Commit 0ed32f1a authored by Andy Lutomirski's avatar Andy Lutomirski Committed by Ingo Molnar
Browse files

x86/fault: Remove sw_error_code 



All of the fault handling code now corrently checks user_mode(regs)
as needed, and nothing depends on the X86_PF_USER bit being munged.
Get rid of the sw_error code and use hw_error_code everywhere.

Signed-off-by: default avatarAndy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@surriel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Yu-cheng Yu <yu-cheng.yu@intel.com>
Link: http://lkml.kernel.org/r/078f5b8ae6e8c79ff8ee7345b5c476c45003e5ac.1542841400.git.luto@kernel.org


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 1ad33f5a

arch/x86/mm/fault.c

+11 −39
Original line number Diff line number Diff line
@@ -1217,7 +1217,6 @@ void do_user_addr_fault(struct pt_regs *regs, 
			unsigned long hw_error_code,

			unsigned long address)

{

	unsigned long sw_error_code;

	struct vm_area_struct *vma;

	struct task_struct *tsk;

	struct mm_struct *mm;
@@ -1262,13 +1261,6 @@ void do_user_addr_fault(struct pt_regs *regs, 
		return;

	}



	/*

	 * hw_error_code is literally the "page fault error code" passed to

	 * the kernel directly from the hardware.  But, we will shortly be

	 * modifying it in software, so give it a new name.

	 */

	sw_error_code = hw_error_code;



	/*

	 * It's safe to allow irq's after cr2 has been saved and the

	 * vmalloc fault has been handled.
@@ -1278,26 +1270,6 @@ void do_user_addr_fault(struct pt_regs *regs, 
	 */

	if (user_mode(regs)) {

		local_irq_enable();

		/*

		 * Up to this point, X86_PF_USER set in hw_error_code

		 * indicated a user-mode access.  But, after this,

		 * X86_PF_USER in sw_error_code will indicate either

		 * that, *or* an implicit kernel(supervisor)-mode access

		 * which originated from user mode.

		 */

		if (!(hw_error_code & X86_PF_USER)) {

			/*

			 * The CPU was in user mode, but the CPU says

			 * the fault was not a user-mode access.

			 * Must be an implicit kernel-mode access,

			 * which we do not expect to happen in the

			 * user address space.

			 */

			pr_warn_once("kernel-mode error from user-mode: %lx\n",

					hw_error_code);



			sw_error_code |= X86_PF_USER;

		}

		flags |= FAULT_FLAG_USER;

	} else {

		if (regs->flags & X86_EFLAGS_IF)
@@ -1306,9 +1278,9 @@ void do_user_addr_fault(struct pt_regs *regs, 


	perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);



	if (sw_error_code & X86_PF_WRITE)

	if (hw_error_code & X86_PF_WRITE)

		flags |= FAULT_FLAG_WRITE;

	if (sw_error_code & X86_PF_INSTR)

	if (hw_error_code & X86_PF_INSTR)

		flags |= FAULT_FLAG_INSTRUCTION;



#ifdef CONFIG_X86_64
@@ -1321,7 +1293,7 @@ void do_user_addr_fault(struct pt_regs *regs, 
	 * The vsyscall page does not have a "real" VMA, so do this

	 * emulation before we go searching for VMAs.

	 */

	if ((sw_error_code & X86_PF_INSTR) && is_vsyscall_vaddr(address)) {

	if ((hw_error_code & X86_PF_INSTR) && is_vsyscall_vaddr(address)) {

		if (emulate_vsyscall(regs, address))

			return;

	}
@@ -1345,7 +1317,7 @@ void do_user_addr_fault(struct pt_regs *regs, 
			 * Fault from code in kernel from

			 * which we do not expect faults.

			 */

			bad_area_nosemaphore(regs, sw_error_code, address);

			bad_area_nosemaphore(regs, hw_error_code, address);

			return;

		}

retry:
@@ -1361,17 +1333,17 @@ retry: 


	vma = find_vma(mm, address);

	if (unlikely(!vma)) {

		bad_area(regs, sw_error_code, address);

		bad_area(regs, hw_error_code, address);

		return;

	}

	if (likely(vma->vm_start <= address))

		goto good_area;

	if (unlikely(!(vma->vm_flags & VM_GROWSDOWN))) {

		bad_area(regs, sw_error_code, address);

		bad_area(regs, hw_error_code, address);

		return;

	}

	if (unlikely(expand_stack(vma, address))) {

		bad_area(regs, sw_error_code, address);

		bad_area(regs, hw_error_code, address);

		return;

	}
@@ -1380,8 +1352,8 @@ retry: 
	 * we can handle it..

	 */

good_area:

	if (unlikely(access_error(sw_error_code, vma))) {

		bad_area_access_error(regs, sw_error_code, address, vma);

	if (unlikely(access_error(hw_error_code, vma))) {

		bad_area_access_error(regs, hw_error_code, address, vma);

		return;

	}
@@ -1420,13 +1392,13 @@ good_area: 
			return;



		/* Not returning to user mode? Handle exceptions or die: */

		no_context(regs, sw_error_code, address, SIGBUS, BUS_ADRERR);

		no_context(regs, hw_error_code, address, SIGBUS, BUS_ADRERR);

		return;

	}



	up_read(&mm->mmap_sem);

	if (unlikely(fault & VM_FAULT_ERROR)) {

		mm_fault_error(regs, sw_error_code, address, fault);

		mm_fault_error(regs, hw_error_code, address, fault);

		return;

	}

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