diff options
Diffstat (limited to 'arch/x86/kernel/traps.c')
| -rw-r--r-- | arch/x86/kernel/traps.c | 119 |
1 files changed, 108 insertions, 11 deletions
diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c index 1b9177b93433..bcf1dedc1d00 100644 --- a/arch/x86/kernel/traps.c +++ b/arch/x86/kernel/traps.c @@ -31,6 +31,7 @@ #include <linux/kexec.h> #include <linux/sched.h> #include <linux/sched/task_stack.h> +#include <linux/static_call.h> #include <linux/timer.h> #include <linux/init.h> #include <linux/bug.h> @@ -102,25 +103,37 @@ __always_inline int is_valid_bugaddr(unsigned long addr) * UBSan{0}: 67 0f b9 00 ud1 (%eax),%eax * UBSan{10}: 67 0f b9 40 10 ud1 0x10(%eax),%eax * static_call: 0f b9 cc ud1 %esp,%ecx + * __WARN_trap: 67 48 0f b9 3a ud1 (%edx),%reg * - * Notably UBSAN uses EAX, static_call uses ECX. + * Notable, since __WARN_trap can use all registers, the distinction between + * UD1 users is through R/M. */ __always_inline int decode_bug(unsigned long addr, s32 *imm, int *len) { unsigned long start = addr; + u8 v, reg, rm, rex = 0; + int type = BUG_UD1; bool lock = false; - u8 v; if (addr < TASK_SIZE_MAX) return BUG_NONE; - v = *(u8 *)(addr++); - if (v == INSN_ASOP) + for (;;) { v = *(u8 *)(addr++); + if (v == INSN_ASOP) + continue; - if (v == INSN_LOCK) { - lock = true; - v = *(u8 *)(addr++); + if (v == INSN_LOCK) { + lock = true; + continue; + } + + if ((v & 0xf0) == 0x40) { + rex = v; + continue; + } + + break; } switch (v) { @@ -156,18 +169,33 @@ __always_inline int decode_bug(unsigned long addr, s32 *imm, int *len) if (X86_MODRM_MOD(v) != 3 && X86_MODRM_RM(v) == 4) addr++; /* SIB */ + reg = X86_MODRM_REG(v) + 8*!!X86_REX_R(rex); + rm = X86_MODRM_RM(v) + 8*!!X86_REX_B(rex); + /* Decode immediate, if present */ switch (X86_MODRM_MOD(v)) { case 0: if (X86_MODRM_RM(v) == 5) - addr += 4; /* RIP + disp32 */ + addr += 4; /* RIP + disp32 */ + + if (rm == 0) /* (%eax) */ + type = BUG_UD1_UBSAN; + + if (rm == 2) { /* (%edx) */ + *imm = reg; + type = BUG_UD1_WARN; + } break; case 1: *imm = *(s8 *)addr; addr += 1; + if (rm == 0) /* (%eax) */ + type = BUG_UD1_UBSAN; break; case 2: *imm = *(s32 *)addr; addr += 4; + if (rm == 0) /* (%eax) */ + type = BUG_UD1_UBSAN; break; case 3: break; @@ -176,12 +204,76 @@ __always_inline int decode_bug(unsigned long addr, s32 *imm, int *len) /* record instruction length */ *len = addr - start; - if (X86_MODRM_REG(v) == 0) /* EAX */ - return BUG_UD1_UBSAN; + return type; +} - return BUG_UD1; +static inline unsigned long pt_regs_val(struct pt_regs *regs, int nr) +{ + int offset = pt_regs_offset(regs, nr); + if (WARN_ON_ONCE(offset < -0)) + return 0; + return *((unsigned long *)((void *)regs + offset)); } +#ifdef HAVE_ARCH_BUG_FORMAT_ARGS +DEFINE_STATIC_CALL(WARN_trap, __WARN_trap); +EXPORT_STATIC_CALL_TRAMP(WARN_trap); + +/* + * Create a va_list from an exception context. + */ +void *__warn_args(struct arch_va_list *args, struct pt_regs *regs) +{ + /* + * Register save area; populate with function call argument registers + */ + args->regs[0] = regs->di; + args->regs[1] = regs->si; + args->regs[2] = regs->dx; + args->regs[3] = regs->cx; + args->regs[4] = regs->r8; + args->regs[5] = regs->r9; + + /* + * From the ABI document: + * + * @gp_offset - the element holds the offset in bytes from + * reg_save_area to the place where the next available general purpose + * argument register is saved. In case all argument registers have + * been exhausted, it is set to the value 48 (6*8). + * + * @fp_offset - the element holds the offset in bytes from + * reg_save_area to the place where the next available floating point + * argument is saved. In case all argument registers have been + * exhausted, it is set to the value 176 (6*8 + 8*16) + * + * @overflow_arg_area - this pointer is used to fetch arguments passed + * on the stack. It is initialized with the address of the first + * argument passed on the stack, if any, and then always updated to + * point to the start of the next argument on the stack. + * + * @reg_save_area - the element points to the start of the register + * save area. + * + * Notably the vararg starts with the second argument and there are no + * floating point arguments in the kernel. + */ + args->args.gp_offset = 1*8; + args->args.fp_offset = 6*8 + 8*16; + args->args.reg_save_area = &args->regs; + args->args.overflow_arg_area = (void *)regs->sp; + + /* + * If the exception came from __WARN_trap, there is a return + * address on the stack, skip that. This is why any __WARN_trap() + * caller must inhibit tail-call optimization. + */ + if ((void *)regs->ip == &__WARN_trap) + args->args.overflow_arg_area += 8; + + return &args->args; +} +#endif /* HAVE_ARCH_BUG_FORMAT */ static nokprobe_inline int do_trap_no_signal(struct task_struct *tsk, int trapnr, const char *str, @@ -334,6 +426,11 @@ static noinstr bool handle_bug(struct pt_regs *regs) raw_local_irq_enable(); switch (ud_type) { + case BUG_UD1_WARN: + if (report_bug_entry((void *)pt_regs_val(regs, ud_imm), regs) == BUG_TRAP_TYPE_WARN) + handled = true; + break; + case BUG_UD2: if (report_bug(regs->ip, regs) == BUG_TRAP_TYPE_WARN) { handled = true; |