diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c index ca38bd0472f2..f5efbdba2b6d 100644 --- a/arch/x86/mm/fault.c +++ b/arch/x86/mm/fault.c @@ -27,6 +27,7 @@ #include /* struct vm86 */ #include /* vma_pkey() */ #include /* efi_recover_from_page_fault()*/ +#include /* store_idt(), ... */ #define CREATE_TRACE_POINTS #include @@ -571,10 +572,53 @@ static int is_f00f_bug(struct pt_regs *regs, unsigned long address) return 0; } +static void show_ldttss(const struct desc_ptr *gdt, const char *name, u16 index) +{ + u32 offset = (index >> 3) * sizeof(struct desc_struct); + unsigned long addr; + struct ldttss_desc desc; + + if (index == 0) { + pr_alert("%s: NULL\n", name); + return; + } + + if (offset + sizeof(struct ldttss_desc) >= gdt->size) { + pr_alert("%s: 0x%hx -- out of bounds\n", name, index); + return; + } + + if (probe_kernel_read(&desc, (void *)(gdt->address + offset), + sizeof(struct ldttss_desc))) { + pr_alert("%s: 0x%hx -- GDT entry is not readable\n", + name, index); + return; + } + + addr = desc.base0 | (desc.base1 << 16) | (desc.base2 << 24); +#ifdef CONFIG_X86_64 + addr |= ((u64)desc.base3 << 32); +#endif + pr_alert("%s: 0x%hx -- base=0x%lx limit=0x%x\n", + name, index, addr, (desc.limit0 | (desc.limit1 << 16))); +} + +static void errstr(unsigned long ec, char *buf, unsigned long mask, + const char *txt) +{ + if (ec & mask) { + if (buf[0]) + strcat(buf, " "); + strcat(buf, txt); + } +} + static void show_fault_oops(struct pt_regs *regs, unsigned long error_code, unsigned long address) { + char errtxt[64]; + if (!oops_may_print()) return; @@ -602,6 +646,46 @@ show_fault_oops(struct pt_regs *regs, unsigned long error_code, address < PAGE_SIZE ? "NULL pointer dereference" : "paging request", (void *)address); + errtxt[0] = 0; + errstr(error_code, errtxt, X86_PF_PROT, "PROT"); + errstr(error_code, errtxt, X86_PF_WRITE, "WRITE"); + errstr(error_code, errtxt, X86_PF_USER, "USER"); + errstr(error_code, errtxt, X86_PF_RSVD, "RSVD"); + errstr(error_code, errtxt, X86_PF_INSTR, "INSTR"); + errstr(error_code, errtxt, X86_PF_PK, "PK"); + pr_alert("HW error: %s\n", error_code ? errtxt : + "normal kernel read fault"); + if (!(error_code & X86_PF_USER) && user_mode(regs)) { + struct desc_ptr idt, gdt; + u16 ldtr, tr; + + pr_alert("This was a system access from user code\n"); + + /* + * This can happen for quite a few reasons. The more obvious + * ones are faults accessing the GDT, or LDT. Perhaps + * surprisingly, if the CPU tries to deliver a benign or + * contributory exception from user code and gets a page fault + * during delivery, the page fault can be delivered as though + * it originated directly from user code. This could happen + * due to wrong permissions on the IDT, GDT, LDT, TSS, or + * kernel or IST stack. + */ + store_idt(&idt); + + /* Usable even on Xen PV -- it's just slow. */ + native_store_gdt(&gdt); + + pr_alert("IDT: 0x%lx (limit=0x%hx) GDT: 0x%lx (limit=0x%hx)\n", + idt.address, idt.size, gdt.address, gdt.size); + + store_ldt(ldtr); + show_ldttss(&gdt, "LDTR", ldtr); + + store_tr(tr); + show_ldttss(&gdt, "TR", tr); + } + dump_pagetable(address); }