CODEWITHSUNDEEP
winapi
Roland Pihlakas
Roland Pihlakas

Reputation: 4573

ReadProcessMemory and WriteProcessMemory atomicity

Are ReadProcessMemory() and WriteProcessMemory() atomic when reading/writing a machine-word (32 bits under 32-bit mode and 64 bits for 64-bit mode) from/to properly aligned memory location?

PS. There is a tag 'readprocessmemory' available in SO, but no tag 'writeprocessmemory'. Perhaps it should be created by someone with enough rights?

Upvotes: 1

Views: 533

Answers (1)

Necrolis
Necrolis

Reputation: 26171

If MSDN doesn't state that they provide atomicity on aligned machine-word reads & writes (which it doesn't), then they don't; even if they underlying implementation does, either through HW or software mechanisms you cannot rely on this, this is especially true for code that my be in the I-cache and must be flushed with FlushInstructionCache.

If you want an atomic read/write, you need to use one explicitly, in conjunction with VirtualProtect and possibly some additional tricks if you are writing outside your own address space (ie: into a debuggees address space).

Upvotes: 2

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