[llvm-objcopy][ELF] Allow setting SHF_EXCLUDE flag for ELF sections

Summary: This patch adds support for setting SHF_EXCLUDE flag for ELF sections.

Reviewers: jhenderson, grimar, MaskRay, mstorsjo, espindola, alexshap, rupprecht

Reviewed By: jhenderson, MaskRay

Subscribers: emaste, abrachet, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D72128

llvm/docs/CommandGuide/llvm-objcopy.rst

@@ -418,6 +418,7 @@ them.
  - `load` = if the section has `SHT_NOBITS` type, mark it as a `SHT_PROGBITS`
    section.
  - `readonly` = if this flag is not specified, add the `SHF_WRITE` flag.
+ - `exclude` = add the `SHF_EXCLUDE` flag.
  - `code` = add the `SHF_EXECINSTR` flag.
  - `merge` = add the `SHF_MERGE` flag.
  - `strings` = add the `SHF_STRINGS` flag.

llvm/test/tools/llvm-objcopy/ELF/rename-section-flag-osproc-mask.test

@@ -76,15 +76,13 @@ Sections:
 # MIPS-NEXT:   Type: SHT_PROGBITS
 # MIPS-NEXT:   Flags [
 # MIPS-NEXT:     SHF_ALLOC (0x2)
-# MIPS-NEXT:     SHF_EXCLUDE (0x80000000)
 # MIPS-NEXT:     SHF_MIPS_ADDR (0x40000000)
 # MIPS-NEXT:     SHF_MIPS_GPREL (0x10000000)
 # MIPS-NEXT:     SHF_MIPS_LOCAL (0x4000000)
 # MIPS-NEXT:     SHF_MIPS_MERGE (0x20000000)
 # MIPS-NEXT:     SHF_MIPS_NAMES (0x2000000)
 # MIPS-NEXT:     SHF_MIPS_NODUPES (0x1000000)
 # MIPS-NEXT:     SHF_MIPS_NOSTRIP (0x8000000)
-# MIPS-NEXT:     SHF_MIPS_STRING (0x80000000)
 # MIPS-NEXT:     SHF_WRITE (0x1)
 # MIPS-NEXT:   ]
 

llvm/test/tools/llvm-objcopy/ELF/rename-section-flag-preserved.test

@@ -25,6 +25,8 @@
 # RUN: llvm-readobj --sections %t.strings | FileCheck %s --check-prefixes=CHECK,STRINGS,WRITE
 # RUN: llvm-objcopy --rename-section=.foo=.bar,share %t %t.share
 # RUN: llvm-readobj --sections %t.share | FileCheck %s --check-prefixes=CHECK,WRITE
+# RUN: llvm-objcopy --rename-section=.foo=.bar,exclude %t %t.exclude
+# RUN: llvm-readobj --sections %t.exclude | FileCheck %s --check-prefixes=CHECK,WRITE,EXCLUDE
 
 !ELF
 FileHeader:
@@ -59,7 +61,7 @@ Symbols:
 # CHECK-NEXT:   Flags [
 # ALLOC-NEXT:     SHF_ALLOC (0x2)
 # CHECK-NEXT:     SHF_COMPRESSED (0x800)
-# CHECK-NEXT:     SHF_EXCLUDE (0x80000000)
+# EXCLUDE-NEXT:   SHF_EXCLUDE (0x80000000)
 # EXEC-NEXT:      SHF_EXECINSTR (0x4)
 # CHECK-NEXT:     SHF_GROUP (0x200)
 # CHECK-NEXT:     SHF_INFO_LINK (0x40)
@@ -69,5 +71,3 @@ Symbols:
 # CHECK-NEXT:     SHF_TLS (0x400)
 # WRITE-NEXT:     SHF_WRITE (0x1)
 # CHECK-NEXT:   ]
-
-# BAD-FLAG: unrecognized section flag 'xyzzy'

llvm/test/tools/llvm-objcopy/ELF/rename-section-flag.test

@@ -13,6 +13,9 @@
 # RUN: llvm-objcopy --rename-section=.foo=.bar,readonly  \
 # RUN:   --rename-section=.baz=.blah,readonly %t %t.readonly
 # RUN: llvm-readobj --sections %t.readonly | FileCheck %s --check-prefixes=CHECK,PROGBITS
+# RUN: llvm-objcopy --rename-section=.foo=.bar,exclude  \
+# RUN:   --rename-section=.baz=.blah,exclude %t %t.exclude
+# RUN: llvm-readobj --sections %t.exclude | FileCheck %s --check-prefixes=CHECK,PROGBITS,EXCLUDE,WRITE
 # RUN: llvm-objcopy --rename-section=.foo=.bar,debug  \
 # RUN:   --rename-section=.baz=.blah,debug %t %t.debug
 # RUN: llvm-readobj --sections %t.debug | FileCheck %s --check-prefixes=CHECK,PROGBITS,WRITE
@@ -81,6 +84,7 @@ Sections:
 # EXEC-NEXT:       SHF_EXECINSTR (0x4)
 # MERGE-NEXT:      SHF_MERGE (0x10)
 # STRINGS-NEXT:    SHF_STRINGS (0x20)
+# EXCLUDE-NEXT:    SHF_EXCLUDE (0x80000000)
 # WRITE-NEXT:      SHF_WRITE (0x1)
 # CHECK-NEXT:    ]
 
@@ -92,7 +96,8 @@ Sections:
 # EXEC-NEXT:       SHF_EXECINSTR (0x4)
 # MERGE-NEXT:      SHF_MERGE (0x10)
 # STRINGS-NEXT:    SHF_STRINGS (0x20)
+# EXCLUDE-NEXT:    SHF_EXCLUDE (0x80000000)
 # WRITE-NEXT:      SHF_WRITE (0x1)
 # CHECK-NEXT:    ]
 
-# BAD-FLAG: unrecognized section flag 'xyzzy'. Flags supported for GNU compatibility: alloc, load, noload, readonly, debug, code, data, rom, share, contents, merge, strings
+# BAD-FLAG: unrecognized section flag 'xyzzy'. Flags supported for GNU compatibility: alloc, load, noload, readonly, exclude, debug, code, data, rom, share, contents, merge, strings

llvm/test/tools/llvm-objcopy/ELF/set-section-flags.test

@@ -13,6 +13,9 @@
 # RUN: llvm-objcopy --set-section-flags=.foo=readonly \
 # RUN:   --set-section-flags=.baz=readonly --set-section-flags=.rela.baz=readonly %t %t.readonly
 # RUN: llvm-readobj --sections %t.readonly | FileCheck %s --check-prefixes=CHECK,PROGBITS
+# RUN: llvm-objcopy --set-section-flags=.foo=exclude \
+# RUN:   --set-section-flags=.baz=exclude --set-section-flags=.rela.baz=exclude %t %t.exclude
+# RUN: llvm-readobj --sections %t.exclude | FileCheck %s --check-prefixes=CHECK,PROGBITS,EXCLUDE,WRITE
 # RUN: llvm-objcopy --set-section-flags=.foo=debug \
 # RUN:   --set-section-flags=.baz=debug --set-section-flags=.rela.baz=debug %t %t.debug
 # RUN: llvm-readobj --sections %t.debug | FileCheck %s --check-prefixes=CHECK,PROGBITS,WRITE
@@ -93,6 +96,7 @@ Sections:
 # EXEC-NEXT:       SHF_EXECINSTR (0x4)
 # MERGE-NEXT:      SHF_MERGE (0x10)
 # STRINGS-NEXT:    SHF_STRINGS (0x20)
+# EXCLUDE-NEXT:    SHF_EXCLUDE (0x80000000)
 # WRITE-NEXT:      SHF_WRITE (0x1)
 # CHECK-NEXT:    ]
 
@@ -104,6 +108,7 @@ Sections:
 # EXEC-NEXT:       SHF_EXECINSTR (0x4)
 # MERGE-NEXT:      SHF_MERGE (0x10)
 # STRINGS-NEXT:    SHF_STRINGS (0x20)
+# EXCLUDE-NEXT:    SHF_EXCLUDE (0x80000000)
 # WRITE-NEXT:      SHF_WRITE (0x1)
 # CHECK-NEXT:    ]
 
@@ -114,10 +119,11 @@ Sections:
 # EXEC-NEXT:       SHF_EXECINSTR (0x4)
 # MERGE-NEXT:      SHF_MERGE (0x10)
 # STRINGS-NEXT:    SHF_STRINGS (0x20)
+# EXCLUDE-NEXT:    SHF_EXCLUDE (0x80000000)
 # WRITE-NEXT:      SHF_WRITE (0x1)
 # CHECK-NEXT:    ]
 
 # BAD-FORMAT: bad format for --set-section-flags: missing '='
 # MULTIPLE-SETS: --set-section-flags set multiple times for section '.foo'
 
-# BAD-FLAG: unrecognized section flag 'xyzzy'. Flags supported for GNU compatibility: alloc, load, noload, readonly, debug, code, data, rom, share, contents, merge, strings
+# BAD-FLAG: unrecognized section flag 'xyzzy'. Flags supported for GNU compatibility: alloc, load, noload, readonly, exclude, debug, code, data, rom, share, contents, merge, strings

llvm/tools/llvm-objcopy/CopyConfig.cpp

@@ -146,6 +146,7 @@ static SectionFlag parseSectionRenameFlag(StringRef SectionName) {
       .CaseLower("strings", SectionFlag::SecStrings)
       .CaseLower("contents", SectionFlag::SecContents)
       .CaseLower("share", SectionFlag::SecShare)
+      .CaseLower("exclude", SectionFlag::SecExclude)
       .Default(SectionFlag::SecNone);
 }
 
@@ -158,8 +159,8 @@ parseSectionFlagSet(ArrayRef<StringRef> SectionFlags) {
       return createStringError(
           errc::invalid_argument,
           "unrecognized section flag '%s'. Flags supported for GNU "
-          "compatibility: alloc, load, noload, readonly, debug, code, data, "
-          "rom, share, contents, merge, strings",
+          "compatibility: alloc, load, noload, readonly, exclude, debug, "
+          "code, data, rom, share, contents, merge, strings",
           Flag.str().c_str());
     ParsedFlags |= ParsedFlag;
   }

llvm/tools/llvm-objcopy/CopyConfig.h

@@ -69,7 +69,8 @@ enum SectionFlag {
   SecStrings = 1 << 9,
   SecContents = 1 << 10,
   SecShare = 1 << 11,
-  LLVM_MARK_AS_BITMASK_ENUM(/* LargestValue = */ SecShare)
+  SecExclude = 1 << 12,
+  LLVM_MARK_AS_BITMASK_ENUM(/*LargestValue=*/SecExclude)
 };
 
 struct SectionRename {

llvm/tools/llvm-objcopy/ELF/ELFObjcopy.cpp

@@ -83,17 +83,20 @@ uint64_t getNewShfFlags(SectionFlag AllFlags) {
     NewFlags |= ELF::SHF_MERGE;
   if (AllFlags & SectionFlag::SecStrings)
     NewFlags |= ELF::SHF_STRINGS;
+  if (AllFlags & SectionFlag::SecExclude)
+    NewFlags |= ELF::SHF_EXCLUDE;
   return NewFlags;
 }
 
 static uint64_t getSectionFlagsPreserveMask(uint64_t OldFlags,
                                             uint64_t NewFlags) {
   // Preserve some flags which should not be dropped when setting flags.
   // Also, preserve anything OS/processor dependant.
-  const uint64_t PreserveMask = ELF::SHF_COMPRESSED | ELF::SHF_EXCLUDE |
-                                ELF::SHF_GROUP | ELF::SHF_LINK_ORDER |
-                                ELF::SHF_MASKOS | ELF::SHF_MASKPROC |
-                                ELF::SHF_TLS | ELF::SHF_INFO_LINK;
+  const uint64_t PreserveMask =
+      (ELF::SHF_COMPRESSED | ELF::SHF_GROUP | ELF::SHF_LINK_ORDER |
+       ELF::SHF_MASKOS | ELF::SHF_MASKPROC | ELF::SHF_TLS |
+       ELF::SHF_INFO_LINK) &
+      ~ELF::SHF_EXCLUDE;
   return (OldFlags & PreserveMask) | (NewFlags & ~PreserveMask);
 }