riscv: vector: init vector context with proper vlenb

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[ Upstream commit ef3ff40346 ]

The vstate in thread_struct is zeroed when the vector context is
initialized. That includes read-only register vlenb, which holds
the vector register length in bytes. Zeroed state persists until
mstatus.VS becomes 'dirty' and a context switch saves the actual
hardware values.

This can expose the zero vlenb value to the user-space in early
debug scenarios, e.g. when ptrace attaches to a traced process
early, before any vector instruction except the first one was
executed.

Fix this by specifying proper vlenb on vector context init.

Signed-off-by: Sergey Matyukevich <geomatsi@gmail.com>
Reviewed-by: Andy Chiu <andybnac@gmail.com>
Tested-by: Andy Chiu <andybnac@gmail.com>
Link: https://patch.msgid.link/20251214163537.1054292-3-geomatsi@gmail.com
Signed-off-by: Paul Walmsley <pjw@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

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Sergey Matyukevich 2026-01-25 21:09:56 -07:00 • committed by Sasha Levin

parent d42ec56b30

commit f7fc25362c

1 changed files with 8 additions and 4 deletions

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arch/riscv/kernel/vector.c

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