[llvm-branch-commits] [lld] f5b2787 - [ELF] Allow R_386_GOTOFF from .debug_info

[Tom Stellard via llvm-branch-commits]

Author: Fangrui Song
Date: 2021-02-15T14:16:40-08:00
New Revision: f5b2787d07c1c61ebbda3f11dd770b6c57e2b662

URL: https://github.com/llvm/llvm-project/commit/f5b2787d07c1c61ebbda3f11dd770b6c57e2b662
DIFF: https://github.com/llvm/llvm-project/commit/f5b2787d07c1c61ebbda3f11dd770b6c57e2b662.diff

LOG: [ELF] Allow R_386_GOTOFF from .debug_info

In GCC emitted .debug_info sections, R_386_GOTOFF may be used to
relocate DW_AT_GNU_call_site_value values
(https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98946).

R_386_GOTOFF (`S + A - GOT`) is one of the `isStaticLinkTimeConstant` relocation
type which is not PC-relative, so it can be used from non-SHF_ALLOC sections. We
current allow new relocation types as needs come. The diagnostic has caught some
bugs in the past.

Differential Revision: https://reviews.llvm.org/D95994

(cherry picked from commit b3165a70ae83b46dc145f335dfa9690ece361e92)

Added: 
    

Modified: 
    lld/ELF/InputSection.cpp
    lld/test/ELF/non-abs-reloc.s

Removed: 
    


################################################################################
diff  --git a/lld/ELF/InputSection.cpp b/lld/ELF/InputSection.cpp
index f40bb258b9af..6f16fc7abc48 100644
--- a/lld/ELF/InputSection.cpp
+++ b/lld/ELF/InputSection.cpp
@@ -901,7 +901,10 @@ void InputSection::relocateNonAlloc(uint8_t *buf, ArrayRef<RelTy> rels) {
       continue;
     }
 
-    if (expr != R_ABS && expr != R_DTPREL && expr != R_RISCV_ADD) {
+    // R_ABS/R_DTPREL and some other relocations can be used from non-SHF_ALLOC
+    // sections.
+    if (expr != R_ABS && expr != R_DTPREL && expr != R_GOTPLTREL &&
+        expr != R_RISCV_ADD) {
       std::string msg = getLocation<ELFT>(offset) +
                         ": has non-ABS relocation " + toString(type) +
                         " against symbol '" + toString(sym) + "'";

diff  --git a/lld/test/ELF/non-abs-reloc.s b/lld/test/ELF/non-abs-reloc.s
index 72a65424ed1f..82f913efe4d8 100644
--- a/lld/test/ELF/non-abs-reloc.s
+++ b/lld/test/ELF/non-abs-reloc.s
@@ -1,17 +1,17 @@
 // REQUIRES: x86
 // RUN: split-file %s %t
-// RUN: llvm-mc -filetype=obj -triple=x86_64 %t/asm -o %t.o
-// RUN: ld.lld -T %t/lds %t.o -o %t.exe 2>&1 | FileCheck %s
-// CHECK:      warning: {{.*}}.o:(.nonalloc1+0x1): has non-ABS relocation R_X86_64_PC32 against symbol '_start'
-// CHECK-NEXT: warning: {{.*}}.o:(.nonalloc1+0x6): has non-ABS relocation R_X86_64_PC32 against symbol '_start'
+// RUN: llvm-mc -filetype=obj -triple=i386 %t/asm -o %t.o
+// RUN: ld.lld -T %t/lds %t.o -o %t.exe 2>&1 | FileCheck %s --implicit-check-not=warning: --implicit-check-not=error:
+// CHECK:      warning: {{.*}}.o:(.nonalloc1+0x1): has non-ABS relocation R_386_PC32 against symbol '_start'
+// CHECK-NEXT: warning: {{.*}}.o:(.nonalloc1+0x6): has non-ABS relocation R_386_PC32 against symbol '_start'
 
 // RUN: llvm-objdump -D --no-show-raw-insn %t.exe | FileCheck --check-prefix=DISASM %s
 // DISASM:      Disassembly of section .nonalloc:
 // DISASM-EMPTY:
 // DISASM-NEXT: <.nonalloc>:
 // DISASM-NEXT:   0: nop
-// DISASM-NEXT:   1: callq 0x0
-// DISASM-NEXT:   6: callq 0x0
+// DISASM-NEXT:   1: calll 0x0
+// DISASM-NEXT:   6: calll 0x0
 
 //--- lds
 SECTIONS {
@@ -20,6 +20,7 @@ SECTIONS {
 //--- asm
 .globl _start
 _start:
+.L0:
   nop
 
 .section .nonalloc0
@@ -30,3 +31,8 @@ _start:
   .long _start - . - 4
   .byte 0xe8
   .long _start - . - 4
+
+// GCC may relocate DW_AT_GNU_call_site_value with R_386_GOTOFF.
+// https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98946
+.section .debug_info
+  .long .L0 at gotoff