This is a follow up patch of https://reviews.llvm.org/D88755.
When set 0 label for an address range, we can release pages within the
corresponding shadow address range to OS, and set only addresses outside
the pages to be 0.
Reviewed-by: morehouse, eugenis
Differential Revision: https://reviews.llvm.org/D89199
After D88686, munmap uses MADV_DONTNEED to ensure zero-out before the
next access. Because the entire shadow space is created by MAP_PRIVATE
and MAP_ANONYMOUS, the first access is also on zero-filled values.
So it is fine to not zero-out data, but use madvise(MADV_DONTNEED) at
mmap. This reduces runtime
overhead.
Reviewed-by: morehouse
Differential Revision: https://reviews.llvm.org/D88755
When an application does a lot of pairs of mmap and munmap, if we did
not release shadoe memory used by mmap addresses, this would increase
memory usage.
Reviewed-by: morehouse
Differential Revision: https://reviews.llvm.org/D88686
InitializeInterceptors() calls dlsym(), which calls calloc(). Depending
on the allocator implementation, calloc() may invoke mmap(), which
results in a segfault since REAL(mmap) is still being resolved.
We fix this by doing a direct syscall if interceptors haven't been fully
resolved yet.
Reviewed By: vitalybuka
Differential Revision: https://reviews.llvm.org/D86168
Jianzhou Zhao