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Message-ID: <20250402094540.3586683-4-mingo@kernel.org>
Date: Wed, 2 Apr 2025 11:45:36 +0200
From: Ingo Molnar <mingo@...nel.org>
To: linux-kernel@...r.kernel.org
Cc: Andy Lutomirski <luto@...nel.org>,
Rik van Riel <riel@...riel.com>,
"H . Peter Anvin" <hpa@...or.com>,
Peter Zijlstra <peterz@...radead.org>,
Linus Torvalds <torvalds@...ux-foundation.org>,
Andrew Morton <akpm@...ux-foundation.org>,
Ingo Molnar <mingo@...nel.org>
Subject: [PATCH 3/7] x86/mm: Make use_/unuse_temporary_mm() non-static
From: Andy Lutomirski <luto@...nel.org>
This prepares them for use outside of the alternative machinery.
The code is unchanged.
Signed-off-by: Andy Lutomirski <luto@...nel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Signed-off-by: Ingo Molnar <mingo@...nel.org>
Cc: Rik van Riel <riel@...riel.com>
Cc: "H. Peter Anvin" <hpa@...or.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Link: https://lore.kernel.org/r/20241119163035.533822339@infradead.org
---
arch/x86/include/asm/mmu_context.h | 3 ++
arch/x86/kernel/alternative.c | 64 --------------------------------------
arch/x86/mm/tlb.c | 64 ++++++++++++++++++++++++++++++++++++++
3 files changed, 67 insertions(+), 64 deletions(-)
diff --git a/arch/x86/include/asm/mmu_context.h b/arch/x86/include/asm/mmu_context.h
index 2398058b6e83..b103e1709a67 100644
--- 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 cfffcb80f564..25abadaf8751 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);
diff --git a/arch/x86/mm/tlb.c b/arch/x86/mm/tlb.c
index 0925768d00cb..06a1ad39be74 100644
--- a/arch/x86/mm/tlb.c
+++ b/arch/x86/mm/tlb.c
@@ -972,6 +972,70 @@ 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:
--
2.45.2
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