[PATCH] D83247: [compiler-rt][asan][hwasan] Refactor shadow setup into sanitizer_common (NFCI)

[Kostya Serebryany via Phabricator via llvm-commits]

kcc added a comment.

No strong opinion on whether this needs to be done. 
If you feel strong, and if it will help, sure. (you may indeed have to test on various platforms, or rely on the post-commit bots)
OTOH, the new profiler should not require all of these functions, you can probably get away with a custom-tailored variant of MapDynamicShadow.

(Vitaly, please do the review)



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Comment at: compiler-rt/lib/asan/asan_linux.cpp:122
-  uptr granularity = GetMmapGranularity();
-  uptr alignment = granularity * 8;
-  uptr left_padding = granularity;
----------------
tejohnson wrote:
> The code in asan is multiplying the mmap granularity by 8, whereas the hwasan version shifts it by kShadowScale. I wasn't sure if the 8 here is supposed to be equivalent to a left shift by the shadow scale (which is typically 3 in asan), or is specifically hardcoded separately not using SHADOW_SCALE since it could be something other than 3 in some cases (e.g. 5 for myriad, or user set via ASAN_SHADOW_SCALE). Depending on what was intended here, I would keep the hardcoding of "3" passed to my refactored MapDynamicShadow, or change that to SHADOW_SCALE.
I frankly don't remember :(


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