diff options
| -rw-r--r-- | src/common/linux/dwarf_line_to_module.cc | 8 | ||||
| -rw-r--r-- | src/common/linux/dwarf_line_to_module.h | 62 | ||||
| -rw-r--r-- | src/common/linux/dwarf_line_to_module_unittest.cc | 72 |
3 files changed, 142 insertions, 0 deletions
diff --git a/src/common/linux/dwarf_line_to_module.cc b/src/common/linux/dwarf_line_to_module.cc index bc1cd507..c740fa30 100644 --- a/src/common/linux/dwarf_line_to_module.cc +++ b/src/common/linux/dwarf_line_to_module.cc @@ -102,6 +102,14 @@ void DwarfLineToModule::AddLine(uint64 address, uint64 length, if (address + length < address) length = -address; + // Should we omit this line? (See the comments for omitted_line_end_.) + if (address == 0 || address == omitted_line_end_) { + omitted_line_end_ = address + length; + return; + } else { + omitted_line_end_ = 0; + } + // Find the source file being referred to. Module::File *file = files_[file_num]; if (!file) { diff --git a/src/common/linux/dwarf_line_to_module.h b/src/common/linux/dwarf_line_to_module.h index ab8bf11d..7ff466d7 100644 --- a/src/common/linux/dwarf_line_to_module.h +++ b/src/common/linux/dwarf_line_to_module.h @@ -52,6 +52,62 @@ namespace google_breakpad { // uses it to produce a vector of google_breakpad::Module::Line // objects, referring to google_breakpad::Module::File objects added // to a particular google_breakpad::Module. +// +// GNU toolchain omitted sections support: +// ====================================== +// +// Given the right options, the GNU toolchain will omit unreferenced +// functions from the final executable. Unfortunately, when it does so, it +// does not remove the associated portions of the DWARF line number +// program; instead, it gives the DW_LNE_set_address instructions referring +// to the now-deleted code addresses of zero. Given this input, the DWARF +// line parser will call AddLine with a series of lines starting at address +// zero. For example, here is the output from 'readelf -wl' for a program +// with four functions, the first three of which have been omitted: +// +// Line Number Statements: +// Extended opcode 2: set Address to 0x0 +// Advance Line by 14 to 15 +// Copy +// Special opcode 48: advance Address by 3 to 0x3 and Line by 1 to 16 +// Special opcode 119: advance Address by 8 to 0xb and Line by 2 to 18 +// Advance PC by 2 to 0xd +// Extended opcode 1: End of Sequence +// +// Extended opcode 2: set Address to 0x0 +// Advance Line by 14 to 15 +// Copy +// Special opcode 48: advance Address by 3 to 0x3 and Line by 1 to 16 +// Special opcode 119: advance Address by 8 to 0xb and Line by 2 to 18 +// Advance PC by 2 to 0xd +// Extended opcode 1: End of Sequence +// +// Extended opcode 2: set Address to 0x0 +// Advance Line by 19 to 20 +// Copy +// Special opcode 48: advance Address by 3 to 0x3 and Line by 1 to 21 +// Special opcode 76: advance Address by 5 to 0x8 and Line by 1 to 22 +// Advance PC by 2 to 0xa +// Extended opcode 1: End of Sequence +// +// Extended opcode 2: set Address to 0x80483a4 +// Advance Line by 23 to 24 +// Copy +// Special opcode 202: advance Address by 14 to 0x80483b2 and Line by 1 to 25 +// Special opcode 76: advance Address by 5 to 0x80483b7 and Line by 1 to 26 +// Advance PC by 6 to 0x80483bd +// Extended opcode 1: End of Sequence +// +// Instead of collecting runs of lines describing code that is not there, +// we try to recognize and drop them. Since the linker doesn't explicitly +// distinguish references to dropped sections from genuine references to +// code at address zero, we must use a heuristic. We have chosen: +// +// - If a line starts at address zero, omit it. (On the platforms +// breakpad targets, it is extremely unlikely that there will be code +// at address zero.) +// +// - If a line starts immediately after an omitted line, omit it too. class DwarfLineToModule: public dwarf2reader::LineInfoHandler { public: // As the DWARF line info parser passes us line records, add source @@ -65,6 +121,7 @@ class DwarfLineToModule: public dwarf2reader::LineInfoHandler { : module_(module), lines_(lines), highest_file_number_(-1), + omitted_line_end_(0), warned_bad_file_number_(false), warned_bad_directory_number_(false) { } @@ -106,6 +163,11 @@ class DwarfLineToModule: public dwarf2reader::LineInfoHandler { // The highest file number we've seen so far, or -1 if we've seen // none. Used for dynamically defined file numbers. int32 highest_file_number_; + + // This is the ending address of the last line we omitted, or zero if we + // didn't omit the previous line. It is zero before we have received any + // AddLine calls. + uint64 omitted_line_end_; // True if we've warned about: bool warned_bad_file_number_; // bad file numbers diff --git a/src/common/linux/dwarf_line_to_module_unittest.cc b/src/common/linux/dwarf_line_to_module_unittest.cc index 4b9743ce..54411591 100644 --- a/src/common/linux/dwarf_line_to_module_unittest.cc +++ b/src/common/linux/dwarf_line_to_module_unittest.cc @@ -265,3 +265,75 @@ TEST(Errors, BigLine) { ASSERT_EQ(1U, lines.size()); EXPECT_EQ(1U, lines[0].size); } + +// The 'Omitted' tests verify that we correctly omit line information +// for code in sections that the linker has dropped. See "GNU +// toolchain omitted sections support" at the top of the +// DwarfLineToModule class. + +TEST(Omitted, DroppedThenGood) { + Module m("name", "os", "architecture", "id"); + vector<Module::Line> lines; + DwarfLineToModule h(&m, &lines); + + h.DefineFile("filename1", 1, 0, 0, 0); + h.AddLine(0, 10, 1, 83816211, 0); // should be omitted + h.AddLine(20, 10, 1, 13059195, 0); // should be recorded + + ASSERT_EQ(1U, lines.size()); + EXPECT_EQ(13059195, lines[0].number); +} + +TEST(Omitted, GoodThenDropped) { + Module m("name", "os", "architecture", "id"); + vector<Module::Line> lines; + DwarfLineToModule h(&m, &lines); + + h.DefineFile("filename1", 1, 0, 0, 0); + h.AddLine(0x9dd6a372, 10, 1, 41454594, 0); // should be recorded + h.AddLine(0, 10, 1, 44793413, 0); // should be omitted + + ASSERT_EQ(1U, lines.size()); + EXPECT_EQ(41454594, lines[0].number); +} + +TEST(Omitted, Mix1) { + Module m("name", "os", "architecture", "id"); + vector<Module::Line> lines; + DwarfLineToModule h(&m, &lines); + + h.DefineFile("filename1", 1, 0, 0, 0); + h.AddLine(0x679ed72f, 10, 1, 58932642, 0); // should be recorded + h.AddLine(0xdfb5a72d, 10, 1, 39847385, 0); // should be recorded + h.AddLine(0, 0x78, 1, 23053829, 0); // should be omitted + h.AddLine(0x78, 0x6a, 1, 65317783, 0); // should be omitted + h.AddLine(0x78 + 0x6a, 0x2a, 1, 77601423, 0); // should be omitted + h.AddLine(0x9fe0cea5, 10, 1, 91806582, 0); // should be recorded + h.AddLine(0x7e41a109, 10, 1, 56169221, 0); // should be recorded + + ASSERT_EQ(4U, lines.size()); + EXPECT_EQ(58932642, lines[0].number); + EXPECT_EQ(39847385, lines[1].number); + EXPECT_EQ(91806582, lines[2].number); + EXPECT_EQ(56169221, lines[3].number); +} + +TEST(Omitted, Mix2) { + Module m("name", "os", "architecture", "id"); + vector<Module::Line> lines; + DwarfLineToModule h(&m, &lines); + + h.DefineFile("filename1", 1, 0, 0, 0); + h.AddLine(0, 0xf2, 1, 58802211, 0); // should be omitted + h.AddLine(0xf2, 0xb9, 1, 78958222, 0); // should be omitted + h.AddLine(0xf2 + 0xb9, 0xf7, 1, 64861892, 0); // should be omitted + h.AddLine(0x4e4d271e, 9, 1, 67355743, 0); // should be recorded + h.AddLine(0xdfb5a72d, 30, 1, 23365776, 0); // should be recorded + h.AddLine(0, 0x64, 1, 76196762, 0); // should be omitted + h.AddLine(0x64, 0x33, 1, 71066611, 0); // should be omitted + h.AddLine(0x64 + 0x33, 0xe3, 1, 61749337, 0); // should be omitted + + ASSERT_EQ(2U, lines.size()); + EXPECT_EQ(67355743, lines[0].number); + EXPECT_EQ(23365776, lines[1].number); +} |