From 0ed32f1aa66ee758e6c8164f549f7ff9d399a20e Mon Sep 17 00:00:00 2001 From: Andy Lutomirski Date: Wed, 21 Nov 2018 15:11:22 -0800 Subject: [PATCH] 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 Cc: Borislav Petkov Cc: Dave Hansen Cc: H. Peter Anvin Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Rik van Riel Cc: Thomas Gleixner Cc: Yu-cheng Yu Link: http://lkml.kernel.org/r/078f5b8ae6e8c79ff8ee7345b5c476c45003e5ac.1542841400.git.luto@kernel.org Signed-off-by: Ingo Molnar --- arch/x86/mm/fault.c | 50 ++++++++++----------------------------------- 1 file 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; @@ -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 @@ void do_user_addr_fault(struct pt_regs *regs, 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 @@ void do_user_addr_fault(struct pt_regs *regs, * 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 @@ void do_user_addr_fault(struct pt_regs *regs, 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; }