[llvm-readobj] - Teach tool to dump objects with >= SHN_LORESERVE of sections.

http://www.sco.com/developers/gabi/2003-12-17/ch4.eheader.html

says that e_shnum and/or e_shstrndx may have special values if
"the number of sections is greater than or equal to SHN_LORESERVE" or
"the section name string table section index is greater than or equal to SHN_LORESERVE (0xff00)"

Previously llvm-readobj was unable to dump such files, patch changes that.

I had to add a precompiled test case because it does not seem possible to
prepare a test using yaml2obj or llvm-mc (not clear how to make .shstrtab
to have index >= SHN_LORESERVE).

Differential revision: https://reviews.llvm.org/D49369

llvm-svn: 337360

3 files changed, 36 insertions, 0 deletions

diff --git a/llvm/test/tools/llvm-readobj/Inputs/many-sections-stripped.elf-x86_64 b/llvm/test/tools/llvm-readobj/Inputs/many-sections-stripped.elf-x86_64
new file mode 100644
index 00000000000..a589dc5d6a9
--- /dev/null
+++ b/llvm/test/tools/llvm-readobj/Inputs/many-sections-stripped.elf-x86_64
diff --git a/llvm/test/tools/llvm-readobj/Inputs/many-sections.elf-x86_64 b/llvm/test/tools/llvm-readobj/Inputs/many-sections.elf-x86_64
new file mode 100644
index 00000000000..1abb98a01b8
--- /dev/null
+++ b/llvm/test/tools/llvm-readobj/Inputs/many-sections.elf-x86_64
diff --git a/llvm/test/tools/llvm-readobj/many-sections.s b/llvm/test/tools/llvm-readobj/many-sections.s
new file mode 100644
index 00000000000..383df266139
--- /dev/null
+++ b/llvm/test/tools/llvm-readobj/many-sections.s
@@ -0,0 +1,36 @@
+## many-sections.elf-x86_64 is a file that was generated to simulate
+## an object with more than ~65k sections. When an ELF object
+## has SHN_LORESERVE (0xff00) or more sections, its e_shnum field
+## should be zero and sh_size of the section header at index 0 is used
+## to store the value. If the section name string table section index is
+## greater than or equal to SHN_LORESERVE, then e_shstrndx field
+## should have the value of SHN_XINDEX and sh_link of the section header
+## at index 0 is used to store the value.
+##
+## many-sections.elf-x86_64 has few sections to save disk
+## space, but its e_shnum, e_shstrndx, sh_size and sh_link fields are set
+## according to the above description, so that we can test the dumper.
+
+# RUN: llvm-readobj -file-headers -elf-output-style GNU \
+# RUN:   %p/Inputs/many-sections.elf-x86_64 | FileCheck %s --check-prefix=GNU1
+# GNU1: Number of section headers:         0 (5)
+# GNU1: Section header string table index: 65535 (3)
+
+# RUN: llvm-readobj -file-headers -elf-output-style LLVM \
+# RUN:   %p/Inputs/many-sections.elf-x86_64 | FileCheck %s --check-prefix=LLVM1
+# LLVM1: SectionHeaderCount: 0 (5)
+# LLVM1: StringTableSectionIndex: 65535 (3)
+
+## many-sections-stripped.elf-x86_64 is many-sections.elf-x86_64 with
+## e_shoff field set to zero, but not e_shstrndx, to show that
+## this corrupt case is handled correctly.
+
+# RUN: llvm-readobj -file-headers -elf-output-style GNU \
+# RUN:   %p/Inputs/many-sections-stripped.elf-x86_64 | FileCheck %s --check-prefix=GNU2
+# GNU2: Number of section headers:         0
+# GNU2: Section header string table index: 65535 (corrupt: out of range)
+
+# RUN: llvm-readobj -file-headers -elf-output-style LLVM \
+# RUN:   %p/Inputs/many-sections-stripped.elf-x86_64 | FileCheck %s --check-prefix=LLVM2
+# LLVM2: SectionHeaderCount: 0
+# LLVM2: StringTableSectionIndex: 65535 (corrupt: out of range)