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x86: Allow atomic MM_CONTEXT flags setting

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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>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: Alexander Potapenko <glider@google.com>
Link: https://lore.kernel.org/all/20230312112612.31869-3-kirill.shutemov%40linux.intel.com
This commit is contained in:
Kirill A. Shutemov 2023-03-12 14:25:57 +03:00 committed by Dave Hansen
parent b19b74bc99
commit 5ef495e55f
4 changed files with 7 additions and 7 deletions
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2
arch/x86/entry/vsyscall/vsyscall_64.c
View File

@ -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)

6
arch/x86/include/asm/mmu.h
View File

@ -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;

2
arch/x86/include/asm/mmu_context.h
View File

@ -182,7 +182,7 @@ 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)

4
arch/x86/kernel/process_64.c
View File

@ -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;