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8361487: [ubsan] test_committed_virtualmemory.cpp check_covered_pages shows overflow #28151

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8361487: [ubsan] test_committed_virtualmemory.cpp check_covered_pages shows overflow #28151

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8361487: [ubsan] test_committed_virtualmemory.cpp check_covered_pages…
afshin-zafari Nov 5, 2025
d45208d
more descriptive
afshin-zafari Nov 13, 2025
f3f3fe0
better comment
afshin-zafari Nov 13, 2025
84a1e3c
style and not constexpr
afshin-zafari Nov 13, 2025
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11 changes: 9 additions & 2 deletions test/hotspot/gtest/runtime/test_committed_virtualmemory.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -83,14 +83,21 @@ class CommittedVirtualMemoryTest {
ASSERT_TRUE(found_stack_top);
}

static const int PAGE_CONTAINED_IN_RANGE_TAG = -1;
static bool is_page_in_committed_region(int a) { return (a == PAGE_CONTAINED_IN_RANGE_TAG); }
static void set_page_as_contained_in_committed_region(int &a) { a = PAGE_CONTAINED_IN_RANGE_TAG; }

static void check_covered_pages(address addr, size_t size, address base, size_t touch_pages, int* page_num) {
const size_t page_sz = os::vm_page_size();
size_t index;
for (index = 0; index < touch_pages; index ++) {
if (is_page_in_committed_region(page_num[index])) { // Already tagged?
continue;
}
address page_addr = base + page_num[index] * page_sz;
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@Arraying Arraying Nov 14, 2025

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What if we assert(page_num[index] >= 0) at this point if we know that negative numbers may cause overflows?

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@afshin-zafari afshin-zafari Nov 14, 2025

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Negative numbers are not bug/invalid. They are used as a marker that the page is inside a committed region.
In the test we list/iterate all committed regions of a reserved memory are. For each committed region we check a list of pages whether the page is inside the committed region or not. if yes, we mark the page with -1. There two loops here one for committed regions and for list of page numbers.
After loops, we check and expect that all the pages were marked as being inside committed regions.

// The range covers this page, marks the page
if (page_addr >= addr && page_addr < addr + size) {
page_num[index] = -1;
set_page_as_contained_in_committed_region(page_num[index]);
}
}
}
Expand Down Expand Up @@ -135,7 +142,7 @@ class CommittedVirtualMemoryTest {
if (precise_tracking_supported) {
// All touched pages should be committed
for (size_t index = 0; index < touch_pages; index ++) {
ASSERT_EQ(page_num[index], -1);
ASSERT_TRUE(is_page_in_committed_region(page_num[index]));
}
}

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