From 2d59ed4e62a9842be428f32976760dbb9cf336af Mon Sep 17 00:00:00 2001
From: Georgii Rymar <grimar@accesssoftek.com>
Date: Fri, 23 Oct 2020 12:50:48 +0300
Subject: [PATCH] [yaml2obj] - Add a way to override the sh_addralign field of
 a section.

Imagine the following declaration of a section:
```
Sections:
  - Name:         .dynsym
    Type:         SHT_DYNSYM
    AddressAlign: 0x1111111111111111
```

The aligment is large and yaml2obj reports an error currently:
"the desired output size is greater than permitted. Use the --max-size option to change the limit"

This patch implements the "ShAddrAlign" key, which is similar to other "Sh*" keys we have.
With it it is possible to override the `sh_addralign` field, ignoring the writing of alignment bytes.

Differential revision: https://reviews.llvm.org/D90019
---
 llvm/include/llvm/ObjectYAML/ELFYAML.h             |  3 +++
 llvm/lib/ObjectYAML/ELFEmitter.cpp                 |  2 ++
 llvm/lib/ObjectYAML/ELFYAML.cpp                    |  6 ++---
 .../tools/yaml2obj/ELF/override-shaddralign.yaml   | 30 ++++++++++++++++++++++
 4 files changed, 38 insertions(+), 3 deletions(-)
 create mode 100644 llvm/test/tools/yaml2obj/ELF/override-shaddralign.yaml

diff --git a/llvm/include/llvm/ObjectYAML/ELFYAML.h b/llvm/include/llvm/ObjectYAML/ELFYAML.h
index 28cbf32..f3805a9 100644
--- a/llvm/include/llvm/ObjectYAML/ELFYAML.h
+++ b/llvm/include/llvm/ObjectYAML/ELFYAML.h
@@ -203,6 +203,9 @@ struct Section : public Chunk {
   // The following members are used to override section fields which is
   // useful for creating invalid objects.
 
+  // This can be used to override the sh_addralign field.
+  Optional<llvm::yaml::Hex64> ShAddrAlign;
+
   // This can be used to override the offset stored in the sh_name field.
   // It does not affect the name stored in the string table.
   Optional<llvm::yaml::Hex64> ShName;
diff --git a/llvm/lib/ObjectYAML/ELFEmitter.cpp b/llvm/lib/ObjectYAML/ELFEmitter.cpp
index 4474afb..b811cce 100644
--- a/llvm/lib/ObjectYAML/ELFEmitter.cpp
+++ b/llvm/lib/ObjectYAML/ELFEmitter.cpp
@@ -552,6 +552,8 @@ template <class ELFT>
 static void overrideFields(ELFYAML::Section *From, typename ELFT::Shdr &To) {
   if (!From)
     return;
+  if (From->ShAddrAlign)
+    To.sh_addralign = *From->ShAddrAlign;
   if (From->ShFlags)
     To.sh_flags = *From->ShFlags;
   if (From->ShName)
diff --git a/llvm/lib/ObjectYAML/ELFYAML.cpp b/llvm/lib/ObjectYAML/ELFYAML.cpp
index 978c496..cd4fd33 100644
--- a/llvm/lib/ObjectYAML/ELFYAML.cpp
+++ b/llvm/lib/ObjectYAML/ELFYAML.cpp
@@ -1113,9 +1113,9 @@ static void commonSectionMapping(IO &IO, ELFYAML::Section &Section) {
   // are producing YAML, because yaml2obj sets appropriate values for them
   // automatically when they are not explicitly defined.
   assert(!IO.outputting() ||
-         (!Section.ShOffset.hasValue() && !Section.ShSize.hasValue() &&
-          !Section.ShName.hasValue() && !Section.ShFlags.hasValue() &&
-          !Section.ShType.hasValue()));
+         (!Section.ShOffset && !Section.ShSize && !Section.ShName &&
+          !Section.ShFlags && !Section.ShType && !Section.ShAddrAlign));
+  IO.mapOptional("ShAddrAlign", Section.ShAddrAlign);
   IO.mapOptional("ShName", Section.ShName);
   IO.mapOptional("ShOffset", Section.ShOffset);
   IO.mapOptional("ShSize", Section.ShSize);
diff --git a/llvm/test/tools/yaml2obj/ELF/override-shaddralign.yaml b/llvm/test/tools/yaml2obj/ELF/override-shaddralign.yaml
new file mode 100644
index 0000000..62578c1
--- /dev/null
+++ b/llvm/test/tools/yaml2obj/ELF/override-shaddralign.yaml
@@ -0,0 +1,30 @@
+## Check we are able to set a custom sh_addralign field for different sections
+## and that doing this does not affect the output size.
+
+## Test that we are able to override the sh_addralign section
+## field with use of the "ShAddrAlign" key.
+
+# RUN: yaml2obj %s -o %t
+# RUN: llvm-readelf --sections %t | FileCheck %s --check-prefix=CHECK
+
+# CHECK:      Section Headers:
+# CHECK-NEXT:   [Nr] Name    {{.*}} Off    Size   ES Flg Lk Inf Al
+# CHECK-NEXT:   [ 0]         {{.*}} 000000 000000 00     0   0  0
+# CHECK-NEXT:   [ 1] .foo    {{.*}} 000080 000000 00     0   0 1229782938247303441
+# CHECK-NEXT:   [ 2] .bar    {{.*}} 000100 000000 00     0   0 2459565876494606882
+# CHECK-NEXT:   [ 3] .strtab {{.*}} 000100 000001 00     0   0  1
+
+--- !ELF
+FileHeader:
+  Class: ELFCLASS64
+  Data:  ELFDATA2LSB
+  Type:  ET_REL
+Sections:
+  - Name:         .foo
+    Type:         SHT_PROGBITS
+    AddressAlign: 0x80
+    ShAddrAlign:  0x1111111111111111
+  - Name:         .bar
+    Type:         SHT_PROGBITS
+    AddressAlign: 0x100
+    ShAddrAlign:  0x2222222222222222
-- 
2.7.4