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Subject[PATCHv15 02/17] x86: Allow atomic MM_CONTEXT flags setting
Date
So far there's no need in atomic setting of MM context flags in
mm_context_t::flags. The flags set early in exec and never change
after that.

LAM enabling requires atomic flag setting. The upcoming flag
MM_CONTEXT_FORCE_TAGGED_SVA can be set much later in the process
lifetime where multiple threads exist.

Convert the field to unsigned long and do MM_CONTEXT_* accesses with
__set_bit() and test_bit().

No functional changes.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
---
arch/x86/entry/vsyscall/vsyscall_64.c | 2 +-
arch/x86/include/asm/mmu.h | 6 +++---
arch/x86/include/asm/mmu_context.h | 2 +-
arch/x86/kernel/process_64.c | 4 ++--
4 files changed, 7 insertions(+), 7 deletions(-)

diff --git a/arch/x86/entry/vsyscall/vsyscall_64.c b/arch/x86/entry/vsyscall/vsyscall_64.c
index 4af81df133ee..aa226f451c52 100644
--- a/arch/x86/entry/vsyscall/vsyscall_64.c
+++ b/arch/x86/entry/vsyscall/vsyscall_64.c
@@ -317,7 +317,7 @@ static struct vm_area_struct gate_vma __ro_after_init = {
struct vm_area_struct *get_gate_vma(struct mm_struct *mm)
{
#ifdef CONFIG_COMPAT
- if (!mm || !(mm->context.flags & MM_CONTEXT_HAS_VSYSCALL))
+ if (!mm || !test_bit(MM_CONTEXT_HAS_VSYSCALL, &mm->context.flags))
return NULL;
#endif
if (vsyscall_mode == NONE)
diff --git a/arch/x86/include/asm/mmu.h b/arch/x86/include/asm/mmu.h
index 5d7494631ea9..efa3eaee522c 100644
--- a/arch/x86/include/asm/mmu.h
+++ b/arch/x86/include/asm/mmu.h
@@ -9,9 +9,9 @@
#include <linux/bits.h>

/* Uprobes on this MM assume 32-bit code */
-#define MM_CONTEXT_UPROBE_IA32 BIT(0)
+#define MM_CONTEXT_UPROBE_IA32 0
/* vsyscall page is accessible on this MM */
-#define MM_CONTEXT_HAS_VSYSCALL BIT(1)
+#define MM_CONTEXT_HAS_VSYSCALL 1

/*
* x86 has arch-specific MMU state beyond what lives in mm_struct.
@@ -39,7 +39,7 @@ typedef struct {
#endif

#ifdef CONFIG_X86_64
- unsigned short flags;
+ unsigned long flags;
#endif

struct mutex lock;
diff --git a/arch/x86/include/asm/mmu_context.h b/arch/x86/include/asm/mmu_context.h
index b8d40ddeab00..53ef591a6166 100644
--- a/arch/x86/include/asm/mmu_context.h
+++ b/arch/x86/include/asm/mmu_context.h
@@ -181,7 +181,7 @@ static inline void arch_exit_mmap(struct mm_struct *mm)
static inline bool is_64bit_mm(struct mm_struct *mm)
{
return !IS_ENABLED(CONFIG_IA32_EMULATION) ||
- !(mm->context.flags & MM_CONTEXT_UPROBE_IA32);
+ !test_bit(MM_CONTEXT_UPROBE_IA32, &mm->context.flags);
}
#else
static inline bool is_64bit_mm(struct mm_struct *mm)
diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c
index 4e34b3b68ebd..8b06034e8c70 100644
--- a/arch/x86/kernel/process_64.c
+++ b/arch/x86/kernel/process_64.c
@@ -671,7 +671,7 @@ void set_personality_64bit(void)
task_pt_regs(current)->orig_ax = __NR_execve;
current_thread_info()->status &= ~TS_COMPAT;
if (current->mm)
- current->mm->context.flags = MM_CONTEXT_HAS_VSYSCALL;
+ __set_bit(MM_CONTEXT_HAS_VSYSCALL, &current->mm->context.flags);

/* TBD: overwrites user setup. Should have two bits.
But 64bit processes have always behaved this way,
@@ -708,7 +708,7 @@ static void __set_personality_ia32(void)
* uprobes applied to this MM need to know this and
* cannot use user_64bit_mode() at that time.
*/
- current->mm->context.flags = MM_CONTEXT_UPROBE_IA32;
+ __set_bit(MM_CONTEXT_UPROBE_IA32, &current->mm->context.flags);
}

current->personality |= force_personality32;
--
2.39.1
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