Summary:
This refactors some common support related to shadow memory setup from
asan and hwasan into sanitizer_common. This should not only reduce code
duplication but also make these facilities available for new compiler-rt
uses (e.g. heap profiling).
In most cases the separate copies of the code were either identical, or
at least functionally identical. A few notes:
In ProtectGap, the asan version checked the address against an upper
bound (kZeroBaseMaxShadowStart, which is (2^18). I have created a copy
of kZeroBaseMaxShadowStart in hwasan_mapping.h, with the same value, as
it isn't clear why that code should not do the same check. If it
shouldn't, I can remove this and guard this check so that it only
happens for asan.
In asan's InitializeShadowMemory, in the dynamic shadow case it was
setting __asan_shadow_memory_dynamic_address to 0 (which then sets both
macro SHADOW_OFFSET as well as macro kLowShadowBeg to 0) before calling
FindDynamicShadowStart(). AFAICT this is only needed because
FindDynamicShadowStart utilizes kHighShadowEnd to
get the shadow size, and kHighShadowEnd is a macro invoking
MEM_TO_SHADOW(kHighMemEnd) which in turn invokes:
(((kHighMemEnd) >> SHADOW_SCALE) + (SHADOW_OFFSET))
I.e. it computes the shadow space needed by kHighMemEnd (the shift), and
adds the offset. Since we only want the shadow space here, the earlier
setting of SHADOW_OFFSET to 0 via __asan_shadow_memory_dynamic_address
accomplishes this. In the hwasan version, it simply gets the shadow
space via "MemToShadowSize(kHighMemEnd)", where MemToShadowSize just
does the shift. I've simplified the asan handling to do the same
thing, and therefore was able to remove the setting of the SHADOW_OFFSET
via __asan_shadow_memory_dynamic_address to 0.
Reviewers: vitalybuka, kcc, eugenis
Subscribers: dberris, #sanitizers, llvm-commits, davidxl
Tags: #sanitizers
Differential Revision: https://reviews.llvm.org/D83247
to reflect the new license.
We understand that people may be surprised that we're moving the header
entirely to discuss the new license. We checked this carefully with the
Foundation's lawyer and we believe this is the correct approach.
Essentially, all code in the project is now made available by the LLVM
project under our new license, so you will see that the license headers
include that license only. Some of our contributors have contributed
code under our old license, and accordingly, we have retained a copy of
our old license notice in the top-level files in each project and
repository.
llvm-svn: 351636
This commit causes internal errors with ld.bfd 2.24. My guess is that
the ifunc usage in this commit is causing problems. This is the default
system linker on Trusty Tahr, which is from 2014. I claim it's still in
our support window. Maybe we will decide to drop support for it, but
let's get the bots green while we do the investigation and have that
discussion.
Discovered here: https://crbug.com/835864
llvm-svn: 330619
Summary:
Retire the fixed shadow memory mapping to avoid conflicts with default
process memory mapping (currently manifests on Android).
Tests on AArch64 show <1% performance loss and code size increase,
making it possible to use dynamic shadow memory by default.
For the simplicity and unifirmity sake, use dynamic shadow memory mapping
with base address accessed via ifunc resolver on all supported platforms.
Keep the fixed shadow memory mapping around to be able to run
performance comparison tests later.
Complementing D45840.
Reviewers: eugenis
Subscribers: srhines, kubamracek, dberris, mgorny, kristof.beyls, delcypher, #sanitizers, llvm-commits
Differential Revision: https://reviews.llvm.org/D45847
llvm-svn: 330474
Teresa Johnson