[lld] 0de0b6d - [ELF] Postpone "unable to move location counter backward" error (#66854)
via llvm-commits
llvm-commits at lists.llvm.org
Wed Sep 20 09:06:48 PDT 2023
Author: Fangrui Song
Date: 2023-09-20T09:06:45-07:00
New Revision: 0de0b6dded4752040350feb9c81415d82478d065
URL: https://github.com/llvm/llvm-project/commit/0de0b6dded4752040350feb9c81415d82478d065
DIFF: https://github.com/llvm/llvm-project/commit/0de0b6dded4752040350feb9c81415d82478d065.diff
LOG: [ELF] Postpone "unable to move location counter backward" error (#66854)
The size of .ARM.exidx may shrink across `assignAddress` calls. It is
possible
that the initial iteration has a larger location counter, causing
`__code_size =
__code_end - .; osec : { . += __code_size; }` to report an error, while
the error would
have been suppressed for subsequent `assignAddress` iterations.
Other sections like .relr.dyn may change sizes across `assignAddress`
calls as
well. However, their initial size is zero, so it is difficiult to
trigger a
similar error.
Similar to https://reviews.llvm.org/D152170, postpone the error
reporting.
Fix #66836. While here, add more information to the error message.
Added:
Modified:
lld/ELF/LinkerScript.cpp
lld/ELF/LinkerScript.h
lld/ELF/Writer.cpp
lld/test/ELF/linkerscript/locationcountererr-arm-exidx.test
lld/test/ELF/linkerscript/locationcountererr.test
Removed:
################################################################################
diff --git a/lld/ELF/LinkerScript.cpp b/lld/ELF/LinkerScript.cpp
index 943fd865ae0c15c..df091613dc0a144 100644
--- a/lld/ELF/LinkerScript.cpp
+++ b/lld/ELF/LinkerScript.cpp
@@ -169,9 +169,16 @@ void LinkerScript::expandOutputSection(uint64_t size) {
void LinkerScript::setDot(Expr e, const Twine &loc, bool inSec) {
uint64_t val = e().getValue();
- if (val < dot && inSec)
- error(loc + ": unable to move location counter backward for: " +
- state->outSec->name);
+ // If val is smaller and we are in an output section, record the error and
+ // report it if this is the last assignAddresses iteration. dot may be smaller
+ // if there is another assignAddresses iteration.
+ if (val < dot && inSec) {
+ backwardDotErr =
+ (loc + ": unable to move location counter (0x" + Twine::utohexstr(dot) +
+ ") backward to 0x" + Twine::utohexstr(val) + " for section '" +
+ state->outSec->name + "'")
+ .str();
+ }
// Update to location counter means update to section size.
if (inSec)
@@ -1343,6 +1350,7 @@ const Defined *LinkerScript::assignAddresses() {
state = &st;
errorOnMissingSection = true;
st.outSec = aether;
+ backwardDotErr.clear();
SymbolAssignmentMap oldValues = getSymbolAssignmentValues(sectionCommands);
for (SectionCommand *cmd : sectionCommands) {
@@ -1494,7 +1502,9 @@ static void checkMemoryRegion(const MemoryRegion *region,
}
}
-void LinkerScript::checkMemoryRegions() const {
+void LinkerScript::checkFinalScriptConditions() const {
+ if (backwardDotErr.size())
+ errorOrWarn(backwardDotErr);
for (const OutputSection *sec : outputSections) {
if (const MemoryRegion *memoryRegion = sec->memRegion)
checkMemoryRegion(memoryRegion, sec, sec->addr);
diff --git a/lld/ELF/LinkerScript.h b/lld/ELF/LinkerScript.h
index 89780bb60f48244..18eaf58b785e370 100644
--- a/lld/ELF/LinkerScript.h
+++ b/lld/ELF/LinkerScript.h
@@ -345,8 +345,8 @@ class LinkerScript final {
// Describe memory region usage.
void printMemoryUsage(raw_ostream &os);
- // Verify memory/lma overflows.
- void checkMemoryRegions() const;
+ // Check backward location counter assignment and memory region/LMA overflows.
+ void checkFinalScriptConditions() const;
// SECTIONS command list.
SmallVector<SectionCommand *, 0> sectionCommands;
@@ -358,6 +358,7 @@ class LinkerScript final {
bool seenDataAlign = false;
bool seenRelroEnd = false;
bool errorOnMissingSection = false;
+ std::string backwardDotErr;
// List of section patterns specified with KEEP commands. They will
// be kept even if they are unused and --gc-sections is specified.
diff --git a/lld/ELF/Writer.cpp b/lld/ELF/Writer.cpp
index 40f7d7981d9d441..d6adc4ff3d644db 100644
--- a/lld/ELF/Writer.cpp
+++ b/lld/ELF/Writer.cpp
@@ -2187,7 +2187,7 @@ template <class ELFT> void Writer<ELFT>::finalizeSections() {
for (OutputSection *sec : outputSections)
sec->finalize();
- script->checkMemoryRegions();
+ script->checkFinalScriptConditions();
if (config->emachine == EM_ARM && !config->isLE && config->armBe8) {
addArmInputSectionMappingSymbols();
diff --git a/lld/test/ELF/linkerscript/locationcountererr-arm-exidx.test b/lld/test/ELF/linkerscript/locationcountererr-arm-exidx.test
index 4dd7ae05d067416..791a9ae178fa94a 100644
--- a/lld/test/ELF/linkerscript/locationcountererr-arm-exidx.test
+++ b/lld/test/ELF/linkerscript/locationcountererr-arm-exidx.test
@@ -8,22 +8,24 @@
# RUN: not ld.lld -z norelro -z max-page-size=4096 -T a.t a.o -o /dev/null --no-merge-exidx-entries 2>&1 | \
# RUN: FileCheck %s --check-prefix=ERR --implicit-check-not=error:
-# ERR: error: a.t:14: unable to move location counter backward for: code.unused_space
-# ERR-NEXT: error: a.t:9: unable to move location counter backward for: dummy1
-# ERR-NEXT: error: a.t:10: unable to move location counter backward for: dummy2
-# ERR-NEXT: error: a.t:14: unable to move location counter backward for: code.unused_space
-# ERR-NEXT: error: a.t:9: unable to move location counter backward for: dummy1
-# ERR-NEXT: error: a.t:10: unable to move location counter backward for: dummy2
-# ERR-NEXT: error: a.t:14: unable to move location counter backward for: code.unused_space
+# ERR: error: a.t:14: unable to move location counter (0x4104) backward to 0x4070 for section 'code.unused_space'
+# ERR-NEXT: error: section '.ARM.exidx' will not fit in region 'CODE': overflowed by 148 bytes
# ERR-NEXT: error: section dummy1 at 0x1000 of size 0xFFFFFFFFFFFFFF6C exceeds available address space
# ERR-NEXT: error: section dummy2 at 0x2000 of size 0xFFFFFFFFFFFFFF6C exceeds available address space
# ERR-NEXT: error: section code.unused_space at 0x4104 of size 0xFFFFFFFFFFFFFF6C exceeds available address space
## If we merge adjacent duplicate entries, we will have enough space. Don't report
## a spurious error https://github.com/llvm/llvm-project/issues/66836
-# RUN: not ld.lld -z norelro -z max-page-size=4096 -T a.t a.o -o /dev/null 2>&1 | FileCheck %s --check-prefix=ERR2
+# RUN: ld.lld -z norelro -z max-page-size=4096 -T a.t a.o -o a
+# RUN: llvm-readelf -S a | FileCheck %s
-# ERR2: error: a.t:14: unable to move location counter backward for: code.unused_space
+# CHECK: [Nr] Name Type Address Off Size ES Flg Lk Inf Al
+# CHECK-NEXT: [ 0] NULL 00000000 000000 000000 00 0 0 0
+# CHECK-NEXT: [ 1] dummy1 NOBITS 00001000 001000 00000c 00 A 0 0 1
+# CHECK-NEXT: [ 2] dummy2 NOBITS 00002000 001000 00000c 00 A 0 0 1
+# CHECK-NEXT: [ 3] .text PROGBITS 00004000 001000 000054 00 AX 0 0 4
+# CHECK-NEXT: [ 4] .ARM.exidx ARM_EXIDX 00004054 001054 000010 00 AL 3 0 4
+# CHECK-NEXT: [ 5] code.unused_space NOBITS 00004064 001064 00000c 00 A 0 0 1
#--- a.s
.globl _start
diff --git a/lld/test/ELF/linkerscript/locationcountererr.test b/lld/test/ELF/linkerscript/locationcountererr.test
index 086bfeba1e3d455..2ab6d7a3ce2cbec 100644
--- a/lld/test/ELF/linkerscript/locationcountererr.test
+++ b/lld/test/ELF/linkerscript/locationcountererr.test
@@ -1,7 +1,7 @@
# REQUIRES: x86
# RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux /dev/null -o %t
# RUN: not ld.lld %t --script %s -o /dev/null 2>&1 | FileCheck %s
-# CHECK: {{.*}}.test:8: unable to move location counter backward for: .text
+# CHECK: {{.*}}.test:8: unable to move location counter (0x2000) backward to 0x10 for section '.text'
SECTIONS {
.text 0x2000 : {
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