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Release pages to OS when setting 0 label

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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
This commit is contained in:
Jianzhou Zhao 2020-10-11 01:26:47 +00:00
parent 2e58010208
commit cc07fbe37d
2 changed files with 40 additions and 16 deletions
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39
compiler-rt/lib/dfsan/dfsan.cpp
View File

@ -274,9 +274,10 @@ dfsan_label dfsan_create_label(const char *desc, void *userdata) {
return label;
}
extern "C" SANITIZER_INTERFACE_ATTRIBUTE
void __dfsan_set_label(dfsan_label label, void *addr, uptr size) {
for (dfsan_label *labelp = shadow_for(addr); size != 0; --size, ++labelp) {
static void WriteShadowIfDifferent(dfsan_label label, uptr shadow_addr,
uptr size) {
dfsan_label *labelp = (dfsan_label *)shadow_addr;
for (; size != 0; --size, ++labelp) {
// Don't write the label if it is already the value we need it to be.
// In a program where most addresses are not labeled, it is common that
// a page of shadow memory is entirely zeroed. The Linux copy-on-write
@ -292,6 +293,38 @@ void __dfsan_set_label(dfsan_label label, void *addr, uptr size) {
}
}
extern "C" SANITIZER_INTERFACE_ATTRIBUTE void __dfsan_set_label(
dfsan_label label, void *addr, uptr size) {
const uptr beg_shadow_addr = (uptr)__dfsan::shadow_for(addr);
if (0 != label) {
WriteShadowIfDifferent(label, beg_shadow_addr, size);
return;
}
// If label is 0, releases the pages within the shadow address range, and sets
// the shadow addresses not on the pages to be 0.
const void *end_addr = (void *)((uptr)addr + size);
const uptr end_shadow_addr = (uptr)__dfsan::shadow_for(end_addr);
const uptr page_size = GetPageSizeCached();
const uptr beg_aligned = RoundUpTo(beg_shadow_addr, page_size);
const uptr end_aligned = RoundDownTo(end_shadow_addr, page_size);
// dfsan_set_label can be called from the following cases
// 1) mapped ranges by new/delete and malloc/free. This case has shadow memory
// size > 100k, and happens less frequently.
// 2) zero-filling internal data structures by utility libraries. This case
// has shadow memory size < 32k, and happens more often.
// Set kNumPagesThreshold to be 8 to avoid releasing small pages.
const int kNumPagesThreshold = 8;
if (beg_aligned + kNumPagesThreshold * page_size >= end_aligned)
return WriteShadowIfDifferent(label, beg_shadow_addr, size);
WriteShadowIfDifferent(label, beg_shadow_addr, beg_aligned - beg_shadow_addr);
ReleaseMemoryPagesToOS(beg_aligned, end_aligned);
WriteShadowIfDifferent(label, end_aligned, end_shadow_addr - end_aligned);
}
SANITIZER_INTERFACE_ATTRIBUTE
void dfsan_set_label(dfsan_label label, void *addr, uptr size) {
__dfsan_set_label(label, addr, size);

17
compiler-rt/lib/dfsan/dfsan_interceptors.cpp
View File

@ -24,14 +24,6 @@ namespace {
bool interceptors_initialized;
void ReleaseShadowMemoryPagesToOS(void *addr, SIZE_T length) {
uptr beg_shadow_addr = (uptr)__dfsan::shadow_for(addr);
void *end_addr =
(void *)((uptr)addr + RoundUpTo(length, GetPageSizeCached()));
uptr end_shadow_addr = (uptr)__dfsan::shadow_for(end_addr);
ReleaseMemoryPagesToOS(beg_shadow_addr, end_shadow_addr);
}
} // namespace
INTERCEPTOR(void *, mmap, void *addr, SIZE_T length, int prot, int flags,
@ -46,7 +38,7 @@ INTERCEPTOR(void *, mmap, void *addr, SIZE_T length, int prot, int flags,
res = REAL(mmap)(addr, length, prot, flags, fd, offset);
if (res != (void *)-1)
ReleaseShadowMemoryPagesToOS(res, length);
dfsan_set_label(0, res, RoundUpTo(length, GetPageSizeCached()));
return res;
}
@ -54,15 +46,14 @@ INTERCEPTOR(void *, mmap64, void *addr, SIZE_T length, int prot, int flags,
int fd, OFF64_T offset) {
void *res = REAL(mmap64)(addr, length, prot, flags, fd, offset);
if (res != (void *)-1)
ReleaseShadowMemoryPagesToOS(res, length);
dfsan_set_label(0, res, RoundUpTo(length, GetPageSizeCached()));
return res;
}
INTERCEPTOR(int, munmap, void *addr, SIZE_T length) {
int res = REAL(munmap)(addr, length);
if (res != -1) {
ReleaseShadowMemoryPagesToOS(addr, length);
}
if (res != -1)
dfsan_set_label(0, addr, RoundUpTo(length, GetPageSizeCached()));
return res;
}