[llvm-objcopy][MachO] Implement --remove-section

Reviewers: alexshap, rupprecht, jhenderson

Reviewed By: rupprecht, jhenderson

Subscribers: jakehehrlich, abrachet, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D66282

3 files changed, 142 insertions, 5 deletions

diff --git a/llvm/docs/CommandGuide/llvm-objcopy.rst b/llvm/docs/CommandGuide/llvm-objcopy.rst
index 9d7cab99e75..689ebb7549f 100644
--- a/llvm/docs/CommandGuide/llvm-objcopy.rst
+++ b/llvm/docs/CommandGuide/llvm-objcopy.rst
@@ -107,6 +107,9 @@ multiple file formats.
  Remove the specified section from the output. Can be specified multiple times
  to remove multiple sections simultaneously.
 
+ For MachO objects, ``<section>`` must be formatted as
+ ``<segment name>,<section name>``.
+
 .. option:: --set-section-alignment <section>=<align>
 
  Set the alignment of section ``<section>`` to `<align>``. Can be specified
diff --git a/llvm/test/tools/llvm-objcopy/MachO/remove-section.test b/llvm/test/tools/llvm-objcopy/MachO/remove-section.test
new file mode 100644
index 00000000000..beb4dd8ba5a
--- /dev/null
+++ b/llvm/test/tools/llvm-objcopy/MachO/remove-section.test
@@ -0,0 +1,127 @@
+## Show that if --remove-section is given, llvm-objcopy removes sections
+## specified by the option.
+
+# RUN: yaml2obj %s > %t
+
+## Remove only __TEXT,__text section.
+# RUN: llvm-objcopy --remove-section __TEXT,__text %t %t2
+# RUN: llvm-readobj --sections --section-data %t2 \
+# RUN:   | FileCheck %s --check-prefixes=COMMON,REMOVE-TEXT-ONLY
+
+## Remove multiple sections.
+# RUN: llvm-objcopy --remove-section __TEXT,__text --remove-section __DATA,__data %t %t3
+# RUN: llvm-readobj --sections --section-data %t3 \
+# RUN:   | FileCheck %s --check-prefixes=COMMON,REMOVE-TEXT-AND-DATA
+
+# COMMON:                    Sections [
+# REMOVE-TEXT-ONLY-NEXT:       Section {
+# REMOVE-TEXT-ONLY-NEXT:         Index: 0
+# REMOVE-TEXT-ONLY-NEXT:         Name: __data (5F 5F 64 61 74 61 00 00 00 00 00 00 00 00 00 00)
+# REMOVE-TEXT-ONLY-NEXT:         Segment: __DATA (5F 5F 44 41 54 41 00 00 00 00 00 00 00 00 00 00)
+# REMOVE-TEXT-ONLY-NEXT:         Address: 0x4
+# REMOVE-TEXT-ONLY-NEXT:         Size: 0x4
+# REMOVE-TEXT-ONLY-NEXT:         Offset: 264
+# REMOVE-TEXT-ONLY-NEXT:         Alignment: 0
+# REMOVE-TEXT-ONLY-NEXT:         RelocationOffset: 0x0
+# REMOVE-TEXT-ONLY-NEXT:         RelocationCount: 0
+# REMOVE-TEXT-ONLY-NEXT:         Type: Regular (0x0)
+# REMOVE-TEXT-ONLY-NEXT:         Attributes [ (0x0)
+# REMOVE-TEXT-ONLY-NEXT:         ]
+# REMOVE-TEXT-ONLY-NEXT:         Reserved1: 0x0
+# REMOVE-TEXT-ONLY-NEXT:         Reserved2: 0x0
+# REMOVE-TEXT-ONLY-NEXT:         Reserved3: 0x0
+# REMOVE-TEXT-ONLY-NEXT:         SectionData (
+# REMOVE-TEXT-ONLY-NEXT:           0000: DDAADDAA                             |....|
+# REMOVE-TEXT-ONLY-NEXT:         )
+# REMOVE-TEXT-ONLY-NEXT:       }
+# COMMON-NEXT:                 Section {
+# REMOVE-TEXT-ONLY-NEXT:         Index: 1
+# REMOVE-TEXT-AND-DATA-NEXT:     Index: 0
+# COMMON-NEXT:                   Name: __const (5F 5F 63 6F 6E 73 74 00 00 00 00 00 00 00 00 00)
+# COMMON-NEXT:                   Segment: __TEXT (5F 5F 54 45 58 54 00 00 00 00 00 00 00 00 00 00)
+# COMMON-NEXT:                   Address: 0x8
+# COMMON-NEXT:                   Size: 0x4
+# REMOVE-TEXT-ONLY-NEXT:         Offset: 268
+# REMOVE-TEXT-AND-DATA-NEXT:     Offset: 184
+# COMMON-NEXT:                   Alignment: 0
+# COMMON-NEXT:                   RelocationOffset: 0x0
+# COMMON-NEXT:                   RelocationCount: 0
+# COMMON-NEXT:                   Type: Regular (0x0)
+# COMMON-NEXT:                   Attributes [ (0x0)
+# COMMON-NEXT:                   ]
+# COMMON-NEXT:                   Reserved1: 0x0
+# COMMON-NEXT:                   Reserved2: 0x0
+# COMMON-NEXT:                   Reserved3: 0x0
+# COMMON-NEXT:                   SectionData (
+# COMMON-NEXT:                     0000: EEFFEEFF                             |....|
+# COMMON-NEXT:                   )
+# COMMON-NEXT:                 }
+# COMMON-NEXT:               ]
+
+## Keep all sections if the specified section name is not present in the
+## input. The output file should be the same as the input.
+# RUN: llvm-objcopy --remove-section __TEXT,__foo %t %t4
+# RUN: cmp %t %t4
+
+--- !mach-o
+FileHeader:
+  magic:           0xFEEDFACF
+  cputype:         0x01000007
+  cpusubtype:      0x00000003
+  filetype:        0x00000001
+  ncmds:           1
+  sizeofcmds:      312
+  flags:           0x00002000
+  reserved:        0x00000000
+LoadCommands:
+  - cmd:             LC_SEGMENT_64
+    cmdsize:         312
+    segname:         ''
+    vmaddr:          0
+    vmsize:          12
+    fileoff:         344
+    filesize:        12
+    maxprot:         7
+    initprot:        7
+    nsects:          3
+    flags:           0
+    Sections:
+      - sectname:        __text
+        segname:         __TEXT
+        addr:            0x0000000000000000
+        content:         'AABBCCDD'
+        size:            4
+        offset:          344
+        align:           0
+        reloff:          0x00000000
+        nreloc:          0
+        flags:           0x80000400
+        reserved1:       0x00000000
+        reserved2:       0x00000000
+        reserved3:       0x00000000
+      - sectname:        __data
+        segname:         __DATA
+        addr:            0x0000000000000004
+        content:         'DDAADDAA'
+        size:            4
+        offset:          348
+        align:           0
+        reloff:          0x00000000
+        nreloc:          0
+        flags:           0x00000000
+        reserved1:       0x00000000
+        reserved2:       0x00000000
+        reserved3:       0x00000000
+      - sectname:        __const
+        segname:         __TEXT
+        addr:            0x0000000000000008
+        content:         'EEFFEEFF'
+        size:            4
+        offset:          352
+        align:           0
+        reloff:          0x00000000
+        nreloc:          0
+        flags:           0x00000000
+        reserved1:       0x00000000
+        reserved2:       0x00000000
+        reserved3:       0x00000000
diff --git a/llvm/tools/llvm-objcopy/MachO/MachOObjcopy.cpp b/llvm/tools/llvm-objcopy/MachO/MachOObjcopy.cpp
index d14354e8d06..cad96665847 100644
--- a/llvm/tools/llvm-objcopy/MachO/MachOObjcopy.cpp
+++ b/llvm/tools/llvm-objcopy/MachO/MachOObjcopy.cpp
@@ -23,6 +23,12 @@ using SectionPred = std::function<bool(const Section &Sec)>;
 static void removeSections(const CopyConfig &Config, Object &Obj) {
   SectionPred RemovePred = [](const Section &) { return false; };
 
+  if (!Config.ToRemove.empty()) {
+    RemovePred = [&Config, RemovePred](const Section &Sec) {
+      return Config.ToRemove.matches(Sec.CanonicalName);
+    };
+  }
+
   if (Config.StripAll) {
     // Remove all debug sections.
     RemovePred = [RemovePred](const Section &Sec) {
@@ -34,7 +40,8 @@ static void removeSections(const CopyConfig &Config, Object &Obj) {
   }
 
   if (!Config.OnlySection.empty()) {
-    RemovePred = [&Config, RemovePred](const Section &Sec) {
+    // Overwrite RemovePred because --only-section takes priority.
+    RemovePred = [&Config](const Section &Sec) {
       return !Config.OnlySection.matches(Sec.CanonicalName);
     };
   }
@@ -71,10 +78,10 @@ static Error handleArgs(const CopyConfig &Config, Object &Obj) {
       !Config.SectionsToRename.empty() || !Config.SymbolsToRename.empty() ||
       !Config.UnneededSymbolsToRemove.empty() ||
       !Config.SetSectionAlignment.empty() || !Config.SetSectionFlags.empty() ||
-      !Config.ToRemove.empty() || Config.ExtractDWO || Config.KeepFileSymbols ||
-      Config.LocalizeHidden || Config.PreserveDates || Config.StripAllGNU ||
-      Config.StripDWO || Config.StripNonAlloc || Config.StripSections ||
-      Config.Weaken || Config.DecompressDebugSections || Config.StripDebug ||
+      Config.ExtractDWO || Config.KeepFileSymbols || Config.LocalizeHidden ||
+      Config.PreserveDates || Config.StripAllGNU || Config.StripDWO ||
+      Config.StripNonAlloc || Config.StripSections || Config.Weaken ||
+      Config.DecompressDebugSections || Config.StripDebug ||
       Config.StripNonAlloc || Config.StripSections || Config.StripUnneeded ||
       Config.DiscardMode != DiscardType::None || !Config.SymbolsToAdd.empty() ||
       Config.EntryExpr) {