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: Andy 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: Ingo Molnar <mingo@kernel.org>

1 files changed, 11 insertions, 39 deletions

diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index b898a38093a3..82881bc5feef 100644
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -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;
@@ -1263,13 +1262,6 @@ void do_user_addr_fault(struct pt_regs *regs,
         }
 
         /*
-         * 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;
         }