[Compiler-rt][CFI] Enabling CFI for MIPS64

[mohit.bhakkad]

Summary

Current test results are:

Failing Tests (2):

  cfi :: cross-dso/dlopen.cpp
  cfi :: cross-dso/simple-fail.cpp

Expected Passes    : 15
Expected Failures  : 1
Unsupported Tests  : 6
Unexpected Failures: 2

[mohit.bhakkad]

I am debugging the cause of failing test cases. Both these cases fail as we are
not getting string "vtable is of type '{{(struct )?}}B'"

To get this error, condition at lib/cfi/cfi.cc:99 should pass.
i.e. MemToShadowOffset(addr) > ShadowSize()

Now looking at code,
shadow size is calculated as (vma >> kShadowGranularity)
shadow offset for addr is calculated as (addr >> kShadowGranularity)

In my understanding (addr > vma) is impossible, failing above condition forever.

Could you please throw some light here?

[eugenis]

In D19531#411879, @mohit.bhakkad wrote:

I am debugging the cause of failing test cases. Both these cases fail as we are
not getting string "vtable is of type '{{(struct )?}}B'"

To get this error, condition at lib/cfi/cfi.cc:99 should pass.
i.e. MemToShadowOffset(addr) > ShadowSize()

Now looking at code,
shadow size is calculated as (vma >> kShadowGranularity)
shadow offset for addr is calculated as (addr >> kShadowGranularity)

In my understanding (addr > vma) is impossible, failing above condition forever.

Could you please throw some light here?

I don't think this is right. That condition protects against wild access when addr > vma; i've just removed the check and all tests still pass (which is actually bad and should be fixed by adding more tests).

[eugenis]

This change LGTM

cmake/config-ix.cmake

 set(ALL_LSAN_SUPPORTED_ARCH ${X86_64} ${MIPS64} ${ARM64})
 set(ALL_MSAN_SUPPORTED_ARCH ${X86_64} ${MIPS64} ${ARM64})
 set(ALL_PROFILE_SUPPORTED_ARCH ${X86} ${X86_64} ${ARM32} ${ARM64} ${PPC64}
     ${MIPS32} ${MIPS64})
 set(ALL_TSAN_SUPPORTED_ARCH ${X86_64} ${MIPS64} ${ARM64} ${PPC64})
 set(ALL_UBSAN_SUPPORTED_ARCH ${X86} ${X86_64} ${ARM32} ${ARM64}
     ${MIPS32} ${MIPS64} ${PPC64} ${S390X})
 set(ALL_SAFESTACK_SUPPORTED_ARCH ${X86} ${X86_64} ${ARM64} ${MIPS32} ${MIPS64})
-set(ALL_CFI_SUPPORTED_ARCH ${X86} ${X86_64})
+set(ALL_CFI_SUPPORTED_ARCH ${X86} ${X86_64} ${MIPS64})
 set(ALL_ESAN_SUPPORTED_ARCH ${X86_64})
 
 if(APPLE)
   include(CompilerRTDarwinUtils)
 
   # On Darwin if /usr/include doesn't exist, the user probably has Xcode but not
   # the command line tools. If this is the case, we need to find the OS X
   # sysroot to pass to clang.