[llvm-dev] lld-link crash when linking intrinsics lib

[Shi, Steven via llvm-dev]

>Steven,
>Do you need to use LTO? I thought that LTO is a workaround to not produce an object file that cannot be handled by your ELF-to-COFF translation tool. If you are now doing a regular cross build, I guess you can remove -flto.
Yes, I need the LTO for the smallest code size. Without LTO, my firmware image will be +30% larger which is not competitive with MSVC.


Thanks
Steven

From: Rui Ueyama [mailto:ruiu at google.com]
Sent: Thursday, February 28, 2019 8:01 AM
To: Shi, Steven <steven.shi at intel.com>; Peter Collingbourne <pcc at chromium.org>
Cc: Peter Smith <peter.smith at linaro.org>; Martin Storsjö <martin at martin.st>; llvm-dev at lists.llvm.org
Subject: Re: lld-link crash when linking intrinsics lib

+Peter Collingbourne<mailto:pcc at chromium.org>

LTO is used in this test case, and one source file defines its own `memset` function while the other file uses llvm.memset. Looks like LTO is confused by the user-defined memset. Could you take a look?

Steven,

Do you need to use LTO? I thought that LTO is a workaround to not produce an object file that cannot be handled by your ELF-to-COFF translation tool. If you are now doing a regular cross build, I guess you can remove -flto.

On Wed, Feb 27, 2019 at 3:00 PM Rui Ueyama <ruiu at google.com<mailto:ruiu at google.com>> wrote:
Hi Steven,

I confirmed that lld-link crashes with these inputs. That shouldn't happen. I'll debug this and get back to you. Thank you for reporting.

On Tue, Feb 26, 2019 at 8:20 PM Shi, Steven <steven.shi at intel.com<mailto:steven.shi at intel.com>> wrote:
Hello Rui,
I met couples of lld-link crash when enable the clang-cl + lld-link build toolchain for Uefi firmware. Below is a simplified example (main.c and intrinsics.c).
Uefi firmware is self-contained and doesn’t depend on the compiler intrinsics implementation, so we have our own intrinsics lib. It is weird that if I don’t use the llvm-lib but directly “lld-link /NODEFAULTLIB /ENTRY:main  main.obj intrinsics.obj”, the below example can pass link. Please advise what’s wrong in this example.


$ cat main.c
typedef struct {
  struct MAP_LIST {
    unsigned long long  VirtualAddress;
    void              *MapCookie;
  } MapList[100];
} SNP_DRIVER;
SNP_DRIVER snp_instance;
int main()
{
  SNP_DRIVER  *Snp;
  Snp = &snp_instance;
  for (int Index = 0; Index < 100; Index++) {
    Snp->MapList[Index].VirtualAddress = 0;
    Snp->MapList[Index].MapCookie      = 0;
  }
  return 0;
}

$ cat intrinsics.c
void * memset (void *dest, int ch, size_t count)
{
  volatile char  *Pointer;
  Pointer = (char *)dest;
  while (count-- != 0) {
    *(Pointer++) = (char)ch;
  }
  return dest;
}


$ "/home/jshi19/llvm/releaseinstall/bin/clang-cl" /Fomain.obj /c --target=x86_64-pc-win32-coff -m64 /O1b2s -flto main.c
$ "/home/jshi19/llvm/releaseinstall/bin/clang-cl" /Fointrinsics.obj /c --target=x86_64-pc-win32-coff -m64 /O1b2s -flto intrinsics.c
$ "/home/jshi19/llvm/releaseinstall/bin/llvm-lib" /OUT:intrinsics.lib intrinsics.obj
$ "/home/jshi19/llvm/releaseinstall/bin/lld-link" /NODEFAULTLIB /ENTRY:main  main.obj intrinsics.lib
Stack dump:
0.      Program arguments: /home/jshi19/llvm/releaseinstall/bin/lld-link /NODEFAULTLIB /ENTRY:main main.obj intrinsics.lib
#0 0x0000559a34ba5e4a llvm::sys::PrintStackTrace(llvm::raw_ostream&) (/home/jshi19/llvm/releaseinstall/bin/lld-link+0x272e4a)
#1 0x0000559a34ba3d14 llvm::sys::RunSignalHandlers() (/home/jshi19/llvm/releaseinstall/bin/lld-link+0x270d14)
#2 0x0000559a34ba3e52 SignalHandler(int) (/home/jshi19/llvm/releaseinstall/bin/lld-link+0x270e52)
#3 0x00007f896c8ea890 __restore_rt (/lib/x86_64-linux-gnu/libpthread.so.0+0x12890)
#4 0x0000559a34c11325 lld::coff::markLive(llvm::ArrayRef<lld::coff::Chunk*>) (/home/jshi19/llvm/releaseinstall/bin/lld-link+0x2de325)
#5 0x0000559a34bf0220 lld::coff::LinkerDriver::link(llvm::ArrayRef<char const*>) (/home/jshi19/llvm/releaseinstall/bin/lld-link+0x2bd220)
#6 0x0000559a34bf0478 lld::coff::link(llvm::ArrayRef<char const*>, bool, llvm::raw_ostream&) (/home/jshi19/llvm/releaseinstall/bin/lld-link+0x2bd478)
#7 0x0000559a34b2a300 main (/home/jshi19/llvm/releaseinstall/bin/lld-link+0x1f7300)
#8 0x00007f896b3c1b97 __libc_start_main /build/glibc-OTsEL5/glibc-2.27/csu/../csu/libc-start.c:344:0
#9 0x0000559a34b8c27a _start (/home/jshi19/llvm/releaseinstall/bin/lld-link+0x25927a)
Segmentation fault (core dumped)

$ "/home/jshi19/llvm/releaseinstall/bin/clang-cl" --version
clang version 9.0.0 (https://github.com/llvm-mirror/clang.git 1f02068469ff18f5fc5728cafe9d96ee5f66c5b9) (https://github.com/llvm-project/llvm.git 330395ea4fce35b019b33797ff751be029a1f866)
Target: x86_64-pc-windows-msvc
Thread model: posix
InstalledDir: /home/jshi19/llvm/releaseinstall/bin

$ "/home/jshi19/llvm/releaseinstall/bin/lld-link" --version
LLD 9.0.0 (https://github.com/llvm-mirror/lld.git aa7adc0ec804b689771f11d52e39f83a16378f5f)




Thanks

Steven Shi
Intel\SSG\FID\Firmware Infrastructure

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