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Diffstat (limited to 'llvm_mode/README.lto.md')
| -rw-r--r-- | llvm_mode/README.lto.md | 25 |
1 files changed, 23 insertions, 2 deletions
diff --git a/llvm_mode/README.lto.md b/llvm_mode/README.lto.md index 9af9ffff..bb66b5e7 100644 --- a/llvm_mode/README.lto.md +++ b/llvm_mode/README.lto.md @@ -95,6 +95,17 @@ target binary based on string compare and memory compare functions. afl-fuzz will automatically get these transmitted when starting to fuzz. This improves coverage on a lot of targets. +## Fixed memory map + +To speed up fuzzing, the shared memory map is hard set to a specific address, +by default 0x10000. In most cases this will work without any problems. +On unusual operating systems/processors/kernels or weird libraries this might +fail so to change the fixed address at compile time set +AFL_LLVM_MAP_ADDR with a better value (a value of 0 or empty sets the map address +to be dynamic - the original afl way, which is slower). +AFL_LLVM_MAP_DYNAMIC can be set so the shared memory address is dynamic (which +is safer but also slower). + ## Potential issues ### compiling libraries fails @@ -110,12 +121,22 @@ Solution: ``` AR=llvm-ar RANLIB=llvm-ranlib CC=afl-clang-lto CXX=afl-clang-lto++ ./configure --disable-shared ``` -and on some target you have to to AR=/RANLIB= even for make as the configure script does not save it ... +and on some target you have to to AR=/RANLIB= even for make as the configure script does not save it. +Other targets ignore environment variables and need the parameters set via +`./configure --cc=... --cxx= --ranlib= ...` etc. (I am looking at you ffmpeg!). ### compiling programs still fail afl-clang-lto is still work in progress. -Please report issues at: + +Known issues: + * Anything that llvm11 cannot compile, afl-clang-lto can not compile either - obviously + * Anything that does not compile with LTO, afl-clang-lto can not compile either - obviously + +Hence if building a target with afl-clang-lto fails try to build it with llvm11 +and LTO enabled (`CC=clang-11` `CXX=clang++-11` `CFLAGS=-flto=full` and +`CXXFLAGS=-flto=full`). +If this succeeeds then there is an issue with afl-clang-lto. Please report at [https://github.com/AFLplusplus/AFLplusplus/issues/226](https://github.com/AFLplusplus/AFLplusplus/issues/226) ## Upcoming Work |