[llvm-bugs] [Bug 49068] New: x86-64 COFF driver doesn't relocate ADDR32 relocations correctly

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=49068

            Bug ID: 49068
           Summary: x86-64 COFF driver doesn't relocate ADDR32 relocations
                    correctly
           Product: lld
           Version: unspecified
          Hardware: PC
                OS: Windows NT
            Status: NEW
          Severity: normal
          Priority: P
         Component: COFF
          Assignee: unassignedbugs at nondot.org
          Reporter: axel.y.rivera at intel.com
                CC: llvm-bugs at lists.llvm.org

Created attachment 24489
  --> https://bugs.llvm.org/attachment.cgi?id=24489&action=edit
Simple test case

Hi,

I attached a simple example that contains inline assembly code (__asm). It
compiles and links, but produces a segmentation fault during execution.

bash-3.2$ clang-cl -c -Od -Zi simple.c
bash-3.2$ clang-cl -fuse-ld=lld -o simple.exe -Od -Zi simple.obj /link
/LARGEADDRESSAWARE:NO
clang-cl: warning: argument unused during compilation: '-Od'
[-Wunused-command-line-argument]
bash-3.2$ ./simple.exe
Segmentation fault

The test case pass if it is linked with MS-LINK:

bash-3.2$ clang-cl -o simple.exe -Od -Zi simple.obj /link /LARGEADDRESSAWARE:NO
clang-cl: warning: argument unused during compilation: '-Od'
[-Wunused-command-line-argument]
bash-3.2$ ./simple.exe
RESULT: 7

The generated object by clang-cl (simple.obj) contains an ADDR32 relocation:

RELOCATIONS #1
                                                Symbol    Symbol
 Offset    Type              Applied To         Index     Name
 --------  ----------------  -----------------  --------  ------
 00000007  REL32                      00000000        4D  __security_cookie
 0000001D  REL32                      00000014        50  arr
 00000033  ADDR32                     00000000        50  arr
 00000042  REL32                      00000000        35 
??_C at _0M@HGMGLEGP at RESULT?3?5?$CFd?6?$AA@ (`string')
 00000047  REL32                      00000000        1E  printf
 0000005A  REL32                      00000000        4E 
__security_check_cookie


And the executable generated by MS-LINK contains the relocation section:

BASE RELOCATIONS #8
    6000 RVA,        C SizeOfBlock
     EC3  HIGHLOW            00483070  arr
       0  ABS

But the executable generated by lld-link doesn't contain the relocatable
section, which produce a seg-fault when accessing arr inside the inline asm
code.

I noticed that the collection for the relocation base type
(lld/COFF/Chunks.cpp, getBaserelType) only checks for ADDR64 when the machine
is 64bits:

static uint8_t getBaserelType(const coff_relocation &rel) {
  switch (config->machine) {
  case AMD64:
    if (rel.Type == IMAGE_REL_AMD64_ADDR64)
      return IMAGE_REL_BASED_DIR64;
    return IMAGE_REL_BASED_ABSOLUTE;

It is ignoring the image when the relocation type is IMAGE_REL_AMD64_ADDR32 and
returns IMAGE_REL_BASED_ABSOLUTE, when the relocation needs the high and low
address information. This is producing that the relocation data is not being
inserted into the executable. I made this patch the returns the HIGHLOW image
base when the relocation type is AMD64_ADDR32:

diff --git a/lld/COFF/Chunks.cpp b/lld/COFF/Chunks.cpp
index 9d60bc746c96..c11f15e401d8 100644
--- a/lld/COFF/Chunks.cpp
+++ b/lld/COFF/Chunks.cpp
@@ -424,6 +424,8 @@ static uint8_t getBaserelType(const coff_relocation &rel) {
   case AMD64:
     if (rel.Type == IMAGE_REL_AMD64_ADDR64)
       return IMAGE_REL_BASED_DIR64;
+    if (rel.Type == IMAGE_REL_AMD64_ADDR32)
+      return IMAGE_REL_BASED_HIGHLOW;
     return IMAGE_REL_BASED_ABSOLUTE;
   case I386:
     if (rel.Type == IMAGE_REL_I386_DIR32)


bash-3.2$ clang-cl -fuse-ld=lld -Zi -o simple.exe -Od simple.obj /link
/LARGEADDRESSAWARE:NO
clang-cl: warning: argument unused during compilation: '-Od'
[-Wunused-command-line-argument]
bash-3.2$ ./simple.exe
RESULT: 7

The relocation section is now inserted into the executable generated by
lld-link:

BASE RELOCATIONS #8
    1000 RVA,        C SizeOfBlock
      33  HIGHLOW            4005FBC0
       0  ABS

It seems that the HIGHLOW address information needs to be inserted in the
relocation section when ADDR32 is found.

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