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gbuenoandradelabath
gbuenoandrade
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labath
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[lldb] Fix offset intersection bug between MPX and AVX registers
Summary: This change increases the offset of MPX registers (by 128) so they do not overlap with the offset associated with AVX registers. That was causing MPX data in GDBRemoteRegisterContext::m_reg_data to get overwritten. Reviewers: labath Reviewed By: labath Subscribers: JDevlieghere, lldb-commits Tags: #lldb Differential Revision: https://reviews.llvm.org/D68874
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‎lldb/packages/Python/lldbsuite/test/commands/register/register/intel_xtended_registers/mpx_offset_intersection/Makefile

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CXX_SOURCES := main.cpp
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include Makefile.rules

‎lldb/packages/Python/lldbsuite/test/commands/register/register/intel_xtended_registers/mpx_offset_intersection/TestMPXOffsetIntersection.py

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"""
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Test Intel(R) MPX registers do not get overwritten by AVX data.
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"""
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from __future__ import print_function
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import lldb
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from lldbsuite.test.decorators import *
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from lldbsuite.test.lldbtest import *
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from lldbsuite.test import lldbutil
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class MPXOffsetIntersectionTestCase(TestBase):
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mydir = TestBase.compute_mydir(__file__)
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AVX_REGS = ('ymm' + str(i) for i in range(16))
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YMM_VALUE = '{' + ' '.join(('0x00' for _ in range(32))) + '}'
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MPX_REGULAR_REGS = ('bnd0', 'bnd1', 'bnd2', 'bnd3')
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MPX_CONFIG_REGS = ('bndcfgu', 'bndstatus')
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BND_VALUE = '{' + ' '.join(('0xff' for _ in range(16))) + '}'
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def setUp(self):
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TestBase.setUp(self)
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@skipIf(oslist=no_match(['linux']))
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@skipIf(archs=no_match(['x86_64']))
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def test_mpx_registers_offset_intersection(self):
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"""Test if AVX data does not overwrite MPX values."""
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self.build()
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self.mpx_registers_offset_intersection()
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def mpx_registers_offset_intersection(self):
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exe = self.getBuildArtifact('a.out')
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self.runCmd('file ' + exe, CURRENT_EXECUTABLE_SET)
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self.runCmd('run', RUN_SUCCEEDED)
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target = self.dbg.GetSelectedTarget()
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process = target.GetProcess()
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thread = process.GetThreadAtIndex(0)
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currentFrame = thread.GetFrameAtIndex(0)
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has_avx = False
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has_mpx = False
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for registerSet in currentFrame.GetRegisters():
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if 'advanced vector extensions' in registerSet.GetName().lower():
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has_avx = True
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if 'memory protection extension' in registerSet.GetName().lower():
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has_mpx = True
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if not (has_avx and has_mpx):
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self.skipTest('Both AVX and MPX registers must be supported.')
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for reg in self.AVX_REGS:
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self.runCmd('register write ' + reg + " '" + self.YMM_VALUE + " '")
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for reg in self.MPX_REGULAR_REGS + self.MPX_CONFIG_REGS:
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self.runCmd('register write ' + reg + " '" + self.BND_VALUE + " '")
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self.verify_mpx()
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self.verify_avx()
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self.verify_mpx()
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def verify_mpx(self):
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for reg in self.MPX_REGULAR_REGS:
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self.expect('register read ' + reg,
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substrs = [reg + ' = {0xffffffffffffffff 0xffffffffffffffff}'])
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for reg in self.MPX_CONFIG_REGS:
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self.expect('register read ' + reg,
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substrs = [reg + ' = {0xff 0xff 0xff 0xff 0xff 0xff 0xff 0xff}'])
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def verify_avx(self):
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for reg in self.AVX_REGS:
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self.expect('register read ' + reg, substrs = [reg + ' = ' + self.YMM_VALUE])

‎lldb/packages/Python/lldbsuite/test/commands/register/register/intel_xtended_registers/mpx_offset_intersection/main.cpp

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#include <cstdint>
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int main() {
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asm volatile("int3");
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return 0;
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}

‎lldb/source/Plugins/Process/Linux/NativeRegisterContextLinux.cpp

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@@ -34,7 +34,7 @@ Status NativeRegisterContextLinux::ReadRegisterRaw(uint32_t reg_index,
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if (!reg_info)
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return Status("register %" PRIu32 " not found", reg_index);
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return DoReadRegisterValue(reg_info->byte_offset, reg_info->name,
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return DoReadRegisterValue(GetPtraceOffset(reg_index), reg_info->name,
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reg_info->byte_size, reg_value);
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}
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@@ -91,7 +91,8 @@ NativeRegisterContextLinux::WriteRegisterRaw(uint32_t reg_index,
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"for write register index %" PRIu32,
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__FUNCTION__, reg_to_write);
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return DoWriteRegisterValue(reg_info->byte_offset, reg_info->name, reg_value);
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return DoWriteRegisterValue(GetPtraceOffset(reg_index), reg_info->name,
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reg_value);
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}
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Status NativeRegisterContextLinux::ReadGPR() {

‎lldb/source/Plugins/Process/Linux/NativeRegisterContextLinux.h

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@@ -60,6 +60,10 @@ class NativeRegisterContextLinux : public NativeRegisterContextRegisterInfo {
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virtual size_t GetFPRSize() = 0;
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virtual uint32_t GetPtraceOffset(uint32_t reg_index) {
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return GetRegisterInfoAtIndex(reg_index)->byte_offset;
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}
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// The Do*** functions are executed on the privileged thread and can perform
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// ptrace
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// operations directly.

‎lldb/source/Plugins/Process/Linux/NativeRegisterContextLinux_x86_64.cpp

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return 4;
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}
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uint32_t
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NativeRegisterContextLinux_x86_64::GetPtraceOffset(uint32_t reg_index) {
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// If register is MPX, remove extra factor from gdb offset
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return GetRegisterInfoAtIndex(reg_index)->byte_offset -
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(IsMPX(reg_index) ? 128 : 0);
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}
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#endif // defined(__i386__) || defined(__x86_64__)

‎lldb/source/Plugins/Process/Linux/NativeRegisterContextLinux_x86_64.h

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@@ -75,6 +75,8 @@ class NativeRegisterContextLinux_x86_64 : public NativeRegisterContextLinux {
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Status WriteFPR() override;
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uint32_t GetPtraceOffset(uint32_t reg_index) override;
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private:
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// Private member types.
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enum class XStateType { Invalid, FXSAVE, XSAVE };

‎lldb/source/Plugins/Process/Utility/RegisterInfos_x86_64.h

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LLVM_EXTENSION offsetof(FPR, xsave) + \
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LLVM_EXTENSION offsetof(XSAVE, ymmh[0]) + (32 * reg_index))
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// Guarantees BNDR/BNDC offsets do not overlap with YMM offsets.
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#define GDB_REMOTE_OFFSET 128
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#define BNDR_OFFSET(reg_index) \
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(LLVM_EXTENSION offsetof(UserArea, fpr) + \
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LLVM_EXTENSION offsetof(FPR, xsave) + \
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LLVM_EXTENSION offsetof(XSAVE, mpxr[reg_index]))
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LLVM_EXTENSION offsetof(XSAVE, mpxr[reg_index]) + GDB_REMOTE_OFFSET)
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#define BNDC_OFFSET(reg_index) \
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(LLVM_EXTENSION offsetof(UserArea, fpr) + \
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LLVM_EXTENSION offsetof(FPR, xsave) + \
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LLVM_EXTENSION offsetof(XSAVE, mpxc[reg_index]))
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LLVM_EXTENSION offsetof(XSAVE, mpxc[reg_index]) + GDB_REMOTE_OFFSET)
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#ifdef DECLARE_REGISTER_INFOS_X86_64_STRUCT
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