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A Time Consuming Pitfall for 32-Bit Applications on AArch64
When running legacy applications on AArch64, an interesting pitfall can arise.
If you simply enable CONFIG_COMPAT without setting up CROSS_COMPILE_COMPAT to an AArch32 cross compiler, the resulting kernel won’t supply a vDSO to 32-bit applications. Instead, the kernel places sufficient information into a memory region accessible to userspace to achieve the same functionality. Utilizing the vDSO for querying the current time eliminates the need for a context switch, resulting in a faster operation.
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