forked from OSchip/llvm-project
[DFSan] Optimize code for writing to shadow. Move SetShadow to namespace.
Writing zeros to shadow (including checking for existing zero) is now ~2x faster on one example. Reviewed By: morehouse Differential Revision: https://reviews.llvm.org/D110733
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@ -369,37 +369,6 @@ static void SetOrigin(const void *dst, uptr size, u32 origin) {
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*(u32 *)(end - kOriginAlign) = origin;
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}
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static void WriteShadowInRange(dfsan_label label, uptr beg_shadow_addr,
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uptr end_shadow_addr) {
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// TODO: After changing dfsan_label to 8bit, use internal_memset when label
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// is not 0.
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dfsan_label *labelp = (dfsan_label *)beg_shadow_addr;
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if (label) {
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for (; (uptr)labelp < end_shadow_addr; ++labelp) *labelp = label;
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return;
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}
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for (; (uptr)labelp < end_shadow_addr; ++labelp) {
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// Don't write the label if it is already the value we need it to be.
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// In a program where most addresses are not labeled, it is common that
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// a page of shadow memory is entirely zeroed. The Linux copy-on-write
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// implementation will share all of the zeroed pages, making a copy of a
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// page when any value is written. The un-sharing will happen even if
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// the value written does not change the value in memory. Avoiding the
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// write when both |label| and |*labelp| are zero dramatically reduces
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// the amount of real memory used by large programs.
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if (!*labelp)
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continue;
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*labelp = 0;
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}
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}
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static void WriteShadowWithSize(dfsan_label label, uptr shadow_addr,
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uptr size) {
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WriteShadowInRange(label, shadow_addr, shadow_addr + size * sizeof(label));
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}
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#define RET_CHAIN_ORIGIN(id) \
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GET_CALLER_PC_BP_SP; \
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(void)sp; \
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@ -451,21 +420,6 @@ void dfsan_copy_memory(void *dst, const void *src, uptr size) {
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dfsan_mem_origin_transfer(dst, src, size);
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}
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} // namespace __dfsan
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// If the label s is tainted, set the size bytes from the address p to be a new
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// origin chain with the previous ID o and the current stack trace. This is
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// used by instrumentation to reduce code size when too much code is inserted.
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extern "C" SANITIZER_INTERFACE_ATTRIBUTE void __dfsan_maybe_store_origin(
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dfsan_label s, void *p, uptr size, dfsan_origin o) {
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if (UNLIKELY(s)) {
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GET_CALLER_PC_BP_SP;
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(void)sp;
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GET_STORE_STACK_TRACE_PC_BP(pc, bp);
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SetOrigin(p, size, ChainOrigin(o, &stack));
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}
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}
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// Releases the pages within the origin address range.
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static void ReleaseOrigins(void *addr, uptr size) {
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const uptr beg_origin_addr = (uptr)__dfsan::origin_for(addr);
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@ -484,6 +438,19 @@ static void ReleaseOrigins(void *addr, uptr size) {
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Die();
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}
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static void WriteZeroShadowInRange(uptr beg, uptr end) {
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// Don't write the label if it is already the value we need it to be.
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// In a program where most addresses are not labeled, it is common that
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// a page of shadow memory is entirely zeroed. The Linux copy-on-write
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// implementation will share all of the zeroed pages, making a copy of a
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// page when any value is written. The un-sharing will happen even if
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// the value written does not change the value in memory. Avoiding the
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// write when both |label| and |*labelp| are zero dramatically reduces
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// the amount of real memory used by large programs.
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if (!mem_is_zero((const char *)beg, end - beg))
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internal_memset((void *)beg, 0, end - beg);
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}
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// Releases the pages within the shadow address range, and sets
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// the shadow addresses not on the pages to be 0.
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static void ReleaseOrClearShadows(void *addr, uptr size) {
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@ -492,20 +459,22 @@ static void ReleaseOrClearShadows(void *addr, uptr size) {
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const uptr end_shadow_addr = (uptr)__dfsan::shadow_for(end_addr);
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if (end_shadow_addr - beg_shadow_addr <
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common_flags()->clear_shadow_mmap_threshold)
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return WriteShadowWithSize(0, beg_shadow_addr, size);
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common_flags()->clear_shadow_mmap_threshold) {
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WriteZeroShadowInRange(beg_shadow_addr, end_shadow_addr);
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return;
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}
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const uptr page_size = GetPageSizeCached();
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const uptr beg_aligned = RoundUpTo(beg_shadow_addr, page_size);
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const uptr end_aligned = RoundDownTo(end_shadow_addr, page_size);
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if (beg_aligned >= end_aligned) {
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WriteShadowWithSize(0, beg_shadow_addr, size);
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WriteZeroShadowInRange(beg_shadow_addr, end_shadow_addr);
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} else {
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if (beg_aligned != beg_shadow_addr)
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WriteShadowInRange(0, beg_shadow_addr, beg_aligned);
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WriteZeroShadowInRange(beg_shadow_addr, beg_aligned);
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if (end_aligned != end_shadow_addr)
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WriteShadowInRange(0, end_aligned, end_shadow_addr);
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WriteZeroShadowInRange(end_aligned, end_shadow_addr);
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if (!MmapFixedSuperNoReserve(beg_aligned, end_aligned - beg_aligned))
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Die();
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}
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@ -514,7 +483,7 @@ static void ReleaseOrClearShadows(void *addr, uptr size) {
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void SetShadow(dfsan_label label, void *addr, uptr size, dfsan_origin origin) {
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if (0 != label) {
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const uptr beg_shadow_addr = (uptr)__dfsan::shadow_for(addr);
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WriteShadowWithSize(label, beg_shadow_addr, size);
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internal_memset((void *)beg_shadow_addr, label, size);
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if (dfsan_get_track_origins())
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SetOrigin(addr, size, origin);
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return;
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@ -526,9 +495,24 @@ void SetShadow(dfsan_label label, void *addr, uptr size, dfsan_origin origin) {
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ReleaseOrClearShadows(addr, size);
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}
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} // namespace __dfsan
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// If the label s is tainted, set the size bytes from the address p to be a new
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// origin chain with the previous ID o and the current stack trace. This is
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// used by instrumentation to reduce code size when too much code is inserted.
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extern "C" SANITIZER_INTERFACE_ATTRIBUTE void __dfsan_maybe_store_origin(
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dfsan_label s, void *p, uptr size, dfsan_origin o) {
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if (UNLIKELY(s)) {
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GET_CALLER_PC_BP_SP;
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(void)sp;
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GET_STORE_STACK_TRACE_PC_BP(pc, bp);
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SetOrigin(p, size, ChainOrigin(o, &stack));
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}
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}
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extern "C" SANITIZER_INTERFACE_ATTRIBUTE void __dfsan_set_label(
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dfsan_label label, dfsan_origin origin, void *addr, uptr size) {
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SetShadow(label, addr, size, origin);
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__dfsan::SetShadow(label, addr, size, origin);
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}
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SANITIZER_INTERFACE_ATTRIBUTE
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@ -539,7 +523,7 @@ void dfsan_set_label(dfsan_label label, void *addr, uptr size) {
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GET_STORE_STACK_TRACE_PC_BP(pc, bp);
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init_origin = ChainOrigin(0, &stack, true);
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}
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SetShadow(label, addr, size, init_origin);
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__dfsan::SetShadow(label, addr, size, init_origin);
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}
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SANITIZER_INTERFACE_ATTRIBUTE
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