x86/mm: Make use_/unuse_temporary_mm() non-static

This prepares them for use outside of the alternative machinery.
The code is unchanged.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: Rik van Riel <riel@surriel.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Link: https://lore.kernel.org/r/20250402094540.3586683-4-mingo@kernel.org

1 files changed, 0 insertions, 64 deletions

diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c
index 95053e8a1378..bdbdfa0e4d06 100644
--- a/arch/x86/kernel/alternative.c
+++ b/arch/x86/kernel/alternative.c
@@ -2111,73 +2111,9 @@ void __init_or_module text_poke_early(void *addr, const void *opcode,
 	}
 }
 
-/*
- * Using a temporary mm allows to set temporary mappings that are not accessible
- * by other CPUs. Such mappings are needed to perform sensitive memory writes
- * that override the kernel memory protections (e.g., W^X), without exposing the
- * temporary page-table mappings that are required for these write operations to
- * other CPUs. Using a temporary mm also allows to avoid TLB shootdowns when the
- * mapping is torn down.
- *
- * Context: The temporary mm needs to be used exclusively by a single core. To
- *          harden security IRQs must be disabled while the temporary mm is
- *          loaded, thereby preventing interrupt handler bugs from overriding
- *          the kernel memory protection.
- */
-static inline struct mm_struct *use_temporary_mm(struct mm_struct *temp_mm)
-{
-	struct mm_struct *prev_mm;
-
-	lockdep_assert_irqs_disabled();
-
-	/*
-	 * Make sure not to be in TLB lazy mode, as otherwise we'll end up
-	 * with a stale address space WITHOUT being in lazy mode after
-	 * restoring the previous mm.
-	 */
-	if (this_cpu_read(cpu_tlbstate_shared.is_lazy))
-		leave_mm();
-
-	prev_mm = this_cpu_read(cpu_tlbstate.loaded_mm);
-	switch_mm_irqs_off(NULL, temp_mm, current);
-
-	/*
-	 * If breakpoints are enabled, disable them while the temporary mm is
-	 * used. Userspace might set up watchpoints on addresses that are used
-	 * in the temporary mm, which would lead to wrong signals being sent or
-	 * crashes.
-	 *
-	 * Note that breakpoints are not disabled selectively, which also causes
-	 * kernel breakpoints (e.g., perf's) to be disabled. This might be
-	 * undesirable, but still seems reasonable as the code that runs in the
-	 * temporary mm should be short.
-	 */
-	if (hw_breakpoint_active())
-		hw_breakpoint_disable();
-
-	return prev_mm;
-}
-
 __ro_after_init struct mm_struct *text_poke_mm;
 __ro_after_init unsigned long text_poke_mm_addr;
 
-static inline void unuse_temporary_mm(struct mm_struct *mm, struct mm_struct *prev_mm)
-{
-	lockdep_assert_irqs_disabled();
-
-	switch_mm_irqs_off(NULL, prev_mm, current);
-
-	/* Clear the cpumask, to indicate no TLB flushing is needed anywhere */
-	cpumask_clear_cpu(raw_smp_processor_id(), mm_cpumask(mm));
-
-	/*
-	 * Restore the breakpoints if they were disabled before the temporary mm
-	 * was loaded.
-	 */
-	if (hw_breakpoint_active())
-		hw_breakpoint_restore();
-}
-
 static void text_poke_memcpy(void *dst, const void *src, size_t len)
 {
 	memcpy(dst, src, len);