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

diff --git a/arch/x86/include/asm/mmu_context.h b/arch/x86/include/asm/mmu_context.h
index 2398058b6e83cba9bc720f83a09512011326220e..b103e1709a67436ac9f49d9dedb5c298ef123609 100644 (file)
--- a/arch/x86/include/asm/mmu_context.h
+++ b/arch/x86/include/asm/mmu_context.h
@@ -272,4 +272,7 @@ unsigned long __get_current_cr3_fast(void);
 
 #include <asm-generic/mmu_context.h>
 
+extern struct mm_struct *use_temporary_mm(struct mm_struct *temp_mm);
+extern void unuse_temporary_mm(struct mm_struct *mm, struct mm_struct *prev_mm);
+
 #endif /* _ASM_X86_MMU_CONTEXT_H */

diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c
index 95053e8a1378bb8e05f67721c9e9b8735db74f67..bdbdfa0e4d0608a48503c341634bb1749d8314d5 100644 (file)
--- 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);

diff --git a/arch/x86/mm/tlb.c b/arch/x86/mm/tlb.c
index e459d97ef397725d3754e2e181c82f208ada1440..f3da20bfcf0e12a1f10b7b2125194a53818e28f0 100644 (file)
--- a/arch/x86/mm/tlb.c
+++ b/arch/x86/mm/tlb.c
@@ -971,6 +971,70 @@ void enter_lazy_tlb(struct mm_struct *mm, struct task_struct *tsk)
        this_cpu_write(cpu_tlbstate_shared.is_lazy, true);
 }
 
+/*
+ * 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.
+ */
+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;
+}
+
+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();
+}
+
 /*
  * Call this when reinitializing a CPU.  It fixes the following potential
  * problems: