From 38b632c16e0fdfd5f5a69bcfd4aecf6f69ea0186 Mon Sep 17 00:00:00 2001 From: Fangrui Song Date: Mon, 19 Oct 2020 16:45:56 -0700 Subject: [PATCH] [ELF] --gdb-index: support --icf={safe,all} The combination has not been tested before. In the case of ICF, `e.section->getVA(0)` equals the start address of the output section. This can cause incorrect overlapping with the actual function at the start of the output section and potentially trigger a GDB internal error in `dw2_find_pc_sect_compunit_symtab` (presumably because: if a short address range incorrectly starts at the start address of the output section, GDB may pick it instead of the correct longer address range. When mapping an address within the long address range but out of the scope of the short address range, the routine may find nothing - while the code asserts that it can find something). Note that in the case of ICF there may be duplicate address range entries, but GDB appears to be fine with them. Reviewed By: grimar Differential Revision: https://reviews.llvm.org/D89751 --- lld/ELF/SyntheticSections.cpp | 3 +- lld/test/ELF/gdb-index-icf.s | 67 +++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 69 insertions(+), 1 deletion(-) create mode 100644 lld/test/ELF/gdb-index-icf.s diff --git a/lld/ELF/SyntheticSections.cpp b/lld/ELF/SyntheticSections.cpp index 6c9651d..7769848 100644 --- a/lld/ELF/SyntheticSections.cpp +++ b/lld/ELF/SyntheticSections.cpp @@ -2914,7 +2914,8 @@ void GdbIndexSection::writeTo(uint8_t *buf) { uint32_t cuOff = 0; for (GdbChunk &chunk : chunks) { for (AddressEntry &e : chunk.addressAreas) { - uint64_t baseAddr = e.section->getVA(0); + // In the case of ICF there may be duplicate address range entries. + const uint64_t baseAddr = e.section->repl->getVA(0); write64le(buf, baseAddr + e.lowAddress); write64le(buf + 8, baseAddr + e.highAddress); write32le(buf + 16, e.cuIndex + cuOff); diff --git a/lld/test/ELF/gdb-index-icf.s b/lld/test/ELF/gdb-index-icf.s new file mode 100644 index 0000000..3f0f123 --- /dev/null +++ b/lld/test/ELF/gdb-index-icf.s @@ -0,0 +1,67 @@ +# REQUIRES: x86 +## Test that the address range contributed by an ICF folded function is identical +## to that of the folded-in function. Not considering ICF may lead to an address +## range whose low address equals the start address of the output section. + +# RUN: llvm-mc -filetype=obj -triple=x86_64 %s -o %t.o +# RUN: ld.lld --gdb-index --icf=all -Ttext=0x1000 %t.o -o %t +# RUN: llvm-dwarfdump --gdb-index %t | FileCheck %s + +# CHECK: Address area offset = 0x38, has 2 entries: +# CHECK-NEXT: Low/High address = [0x1001, 0x1002) (Size: 0x1), CU id = 0 +# CHECK-NEXT: Low/High address = [0x1001, 0x1002) (Size: 0x1), CU id = 1 + +.text +nop + +.section .text.0,"ax" +.Lfunc_begin0: + ret +.Lfunc_end0: + +.section .text.1,"ax" +.Lfunc_begin1: + ret +.Lfunc_end1: + +.section .debug_abbrev,"",@progbits + .byte 1 # Abbreviation Code + .byte 65 # DW_TAG_type_unit + .byte 0 # DW_CHILDREN_no + .byte 0 # EOM(1) + .byte 0 # EOM(2) + + .byte 2 # Abbreviation Code + .byte 17 # DW_TAG_compile_unit + .byte 0 # DW_CHILDREN_no + .byte 17 # DW_AT_low_pc + .byte 1 # DW_FORM_addr + .byte 18 # DW_AT_high_pc + .byte 6 # DW_FORM_data4 + .byte 0 # EOM(1) + .byte 0 # EOM(2) + + .byte 0 # EOM(3) + +.section .debug_info,"",@progbits +.Lcu_begin0: + .long .Lcu_end0-.Lcu_begin0-4 # Length of Unit + .short 5 # DWARF version number + .byte 1 # DWARF Unit Type + .byte 8 # Address Size + .long .debug_abbrev # Offset Into Abbrev. Section + .byte 2 # Abbrev [2] DW_TAG_compile_unit + .quad .Lfunc_begin0 # DW_AT_low_pc + .long .Lfunc_end0-.Lfunc_begin0 # DW_AT_high_pc +.Lcu_end0: + +.Lcu_begin1: + .long .Lcu_end1-.Lcu_begin1-4 # Length of Unit + .short 5 # DWARF version number + .byte 1 # DWARF Unit Type + .byte 8 # Address Size + .long .debug_abbrev # Offset Into Abbrev. Section + .byte 2 # Abbrev [2] DW_TAG_compile_unit + .quad .Lfunc_begin1 # DW_AT_low_pc + .long .Lfunc_end1-.Lfunc_begin1 # DW_AT_high_pc +.Lcu_end1: -- 2.7.4