[lld] b3d5bb3 - [ELF] Change (NOLOAD) type mismatch to use SHT_NOBITS instead of SHT_PROGBITS

[Fangrui Song via llvm-commits]

Author: Fangrui Song
Date: 2022-05-06T07:49:42-07:00
New Revision: b3d5bb3b308f9a41022cdd30542991840b826a6b

URL: https://github.com/llvm/llvm-project/commit/b3d5bb3b308f9a41022cdd30542991840b826a6b
DIFF: https://github.com/llvm/llvm-project/commit/b3d5bb3b308f9a41022cdd30542991840b826a6b.diff

LOG: [ELF] Change (NOLOAD) type mismatch to use SHT_NOBITS instead of SHT_PROGBITS

Placing a non-SHT_NOBITS input section in an output section specified with
(NOLOAD) is fishy but used by some projects. D118840 changed the output type to
SHT_PROGBITS, but using the specified type seems to make more sense and improve
GNU ld compatibility: `(NOLOAD)` seems to change the output section type
regardless of input.

I think we should keep the current type mismatch warning as it does indicate an
error-prone usage.

Reviewed By: peter.smith

Differential Revision: https://reviews.llvm.org/D125074

Added: 
    

Modified: 
    lld/ELF/OutputSections.cpp
    lld/test/ELF/linkerscript/custom-section-type.s
    lld/test/ELF/linkerscript/noload.s

Removed: 
    


################################################################################
diff  --git a/lld/ELF/OutputSections.cpp b/lld/ELF/OutputSections.cpp
index ee9162ac6b41..44d3d3c7ca28 100644
--- a/lld/ELF/OutputSections.cpp
+++ b/lld/ELF/OutputSections.cpp
@@ -123,7 +123,8 @@ void OutputSection::commitSection(InputSection *isec) {
                  "\n>>> output section " + name + ": " +
                  getELFSectionTypeName(config->emachine, type));
       }
-      type = SHT_PROGBITS;
+      if (!typeIsSet)
+        type = SHT_PROGBITS;
     } else {
       type = isec->type;
     }

diff  --git a/lld/test/ELF/linkerscript/custom-section-type.s b/lld/test/ELF/linkerscript/custom-section-type.s
index 21ef9922e25e..68454f4df1c8 100644
--- a/lld/test/ELF/linkerscript/custom-section-type.s
+++ b/lld/test/ELF/linkerscript/custom-section-type.s
@@ -37,7 +37,7 @@
 ## Mismatched progbits and expr are changed to SHT_PROGBITS.
 # MISMATCH: progbits PROGBITS
 # MISMATCH: note     NOTE
-# MISMATCH: expr     PROGBITS
+# MISMATCH: expr     0x42: <unknown>
 
 # RUN: not ld.lld -T %t/unknown1.lds %t/a.o -o /dev/null 2>&1 | FileCheck %s --check-prefix=UNKNOWN1
 # UNKNOWN1: error: {{.*}}.lds:1: symbol not found: foo

diff  --git a/lld/test/ELF/linkerscript/noload.s b/lld/test/ELF/linkerscript/noload.s
index fbee54b9e5b4..5c9cff33e235 100644
--- a/lld/test/ELF/linkerscript/noload.s
+++ b/lld/test/ELF/linkerscript/noload.s
@@ -24,7 +24,7 @@
 
 # WARN:   warning: section type mismatch for .data_noload_a
 # CHECK2:      Name                 Type     Address          Off               Size
-# CHECK2:      .data_noload_a       PROGBITS 0000000000000000 [[OFF:[0-9a-f]+]] 001001
+# CHECK2:      .data_noload_a       NOBITS   0000000000000000 [[OFF:[0-9a-f]+]] 001001
 
 #--- asm
 .section .text,"ax", at progbits