dqn: Reguard pages on arena memory pop
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adb429babd
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83
dqn.h
83
dqn.h
@ -1338,9 +1338,9 @@ enum Dqn_VMemPage
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Dqn_VMemPage_ReadWrite = Dqn_VMemPage_Read | Dqn_VMemPage_Write,
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/// Modifier used in conjunction with previous flags. This flag is *only* supported on Windows
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/// ignored in other OS's. Exception on first access to the page, then, the underlying
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/// protection flags are active.
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/// Modifier used in conjunction with previous flags. Raises exception on first access to the
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/// page, then, the underlying protection flags are active. This is supported on Windows, on
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/// other OS's using this flag will set the OS equivalent of Dqn_VMemPage_NoAccess.
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Dqn_VMemPage_Guard = 1 << 3,
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};
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@ -1364,7 +1364,7 @@ static_assert(DQN_VMEM_COMMIT_GRANULARITY < DQN_VMEM_RESERVE_GRANULARITY,
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"Minimum commit size must be lower than the reserve size to avoid OOB math on pointers in this library");
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DQN_API void *Dqn_VMem_Reserve (Dqn_usize size, Dqn_VMemCommit commit, uint32_t page_flags);
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DQN_API bool Dqn_VMem_Commit (void *ptr, Dqn_usize size);
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DQN_API bool Dqn_VMem_Commit (void *ptr, Dqn_usize size, uint32_t page_flags);
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DQN_API void Dqn_VMem_Decommit(void *ptr, Dqn_usize size);
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DQN_API void Dqn_VMem_Release (void *ptr, Dqn_usize size);
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DQN_API int Dqn_VMem_Protect (void *ptr, Dqn_usize size, uint32_t page_flags);
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@ -1453,8 +1453,7 @@ DQN_API int Dqn_VMem_Protect (void *ptr, Dqn_usize size, uint32_t page_flags);
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enum Dqn_ArenaBlockFlags
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{
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Dqn_ArenaBlockFlags_Private = 1 << 0, ///< Private blocks can only allocate its memory when used in the 'FromBlock' API variants
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Dqn_ArenaBlockFlags_UseAfterFreeGuard = 1 << 1, ///< Pages guards are placed on freed memory ranges
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Dqn_ArenaBlockFlags_Private = 1 << 0, ///< Private blocks can only allocate its memory when used in the 'FromBlock' API variants
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};
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struct Dqn_ArenaStat
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@ -5053,7 +5052,7 @@ DQN_FILE_SCOPE uint32_t Dqn_VMem_ConvertPageToOSFlags_(uint32_t protect)
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DQN_ASSERTF(result != PAGE_GUARD, "Page guard is a modifier, you must also specify a page permission like read or/and write");
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#else
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if (protect & Dqn_VMemPage_NoAccess) {
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if (protect & (Dqn_VMemPage_NoAccess | Dqn_VMemPage_Guard)) {
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result = PROT_NONE;
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} else {
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if (protect & Dqn_VMemPage_Read)
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@ -5088,12 +5087,13 @@ DQN_API void *Dqn_VMem_Reserve(Dqn_usize size, Dqn_VMemCommit commit, uint32_t p
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return result;
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}
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DQN_API bool Dqn_VMem_Commit(void *ptr, Dqn_usize size)
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DQN_API bool Dqn_VMem_Commit(void *ptr, Dqn_usize size, uint32_t page_flags)
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{
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unsigned long os_page_flags = Dqn_VMem_ConvertPageToOSFlags_(page_flags);
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#if defined(DQN_OS_WIN32)
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bool result = VirtualAlloc(ptr, size, MEM_COMMIT, PAGE_READWRITE) != nullptr;
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bool result = VirtualAlloc(ptr, size, MEM_COMMIT, os_page_flags) != nullptr;
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#elif defined(DQN_OS_UNIX)
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bool result = mprotect(ptr, size, PROT_READ|PROT_WRITE) == 0;
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bool result = mprotect(ptr, size, os_page_flags) == 0;
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#else
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#error "Missing implementation for Dqn_VMem_Commit"
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#endif
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@ -5129,6 +5129,12 @@ DQN_API int Dqn_VMem_Protect(void *ptr, Dqn_usize size, uint32_t page_flags)
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if (!ptr || size == 0)
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return 0;
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static Dqn_String8 const ALIGNMENT_ERROR_MSG =
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DQN_STRING8("Page protection requires pointers to be page aligned because we "
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"can only guard memory at a multiple of the page boundary.");
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DQN_ASSERTF(Dqn_IsPowerOfTwoAligned(DQN_CAST(uintptr_t)ptr, DQN_VMEM_PAGE_GRANULARITY), "%s", ALIGNMENT_ERROR_MSG.data);
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DQN_ASSERTF(Dqn_IsPowerOfTwoAligned(size, DQN_VMEM_PAGE_GRANULARITY), "%s", ALIGNMENT_ERROR_MSG.data);
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unsigned long os_page_flags = Dqn_VMem_ConvertPageToOSFlags_(page_flags);
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#if defined(DQN_OS_WIN32)
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unsigned long prev_flags = 0;
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@ -6192,10 +6198,6 @@ Dqn_String8 Dqn_String8Builder_Build(Dqn_String8Builder const *builder, Dqn_Allo
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// =================================================================================================
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// [$AREN] Dqn_Arena | | Growing bump allocator
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// =================================================================================================
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DQN_FILE_SCOPE Dqn_String8 DQN_ARENA_USE_AFTER_FREE_PTR_ALIGNMENT_ERROR =
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DQN_STRING8("Use-after-free guard requires that all pointers are page aligned because we "
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"can only guard memory at a multiple of the page boundary.");
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DQN_API void Dqn_Arena_CommitFromBlock(Dqn_ArenaBlock *block, Dqn_usize size, Dqn_ArenaCommit commit)
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{
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Dqn_usize commit_size = 0;
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@ -6213,8 +6215,9 @@ DQN_API void Dqn_Arena_CommitFromBlock(Dqn_ArenaBlock *block, Dqn_usize size, Dq
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}
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if (commit_size) {
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uint32_t page_flags = Dqn_VMemPage_ReadWrite;
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char *commit_ptr = DQN_CAST(char *)block->memory + block->commit;
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Dqn_VMem_Commit(commit_ptr, commit_size);
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Dqn_VMem_Commit(commit_ptr, commit_size, page_flags);
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block->commit += commit_size;
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DQN_ASSERTF(block->commit < block->size,
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@ -6222,13 +6225,8 @@ DQN_API void Dqn_Arena_CommitFromBlock(Dqn_ArenaBlock *block, Dqn_usize size, Dq
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block->size, block->commit);
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// NOTE: Guard new pages being allocated from the block
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if (block->arena->use_after_free_guard) {
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DQN_ASSERTF(Dqn_IsPowerOfTwoAligned(DQN_CAST(uintptr_t)commit_ptr, DQN_VMEM_PAGE_GRANULARITY),
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"%s", DQN_ARENA_USE_AFTER_FREE_PTR_ALIGNMENT_ERROR.data);
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DQN_ASSERTF(Dqn_IsPowerOfTwoAligned(commit_size, DQN_VMEM_PAGE_GRANULARITY),
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"%s", DQN_ARENA_USE_AFTER_FREE_PTR_ALIGNMENT_ERROR.data);
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Dqn_VMem_Protect(commit_ptr, commit_size, Dqn_VMemPage_ReadWrite | Dqn_VMemPage_Guard);
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}
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if (block->arena->use_after_free_guard)
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Dqn_VMem_Protect(commit_ptr, commit_size, page_flags | Dqn_VMemPage_Guard);
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}
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}
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@ -6269,17 +6267,8 @@ DQN_API void *Dqn_Arena_AllocateFromBlock(Dqn_ArenaBlock *block, Dqn_usize size,
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Dqn_Arena_CommitFromBlock(block, allocation_size, Dqn_ArenaCommit_EnsureSpace);
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// NOTE: Unlock the pages requested
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if (block->arena->use_after_free_guard) {
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char const error_msg[] = "Use-after-free guard requires that all pointers are page aligned because we "
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"can only guard memory at a multiple of the page boundary.";
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DQN_ASSERTF(Dqn_IsPowerOfTwoAligned(DQN_CAST(uintptr_t)result, DQN_VMEM_PAGE_GRANULARITY),
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"%s", DQN_ARENA_USE_AFTER_FREE_PTR_ALIGNMENT_ERROR.data);
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DQN_ASSERTF(Dqn_IsPowerOfTwoAligned(DQN_CAST(uintptr_t)allocation_size, DQN_VMEM_PAGE_GRANULARITY),
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"%s", DQN_ARENA_USE_AFTER_FREE_PTR_ALIGNMENT_ERROR.data);
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DQN_ASSERTF(Dqn_IsPowerOfTwoAligned(DQN_CAST(uintptr_t)block->used + allocation_size, DQN_VMEM_PAGE_GRANULARITY),
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"%s", DQN_ARENA_USE_AFTER_FREE_PTR_ALIGNMENT_ERROR.data);
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if (block->arena->use_after_free_guard)
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Dqn_VMem_Protect(result, allocation_size, Dqn_VMemPage_ReadWrite);
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}
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// NOTE: Update arena
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Dqn_Arena *arena = block->arena;
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@ -6338,7 +6327,12 @@ DQN_API void Dqn_Arena_Reset(Dqn_Arena *arena, Dqn_ZeroMem zero_mem)
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arena->curr = block;
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if (zero_mem == Dqn_ZeroMem_Yes)
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DQN_MEMSET(block->memory, DQN_MEMSET_BYTE, block->commit);
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block->used = 0;
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// NOTE: Guard all the committed pages again
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if (arena->use_after_free_guard)
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Dqn_VMem_Protect(block->memory, block->commit, Dqn_VMemPage_ReadWrite | Dqn_VMemPage_Guard);
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}
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arena->stats.used = 0;
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@ -6370,8 +6364,14 @@ DQN_API void Dqn_Arena_EndTempMemory_(DQN_LEAK_TRACE_FUNCTION Dqn_ArenaTempMemor
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// NOTE: Revert the current block to the scope's current block
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arena->curr = scope.curr;
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if (arena->curr)
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arena->curr->used = scope.curr_used;
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if (arena->curr) {
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Dqn_ArenaBlock *curr = arena->curr;
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curr->used = scope.curr_used;
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// NOTE: Reguard the pages
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if (arena->use_after_free_guard)
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Dqn_VMem_Protect(curr->memory, curr->commit, Dqn_VMemPage_ReadWrite | Dqn_VMemPage_Guard);
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}
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// NOTE: Free the tail blocks until we reach the scope's tail block
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while (arena->tail != scope.tail) {
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@ -6384,8 +6384,13 @@ DQN_API void Dqn_Arena_EndTempMemory_(DQN_LEAK_TRACE_FUNCTION Dqn_ArenaTempMemor
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// NOTE: Reset the usage of all the blocks between the tail and current block's
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if (arena->tail) {
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arena->tail->next = nullptr;
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for (Dqn_ArenaBlock *block = arena->tail; block && block != arena->curr; block = block->prev)
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for (Dqn_ArenaBlock *block = arena->tail; block && block != arena->curr; block = block->prev) {
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block->used = 0;
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// NOTE: Reguard the pages
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if (arena->use_after_free_guard)
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Dqn_VMem_Protect(block->memory, block->commit, Dqn_VMemPage_ReadWrite | Dqn_VMemPage_Guard);
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}
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}
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}
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@ -6476,7 +6481,7 @@ DQN_API Dqn_ArenaBlock *Dqn_Arena_Grow_(DQN_LEAK_TRACE_FUNCTION Dqn_Arena *arena
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// NOTE: Commit the amount requested by the user if we did not commit
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// on reserve the initial range.
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if (commit_on_reserve == Dqn_VMemCommit_No) {
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Dqn_VMem_Commit(result, commit_aligned);
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Dqn_VMem_Commit(result, commit_aligned, page_flags);
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} else {
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DQN_ASSERT(commit_aligned == reserve_aligned);
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}
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@ -6493,9 +6498,9 @@ DQN_API Dqn_ArenaBlock *Dqn_Arena_Grow_(DQN_LEAK_TRACE_FUNCTION Dqn_Arena *arena
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result->flags = flags;
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result->arena = arena;
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// NOTE: Guard all the pages
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// NOTE: Guard all the committed pages in the memory block
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if (arena->use_after_free_guard)
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Dqn_VMem_Protect(result->memory, commit_aligned - block_metadata_size, page_flags | Dqn_VMemPage_Guard);
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Dqn_VMem_Protect(result->memory, result->commit, page_flags | Dqn_VMemPage_Guard);
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// NOTE: Attach the block to the arena
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if (arena->tail) {
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@ -6528,7 +6533,7 @@ DQN_API void *Dqn_Arena_Allocate_(DQN_LEAK_TRACE_FUNCTION Dqn_Arena *arena, Dqn_
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if (arena->use_after_free_guard) {
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size = Dqn_PowerOfTwoAlign(size, DQN_VMEM_PAGE_GRANULARITY);
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align = 0;
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align = 1;
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}
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void *result = nullptr;
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@ -66,12 +66,12 @@ Dqn_Tester TestArena()
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DQN_TESTER_TEST("Use-after-free guard on %.1f KiB allocation", size / 1024.0) {
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Dqn_Arena arena = {};
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arena.use_after_free_guard = true;
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Dqn_Arena_Grow(&arena, size, false /*commit*/, 0 /*flags*/);
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// NOTE: Wrap in temp memory, allocate and write
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Dqn_ArenaTempMemory temp_mem = Dqn_Arena_BeginTempMemory(&arena);
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Dqn_usize size = DQN_KILOBYTES(1);
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uintptr_t first_ptr_address = 0;
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void *ptr = Dqn_Arena_Allocate(&arena, size, 1, Dqn_ZeroMem_Yes);
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uintptr_t first_ptr_address = 0;
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void *ptr = Dqn_Arena_Allocate(&arena, size, 1, Dqn_ZeroMem_Yes);
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DQN_MEMSET(ptr, 'z', size);
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Dqn_Arena_EndTempMemory(temp_mem);
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