Commit 5ef495e5 authored by Kirill A. Shutemov's avatar Kirill A. Shutemov Committed by Dave Hansen
Browse files

x86: Allow atomic MM_CONTEXT flags setting 



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: default avatarKirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: default avatarDave Hansen <dave.hansen@linux.intel.com>
Acked-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: default avatarAlexander Potapenko <glider@google.com>
Link: https://lore.kernel.org/all/20230312112612.31869-3-kirill.shutemov%40linux.intel.com
parent b19b74bc

arch/x86/entry/vsyscall/vsyscall_64.c

+1 −1
Original line number Diff line number Diff line
@@ -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)

arch/x86/include/asm/mmu.h

+3 −3
Original line number Diff line number Diff line
@@ -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;

arch/x86/include/asm/mmu_context.h

+1 −1
Original line number Diff line number Diff line
@@ -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)

arch/x86/kernel/process_64.c

+2 −2
Original line number Diff line number Diff line
@@ -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;