From 2d4a71676f4d89418a0d53e60b89e8b804b390b2 Mon Sep 17 00:00:00 2001 From: Ingo Molnar Date: Fri, 20 Feb 2009 19:56:40 +0100 Subject: [PATCH] x86, mm: fault.c cleanup Impact: cleanup, no code changed Clean up various small details, which can be correctness checked automatically: - tidy up the include file section - eliminate unnecessary includes - introduce show_signal_msg() to clean up code flow - standardize the code flow - standardize comments and other style details - more cleanups, pointed out by checkpatch No code changed on either 32-bit nor 64-bit: arch/x86/mm/fault.o: text data bss dec hex filename 4632 32 24 4688 1250 fault.o.before 4632 32 24 4688 1250 fault.o.after the md5 changed due to a change in a single instruction: 2e8a8241e7f0d69706776a5a26c90bc0 fault.o.before.asm c5c3d36e725586eb74f0e10692f0193e fault.o.after.asm Because a __LINE__ reference in a WARN_ONCE() has changed. On 32-bit a few stack offsets changed - no code size difference nor any functionality difference. Cc: Linus Torvalds Signed-off-by: Ingo Molnar --- arch/x86/mm/fault.c | 546 +++++++++++++++++++++++++++----------------- 1 file changed, 331 insertions(+), 215 deletions(-) diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c index e4b9fc5001c6..351d679bf977 100644 --- a/arch/x86/mm/fault.c +++ b/arch/x86/mm/fault.c @@ -1,56 +1,59 @@ /* * Copyright (C) 1995 Linus Torvalds - * Copyright (C) 2001,2002 Andi Kleen, SuSE Labs. + * Copyright (C) 2001, 2002 Andi Kleen, SuSE Labs. */ - -#include -#include -#include -#include -#include -#include -#include -#include -#include -#include -#include #include -#include -#include -#include /* For unblank_screen() */ +#include +#include #include #include -#include /* for max_low_pfn */ -#include -#include #include #include +#include +#include +#include +#include +#include +#include +#include #include +#include #include +#include +#include +#include +#include +#include +#include +#include + +#include -#include -#include -#include -#include -#include #include +#include +#include +#include #include -#include #include +#include /* - * Page fault error code bits - * bit 0 == 0 means no page found, 1 means protection fault - * bit 1 == 0 means read, 1 means write - * bit 2 == 0 means kernel, 1 means user-mode - * bit 3 == 1 means use of reserved bit detected - * bit 4 == 1 means fault was an instruction fetch + * Page fault error code bits: + * + * bit 0 == 0: no page found 1: protection fault + * bit 1 == 0: read access 1: write access + * bit 2 == 0: kernel-mode access 1: user-mode access + * bit 3 == 1: use of reserved bit detected + * bit 4 == 1: fault was an instruction fetch */ -#define PF_PROT (1<<0) -#define PF_WRITE (1<<1) -#define PF_USER (1<<2) -#define PF_RSVD (1<<3) -#define PF_INSTR (1<<4) +enum x86_pf_error_code { + + PF_PROT = 1 << 0, + PF_WRITE = 1 << 1, + PF_USER = 1 << 2, + PF_RSVD = 1 << 3, + PF_INSTR = 1 << 4, +}; static inline int kmmio_fault(struct pt_regs *regs, unsigned long addr) { @@ -82,23 +85,27 @@ static inline int notify_page_fault(struct pt_regs *regs) } /* - * X86_32 - * Sometimes AMD Athlon/Opteron CPUs report invalid exceptions on prefetch. - * Check that here and ignore it. + * Prefetch quirks: + * + * 32-bit mode: + * + * Sometimes AMD Athlon/Opteron CPUs report invalid exceptions on prefetch. + * Check that here and ignore it. * - * X86_64 - * Sometimes the CPU reports invalid exceptions on prefetch. - * Check that here and ignore it. + * 64-bit mode: * - * Opcode checker based on code by Richard Brunner + * Sometimes the CPU reports invalid exceptions on prefetch. + * Check that here and ignore it. + * + * Opcode checker based on code by Richard Brunner. */ -static int is_prefetch(struct pt_regs *regs, unsigned long error_code, - unsigned long addr) +static int +is_prefetch(struct pt_regs *regs, unsigned long error_code, unsigned long addr) { + unsigned char *max_instr; unsigned char *instr; int scan_more = 1; int prefetch = 0; - unsigned char *max_instr; /* * If it was a exec (instruction fetch) fault on NX page, then @@ -114,9 +121,9 @@ static int is_prefetch(struct pt_regs *regs, unsigned long error_code, return 0; while (scan_more && instr < max_instr) { - unsigned char opcode; unsigned char instr_hi; unsigned char instr_lo; + unsigned char opcode; if (probe_kernel_address(instr, opcode)) break; @@ -173,15 +180,17 @@ static int is_prefetch(struct pt_regs *regs, unsigned long error_code, return prefetch; } -static void force_sig_info_fault(int si_signo, int si_code, - unsigned long address, struct task_struct *tsk) +static void +force_sig_info_fault(int si_signo, int si_code, unsigned long address, + struct task_struct *tsk) { siginfo_t info; - info.si_signo = si_signo; - info.si_errno = 0; - info.si_code = si_code; - info.si_addr = (void __user *)address; + info.si_signo = si_signo; + info.si_errno = 0; + info.si_code = si_code; + info.si_addr = (void __user *)address; + force_sig_info(si_signo, &info, tsk); } @@ -189,6 +198,7 @@ static void force_sig_info_fault(int si_signo, int si_code, static int bad_address(void *p) { unsigned long dummy; + return probe_kernel_address((unsigned long *)p, dummy); } #endif @@ -200,13 +210,14 @@ static void dump_pagetable(unsigned long address) page = read_cr3(); page = ((__typeof__(page) *) __va(page))[address >> PGDIR_SHIFT]; + #ifdef CONFIG_X86_PAE printk("*pdpt = %016Lx ", page); if ((page >> PAGE_SHIFT) < max_low_pfn && page & _PAGE_PRESENT) { page &= PAGE_MASK; page = ((__typeof__(page) *) __va(page))[(address >> PMD_SHIFT) - & (PTRS_PER_PMD - 1)]; + & (PTRS_PER_PMD - 1)]; printk(KERN_CONT "*pde = %016Lx ", page); page &= ~_PAGE_NX; } @@ -218,14 +229,15 @@ static void dump_pagetable(unsigned long address) * We must not directly access the pte in the highpte * case if the page table is located in highmem. * And let's rather not kmap-atomic the pte, just in case - * it's allocated already. + * it's allocated already: */ if ((page >> PAGE_SHIFT) < max_low_pfn && (page & _PAGE_PRESENT) && !(page & _PAGE_PSE)) { + page &= PAGE_MASK; page = ((__typeof__(page) *) __va(page))[(address >> PAGE_SHIFT) - & (PTRS_PER_PTE - 1)]; + & (PTRS_PER_PTE - 1)]; printk("*pte = %0*Lx ", sizeof(page)*2, (u64)page); } @@ -239,26 +251,38 @@ static void dump_pagetable(unsigned long address) pgd = (pgd_t *)read_cr3(); pgd = __va((unsigned long)pgd & PHYSICAL_PAGE_MASK); + pgd += pgd_index(address); - if (bad_address(pgd)) goto bad; + if (bad_address(pgd)) + goto bad; + printk("PGD %lx ", pgd_val(*pgd)); - if (!pgd_present(*pgd)) goto ret; + + if (!pgd_present(*pgd)) + goto out; pud = pud_offset(pgd, address); - if (bad_address(pud)) goto bad; + if (bad_address(pud)) + goto bad; + printk("PUD %lx ", pud_val(*pud)); if (!pud_present(*pud) || pud_large(*pud)) - goto ret; + goto out; pmd = pmd_offset(pud, address); - if (bad_address(pmd)) goto bad; + if (bad_address(pmd)) + goto bad; + printk("PMD %lx ", pmd_val(*pmd)); - if (!pmd_present(*pmd) || pmd_large(*pmd)) goto ret; + if (!pmd_present(*pmd) || pmd_large(*pmd)) + goto out; pte = pte_offset_kernel(pmd, address); - if (bad_address(pte)) goto bad; + if (bad_address(pte)) + goto bad; + printk("PTE %lx", pte_val(*pte)); -ret: +out: printk("\n"); return; bad: @@ -285,7 +309,6 @@ static inline pmd_t *vmalloc_sync_one(pgd_t *pgd, unsigned long address) * and redundant with the set_pmd() on non-PAE. As would * set_pud. */ - pud = pud_offset(pgd, address); pud_k = pud_offset(pgd_k, address); if (!pud_present(*pud_k)) @@ -295,11 +318,14 @@ static inline pmd_t *vmalloc_sync_one(pgd_t *pgd, unsigned long address) pmd_k = pmd_offset(pud_k, address); if (!pmd_present(*pmd_k)) return NULL; + if (!pmd_present(*pmd)) { set_pmd(pmd, *pmd_k); arch_flush_lazy_mmu_mode(); - } else + } else { BUG_ON(pmd_page(*pmd) != pmd_page(*pmd_k)); + } + return pmd_k; } #endif @@ -312,29 +338,37 @@ KERN_ERR "******* Please consider a BIOS update.\n" KERN_ERR "******* Disabling USB legacy in the BIOS may also help.\n"; #endif -/* Workaround for K8 erratum #93 & buggy BIOS. - BIOS SMM functions are required to use a specific workaround - to avoid corruption of the 64bit RIP register on C stepping K8. - A lot of BIOS that didn't get tested properly miss this. - The OS sees this as a page fault with the upper 32bits of RIP cleared. - Try to work around it here. - Note we only handle faults in kernel here. - Does nothing for X86_32 +/* + * Workaround for K8 erratum #93 & buggy BIOS. + * + * BIOS SMM functions are required to use a specific workaround + * to avoid corruption of the 64bit RIP register on C stepping K8. + * + * A lot of BIOS that didn't get tested properly miss this. + * + * The OS sees this as a page fault with the upper 32bits of RIP cleared. + * Try to work around it here. + * + * Note we only handle faults in kernel here. + * Does nothing on 32-bit. */ static int is_errata93(struct pt_regs *regs, unsigned long address) { #ifdef CONFIG_X86_64 - static int warned; + static int once; + if (address != regs->ip) return 0; + if ((address >> 32) != 0) return 0; + address |= 0xffffffffUL << 32; if ((address >= (u64)_stext && address <= (u64)_etext) || (address >= MODULES_VADDR && address <= MODULES_END)) { - if (!warned) { + if (!once) { printk(errata93_warning); - warned = 1; + once = 1; } regs->ip = address; return 1; @@ -344,16 +378,17 @@ static int is_errata93(struct pt_regs *regs, unsigned long address) } /* - * Work around K8 erratum #100 K8 in compat mode occasionally jumps to illegal - * addresses >4GB. We catch this in the page fault handler because these - * addresses are not reachable. Just detect this case and return. Any code + * Work around K8 erratum #100 K8 in compat mode occasionally jumps + * to illegal addresses >4GB. + * + * We catch this in the page fault handler because these addresses + * are not reachable. Just detect this case and return. Any code * segment in LDT is compatibility mode. */ static int is_errata100(struct pt_regs *regs, unsigned long address) { #ifdef CONFIG_X86_64 - if ((regs->cs == __USER32_CS || (regs->cs & (1<<2))) && - (address >> 32)) + if ((regs->cs == __USER32_CS || (regs->cs & (1<<2))) && (address >> 32)) return 1; #endif return 0; @@ -363,8 +398,9 @@ static int is_f00f_bug(struct pt_regs *regs, unsigned long address) { #ifdef CONFIG_X86_F00F_BUG unsigned long nr; + /* - * Pentium F0 0F C7 C8 bug workaround. + * Pentium F0 0F C7 C8 bug workaround: */ if (boot_cpu_data.f00f_bug) { nr = (address - idt_descr.address) >> 3; @@ -378,8 +414,9 @@ static int is_f00f_bug(struct pt_regs *regs, unsigned long address) return 0; } -static void show_fault_oops(struct pt_regs *regs, unsigned long error_code, - unsigned long address) +static void +show_fault_oops(struct pt_regs *regs, unsigned long error_code, + unsigned long address) { #ifdef CONFIG_X86_32 if (!oops_may_print()) @@ -389,12 +426,14 @@ static void show_fault_oops(struct pt_regs *regs, unsigned long error_code, #ifdef CONFIG_X86_PAE if (error_code & PF_INSTR) { unsigned int level; + pte_t *pte = lookup_address(address, &level); - if (pte && pte_present(*pte) && !pte_exec(*pte)) + if (pte && pte_present(*pte) && !pte_exec(*pte)) { printk(KERN_CRIT "kernel tried to execute " "NX-protected page - exploit attempt? " "(uid: %d)\n", current_uid()); + } } #endif @@ -403,34 +442,45 @@ static void show_fault_oops(struct pt_regs *regs, unsigned long error_code, printk(KERN_CONT "NULL pointer dereference"); else printk(KERN_CONT "paging request"); + printk(KERN_CONT " at %p\n", (void *) address); printk(KERN_ALERT "IP:"); printk_address(regs->ip, 1); + dump_pagetable(address); } #ifdef CONFIG_X86_64 -static noinline void pgtable_bad(struct pt_regs *regs, - unsigned long error_code, unsigned long address) +static noinline void +pgtable_bad(struct pt_regs *regs, unsigned long error_code, + unsigned long address) { - unsigned long flags = oops_begin(); - int sig = SIGKILL; - struct task_struct *tsk = current; + struct task_struct *tsk; + unsigned long flags; + int sig; + + flags = oops_begin(); + tsk = current; + sig = SIGKILL; printk(KERN_ALERT "%s: Corrupted page table at address %lx\n", tsk->comm, address); dump_pagetable(address); - tsk->thread.cr2 = address; - tsk->thread.trap_no = 14; - tsk->thread.error_code = error_code; + + tsk->thread.cr2 = address; + tsk->thread.trap_no = 14; + tsk->thread.error_code = error_code; + if (__die("Bad pagetable", regs, error_code)) sig = 0; + oops_end(flags, regs, sig); } #endif -static noinline void no_context(struct pt_regs *regs, - unsigned long error_code, unsigned long address) +static noinline void +no_context(struct pt_regs *regs, unsigned long error_code, + unsigned long address) { struct task_struct *tsk = current; unsigned long *stackend; @@ -440,18 +490,20 @@ static noinline void no_context(struct pt_regs *regs, int sig; #endif - /* Are we prepared to handle this kernel fault? */ + /* Are we prepared to handle this kernel fault? */ if (fixup_exception(regs)) return; /* - * X86_32 - * Valid to do another page fault here, because if this fault - * had been triggered by is_prefetch fixup_exception would have - * handled it. + * 32-bit: + * + * Valid to do another page fault here, because if this fault + * had been triggered by is_prefetch fixup_exception would have + * handled it. + * + * 64-bit: * - * X86_64 - * Hall of shame of CPU/BIOS bugs. + * Hall of shame of CPU/BIOS bugs. */ if (is_prefetch(regs, error_code, address)) return; @@ -461,7 +513,7 @@ static noinline void no_context(struct pt_regs *regs, /* * Oops. The kernel tried to access some bad page. We'll have to - * terminate things with extreme prejudice. + * terminate things with extreme prejudice: */ #ifdef CONFIG_X86_32 bust_spinlocks(1); @@ -471,7 +523,7 @@ static noinline void no_context(struct pt_regs *regs, show_fault_oops(regs, error_code, address); - stackend = end_of_stack(tsk); + stackend = end_of_stack(tsk); if (*stackend != STACK_END_MAGIC) printk(KERN_ALERT "Thread overran stack, or stack corrupted\n"); @@ -487,28 +539,54 @@ static noinline void no_context(struct pt_regs *regs, sig = SIGKILL; if (__die("Oops", regs, error_code)) sig = 0; + /* Executive summary in case the body of the oops scrolled away */ printk(KERN_EMERG "CR2: %016lx\n", address); + oops_end(flags, regs, sig); #endif } -static void __bad_area_nosemaphore(struct pt_regs *regs, - unsigned long error_code, unsigned long address, - int si_code) +/* + * Print out info about fatal segfaults, if the show_unhandled_signals + * sysctl is set: + */ +static inline void +show_signal_msg(struct pt_regs *regs, unsigned long error_code, + unsigned long address, struct task_struct *tsk) +{ + if (!unhandled_signal(tsk, SIGSEGV)) + return; + + if (!printk_ratelimit()) + return; + + printk(KERN_CONT "%s%s[%d]: segfault at %lx ip %p sp %p error %lx", + task_pid_nr(tsk) > 1 ? KERN_INFO : KERN_EMERG, + tsk->comm, task_pid_nr(tsk), address, + (void *)regs->ip, (void *)regs->sp, error_code); + + print_vma_addr(KERN_CONT " in ", regs->ip); + + printk(KERN_CONT "\n"); +} + +static void +__bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code, + unsigned long address, int si_code) { struct task_struct *tsk = current; /* User mode accesses just cause a SIGSEGV */ if (error_code & PF_USER) { /* - * It's possible to have interrupts off here. + * It's possible to have interrupts off here: */ local_irq_enable(); /* * Valid to do another page fault here because this one came - * from user space. + * from user space: */ if (is_prefetch(regs, error_code, address)) return; @@ -516,22 +594,16 @@ static void __bad_area_nosemaphore(struct pt_regs *regs, if (is_errata100(regs, address)) return; - if (show_unhandled_signals && unhandled_signal(tsk, SIGSEGV) && - printk_ratelimit()) { - printk( - "%s%s[%d]: segfault at %lx ip %p sp %p error %lx", - task_pid_nr(tsk) > 1 ? KERN_INFO : KERN_EMERG, - tsk->comm, task_pid_nr(tsk), address, - (void *) regs->ip, (void *) regs->sp, error_code); - print_vma_addr(" in ", regs->ip); - printk("\n"); - } + if (unlikely(show_unhandled_signals)) + show_signal_msg(regs, error_code, address, tsk); + + /* Kernel addresses are always protection faults: */ + tsk->thread.cr2 = address; + tsk->thread.error_code = error_code | (address >= TASK_SIZE); + tsk->thread.trap_no = 14; - tsk->thread.cr2 = address; - /* Kernel addresses are always protection faults */ - tsk->thread.error_code = error_code | (address >= TASK_SIZE); - tsk->thread.trap_no = 14; force_sig_info_fault(SIGSEGV, si_code, address, tsk); + return; } @@ -541,15 +613,16 @@ static void __bad_area_nosemaphore(struct pt_regs *regs, no_context(regs, error_code, address); } -static noinline void bad_area_nosemaphore(struct pt_regs *regs, - unsigned long error_code, unsigned long address) +static noinline void +bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code, + unsigned long address) { __bad_area_nosemaphore(regs, error_code, address, SEGV_MAPERR); } -static void __bad_area(struct pt_regs *regs, - unsigned long error_code, unsigned long address, - int si_code) +static void +__bad_area(struct pt_regs *regs, unsigned long error_code, + unsigned long address, int si_code) { struct mm_struct *mm = current->mm; @@ -562,67 +635,77 @@ static void __bad_area(struct pt_regs *regs, __bad_area_nosemaphore(regs, error_code, address, si_code); } -static noinline void bad_area(struct pt_regs *regs, - unsigned long error_code, unsigned long address) +static noinline void +bad_area(struct pt_regs *regs, unsigned long error_code, unsigned long address) { __bad_area(regs, error_code, address, SEGV_MAPERR); } -static noinline void bad_area_access_error(struct pt_regs *regs, - unsigned long error_code, unsigned long address) +static noinline void +bad_area_access_error(struct pt_regs *regs, unsigned long error_code, + unsigned long address) { __bad_area(regs, error_code, address, SEGV_ACCERR); } /* TODO: fixup for "mm-invoke-oom-killer-from-page-fault.patch" */ -static void out_of_memory(struct pt_regs *regs, - unsigned long error_code, unsigned long address) +static void +out_of_memory(struct pt_regs *regs, unsigned long error_code, + unsigned long address) { /* * We ran out of memory, call the OOM killer, and return the userspace - * (which will retry the fault, or kill us if we got oom-killed). + * (which will retry the fault, or kill us if we got oom-killed): */ up_read(¤t->mm->mmap_sem); + pagefault_out_of_memory(); } -static void do_sigbus(struct pt_regs *regs, - unsigned long error_code, unsigned long address) +static void +do_sigbus(struct pt_regs *regs, unsigned long error_code, unsigned long address) { struct task_struct *tsk = current; struct mm_struct *mm = tsk->mm; up_read(&mm->mmap_sem); - /* Kernel mode? Handle exceptions or die */ + /* Kernel mode? Handle exceptions or die: */ if (!(error_code & PF_USER)) no_context(regs, error_code, address); + #ifdef CONFIG_X86_32 - /* User space => ok to do another page fault */ + /* User space => ok to do another page fault: */ if (is_prefetch(regs, error_code, address)) return; #endif - tsk->thread.cr2 = address; - tsk->thread.error_code = error_code; - tsk->thread.trap_no = 14; + + tsk->thread.cr2 = address; + tsk->thread.error_code = error_code; + tsk->thread.trap_no = 14; + force_sig_info_fault(SIGBUS, BUS_ADRERR, address, tsk); } -static noinline void mm_fault_error(struct pt_regs *regs, - unsigned long error_code, unsigned long address, unsigned int fault) +static noinline void +mm_fault_error(struct pt_regs *regs, unsigned long error_code, + unsigned long address, unsigned int fault) { - if (fault & VM_FAULT_OOM) + if (fault & VM_FAULT_OOM) { out_of_memory(regs, error_code, address); - else if (fault & VM_FAULT_SIGBUS) - do_sigbus(regs, error_code, address); - else - BUG(); + } else { + if (fault & VM_FAULT_SIGBUS) + do_sigbus(regs, error_code, address); + else + BUG(); + } } static int spurious_fault_check(unsigned long error_code, pte_t *pte) { if ((error_code & PF_WRITE) && !pte_write(*pte)) return 0; + if ((error_code & PF_INSTR) && !pte_exec(*pte)) return 0; @@ -630,16 +713,19 @@ static int spurious_fault_check(unsigned long error_code, pte_t *pte) } /* - * Handle a spurious fault caused by a stale TLB entry. This allows - * us to lazily refresh the TLB when increasing the permissions of a - * kernel page (RO -> RW or NX -> X). Doing it eagerly is very - * expensive since that implies doing a full cross-processor TLB - * flush, even if no stale TLB entries exist on other processors. + * Handle a spurious fault caused by a stale TLB entry. + * + * This allows us to lazily refresh the TLB when increasing the + * permissions of a kernel page (RO -> RW or NX -> X). Doing it + * eagerly is very expensive since that implies doing a full + * cross-processor TLB flush, even if no stale TLB entries exist + * on other processors. + * * There are no security implications to leaving a stale TLB when * increasing the permissions on a page. */ -static noinline int spurious_fault(unsigned long error_code, - unsigned long address) +static noinline int +spurious_fault(unsigned long error_code, unsigned long address) { pgd_t *pgd; pud_t *pud; @@ -678,20 +764,23 @@ static noinline int spurious_fault(unsigned long error_code, return 0; /* - * Make sure we have permissions in PMD - * If not, then there's a bug in the page tables. + * Make sure we have permissions in PMD. + * If not, then there's a bug in the page tables: */ ret = spurious_fault_check(error_code, (pte_t *) pmd); WARN_ONCE(!ret, "PMD has incorrect permission bits\n"); + return ret; } /* - * X86_32 - * Handle a fault on the vmalloc or module mapping area + * 32-bit: + * + * Handle a fault on the vmalloc or module mapping area * - * X86_64 - * Handle a fault on the vmalloc area + * 64-bit: + * + * Handle a fault on the vmalloc area * * This assumes no large pages in there. */ @@ -702,7 +791,7 @@ static noinline int vmalloc_fault(unsigned long address) pmd_t *pmd_k; pte_t *pte_k; - /* Make sure we are in vmalloc area */ + /* Make sure we are in vmalloc area: */ if (!(address >= VMALLOC_START && address < VMALLOC_END)) return -1; @@ -717,9 +806,11 @@ static noinline int vmalloc_fault(unsigned long address) pmd_k = vmalloc_sync_one(__va(pgd_paddr), address); if (!pmd_k) return -1; + pte_k = pte_offset_kernel(pmd_k, address); if (!pte_present(*pte_k)) return -1; + return 0; #else pgd_t *pgd, *pgd_ref; @@ -727,69 +818,84 @@ static noinline int vmalloc_fault(unsigned long address) pmd_t *pmd, *pmd_ref; pte_t *pte, *pte_ref; - /* Make sure we are in vmalloc area */ + /* Make sure we are in vmalloc area: */ if (!(address >= VMALLOC_START && address < VMALLOC_END)) return -1; - /* Copy kernel mappings over when needed. This can also - happen within a race in page table update. In the later - case just flush. */ - + /* + * Copy kernel mappings over when needed. This can also + * happen within a race in page table update. In the later + * case just flush: + */ pgd = pgd_offset(current->active_mm, address); pgd_ref = pgd_offset_k(address); if (pgd_none(*pgd_ref)) return -1; + if (pgd_none(*pgd)) set_pgd(pgd, *pgd_ref); else BUG_ON(pgd_page_vaddr(*pgd) != pgd_page_vaddr(*pgd_ref)); - /* Below here mismatches are bugs because these lower tables - are shared */ + /* + * Below here mismatches are bugs because these lower tables + * are shared: + */ pud = pud_offset(pgd, address); pud_ref = pud_offset(pgd_ref, address); if (pud_none(*pud_ref)) return -1; + if (pud_none(*pud) || pud_page_vaddr(*pud) != pud_page_vaddr(*pud_ref)) BUG(); + pmd = pmd_offset(pud, address); pmd_ref = pmd_offset(pud_ref, address); if (pmd_none(*pmd_ref)) return -1; + if (pmd_none(*pmd) || pmd_page(*pmd) != pmd_page(*pmd_ref)) BUG(); + pte_ref = pte_offset_kernel(pmd_ref, address); if (!pte_present(*pte_ref)) return -1; + pte = pte_offset_kernel(pmd, address); - /* Don't use pte_page here, because the mappings can point - outside mem_map, and the NUMA hash lookup cannot handle - that. */ + + /* + * Don't use pte_page here, because the mappings can point + * outside mem_map, and the NUMA hash lookup cannot handle + * that: + */ if (!pte_present(*pte) || pte_pfn(*pte) != pte_pfn(*pte_ref)) BUG(); + return 0; #endif } int show_unhandled_signals = 1; -static inline int access_error(unsigned long error_code, int write, - struct vm_area_struct *vma) +static inline int +access_error(unsigned long error_code, int write, struct vm_area_struct *vma) { if (write) { - /* write, present and write, not present */ + /* write, present and write, not present: */ if (unlikely(!(vma->vm_flags & VM_WRITE))) return 1; - } else if (unlikely(error_code & PF_PROT)) { - /* read, present */ - return 1; - } else { - /* read, not present */ - if (unlikely(!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE)))) - return 1; + return 0; } + /* read, present: */ + if (unlikely(error_code & PF_PROT)) + return 1; + + /* read, not present: */ + if (unlikely(!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE)))) + return 1; + return 0; } @@ -797,9 +903,9 @@ static int fault_in_kernel_space(unsigned long address) { #ifdef CONFIG_X86_32 return address >= TASK_SIZE; -#else /* !CONFIG_X86_32 */ +#else return address >= TASK_SIZE64; -#endif /* CONFIG_X86_32 */ +#endif } /* @@ -812,18 +918,19 @@ asmlinkage #endif void __kprobes 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; - struct vm_area_struct *vma; int write; int fault; tsk = current; mm = tsk->mm; + prefetchw(&mm->mmap_sem); - /* get the address */ + /* Get the faulting address: */ address = read_cr2(); if (unlikely(kmmio_fault(regs, address))) @@ -847,22 +954,23 @@ void __kprobes do_page_fault(struct pt_regs *regs, unsigned long error_code) vmalloc_fault(address) >= 0) return; - /* Can handle a stale RO->RW TLB */ + /* Can handle a stale RO->RW TLB: */ if (spurious_fault(error_code, address)) return; - /* kprobes don't want to hook the spurious faults. */ + /* kprobes don't want to hook the spurious faults: */ if (notify_page_fault(regs)) return; /* * Don't take the mm semaphore here. If we fixup a prefetch - * fault we could otherwise deadlock. + * fault we could otherwise deadlock: */ bad_area_nosemaphore(regs, error_code, address); + return; } - /* kprobes don't want to hook the spurious faults. */ + /* kprobes don't want to hook the spurious faults: */ if (unlikely(notify_page_fault(regs))) return; /* @@ -870,13 +978,15 @@ void __kprobes do_page_fault(struct pt_regs *regs, unsigned long error_code) * vmalloc fault has been handled. * * User-mode registers count as a user access even for any - * potential system fault or CPU buglet. + * potential system fault or CPU buglet: */ if (user_mode_vm(regs)) { local_irq_enable(); error_code |= PF_USER; - } else if (regs->flags & X86_EFLAGS_IF) - local_irq_enable(); + } else { + if (regs->flags & X86_EFLAGS_IF) + local_irq_enable(); + } #ifdef CONFIG_X86_64 if (unlikely(error_code & PF_RSVD)) @@ -884,8 +994,8 @@ void __kprobes do_page_fault(struct pt_regs *regs, unsigned long error_code) #endif /* - * If we're in an interrupt, have no user context or are running in an - * atomic region then we must not take the fault. + * If we're in an interrupt, have no user context or are running + * in an atomic region then we must not take the fault: */ if (unlikely(in_atomic() || !mm)) { bad_area_nosemaphore(regs, error_code, address); @@ -894,19 +1004,19 @@ void __kprobes do_page_fault(struct pt_regs *regs, unsigned long error_code) /* * When running in the kernel we expect faults to occur only to - * addresses in user space. All other faults represent errors in the - * kernel and should generate an OOPS. Unfortunately, in the case of an - * erroneous fault occurring in a code path which already holds mmap_sem - * we will deadlock attempting to validate the fault against the - * address space. Luckily the kernel only validly references user - * space from well defined areas of code, which are listed in the - * exceptions table. + * addresses in user space. All other faults represent errors in + * the kernel and should generate an OOPS. Unfortunately, in the + * case of an erroneous fault occurring in a code path which already + * holds mmap_sem we will deadlock attempting to validate the fault + * against the address space. Luckily the kernel only validly + * references user space from well defined areas of code, which are + * listed in the exceptions table. * * As the vast majority of faults will be valid we will only perform - * the source reference check when there is a possibility of a deadlock. - * Attempt to lock the address space, if we cannot we then validate the - * source. If this is invalid we can skip the address space check, - * thus avoiding the deadlock. + * the source reference check when there is a possibility of a + * deadlock. Attempt to lock the address space, if we cannot we then + * validate the source. If this is invalid we can skip the address + * space check, thus avoiding the deadlock: */ if (unlikely(!down_read_trylock(&mm->mmap_sem))) { if ((error_code & PF_USER) == 0 && @@ -917,8 +1027,9 @@ void __kprobes do_page_fault(struct pt_regs *regs, unsigned long error_code) down_read(&mm->mmap_sem); } else { /* - * The above down_read_trylock() might have succeeded in which - * case we'll have missed the might_sleep() from down_read(). + * The above down_read_trylock() might have succeeded in + * which case we'll have missed the might_sleep() from + * down_read(): */ might_sleep(); } @@ -938,7 +1049,7 @@ void __kprobes do_page_fault(struct pt_regs *regs, unsigned long error_code) /* * Accessing the stack below %sp is always a bug. * The large cushion allows instructions like enter - * and pusha to work. ("enter $65535,$31" pushes + * and pusha to work. ("enter $65535, $31" pushes * 32 pointers and then decrements %sp by 65535.) */ if (unlikely(address + 65536 + 32 * sizeof(unsigned long) < regs->sp)) { @@ -957,6 +1068,7 @@ void __kprobes do_page_fault(struct pt_regs *regs, unsigned long error_code) */ good_area: write = error_code & PF_WRITE; + if (unlikely(access_error(error_code, write, vma))) { bad_area_access_error(regs, error_code, address); return; @@ -965,13 +1077,15 @@ good_area: /* * If for any reason at all we couldn't handle the fault, * make sure we exit gracefully rather than endlessly redo - * the fault. + * the fault: */ fault = handle_mm_fault(mm, vma, address, write); + if (unlikely(fault & VM_FAULT_ERROR)) { mm_fault_error(regs, error_code, address, fault); return; } + if (fault & VM_FAULT_MAJOR) tsk->maj_flt++; else @@ -1004,13 +1118,13 @@ void vmalloc_sync_all(void) for (address = VMALLOC_START & PMD_MASK; address >= TASK_SIZE && address < FIXADDR_TOP; address += PMD_SIZE) { + unsigned long flags; struct page *page; spin_lock_irqsave(&pgd_lock, flags); list_for_each_entry(page, &pgd_list, lru) { - if (!vmalloc_sync_one(page_address(page), - address)) + if (!vmalloc_sync_one(page_address(page), address)) break; } spin_unlock_irqrestore(&pgd_lock, flags); @@ -1018,12 +1132,14 @@ void vmalloc_sync_all(void) #else /* CONFIG_X86_64 */ for (address = VMALLOC_START & PGDIR_MASK; address <= VMALLOC_END; address += PGDIR_SIZE) { + const pgd_t *pgd_ref = pgd_offset_k(address); unsigned long flags; struct page *page; if (pgd_none(*pgd_ref)) continue; + spin_lock_irqsave(&pgd_lock, flags); list_for_each_entry(page, &pgd_list, lru) { pgd_t *pgd; -- 2.34.1