Query the earliest version in which a kernel API was introduced

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Timeline

Timeline

2026-05-21

init

This article introduces a method for querying the earliest version in which a kernel API was introduced, and illustrates it with a specific API as an example.

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How can you check which version a kernel API was introduced in? Takearray_index_nospecas an example,

git clone https://github.com/torvalds/linux.git

# find the header file where its definition resides: include/linux/nospec.h
git blame include/linux/nospec.h

# find the commit ID
git show f3804203306e0

# view all tags that contain this commit ID
git tag --contains f3804203306e0