffffffdf000-0x0001000000000000) rw- [stack]

ABI plugin removes anything above the 48th bit (48 bit virtual addresses
by default on AArch64, leaving an address of 0.

(lldb)
[0x0000000000000000-0x0000000000400000) ---

You get back a mapping for 0 and get into an infinite loop.
2021-11-26 15:35:02 +00:00
Pavel Labath 6f82264dbb [lldb/gdb-remote] Remove more non-stop mode remnants
The read thread handling is completely dead code now that non-stop mode
no longer exists.
2021-11-24 10:00:43 +01:00
David Spickett fac3f20de5 Reland "[lldb] Remove non address bits when looking up memory regions"
This reverts commit 5fbcf67734.

ProcessDebugger is used in ProcessWindows and NativeProcessWindows.
I thought I was simplifying things by renaming to DoGetMemoryRegionInfo
in ProcessDebugger but the Native process side expects "GetMemoryRegionInfo".

Follow the pattern that WriteMemory uses. So:
* ProcessWindows::DoGetMemoryRegioninfo calls ProcessDebugger::GetMemoryRegionInfo
* NativeProcessWindows::GetMemoryRegionInfo does the same
2021-11-03 13:56:51 +00:00
David Spickett 5fbcf67734 Revert "[lldb] Remove non address bits when looking up memory regions"
This reverts commit 6f5ce43b43 due to
build failure on Windows.
2021-11-03 13:27:41 +00:00
David Spickett 6f5ce43b43 [lldb] Remove non address bits when looking up memory regions
On AArch64 we have various things using the non address bits
of pointers. This means when you lookup their containing region
you won't find it if you don't remove them.

This changes Process GetMemoryRegionInfo to a non virtual method
that uses the current ABI plugin to remove those bits. Then it
calls DoGetMemoryRegionInfo.

That function does the actual work and is virtual to be overriden
by Process implementations.

A test case is added that runs on AArch64 Linux using the top
byte ignore feature.

Reviewed By: omjavaid

Differential Revision: https://reviews.llvm.org/D102757
2021-11-03 11:10:42 +00:00
Pavel Labath 5f4980f004 [lldb] Remove ConstString from Process, ScriptInterpreter and StructuredData plugin names 2021-10-28 10:15:03 +02:00
Pavel Labath a3939e159f [lldb] Return StringRef from PluginInterface::GetPluginName
There is no reason why this function should be returning a ConstString.

While modifying these files, I also fixed several instances where
GetPluginName and GetPluginNameStatic were returning different strings.

I am not changing the return type of GetPluginNameStatic in this patch, as that
would necessitate additional changes, and this patch is big enough as it is.

Differential Revision: https://reviews.llvm.org/D111877
2021-10-18 10:14:42 +02:00
Michał Górny 5849219126 [lldb] [ABI] Apply AugmentRegisterInfo() to DynamicRegisterInfo::Registers
Call ABI::AugmentRegisterInfo() once with a vector of all defined
registers rather than calling it for every individual register.  Move
and rename RemoteRegisterInfo from gdb-remote to
DynamicRegisterInfo::Register, and use this class when augmenting
registers.

Differential Revision: https://reviews.llvm.org/D111142
2021-10-11 17:02:26 +02:00
Pavel Labath 202af507fd Recommit: [lldb] Remove "dwarf dynamic register size expressions" from RegisterInfo
The previous version of the patch did not update the definitions in
conditionally compiled code. This patch includes changes to ARC and
windows targets.

Original commit message was:

These were added to support some mips registers on linux, but linux mips
support has now been removed due.

They are still referenced in the freebds mips implementation, but the
completeness of that implementation is also unknown. All other
architectures just set these fields to zero, which is a cause of
significant bloat in our register info definitions.

Arm also has registers with variable sizes, but they were implemented in
a more gdb-compatible fashion and don't use this feature.

Differential Revision: https://reviews.llvm.org/D110914
2021-10-07 11:15:00 +02:00
Michael Forster b2c906da19 Revert "[lldb] Remove "dwarf dynamic register size expressions" from RegisterInfo"
This reverts commit 00e704bf08.

This commit should should have updated
llvm/llvm-project/lldb/source/Plugins/ABI/ARC/ABISysV_arc.cpp like the other
architectures.
2021-10-06 18:15:25 +02:00
Pavel Labath 00e704bf08 [lldb] Remove "dwarf dynamic register size expressions" from RegisterInfo
These were added to support some mips registers on linux, but linux mips
support has now been removed due.

They are still referenced in the freebds mips implementation, but the
completeness of that implementation is also unknown. All other
architectures just set these fields to zero, which is a cause of
significant bloat in our register info definitions.

Arm also has registers with variable sizes, but they were implemented in
a more gdb-compatible fashion and don't use this feature.

Differential Revision: https://reviews.llvm.org/D110914
2021-10-06 13:22:38 +02:00
Pavel Labath 156cb4cc64 [lldb] Remove non-stop mode code
We added some support for this mode back in 2015, but the feature was
never productionized. It is completely untested, and there are known
major structural lldb issues that need to be resolved before this
feature can really be supported.

It also complicates making further changes to stop reply packet
handling, which is what I am about to do.

Differential Revision: https://reviews.llvm.org/D110553
2021-09-28 14:13:50 +02:00
Michał Górny e2f780fba9 [lldb] [gdb-remote] Use llvm::StringRef.split() and llvm::to_integer()
Replace the uses of StringConvert combined with hand-rolled array
splitting with llvm::StringRef.split() and llvm::to_integer().

Differential Revision: https://reviews.llvm.org/D110472
2021-09-26 21:23:26 +02:00
Michał Górny fa456505b8 [lldb] [gdb-remote] Refactor getting remote regs to use local vector
Refactor remote register getters to collect them into a local
std::vector rather than adding them straight into DynamicRegisterInfo.
The purpose of this change is to lay groundwork for switching value_regs
and invalidate_regs to use local LLDB register numbers rather than
remote numbers.

Differential Revision: https://reviews.llvm.org/D110025
2021-09-23 20:02:00 +02:00
Michał Górny bcb6b97cde Revert "[lldb] [gdb-remote] Refactor getting remote regs to use local vector"
This reverts commit b03e701c14.  This is
causing regressions when XML support is disabled.
2021-09-23 18:17:09 +02:00
Michał Górny b03e701c14 [lldb] [gdb-remote] Refactor getting remote regs to use local vector
Refactor remote register getters to collect them into a local
std::vector rather than adding them straight into DynamicRegisterInfo.
The purpose of this change is to lay groundwork for switching value_regs
and invalidate_regs to use local LLDB register numbers rather than
remote numbers.

Differential Revision: https://reviews.llvm.org/D110025
2021-09-23 17:21:55 +02:00
Pavel Labath b03126768a [lldb] Remove PluginInterface::GetPluginVersion
In all these years, we haven't found a use for this function (it has
zero callers). Lets just remove the boilerplate.

Differential Revision: https://reviews.llvm.org/D109600
2021-09-13 10:29:00 +02:00
Michał Górny 25fbbc5936 [lldb] Support SaveCore() from gdb-remote client
Extend PluginManager::SaveCore() to support saving core dumps
via Process plugins.  Implement the client-side part of qSaveCore
request in the gdb-remote plugin, that creates the core dump
on the remote host and then uses vFile packets to transfer it.

Differential Revision: https://reviews.llvm.org/D101329
2021-09-06 18:33:02 +02:00
Michał Górny 4a2a947317 [lldb] [client] Implement follow-fork-mode
Implement a new target.process.follow-fork-mode setting to control
LLDB's behavior on fork.  If set to 'parent', the forked child is
detached and parent continues being traced.  If set to 'child',
the parent is detached and child becomes traced instead.

Differential Revision: https://reviews.llvm.org/D100503
2021-09-02 12:16:58 +02:00
Michał Górny c568985845 [lldb] [gdb-remote client] Remove breakpoints throughout vfork
Temporarily remove breakpoints for the duration of vfork, in order
to prevent them from triggering in the child process.  Restore them
once the server reports that vfork has finished and it is ready to
resume execution.

Differential Revision: https://reviews.llvm.org/D100267
2021-09-01 10:33:48 +02:00
Michał Górny ceccbb8145 Revert "[lldb] [gdb-remote client] Remove breakpoints throughout vfork"
This reverts commit 199344d832.
It caused regressions on arm, as reported by lldb-arm-ubuntu buildbot.
2021-09-01 08:53:35 +02:00
Michał Górny 199344d832 [lldb] [gdb-remote client] Remove breakpoints throughout vfork
Temporarily remove breakpoints for the duration of vfork, in order
to prevent them from triggering in the child process.  Restore them
once the server reports that vfork has finished and it is ready to
resume execution.

Differential Revision: https://reviews.llvm.org/D100267
2021-09-01 08:16:12 +02:00
Michał Górny 8307869a22 [lldb] [gdb-remote client] Remove breakpoints in forked processes
Remove software breakpoints from forked processes in order to restore
the original program code before detaching it.

Differential Revision: https://reviews.llvm.org/D100263
2021-08-31 13:41:35 +02:00
Michał Górny 0a1d80d56e [lldb] [gdb-remote client] Support minimal fork/vfork handling
Add a support for handling fork/vfork stops in LLGS client.  At this
point, it only sends a detach packet for the newly forked child
(and implicitly resumes the parent).

Differential Revision: https://reviews.llvm.org/D100206
2021-08-30 10:24:38 +02:00
David Spickett 5ea091a817 [lldb][AArch64] Add memory tag writing to lldb
This adds memory tag writing to Process and the
GDB remote code. Supporting work for the
"memory tag write" command. (to follow)

Process WriteMemoryTags is similair to ReadMemoryTags.
It will pack the tags then call DoWriteMemoryTags.
That function will send the QMemTags packet to the gdb-remote.

The QMemTags packet follows the GDB specification in:
https://sourceware.org/gdb/current/onlinedocs/gdb/General-Query-Packets.html#General-Query-Packets

Note that lldb-server will be treating partial writes as
complete failures. So lldb doesn't need to handle the partial
write case in any special way.

Reviewed By: omjavaid

Differential Revision: https://reviews.llvm.org/D105181
2021-07-27 15:18:42 +01:00
David Spickett 5d34362001 [lldb][AArch64] Add MTE memory tag reading to lldb
This adds GDB client support for the qMemTags packet
which reads memory tags. Following the design
which was recently committed to GDB.

https://sourceware.org/gdb/current/onlinedocs/gdb/General-Query-Packets.html#General-Query-Packets
(look for qMemTags)

lldb commands will use the new Process methods
GetMemoryTagManager and ReadMemoryTags.

The former takes a range and checks that:
* The current process architecture has an architecture plugin
* That plugin provides a MemoryTagManager
* That the range of memory requested lies in a tagged range
  (it will expand it to granules for you)

If all that was true you get a MemoryTagManager you
can give to ReadMemoryTags.

This two step process is done to allow commands to get the
tag manager without having to read tags as well. For example
you might just want to remove a logical tag, or error early
if a range with tagged addresses is inverted.

Note that getting a MemoryTagManager doesn't mean that the process
or a specific memory range is tagged. Those are seperate checks.
Having a tag manager just means this architecture *could* have
a tagging feature enabled.

An architecture plugin has been added for AArch64 which
will return a MemoryTagManagerAArch64MTE, which was added in a
previous patch.

Reviewed By: omjavaid

Differential Revision: https://reviews.llvm.org/D95602
2021-06-24 17:17:10 +01:00
David Spickett 8d58fbd09e [lldb][AArch64] Add memory-tagging qSupported feature
This feature "memory-tagging+" indicates that lldb-server
supports memory tagging packets. (added in a later patch)

We check HWCAP2_MTE to decide whether to enable this
feature for Linux.

Reviewed By: omjavaid

Differential Revision: https://reviews.llvm.org/D97282
2021-06-24 15:43:20 +01:00
Michał Górny b601c67192 [lldb] [client] Support for multiprocess extension
Add a minimal support for the multiprocess extension in gdb-remote
client.  It accepts PIDs as part of thread-ids, and rejects PIDs that
do not match the current inferior.

Differential Revision: https://reviews.llvm.org/D99603
2021-04-08 13:45:07 +02:00
Walter Erquinigo 0b69756110 [trace][intel-pt] Implement trace start and trace stop
This implements the interactive trace start and stop methods.

This diff ended up being much larger than I anticipated because, by doing it, I found that I had implemented in the beginning many things in a non optimal way. In any case, the code is much better now.

There's a lot of boilerplate code due to the gdb-remote protocol, but the main changes are:

- New tracing packets: jLLDBTraceStop, jLLDBTraceStart, jLLDBTraceGetBinaryData. The gdb-remote packet definitions are quite comprehensive.
- Implementation of the "process trace start|stop" and "thread trace start|stop" commands.
- Implementaiton of an API in Trace.h to interact with live traces.
- Created an IntelPTDecoder for live threads, that use the debugger's stop id as checkpoint for its internal cache.
- Added a functionality to stop the process in case "process tracing" is enabled and a new thread can't traced.
- Added tests

I have some ideas to unify the code paths for post mortem and live threads, but I'll do that in another diff.

Differential Revision: https://reviews.llvm.org/D91679
2021-03-30 17:31:37 -07:00
Pavel Labath bf3ac994c4 [lldb] Apply gdb-remote timeout to platform connections as well
We have a plugin.process.gdb-remote.packet-timeout setting, which can be
used to control how long the lldb client is willing to wait before
declaring the server side dead. Our test suite makes use of this
feature, and sets the setting value fairly high, as the low default
value can cause flaky tests, particularly on slower bots.

After fixing TestPlatformConnect (one of the few tests exercising the
remote platform capabilities of lldb) in 4b284b9ca, it immediately
started being flaky on the arm bots. It turns out this is because the
packet-timeout setting is not being applied to platform connections.

This patch makes the platform connections also respect the value of this
setting. It also adds a test which checks that the timeout value is
being honored.

Differential Revision: https://reviews.llvm.org/D97769
2021-03-04 14:46:02 +01:00
Walter Erquinigo 4bb6244871 [ThreadPlan] fix exec on Linux 2021-01-25 11:30:48 -08:00
Muhammad Omair Javaid 4fd77668b2 [LLDB] Add per-thread register infos shared pointer in gdb-remote
In gdb-remote process we have register infos defind as a refernce object of
GDBRemoteDynamicRegisterInfo class. In past register infos have remained
constant througout the life time of a process.

This has changed after AArch64 SVE support where register infos will have
per-thread configuration. SVE registers will have per-thread size and can
be updated while running. This patch aims to build up for that support by
changing GDBRemoteDynamicRegisterInfo reference to a shared pointer deinfed
per-thread.

Reviewed By: labath

Differential Revision: https://reviews.llvm.org/D82857
2021-01-15 16:11:17 +05:00
Muhammad Omair Javaid 78cb4562fa Make offset field optional in RegisterInfo packet for Arm64
This patch carries forward our aim to remove offset field from qRegisterInfo
packets and XML register description. I have created a new function which
returns if offset fields are dynamic meaning client can calculate offset on
its own based on register number sequence and register size. For now this
function only returns true for NativeRegisterContextLinux_arm64 but we can
test this for other architectures and make it standard later.

As a consequence we do not send offset field from lldb-server (arm64 for now)
while other stubs dont have an offset field so it wont effect them for now.
On the client side we have replaced previous offset calculation algorithm
with a new scheme, where we sort all primary registers in increasing
order of remote regnum and then calculate offset incrementally.

This committ also includes a test to verify all of above functionality
on Arm64.

Reviewed By: labath

Differential Revision: https://reviews.llvm.org/D91241
2020-12-02 03:19:43 +05:00
Michał Górny 18e4272a4f [lldb] Prevent 'process connect' from using local-only plugins
Add a 'can_connect' parameter to Process plugin initialization, and use
it to filter plugins to these capable of remote connections.  This is
used to prevent 'process connect' from picking up a plugin that can only
be used locally, e.g. the legacy FreeBSD plugin.

Differential Revision: https://reviews.llvm.org/D91810
2020-11-23 09:48:55 +01:00
Walter Erquinigo 21555fff4d [intel-pt][trace] Implement a "get supported trace type" packet
Depends on D89283.

The goal of this packet (jTraceGetSupportedType) is to be able to query the gdb-server for the tracing technology that can work for the current debuggeer, which can make the user experience simpler but allowing the user to simply type

  thread trace start

to start tracing the current thread without even telling the debugger to use "intel-pt", for example. Similarly, `thread trace start [args...]` would accept args beloging to the working trace type.

Also, if the user typed

  help thread trace start

We could directly show the help information of the trace type that is supported for the target, or mention instead that no tracing is supported, if that's the case.

I added some simple tests, besides, when I ran this on my machine with intel-pt support, I got

  $ process plugin packet send "jTraceSupportedType"
    packet: jTraceSupportedType
  response: {"description":"Intel Processor Trace","pluginName":"intel-pt"}

On a machine without intel-pt support, I got

  $ process plugin packet send "jTraceSupportedType"
    packet: jTraceSupportedType
  response: E00;

Reviewed By: clayborg, labath

Differential Revision: https://reviews.llvm.org/D90490
2020-11-11 10:35:58 -08:00
Jonas Devlieghere 32d35fb74b [lldb] Remove unused argument (NFC)
Nobody is writing to the stream so there's no point in passing it
around.
2020-07-13 13:44:51 -07:00
Konrad Kleine eaebcbc679 [lldb] NFC remove DISALLOW_COPY_AND_ASSIGN
Summary:
This is how I applied my clang-tidy check (see
https://reviews.llvm.org/D80531) in order to remove
`DISALLOW_COPY_AND_ASSIGN` and have deleted copy ctors and deleted
assignment operators instead.

```
lang=bash
grep DISALLOW_COPY_AND_ASSIGN /opt/notnfs/kkleine/llvm/lldb -r -l | sort | uniq > files

for i in $(cat files);
do
  clang-tidy \
    --checks="-*,modernize-replace-disallow-copy-and-assign-macro" \
    --format-style=LLVM \
    --header-filter=.* \
    --fix \
    -fix-errors \
    $i;
done
```

Reviewers: espindola, labath, aprantl, teemperor

Reviewed By: labath, aprantl, teemperor

Subscribers: teemperor, aprantl, labath, emaste, sbc100, aheejin, MaskRay, arphaman, usaxena95, lldb-commits

Tags: #lldb

Differential Revision: https://reviews.llvm.org/D80543
2020-06-02 13:23:53 -04:00
Jonas Devlieghere 225f241c84 [lldb/Reproducers] Move connection logic into replay server (NFC)
Move the logic for connecting to the replay server into the replay
server itself, so it can be reused outside of ProcessGDBRemote.
2020-05-19 10:55:35 -07:00
Pavel Labath d4eca120ac [lldb/gdb-remote] Add support for the qOffsets packet
Summary:
This packet is necessary to make lldb work with the remote-gdb stub in
user mode qemu when running position-independent binaries. It reports
the relative position (load bias) of the loaded executable wrt. the
addresses in the file itself.

Lldb needs to know this information in order to correctly set the load
address of the executable. Normally, lldb would be able to find this out
on its own by following the breadcrumbs in the process auxiliary vector,
but we can't do this here because qemu does not support the
qXfer:auxv:read packet.

This patch does not implement full scope of the qOffsets packet (it only
supports packets with identical code, data and bss offsets), because it
is not fully clear how should the different offsets be handled and I am
not aware of a producer which would make use of this feature (qemu will
always
<https://github.com/qemu/qemu/blob/master/linux-user/elfload.c#L2436>
return the same value for code and data offsets). In fact, even gdb
ignores the offset for the bss sections, and uses the "data" offset
instead.  So, until the we need more of this packet, I think it's best
to stick to the simplest solution possible. This patch simply rejects
replies with non-uniform offsets.

Reviewers: clayborg, jasonmolenda

Subscribers: lldb-commits

Tags: #lldb

Differential Revision: https://reviews.llvm.org/D74598
2020-02-26 10:18:58 +01:00