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1.1 |
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18-Jul-2011 |
jym |
branches: 1.1.24; Add a simple test case to check executable mapping rights for mprotect(2).
- provide an exec_prot_support() routine so $ARCH can indicate whether it supports execution protection or not, and skip test accordingly.
- have a trivial 'return_one' shellcode to copy anywhere in a page, and call it. The decision to keep the assembly solution is mine, reasons are twofold:
- all pure-C implementations cannot be controlled easily: bounds detection (beginning/end) of return_one is unpredictable, or requires the use of overkill solutions like libelf. Using dlsym(3) was a good proposal, however I can't use it to know the end address of the payload. It makes copying of the shellcode a bit more difficult: using a constant may be too small (code has not been entirely copied, and can lead to errors that can be erroneously detected as "test passed"), or too big (depending on where it is mapped in memory, copying past the end of the function may trigger SIGSEGV).
- I have to ensure that the resulting assembly is the most compact possible, especially as it will be reused to test other parts of memory (stack, data, rodata, etc.).
Only i386 and amd64 are implemented so far. Others will come in due time. FWIW, writing the exec_prot_support() callback and the return_one payload should be enough. Writing callback requires good knowledge of the platform, depending on chip revision, CPU, board, MMU... the protection level may vary.
Current files are put under lib/libc/arch/* and lib/libc/common/. Feel free to move them around the tests/ tree. Keep in mind that the common/ and arch/ code will be used outside of libc, so please do not hide them too deep in the tree.
I checked a few architectures via build.sh cross-compile, and will keep an eye on buildbot for potential build breakage. Feel free to contact me in case you see any, of course.
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