ac8e1062cb
Unlike Linux kernel which has a static shadow region layout, we have multiple stages in coreboot and thus require a different shadow offset address. Unfortunately, GCC currently only supports adding a static shadow offset at compile time using -fasan-shadow-offset flag. For this reason, we enable GCC to determine asan shadow offset address at runtime using a callback function named __asan_shadow_offset(). This supersedes the need to specify this address at compile time. GCC then makes use of this shadow offset to protect stack buffers by inserting red zones around them. Some other benefits of having this GCC patch are: a. We can place the shadow region in a separate linker section with all its advantages like automatic fit insurance. This ensures if a platform doesn't have enough memory space to hold shadow region, the build will fail. (However, if we use a fixed shadow offset on a platform that actually doesn't have enough memory, it may still build without any errors.) b. We don't modify the memory layout compared to the current one, as we are placing the shadow region at the end of the space already occupied by the program. c. We can be much more flexible later if needed (thinking of other stages like bootblock). d. Since we are appending the shadow buffer to the region already occupied, we make efficient use of the limited memory available which is highly beneficial when using cache as ram. Further, we have made sure that if you compile you tree with ASan enabled but missed this patch, it will end up in the following compilation error: "invalid --param name 'asan-use-shadow-offset-callback'" So, you cannot accidentally enable the feature without having your compiler patched. Change-Id: I401631938532a406a6d41e77c6c9716b6b2bf48d Signed-off-by: Harshit Sharma <harshitsharmajs@gmail.com> Reviewed-on: https://review.coreboot.org/c/coreboot/+/42794 Tested-by: build bot (Jenkins) <no-reply@coreboot.org> Reviewed-by: Werner Zeh <werner.zeh@siemens.com> |
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README
README ------ This is a cross toolchain builder for -elf toolchains (ie. no libc support) known working: i386-elf x86_64-elf powerpc-elf arm-elf armv7a-eabi aarch64-elf known broken: alpha-elf powerpc64-elf