diff options
Diffstat (limited to 'arch/x86/mm/fault.c')
| -rw-r--r-- | arch/x86/mm/fault.c | 61 |
1 files changed, 42 insertions, 19 deletions
diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c index 9d591c895803..a10c8c792161 100644 --- a/arch/x86/mm/fault.c +++ b/arch/x86/mm/fault.c @@ -1001,6 +1001,12 @@ static int fault_in_kernel_space(unsigned long address) static inline bool smap_violation(int error_code, struct pt_regs *regs) { + if (!IS_ENABLED(CONFIG_X86_SMAP)) + return false; + + if (!static_cpu_has(X86_FEATURE_SMAP)) + return false; + if (error_code & PF_USER) return false; @@ -1014,13 +1020,17 @@ static inline bool smap_violation(int error_code, struct pt_regs *regs) * This routine handles page faults. It determines the address, * and the problem, and then passes it off to one of the appropriate * routines. + * + * This function must have noinline because both callers + * {,trace_}do_page_fault() have notrace on. Having this an actual function + * guarantees there's a function trace entry. */ -static void __kprobes -__do_page_fault(struct pt_regs *regs, unsigned long error_code) +static void __kprobes noinline +__do_page_fault(struct pt_regs *regs, unsigned long error_code, + unsigned long address) { struct vm_area_struct *vma; struct task_struct *tsk; - unsigned long address; struct mm_struct *mm; int fault; unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE; @@ -1028,9 +1038,6 @@ __do_page_fault(struct pt_regs *regs, unsigned long error_code) tsk = current; mm = tsk->mm; - /* Get the faulting address: */ - address = read_cr2(); - /* * Detect and handle instructions that would cause a page fault for * both a tracked kernel page and a userspace page. @@ -1087,11 +1094,9 @@ __do_page_fault(struct pt_regs *regs, unsigned long error_code) if (unlikely(error_code & PF_RSVD)) pgtable_bad(regs, error_code, address); - if (static_cpu_has(X86_FEATURE_SMAP)) { - if (unlikely(smap_violation(error_code, regs))) { - bad_area_nosemaphore(regs, error_code, address); - return; - } + if (unlikely(smap_violation(error_code, regs))) { + bad_area_nosemaphore(regs, error_code, address); + return; } /* @@ -1244,32 +1249,50 @@ good_area: up_read(&mm->mmap_sem); } -dotraplinkage void __kprobes +dotraplinkage void __kprobes notrace do_page_fault(struct pt_regs *regs, unsigned long error_code) { + unsigned long address = read_cr2(); /* Get the faulting address */ enum ctx_state prev_state; + /* + * We must have this function tagged with __kprobes, notrace and call + * read_cr2() before calling anything else. To avoid calling any kind + * of tracing machinery before we've observed the CR2 value. + * + * exception_{enter,exit}() contain all sorts of tracepoints. + */ + prev_state = exception_enter(); - __do_page_fault(regs, error_code); + __do_page_fault(regs, error_code, address); exception_exit(prev_state); } -static void trace_page_fault_entries(struct pt_regs *regs, +#ifdef CONFIG_TRACING +static void trace_page_fault_entries(unsigned long address, struct pt_regs *regs, unsigned long error_code) { if (user_mode(regs)) - trace_page_fault_user(read_cr2(), regs, error_code); + trace_page_fault_user(address, regs, error_code); else - trace_page_fault_kernel(read_cr2(), regs, error_code); + trace_page_fault_kernel(address, regs, error_code); } -dotraplinkage void __kprobes +dotraplinkage void __kprobes notrace trace_do_page_fault(struct pt_regs *regs, unsigned long error_code) { + /* + * The exception_enter and tracepoint processing could + * trigger another page faults (user space callchain + * reading) and destroy the original cr2 value, so read + * the faulting address now. + */ + unsigned long address = read_cr2(); enum ctx_state prev_state; prev_state = exception_enter(); - trace_page_fault_entries(regs, error_code); - __do_page_fault(regs, error_code); + trace_page_fault_entries(address, regs, error_code); + __do_page_fault(regs, error_code, address); exception_exit(prev_state); } +#endif /* CONFIG_TRACING */ |