x86/early_printk: Harden early_serial

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Scott found that mem32_serial_in() is an ideal speculation gadget, an
indirectly callable function that takes an adddress and offset and
immediately does a load.

Use static_call() to take away the need for indirect calls and
explicitly seal the functions to ensure they're not callable on IBT
enabled parts.

Reported-by: Scott Constable <scott.d.constable@intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Sami Tolvanen <samitolvanen@google.com>
Link: https://lore.kernel.org/r/20250207122546.919773202@infradead.org

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Peter Zijlstra 2025-02-07 13:15:38 +01:00

parent c4239a72a2

commit 306859de59

1 changed files with 24 additions and 25 deletions

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arch/x86/kernel/early_printk.c

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