[all-commits] [llvm/llvm-project] 2937b2: Reland "[lldb] Remove non address bits when lookin...

David Spickett via All-commits all-commits at lists.llvm.org
Thu Feb 10 02:43:02 PST 2022

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 2937b282188bafb6bdb65ee87c70e9109aa910b7
  Author: David Spickett <david.spickett at linaro.org>
  Date:   2022-02-10 (Thu, 10 Feb 2022)

  Changed paths:
    M lldb/include/lldb/Target/Process.h
    M lldb/source/Commands/CommandObjectMemory.cpp
    M lldb/source/Plugins/Process/Windows/Common/ProcessWindows.cpp
    M lldb/source/Plugins/Process/Windows/Common/ProcessWindows.h
    M lldb/source/Plugins/Process/elf-core/ProcessElfCore.cpp
    M lldb/source/Plugins/Process/elf-core/ProcessElfCore.h
    M lldb/source/Plugins/Process/gdb-remote/ProcessGDBRemote.cpp
    M lldb/source/Plugins/Process/gdb-remote/ProcessGDBRemote.h
    M lldb/source/Plugins/Process/mach-core/ProcessMachCore.cpp
    M lldb/source/Plugins/Process/mach-core/ProcessMachCore.h
    M lldb/source/Plugins/Process/minidump/ProcessMinidump.cpp
    M lldb/source/Plugins/Process/minidump/ProcessMinidump.h
    M lldb/source/Plugins/Process/scripted/ScriptedProcess.cpp
    M lldb/source/Plugins/Process/scripted/ScriptedProcess.h
    M lldb/source/Target/Process.cpp
    A lldb/test/API/linux/aarch64/tagged_memory_region/Makefile
    A lldb/test/API/linux/aarch64/tagged_memory_region/TestAArch64LinuxTaggedMemoryRegion.py
    A lldb/test/API/linux/aarch64/tagged_memory_region/main.c
    M llvm/docs/ReleaseNotes.rst

  Log Message:
  Reland "[lldb] Remove non address bits when looking up memory regions"

This reverts commit 0df522969a7a0128052bd79182c8d58e00556e2f.

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.

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

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