[llvm-branch-commits] [llvm] 60df7c0 - [obj2yaml, yaml2obj] - Fix issues with creating/dumping group sections.

[Georgii Rymar via llvm-branch-commits]

Author: Georgii Rymar
Date: 2021-01-12T14:07:42+03:00
New Revision: 60df7c08b1f4447309c0c07fec1c8bc7267562fc

URL: https://github.com/llvm/llvm-project/commit/60df7c08b1f4447309c0c07fec1c8bc7267562fc
DIFF: https://github.com/llvm/llvm-project/commit/60df7c08b1f4447309c0c07fec1c8bc7267562fc.diff

LOG: [obj2yaml,yaml2obj] - Fix issues with creating/dumping group sections.

We have the following issues related to group sections:
1) yaml2obj is unable to set the custom `sh_entsize` value, because the `EntSize`
   key is currently ignored.
2) obj2yaml is unable to dump the group section which `sh_entsize != 4`.
3) obj2yaml always dumps the "EntSize" for group sections, though
   usually we are trying to omit dumping default values when dumping keys.
   I.e. we should not print the "EntSize" key when `sh_entsize` == 4.

This patch fixes (1),(3) and adds the test case to document the behavior of (2).

Differential revision: https://reviews.llvm.org/D93854

Added: 
    

Modified: 
    llvm/lib/ObjectYAML/ELFEmitter.cpp
    llvm/test/tools/obj2yaml/ELF/section-group.yaml
    llvm/test/tools/yaml2obj/ELF/group.yaml
    llvm/tools/obj2yaml/elf2yaml.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/lib/ObjectYAML/ELFEmitter.cpp b/llvm/lib/ObjectYAML/ELFEmitter.cpp
index 010a881379f3..181b130de621 100644
--- a/llvm/lib/ObjectYAML/ELFEmitter.cpp
+++ b/llvm/lib/ObjectYAML/ELFEmitter.cpp
@@ -1275,7 +1275,10 @@ void ELFState<ELFT>::writeSectionContent(Elf_Shdr &SHeader,
       SN2I.lookup(".symtab", Link))
     SHeader.sh_link = Link;
 
-  SHeader.sh_entsize = 4;
+  if (Section.EntSize)
+    SHeader.sh_entsize = *Section.EntSize;
+  else
+    SHeader.sh_entsize = sizeof(typename ELFT::Word);
 
   if (Section.Signature)
     SHeader.sh_info =

diff  --git a/llvm/test/tools/obj2yaml/ELF/section-group.yaml b/llvm/test/tools/obj2yaml/ELF/section-group.yaml
index 33044ceeb36c..bdd65908992d 100644
--- a/llvm/test/tools/obj2yaml/ELF/section-group.yaml
+++ b/llvm/test/tools/obj2yaml/ELF/section-group.yaml
@@ -1,13 +1,15 @@
 ## Checks that the tool is able to read section groups from ELF.
 
+## Check how groups sections are dumped.
+## Check we don't dump the "EntSize" key when sh_entsize == 4.
+
 # RUN: yaml2obj %s -o %t1.o
 # RUN: obj2yaml %t1.o | FileCheck %s -DSEC=.rodata
 
-# CHECK:      - Name:    .group
-# CHECK-NEXT:   Type:    SHT_GROUP
-# CHECK-NEXT:   Link:    .symtab
-# CHECK-NEXT:   EntSize: 0x4
-# CHECK-NEXT:   Info:    signature
+# CHECK:      - Name: .group
+# CHECK-NEXT:   Type: SHT_GROUP
+# CHECK-NEXT:   Link: .symtab
+# CHECK-NEXT:   Info: signature
 # CHECK-NEXT:   Members:
 # CHECK-NEXT:     - SectionOrType: GRP_COMDAT
 # CHECK-NEXT:     - SectionOrType: [[SEC]]
@@ -19,10 +21,11 @@ FileHeader:
   Data:  ELFDATA2LSB
   Type:  ET_REL
 Sections:
-  - Name: .group
-    Type: SHT_GROUP
-    Link: .symtab
-    Info: [[INFO=signature]]
+  - Name:    .group
+    Type:    SHT_GROUP
+    Link:    .symtab
+    Info:    [[INFO=signature]]
+    EntSize: [[ENTSIZE=<none>]]
     Members:
       - SectionOrType: GRP_COMDAT
       - SectionOrType: [[SEC=.rodata]]
@@ -33,6 +36,14 @@ Symbols:
     Type:    STT_OBJECT
     Section: .rodata
 
+## Document that yaml2obj can't dump the SHT_GROUP section when its sh_entsize != 4.
+
+# RUN: yaml2obj %s -DENTSIZE=0xfe -o %t1.entsize.o
+# RUN: not obj2yaml %t1.entsize.o 2>&1 | \
+# RUN:   FileCheck %s -DFILE=%t1.entsize.o --check-prefix=ENTSIZE
+
+# ENTSIZE: Error reading file: [[FILE]]: section [index 1] has invalid sh_entsize: expected 4, but got 254
+
 ## Check we are able to dump members of the SHT_GROUP section even when
 ## one of them has section index 0.
 

diff  --git a/llvm/test/tools/yaml2obj/ELF/group.yaml b/llvm/test/tools/yaml2obj/ELF/group.yaml
index 56794d9f14d7..1f061ade5769 100644
--- a/llvm/test/tools/yaml2obj/ELF/group.yaml
+++ b/llvm/test/tools/yaml2obj/ELF/group.yaml
@@ -19,6 +19,7 @@ Sections:
     Type:    SHT_GROUP
     Link:    0x1
     Info:    0x2
+    EntSize: [[ENTSIZE=<none>]]
     Size:    [[SIZE=<none>]]
     Content: [[CONTENT=<none>]]
     Members: [[MEMBERS=<none>]]
@@ -68,10 +69,19 @@ Sections:
 # MEMBERS-ERR: error: "Members" cannot be used with "Content" or "Size"
 
 ## Check we create an empty section when none of "Size", "Content" or "Members" are specified.
+## Check that the default value of sh_entsize is 4.
 
 # RUN: yaml2obj %s -o %t.empty.o
 # RUN: llvm-readelf --sections --section-data %t.empty.o | \
 # RUN:   FileCheck %s --check-prefix=EMPTY-SEC
 
-# EMPTY-SEC: [Nr] Name   Type  Address          Off    Size
-# EMPTY-SEC: [ 1] .group GROUP 0000000000000000 000040 000000
+# EMPTY-SEC: [Nr] Name   Type  Address          Off    Size   ES Flg
+# EMPTY-SEC: [ 1] .group GROUP 0000000000000000 000040 000000 04 1
+
+## Check that we are able to set an arbitrary entry size for the group section.
+
+# RUN: yaml2obj %s -DENTSIZE=0xFE -o %t.entsize.o
+# RUN: llvm-readelf --sections %t.entsize.o | FileCheck %s --check-prefix=ENTSIZE
+
+# ENTSIZE: [Nr] Name   Type  Address          Off    Size   ES Flg
+# ENTSIZE: [ 1] .group GROUP 0000000000000000 000040 000000 fe 1

diff  --git a/llvm/tools/obj2yaml/elf2yaml.cpp b/llvm/tools/obj2yaml/elf2yaml.cpp
index dacbaaf482c0..f29b1ebca7de 100644
--- a/llvm/tools/obj2yaml/elf2yaml.cpp
+++ b/llvm/tools/obj2yaml/elf2yaml.cpp
@@ -725,6 +725,8 @@ template <class ELFT>
 static unsigned getDefaultShEntSize(ELFYAML::ELF_SHT SecType,
                                     StringRef SecName) {
   switch (SecType) {
+  case ELF::SHT_GROUP:
+    return sizeof(typename ELFT::Word);
   case ELF::SHT_REL:
     return sizeof(typename ELFT::Rel);
   case ELF::SHT_RELA: