llvmbot wrote:
<!--LLVM PR SUMMARY COMMENT--> @llvm/pr-subscribers-lldb Author: None (jimingham) <details> <summary>Changes</summary> When an intra-module jump doesn't fit in the immediate branch slot, the Darwin linker inserts "branch island" symbols, and emits code to jump from branch island to branch island till it makes it to the actual function. The previous submissions failed because in that environment the linker was putting the `foo.island` symbol at the same address as the `padding` symbol we we emitting to make our faked-up large binary. This submission jams a byte after the padding symbol so that the other symbols can't overlap it. --- Full diff: https://github.com/llvm/llvm-project/pull/139301.diff 9 Files Affected: - (modified) lldb/source/Plugins/DynamicLoader/MacOSX-DYLD/DynamicLoaderDarwin.cpp (+25-7) - (added) lldb/test/API/macosx/branch-islands/Makefile (+16) - (added) lldb/test/API/macosx/branch-islands/TestBranchIslands.py (+35) - (added) lldb/test/API/macosx/branch-islands/foo.c (+6) - (added) lldb/test/API/macosx/branch-islands/main.c (+6) - (added) lldb/test/API/macosx/branch-islands/padding1.s (+5) - (added) lldb/test/API/macosx/branch-islands/padding2.s (+5) - (added) lldb/test/API/macosx/branch-islands/padding3.s (+5) - (added) lldb/test/API/macosx/branch-islands/padding4.s (+5) ``````````diff diff --git a/lldb/source/Plugins/DynamicLoader/MacOSX-DYLD/DynamicLoaderDarwin.cpp b/lldb/source/Plugins/DynamicLoader/MacOSX-DYLD/DynamicLoaderDarwin.cpp index e25c4ff55e408..578ab12268ea3 100644 --- a/lldb/source/Plugins/DynamicLoader/MacOSX-DYLD/DynamicLoaderDarwin.cpp +++ b/lldb/source/Plugins/DynamicLoader/MacOSX-DYLD/DynamicLoaderDarwin.cpp @@ -26,6 +26,7 @@ #include "lldb/Target/Thread.h" #include "lldb/Target/ThreadPlanCallFunction.h" #include "lldb/Target/ThreadPlanRunToAddress.h" +#include "lldb/Target/ThreadPlanStepInstruction.h" #include "lldb/Utility/DataBuffer.h" #include "lldb/Utility/DataBufferHeap.h" #include "lldb/Utility/LLDBLog.h" @@ -923,15 +924,15 @@ DynamicLoaderDarwin::GetStepThroughTrampolinePlan(Thread &thread, if (current_symbol != nullptr) { std::vector<Address> addresses; + ConstString current_name = + current_symbol->GetMangled().GetName(Mangled::ePreferMangled); if (current_symbol->IsTrampoline()) { - ConstString trampoline_name = - current_symbol->GetMangled().GetName(Mangled::ePreferMangled); - if (trampoline_name) { + if (current_name) { const ModuleList &images = target_sp->GetImages(); SymbolContextList code_symbols; - images.FindSymbolsWithNameAndType(trampoline_name, eSymbolTypeCode, + images.FindSymbolsWithNameAndType(current_name, eSymbolTypeCode, code_symbols); for (const SymbolContext &context : code_symbols) { Address addr = context.GetFunctionOrSymbolAddress(); @@ -945,8 +946,8 @@ DynamicLoaderDarwin::GetStepThroughTrampolinePlan(Thread &thread, } SymbolContextList reexported_symbols; - images.FindSymbolsWithNameAndType( - trampoline_name, eSymbolTypeReExported, reexported_symbols); + images.FindSymbolsWithNameAndType(current_name, eSymbolTypeReExported, + reexported_symbols); for (const SymbolContext &context : reexported_symbols) { if (context.symbol) { Symbol *actual_symbol = @@ -968,7 +969,7 @@ DynamicLoaderDarwin::GetStepThroughTrampolinePlan(Thread &thread, } SymbolContextList indirect_symbols; - images.FindSymbolsWithNameAndType(trampoline_name, eSymbolTypeResolver, + images.FindSymbolsWithNameAndType(current_name, eSymbolTypeResolver, indirect_symbols); for (const SymbolContext &context : indirect_symbols) { @@ -1028,6 +1029,23 @@ DynamicLoaderDarwin::GetStepThroughTrampolinePlan(Thread &thread, thread_plan_sp = std::make_shared<ThreadPlanRunToAddress>( thread, load_addrs, stop_others); } + // One more case we have to consider is "branch islands". These are regular + // TEXT symbols but their names end in .island plus maybe a .digit suffix. + // They are to allow arm64 code to branch further than the size of the + // address slot allows. We just need to single-instruction step in that + // case. + static const char *g_branch_island_pattern = "\\.island\\.?[0-9]*$"; + static RegularExpression g_branch_island_regex(g_branch_island_pattern); + + bool is_branch_island = g_branch_island_regex.Execute(current_name); + if (!thread_plan_sp && is_branch_island) { + thread_plan_sp = std::make_shared<ThreadPlanStepInstruction>( + thread, + /* step_over= */ false, /* stop_others */ false, eVoteNoOpinion, + eVoteNoOpinion); + LLDB_LOG(log, "Stepping one instruction over branch island: '{0}'.", + current_name); + } } else { LLDB_LOGF(log, "Could not find symbol for step through."); } diff --git a/lldb/test/API/macosx/branch-islands/Makefile b/lldb/test/API/macosx/branch-islands/Makefile new file mode 100644 index 0000000000000..062e947f6d6ee --- /dev/null +++ b/lldb/test/API/macosx/branch-islands/Makefile @@ -0,0 +1,16 @@ +C_SOURCES := main.c foo.c +CFLAGS_EXTRAS := -std=c99 + +include Makefile.rules + +a.out: main.o padding1.o padding2.o padding3.o padding4.o foo.o + ${CC} ${LDFLAGS} foo.o padding1.o padding2.o padding3.o padding4.o main.o -o a.out + +%.o: $(SRCDIR)/%.s + ${CC} -c $< + +#padding1.o: padding1.s +# ${CC} -c $(SRCDIR)/padding1.s + +#padding2.o: padding2.s +# ${CC} -c $(SRCDIR)/padding2.s diff --git a/lldb/test/API/macosx/branch-islands/TestBranchIslands.py b/lldb/test/API/macosx/branch-islands/TestBranchIslands.py new file mode 100644 index 0000000000000..d4885b6ead63f --- /dev/null +++ b/lldb/test/API/macosx/branch-islands/TestBranchIslands.py @@ -0,0 +1,35 @@ +""" +Make sure that we can step in across an arm64 branch island +""" + + +import lldb +import lldbsuite.test.lldbutil as lldbutil +from lldbsuite.test.lldbtest import * +from lldbsuite.test.decorators import * + + +class TestBranchIslandStepping(TestBase): + NO_DEBUG_INFO_TESTCASE = True + + @skipUnlessAppleSilicon + def test_step_in_branch_island(self): + """Make sure we can step in across a branch island""" + self.build() + self.main_source_file = lldb.SBFileSpec("main.c") + self.do_test() + + def do_test(self): + (target, process, thread, bkpt) = lldbutil.run_to_source_breakpoint( + self, "Set a breakpoint here", self.main_source_file + ) + + # Make sure that we did manage to generate a branch island for foo: + syms = target.FindSymbols("foo.island", lldb.eSymbolTypeCode) + self.assertEqual(len(syms), 1, "We did generate an island for foo") + + thread.StepInto() + stop_frame = thread.frames[0] + self.assertIn("foo", stop_frame.name, "Stepped into foo") + var = stop_frame.FindVariable("a_variable_in_foo") + self.assertTrue(var.IsValid(), "Found the variable in foo") diff --git a/lldb/test/API/macosx/branch-islands/foo.c b/lldb/test/API/macosx/branch-islands/foo.c new file mode 100644 index 0000000000000..a5dd2e59e1d82 --- /dev/null +++ b/lldb/test/API/macosx/branch-islands/foo.c @@ -0,0 +1,6 @@ +#include <stdio.h> + +void foo() { + int a_variable_in_foo = 10; + printf("I am foo: %d.\n", a_variable_in_foo); +} diff --git a/lldb/test/API/macosx/branch-islands/main.c b/lldb/test/API/macosx/branch-islands/main.c new file mode 100644 index 0000000000000..b5578bdd715df --- /dev/null +++ b/lldb/test/API/macosx/branch-islands/main.c @@ -0,0 +1,6 @@ +extern void foo(); + +int main() { + foo(); // Set a breakpoint here + return 0; +} diff --git a/lldb/test/API/macosx/branch-islands/padding1.s b/lldb/test/API/macosx/branch-islands/padding1.s new file mode 100644 index 0000000000000..04abef5455c12 --- /dev/null +++ b/lldb/test/API/macosx/branch-islands/padding1.s @@ -0,0 +1,5 @@ +.text +_padding1: +.p2align 2 +.byte 0x10 +.space 120*1024*1024 diff --git a/lldb/test/API/macosx/branch-islands/padding2.s b/lldb/test/API/macosx/branch-islands/padding2.s new file mode 100644 index 0000000000000..dc66686cc779f --- /dev/null +++ b/lldb/test/API/macosx/branch-islands/padding2.s @@ -0,0 +1,5 @@ +.text +_padding2: +.p2align 2 +.byte 0x10 +.space 120*1024*1024 diff --git a/lldb/test/API/macosx/branch-islands/padding3.s b/lldb/test/API/macosx/branch-islands/padding3.s new file mode 100644 index 0000000000000..bf920e2e4f643 --- /dev/null +++ b/lldb/test/API/macosx/branch-islands/padding3.s @@ -0,0 +1,5 @@ +.text +_padding3: +.p2align 2 +.byte 0x10 +.space 120*1024*1024 diff --git a/lldb/test/API/macosx/branch-islands/padding4.s b/lldb/test/API/macosx/branch-islands/padding4.s new file mode 100644 index 0000000000000..1430fd2fd9729 --- /dev/null +++ b/lldb/test/API/macosx/branch-islands/padding4.s @@ -0,0 +1,5 @@ +.text +_padding4: +.p2align 2 +.byte 0x10 +.space 120*1024*1024 `````````` </details> https://github.com/llvm/llvm-project/pull/139301 _______________________________________________ lldb-commits mailing list lldb-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/lldb-commits
