[ELF] Keep orphan section names (.rodata.foo .text.foo) unchanged if …

…!hasSectionsCommand This behavior matches GNU ld and seems reasonable. ``` // If a SECTIONS command is not specified .text.* -> .text .rodata.* -> .rodata .init_array.* -> .init_array ``` A proposed Linux feature CONFIG_FG_KASLR may depend on the GNU ld behavior. Reword a comment about -z keep-text-section-prefix and a comment about CommonSection (deleted by rL286234). Reviewed By: grimar Differential Revision: https://reviews.llvm.org/D75225
llvm · Mar 23, 2020 · 9e33c09 · 9e33c09
1 parent 9607a11
commit 9e33c09
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Showing 11 changed files with 65 additions and 41 deletions.
diff --git a/lld/ELF/Writer.cpp b/lld/ELF/Writer.cpp
@@ -108,12 +108,21 @@ StringRef getOutputSectionName(const InputSectionBase *s) {
     }
   }
 
-  // This check is for -z keep-text-section-prefix.  This option separates text
-  // sections with prefix ".text.hot", ".text.unlikely", ".text.startup" or
-  // ".text.exit".
-  // When enabled, this allows identifying the hot code region (.text.hot) in
-  // the final binary which can be selectively mapped to huge pages or mlocked,
-  // for instance.
+  // A BssSection created for a common symbol is identified as "COMMON" in
+  // linker scripts. It should go to .bss section.
+  if (s->name == "COMMON")
+    return ".bss";
+
+  if (script->hasSectionsCommand)
+    return s->name;
+
+  // When no SECTIONS is specified, emulate GNU ld's internal linker scripts
+  // by grouping sections with certain prefixes.
+
+  // GNU ld places text sections with prefix ".text.hot.", ".text.unlikely.",
+  // ".text.startup." or ".text.exit." before others. We provide an option -z
+  // keep-text-section-prefix to group such sections into separate output
+  // sections. This is more flexible. See also sortISDBySectionOrder().
   if (config->zKeepTextSectionPrefix)
     for (StringRef v :
          {".text.hot.", ".text.unlikely.", ".text.startup.", ".text.exit."})
@@ -127,11 +136,6 @@ StringRef getOutputSectionName(const InputSectionBase *s) {
     if (isSectionPrefix(v, s->name))
       return v.drop_back();
 
-  // CommonSection is identified as "COMMON" in linker scripts.
-  // By default, it should go to .bss section.
-  if (s->name == "COMMON")
-    return ".bss";
-
   return s->name;
 }
 

diff --git a/lld/test/ELF/linkerscript/data-commands-gc.s b/lld/test/ELF/linkerscript/data-commands-gc.s
@@ -4,7 +4,7 @@
 # RUN: ld.lld --gc-sections -o %t %t.o --script %t.script
 # RUN: llvm-objdump -t %t | FileCheck %s
 
-# CHECK: 0000000000000008 g       .rodata  0000000000000000 bar
+# CHECK: 0000000000000008 g       .rodata.bar    0000000000000000 bar
 
 .section .rodata.bar
 .quad 0x1122334455667788

diff --git a/lld/test/ELF/linkerscript/icf-output-sections.s b/lld/test/ELF/linkerscript/icf-output-sections.s
@@ -28,13 +28,19 @@
 # SEC2:      .text.foo   PROGBITS 0000000000000000 001000 000001
 # SEC2-NEXT: .text.bar   PROGBITS 0000000000000001 001001 000001
 
-## .text.bar* are orphans that get assigned to .text.
+## .text.bar* are orphan sections.
 # RUN: echo 'SECTIONS { .text.foo : {*(.text.foo*)} }' > %t3.script
-# RUN: ld.lld %t.o --script %t3.script --icf=all --print-icf-sections -o %t | FileCheck --check-prefix=ICF2 %s
-# RUN: llvm-readelf -S %t | FileCheck --check-prefix=SEC3 %s
+# RUN: ld.lld %t.o -T %t3.script --icf=all --print-icf-sections -o %t3 | FileCheck --check-prefix=ICF3 %s
+# RUN: llvm-readelf -S %t3 | FileCheck --check-prefix=SEC3 %s
 
+# ICF3:      selected section {{.*}}.o:(.text.foo0)
+# ICF3-NEXT:   removing identical section {{.*}}.o:(.text.foo1)
+
+# SEC3:      Name        Type     Address          Off    Size
 # SEC3:      .text.foo   PROGBITS 0000000000000000 001000 000001
-# SEC3-NEXT: .text       PROGBITS 0000000000000004 001004 000001
+# SEC3-NEXT: .text       PROGBITS 0000000000000004 001004 000000
+# SEC3-NEXT: .text.bar0  PROGBITS 0000000000000004 001004 000001
+# SEC3-NEXT: .text.bar1  PROGBITS 0000000000000005 001005 000001
 
 .section .text.foo0,"ax"
 ret

diff --git a/lld/test/ELF/linkerscript/linkorder.s b/lld/test/ELF/linkerscript/linkorder.s
@@ -1,11 +1,11 @@
 # REQUIRES: x86
 # RUN: llvm-mc -filetype=obj -triple=x86_64-pc-linux %s -o %t.o
 
-# RUN: echo "SECTIONS { .text : { *(.text.bar) *(.text.foo)  } }" > %t.script
+# RUN: echo "SECTIONS { .rodata : {*(.rodata*)} .text : {*(.text.bar) *(.text.foo)} }" > %t.script
 # RUN: ld.lld -o %t --script %t.script %t.o
 # RUN: llvm-objdump -s %t | FileCheck %s
 
-# RUN: echo "SECTIONS { .text : { *(.text.foo) *(.text.bar) } }" > %t.script
+# RUN: echo "SECTIONS { .rodata : {*(.rodata*)} .text : {*(.text.foo) *(.text.bar)} }" > %t.script
 # RUN: ld.lld -o %t --script %t.script %t.o
 # RUN: llvm-objdump -s %t | FileCheck --check-prefix=INV %s
 

diff --git a/lld/test/ELF/linkerscript/linkorder2.s b/lld/test/ELF/linkerscript/linkorder2.s
@@ -1,6 +1,6 @@
 # REQUIRES: x86
 # RUN: llvm-mc -filetype=obj -triple=x86_64-pc-linux %s -o %t.o
-# RUN: echo "SECTIONS { .text : { *(.text.*) } }" > %t.script
+# RUN: echo 'SECTIONS { .rodata : {*(.rodata.*)} .text : {*(.text.*)} }' > %t.script
 
 # RUN: echo "_bar" > %t.ord
 # RUN: echo "_foo" >> %t.ord

diff --git a/lld/test/ELF/linkerscript/memory3.s b/lld/test/ELF/linkerscript/memory3.s
@@ -18,6 +18,6 @@
 # CHECK:   0       00000000 0000000000000000
 # CHECK:   1 .text 00000001 0000000000001000
 
-.section .text.foo,"ax",%progbits
+.section .text,"ax",%progbits
 foo:
   nop
diff --git a/lld/test/ELF/linkerscript/orphan-report.s b/lld/test/ELF/linkerscript/orphan-report.s
@@ -24,7 +24,7 @@
 # RUN:   %t.o 2>&1 | FileCheck %s --check-prefixes=COMMON,DYNSYM,SYMTAB
 
 # COMMON:      {{.*}}.o:(.text) is being placed in '.text'
-# COMMON-NEXT: {{.*}}.o:(.text.2) is being placed in '.text'
+# COMMON-NEXT: {{.*}}.o:(.text.2) is being placed in '.text.2'
 # COMMON-NEXT: <internal>:(.comment) is being placed in '.comment'
 # DYNSYM-NEXT: <internal>:(.dynsym) is being placed in '.dynsym'
 # DYNSYM-NEXT: <internal>:(.gnu.hash) is being placed in '.gnu.hash'

diff --git a/lld/test/ELF/linkerscript/symbol-assign-many-passes2.test b/lld/test/ELF/linkerscript/symbol-assign-many-passes2.test
@@ -22,7 +22,7 @@ SECTIONS {
     b = c + 1;
     c = d + 1;
     d = e + 1;
-    *(.text);
+    *(.text*);
   }
   e = .;
 }
diff --git a/lld/test/ELF/mips-npic-call-pic-script.s b/lld/test/ELF/mips-npic-call-pic-script.s
@@ -87,13 +87,13 @@ __start:
 # ORPH1: Disassembly of section .text:
 # ORPH1-EMPTY:
 # ORPH1-NEXT: <__start>:
-# ORPH1-NEXT:    20000:       jal     131156 <__LA25Thunk_foo1a>
+# ORPH1-NEXT:    20000:       jal     131168 <__LA25Thunk_foo1a>
 # ORPH1-NEXT:    20004:       nop
-# ORPH1-NEXT:    20008:       jal     131208 <__LA25Thunk_foo2>
+# ORPH1-NEXT:    20008:       jal     131216 <__LA25Thunk_foo2>
 # ORPH1-NEXT:    2000c:       nop
-# ORPH1-NEXT:    20010:       jal     131172 <__LA25Thunk_foo1b>
+# ORPH1-NEXT:    20010:       jal     131184 <__LA25Thunk_foo1b>
 # ORPH1-NEXT:    20014:       nop
-# ORPH1-NEXT:    20018:       jal     131208 <__LA25Thunk_foo2>
+# ORPH1-NEXT:    20018:       jal     131216 <__LA25Thunk_foo2>
 # ORPH1-NEXT:    2001c:       nop
 # ORPH1-NEXT:    20020:       jal     131120 <__LA25Thunk_fpic>
 # ORPH1-NEXT:    20024:       nop
@@ -113,16 +113,16 @@ __start:
 # ORPH1-NEXT:    20050:       nop
 
 # ORPH1: <__LA25Thunk_foo1a>:
-# ORPH1-NEXT:    20054:       lui     $25, 2
-# ORPH1-NEXT:    20058:       j       131200 <foo1a>
-# ORPH1-NEXT:    2005c:       addiu   $25, $25, 128
-# ORPH1-NEXT:    20060:       nop
+# ORPH1-NEXT:    20060:       lui     $25, 2
+# ORPH1-NEXT:                 j       131200 <foo1a>
+# ORPH1-NEXT:                 addiu   $25, $25, 128
+# ORPH1-NEXT:                 nop
 
 # ORPH1: <__LA25Thunk_foo1b>:
-# ORPH1-NEXT:    20064:       lui     $25, 2
-# ORPH1-NEXT:    20068:       j       131204 <foo1b>
-# ORPH1-NEXT:    2006c:       addiu   $25, $25, 132
-# ORPH1-NEXT:    20070:       nop
+# ORPH1-NEXT:    20070:       lui     $25, 2
+# ORPH1-NEXT:                 j       131204 <foo1b>
+# ORPH1-NEXT:                 addiu   $25, $25, 132
+# ORPH1-NEXT:                 nop
 
 # ORPH1: <foo1a>:
 # ORPH1-NEXT:    20080:       nop
@@ -131,17 +131,17 @@ __start:
 # ORPH1-NEXT:    20084:       nop
 
 # ORPH1: <__LA25Thunk_foo2>:
-# ORPH1-NEXT:    20088:       lui     $25, 2
-# ORPH1-NEXT:    2008c:       j       131232 <foo2>
-# ORPH1-NEXT:    20090:       addiu   $25, $25, 160
-# ORPH1-NEXT:    20094:       nop
+# ORPH1-NEXT:    20090:       lui     $25, 2
+# ORPH1-NEXT:                 j       131232 <foo2>
+# ORPH1-NEXT:                 addiu   $25, $25, 160
+# ORPH1-NEXT:                 nop
 
 # ORPH1: <foo2>:
 # ORPH1-NEXT:    200a0:       nop
 
 # Test script with orphans added to new OutputSection, the .text.1 and
 # .text.2 sections will form a new OutputSection .text
-# RUN: echo "SECTIONS { .out 0x20000 : { *(.text) }  }" > %t3.script
+# RUN: echo "SECTIONS { .out 0x20000 : { *(.text) } .text : {*(.text*)} }" > %t3.script
 # RUN: ld.lld --script %t3.script %t-npic.o %t-pic.o %t-sto-pic.o -o %t3.exe
 # RUN: llvm-objdump -d --no-show-raw-insn %t3.exe | FileCheck --check-prefix=ORPH2 %s
 

diff --git a/lld/test/ELF/shuffle-sections-init-fini.s b/lld/test/ELF/shuffle-sections-init-fini.s
@@ -30,7 +30,9 @@
 
 ## With a SECTIONS command, SHT_INIT_ARRAY prirotities are ignored.
 ## All .init_array* are shuffled together.
-# RUN: echo 'SECTIONS {}' > %t.script
+# RUN: echo 'SECTIONS { \
+# RUN:   .init_array : { *(.init_array*) } \
+# RUN:   .fini_array : { *(.fini_array*) }}' > %t.script
 # RUN: ld.lld -T %t.script %t.o -o %t2
 # RUN: llvm-readelf -x .init -x .fini -x .init_array -x .fini_array %t2 | \
 # RUN:   FileCheck --check-prefixes=CHECK2,ORDERED2 %s

diff --git a/lld/test/ELF/text-section-prefix.s b/lld/test/ELF/text-section-prefix.s
@@ -1,4 +1,7 @@
 # REQUIRES: x86
+## -z keep-text-section-prefix separates text sections with prefix .text.hot,
+## .text.unlikely, .text.startup, or .text.exit, in the absence of a SECTIONS command.
+
 # RUN: llvm-mc -filetype=obj -triple=x86_64 %s -o %t.o
 # RUN: ld.lld %t.o -o %t1
 # RUN: llvm-readelf -S %t1 | FileCheck --check-prefix=NOKEEP %s
@@ -17,9 +20,18 @@
 # NOKEEP:    [ 1] .text
 # NOKEEP-NOT:     .text
 
+## With a SECTIONS command, orphan sections are created verbatim.
+## No grouping is performed for them.
 # RUN: echo 'SECTIONS {}' > %t.lds
 # RUN: ld.lld -T %t.lds -z keep-text-section-prefix %t.o -o %t.script
-# RUN: llvm-readelf -S %t.script | FileCheck --check-prefix=KEEP %s
+# RUN: llvm-readelf -S %t.script | FileCheck --check-prefix=SCRIPT %s
+
+# SCRIPT:      .text
+# SCRIPT-NEXT: .text.f
+# SCRIPT-NEXT: .text.hot.f_hot
+# SCRIPT-NEXT: .text.startup.f_startup
+# SCRIPT-NEXT: .text.exit.f_exit
+# SCRIPT-NEXT: .text.unlikely.f_unlikely
 
 .globl _start
 _start: