diff options
Diffstat (limited to 'arch/x86/kernel/unwind_orc.c')
| -rw-r--r-- | arch/x86/kernel/unwind_orc.c | 676 |
1 files changed, 676 insertions, 0 deletions
diff --git a/arch/x86/kernel/unwind_orc.c b/arch/x86/kernel/unwind_orc.c new file mode 100644 index 000000000..4f17c1c94 --- /dev/null +++ b/arch/x86/kernel/unwind_orc.c @@ -0,0 +1,676 @@ +#include <linux/module.h> +#include <linux/sort.h> +#include <asm/ptrace.h> +#include <asm/stacktrace.h> +#include <asm/unwind.h> +#include <asm/orc_types.h> +#include <asm/orc_lookup.h> + +#define orc_warn(fmt, ...) \ + printk_deferred_once(KERN_WARNING pr_fmt("WARNING: " fmt), ##__VA_ARGS__) + +extern int __start_orc_unwind_ip[]; +extern int __stop_orc_unwind_ip[]; +extern struct orc_entry __start_orc_unwind[]; +extern struct orc_entry __stop_orc_unwind[]; + +static DEFINE_MUTEX(sort_mutex); +int *cur_orc_ip_table = __start_orc_unwind_ip; +struct orc_entry *cur_orc_table = __start_orc_unwind; + +unsigned int lookup_num_blocks; +bool orc_init; + +static inline unsigned long orc_ip(const int *ip) +{ + return (unsigned long)ip + *ip; +} + +static struct orc_entry *__orc_find(int *ip_table, struct orc_entry *u_table, + unsigned int num_entries, unsigned long ip) +{ + int *first = ip_table; + int *last = ip_table + num_entries - 1; + int *mid = first, *found = first; + + if (!num_entries) + return NULL; + + /* + * Do a binary range search to find the rightmost duplicate of a given + * starting address. Some entries are section terminators which are + * "weak" entries for ensuring there are no gaps. They should be + * ignored when they conflict with a real entry. + */ + while (first <= last) { + mid = first + ((last - first) / 2); + + if (orc_ip(mid) <= ip) { + found = mid; + first = mid + 1; + } else + last = mid - 1; + } + + return u_table + (found - ip_table); +} + +#ifdef CONFIG_MODULES +static struct orc_entry *orc_module_find(unsigned long ip) +{ + struct module *mod; + + mod = __module_address(ip); + if (!mod || !mod->arch.orc_unwind || !mod->arch.orc_unwind_ip) + return NULL; + return __orc_find(mod->arch.orc_unwind_ip, mod->arch.orc_unwind, + mod->arch.num_orcs, ip); +} +#else +static struct orc_entry *orc_module_find(unsigned long ip) +{ + return NULL; +} +#endif + +#ifdef CONFIG_DYNAMIC_FTRACE +static struct orc_entry *orc_find(unsigned long ip); + +/* + * Ftrace dynamic trampolines do not have orc entries of their own. + * But they are copies of the ftrace entries that are static and + * defined in ftrace_*.S, which do have orc entries. + * + * If the undwinder comes across a ftrace trampoline, then find the + * ftrace function that was used to create it, and use that ftrace + * function's orc entrie, as the placement of the return code in + * the stack will be identical. + */ +static struct orc_entry *orc_ftrace_find(unsigned long ip) +{ + struct ftrace_ops *ops; + unsigned long caller; + + ops = ftrace_ops_trampoline(ip); + if (!ops) + return NULL; + + if (ops->flags & FTRACE_OPS_FL_SAVE_REGS) + caller = (unsigned long)ftrace_regs_call; + else + caller = (unsigned long)ftrace_call; + + /* Prevent unlikely recursion */ + if (ip == caller) + return NULL; + + return orc_find(caller); +} +#else +static struct orc_entry *orc_ftrace_find(unsigned long ip) +{ + return NULL; +} +#endif + +/* + * If we crash with IP==0, the last successfully executed instruction + * was probably an indirect function call with a NULL function pointer, + * and we don't have unwind information for NULL. + * This hardcoded ORC entry for IP==0 allows us to unwind from a NULL function + * pointer into its parent and then continue normally from there. + */ +static struct orc_entry null_orc_entry = { + .sp_offset = sizeof(long), + .sp_reg = ORC_REG_SP, + .bp_reg = ORC_REG_UNDEFINED, + .type = ORC_TYPE_CALL +}; + +static struct orc_entry *orc_find(unsigned long ip) +{ + static struct orc_entry *orc; + + if (ip == 0) + return &null_orc_entry; + + /* For non-init vmlinux addresses, use the fast lookup table: */ + if (ip >= LOOKUP_START_IP && ip < LOOKUP_STOP_IP) { + unsigned int idx, start, stop; + + idx = (ip - LOOKUP_START_IP) / LOOKUP_BLOCK_SIZE; + + if (unlikely((idx >= lookup_num_blocks-1))) { + orc_warn("WARNING: bad lookup idx: idx=%u num=%u ip=%pB\n", + idx, lookup_num_blocks, (void *)ip); + return NULL; + } + + start = orc_lookup[idx]; + stop = orc_lookup[idx + 1] + 1; + + if (unlikely((__start_orc_unwind + start >= __stop_orc_unwind) || + (__start_orc_unwind + stop > __stop_orc_unwind))) { + orc_warn("WARNING: bad lookup value: idx=%u num=%u start=%u stop=%u ip=%pB\n", + idx, lookup_num_blocks, start, stop, (void *)ip); + return NULL; + } + + return __orc_find(__start_orc_unwind_ip + start, + __start_orc_unwind + start, stop - start, ip); + } + + /* vmlinux .init slow lookup: */ + if (init_kernel_text(ip)) + return __orc_find(__start_orc_unwind_ip, __start_orc_unwind, + __stop_orc_unwind_ip - __start_orc_unwind_ip, ip); + + /* Module lookup: */ + orc = orc_module_find(ip); + if (orc) + return orc; + + return orc_ftrace_find(ip); +} + +static void orc_sort_swap(void *_a, void *_b, int size) +{ + struct orc_entry *orc_a, *orc_b; + struct orc_entry orc_tmp; + int *a = _a, *b = _b, tmp; + int delta = _b - _a; + + /* Swap the .orc_unwind_ip entries: */ + tmp = *a; + *a = *b + delta; + *b = tmp - delta; + + /* Swap the corresponding .orc_unwind entries: */ + orc_a = cur_orc_table + (a - cur_orc_ip_table); + orc_b = cur_orc_table + (b - cur_orc_ip_table); + orc_tmp = *orc_a; + *orc_a = *orc_b; + *orc_b = orc_tmp; +} + +static int orc_sort_cmp(const void *_a, const void *_b) +{ + struct orc_entry *orc_a; + const int *a = _a, *b = _b; + unsigned long a_val = orc_ip(a); + unsigned long b_val = orc_ip(b); + + if (a_val > b_val) + return 1; + if (a_val < b_val) + return -1; + + /* + * The "weak" section terminator entries need to always be on the left + * to ensure the lookup code skips them in favor of real entries. + * These terminator entries exist to handle any gaps created by + * whitelisted .o files which didn't get objtool generation. + */ + orc_a = cur_orc_table + (a - cur_orc_ip_table); + return orc_a->sp_reg == ORC_REG_UNDEFINED && !orc_a->end ? -1 : 1; +} + +#ifdef CONFIG_MODULES +void unwind_module_init(struct module *mod, void *_orc_ip, size_t orc_ip_size, + void *_orc, size_t orc_size) +{ + int *orc_ip = _orc_ip; + struct orc_entry *orc = _orc; + unsigned int num_entries = orc_ip_size / sizeof(int); + + WARN_ON_ONCE(orc_ip_size % sizeof(int) != 0 || + orc_size % sizeof(*orc) != 0 || + num_entries != orc_size / sizeof(*orc)); + + /* + * The 'cur_orc_*' globals allow the orc_sort_swap() callback to + * associate an .orc_unwind_ip table entry with its corresponding + * .orc_unwind entry so they can both be swapped. + */ + mutex_lock(&sort_mutex); + cur_orc_ip_table = orc_ip; + cur_orc_table = orc; + sort(orc_ip, num_entries, sizeof(int), orc_sort_cmp, orc_sort_swap); + mutex_unlock(&sort_mutex); + + mod->arch.orc_unwind_ip = orc_ip; + mod->arch.orc_unwind = orc; + mod->arch.num_orcs = num_entries; +} +#endif + +void __init unwind_init(void) +{ + size_t orc_ip_size = (void *)__stop_orc_unwind_ip - (void *)__start_orc_unwind_ip; + size_t orc_size = (void *)__stop_orc_unwind - (void *)__start_orc_unwind; + size_t num_entries = orc_ip_size / sizeof(int); + struct orc_entry *orc; + int i; + + if (!num_entries || orc_ip_size % sizeof(int) != 0 || + orc_size % sizeof(struct orc_entry) != 0 || + num_entries != orc_size / sizeof(struct orc_entry)) { + orc_warn("WARNING: Bad or missing .orc_unwind table. Disabling unwinder.\n"); + return; + } + + /* Sort the .orc_unwind and .orc_unwind_ip tables: */ + sort(__start_orc_unwind_ip, num_entries, sizeof(int), orc_sort_cmp, + orc_sort_swap); + + /* Initialize the fast lookup table: */ + lookup_num_blocks = orc_lookup_end - orc_lookup; + for (i = 0; i < lookup_num_blocks-1; i++) { + orc = __orc_find(__start_orc_unwind_ip, __start_orc_unwind, + num_entries, + LOOKUP_START_IP + (LOOKUP_BLOCK_SIZE * i)); + if (!orc) { + orc_warn("WARNING: Corrupt .orc_unwind table. Disabling unwinder.\n"); + return; + } + + orc_lookup[i] = orc - __start_orc_unwind; + } + + /* Initialize the ending block: */ + orc = __orc_find(__start_orc_unwind_ip, __start_orc_unwind, num_entries, + LOOKUP_STOP_IP); + if (!orc) { + orc_warn("WARNING: Corrupt .orc_unwind table. Disabling unwinder.\n"); + return; + } + orc_lookup[lookup_num_blocks-1] = orc - __start_orc_unwind; + + orc_init = true; +} + +unsigned long unwind_get_return_address(struct unwind_state *state) +{ + if (unwind_done(state)) + return 0; + + return __kernel_text_address(state->ip) ? state->ip : 0; +} +EXPORT_SYMBOL_GPL(unwind_get_return_address); + +unsigned long *unwind_get_return_address_ptr(struct unwind_state *state) +{ + if (unwind_done(state)) + return NULL; + + if (state->regs) + return &state->regs->ip; + + if (state->sp) + return (unsigned long *)state->sp - 1; + + return NULL; +} + +static bool stack_access_ok(struct unwind_state *state, unsigned long _addr, + size_t len) +{ + struct stack_info *info = &state->stack_info; + void *addr = (void *)_addr; + + if (!on_stack(info, addr, len) && + (get_stack_info(addr, state->task, info, &state->stack_mask))) + return false; + + return true; +} + +static bool deref_stack_reg(struct unwind_state *state, unsigned long addr, + unsigned long *val) +{ + if (!stack_access_ok(state, addr, sizeof(long))) + return false; + + *val = READ_ONCE_NOCHECK(*(unsigned long *)addr); + return true; +} + +static bool deref_stack_regs(struct unwind_state *state, unsigned long addr, + unsigned long *ip, unsigned long *sp) +{ + struct pt_regs *regs = (struct pt_regs *)addr; + + /* x86-32 support will be more complicated due to the ®s->sp hack */ + BUILD_BUG_ON(IS_ENABLED(CONFIG_X86_32)); + + if (!stack_access_ok(state, addr, sizeof(struct pt_regs))) + return false; + + *ip = READ_ONCE_NOCHECK(regs->ip); + *sp = READ_ONCE_NOCHECK(regs->sp); + return true; +} + +static bool deref_stack_iret_regs(struct unwind_state *state, unsigned long addr, + unsigned long *ip, unsigned long *sp) +{ + struct pt_regs *regs = (void *)addr - IRET_FRAME_OFFSET; + + if (!stack_access_ok(state, addr, IRET_FRAME_SIZE)) + return false; + + *ip = READ_ONCE_NOCHECK(regs->ip); + *sp = READ_ONCE_NOCHECK(regs->sp); + return true; +} + +/* + * If state->regs is non-NULL, and points to a full pt_regs, just get the reg + * value from state->regs. + * + * Otherwise, if state->regs just points to IRET regs, and the previous frame + * had full regs, it's safe to get the value from the previous regs. This can + * happen when early/late IRQ entry code gets interrupted by an NMI. + */ +static bool get_reg(struct unwind_state *state, unsigned int reg_off, + unsigned long *val) +{ + unsigned int reg = reg_off/8; + + if (!state->regs) + return false; + + if (state->full_regs) { + *val = READ_ONCE_NOCHECK(((unsigned long *)state->regs)[reg]); + return true; + } + + if (state->prev_regs) { + *val = READ_ONCE_NOCHECK(((unsigned long *)state->prev_regs)[reg]); + return true; + } + + return false; +} + +bool unwind_next_frame(struct unwind_state *state) +{ + unsigned long ip_p, sp, tmp, orig_ip = state->ip, prev_sp = state->sp; + enum stack_type prev_type = state->stack_info.type; + struct orc_entry *orc; + bool indirect = false; + + if (unwind_done(state)) + return false; + + /* Don't let modules unload while we're reading their ORC data. */ + preempt_disable(); + + /* End-of-stack check for user tasks: */ + if (state->regs && user_mode(state->regs)) + goto the_end; + + /* + * Find the orc_entry associated with the text address. + * + * For a call frame (as opposed to a signal frame), state->ip points to + * the instruction after the call. That instruction's stack layout + * could be different from the call instruction's layout, for example + * if the call was to a noreturn function. So get the ORC data for the + * call instruction itself. + */ + orc = orc_find(state->signal ? state->ip : state->ip - 1); + if (!orc) + goto err; + + /* End-of-stack check for kernel threads: */ + if (orc->sp_reg == ORC_REG_UNDEFINED) { + if (!orc->end) + goto err; + + goto the_end; + } + + /* Find the previous frame's stack: */ + switch (orc->sp_reg) { + case ORC_REG_SP: + sp = state->sp + orc->sp_offset; + break; + + case ORC_REG_BP: + sp = state->bp + orc->sp_offset; + break; + + case ORC_REG_SP_INDIRECT: + sp = state->sp + orc->sp_offset; + indirect = true; + break; + + case ORC_REG_BP_INDIRECT: + sp = state->bp + orc->sp_offset; + indirect = true; + break; + + case ORC_REG_R10: + if (!get_reg(state, offsetof(struct pt_regs, r10), &sp)) { + orc_warn("missing regs for base reg R10 at ip %pB\n", + (void *)state->ip); + goto err; + } + break; + + case ORC_REG_R13: + if (!get_reg(state, offsetof(struct pt_regs, r13), &sp)) { + orc_warn("missing regs for base reg R13 at ip %pB\n", + (void *)state->ip); + goto err; + } + break; + + case ORC_REG_DI: + if (!get_reg(state, offsetof(struct pt_regs, di), &sp)) { + orc_warn("missing regs for base reg DI at ip %pB\n", + (void *)state->ip); + goto err; + } + break; + + case ORC_REG_DX: + if (!get_reg(state, offsetof(struct pt_regs, dx), &sp)) { + orc_warn("missing regs for base reg DX at ip %pB\n", + (void *)state->ip); + goto err; + } + break; + + default: + orc_warn("unknown SP base reg %d for ip %pB\n", + orc->sp_reg, (void *)state->ip); + goto err; + } + + if (indirect) { + if (!deref_stack_reg(state, sp, &sp)) + goto err; + } + + /* Find IP, SP and possibly regs: */ + switch (orc->type) { + case ORC_TYPE_CALL: + ip_p = sp - sizeof(long); + + if (!deref_stack_reg(state, ip_p, &state->ip)) + goto err; + + state->ip = ftrace_graph_ret_addr(state->task, &state->graph_idx, + state->ip, (void *)ip_p); + + state->sp = sp; + state->regs = NULL; + state->prev_regs = NULL; + state->signal = false; + break; + + case ORC_TYPE_REGS: + if (!deref_stack_regs(state, sp, &state->ip, &state->sp)) { + orc_warn("can't dereference registers at %p for ip %pB\n", + (void *)sp, (void *)orig_ip); + goto err; + } + + state->regs = (struct pt_regs *)sp; + state->prev_regs = NULL; + state->full_regs = true; + state->signal = true; + break; + + case ORC_TYPE_REGS_IRET: + if (!deref_stack_iret_regs(state, sp, &state->ip, &state->sp)) { + orc_warn("can't dereference iret registers at %p for ip %pB\n", + (void *)sp, (void *)orig_ip); + goto err; + } + + if (state->full_regs) + state->prev_regs = state->regs; + state->regs = (void *)sp - IRET_FRAME_OFFSET; + state->full_regs = false; + state->signal = true; + break; + + default: + orc_warn("unknown .orc_unwind entry type %d for ip %pB\n", + orc->type, (void *)orig_ip); + goto err; + } + + /* Find BP: */ + switch (orc->bp_reg) { + case ORC_REG_UNDEFINED: + if (get_reg(state, offsetof(struct pt_regs, bp), &tmp)) + state->bp = tmp; + break; + + case ORC_REG_PREV_SP: + if (!deref_stack_reg(state, sp + orc->bp_offset, &state->bp)) + goto err; + break; + + case ORC_REG_BP: + if (!deref_stack_reg(state, state->bp + orc->bp_offset, &state->bp)) + goto err; + break; + + default: + orc_warn("unknown BP base reg %d for ip %pB\n", + orc->bp_reg, (void *)orig_ip); + goto err; + } + + /* Prevent a recursive loop due to bad ORC data: */ + if (state->stack_info.type == prev_type && + on_stack(&state->stack_info, (void *)state->sp, sizeof(long)) && + state->sp <= prev_sp) { + orc_warn("stack going in the wrong direction? ip=%pB\n", + (void *)orig_ip); + goto err; + } + + preempt_enable(); + return true; + +err: + state->error = true; + +the_end: + preempt_enable(); + state->stack_info.type = STACK_TYPE_UNKNOWN; + return false; +} +EXPORT_SYMBOL_GPL(unwind_next_frame); + +void __unwind_start(struct unwind_state *state, struct task_struct *task, + struct pt_regs *regs, unsigned long *first_frame) +{ + memset(state, 0, sizeof(*state)); + state->task = task; + + if (!orc_init) + goto err; + + /* + * Refuse to unwind the stack of a task while it's executing on another + * CPU. This check is racy, but that's ok: the unwinder has other + * checks to prevent it from going off the rails. + */ + if (task_on_another_cpu(task)) + goto err; + + if (regs) { + if (user_mode(regs)) + goto the_end; + + state->ip = regs->ip; + state->sp = kernel_stack_pointer(regs); + state->bp = regs->bp; + state->regs = regs; + state->full_regs = true; + state->signal = true; + + } else if (task == current) { + asm volatile("lea (%%rip), %0\n\t" + "mov %%rsp, %1\n\t" + "mov %%rbp, %2\n\t" + : "=r" (state->ip), "=r" (state->sp), + "=r" (state->bp)); + + } else { + struct inactive_task_frame *frame = (void *)task->thread.sp; + + state->sp = task->thread.sp + sizeof(*frame); + state->bp = READ_ONCE_NOCHECK(frame->bp); + state->ip = READ_ONCE_NOCHECK(frame->ret_addr); + state->signal = (void *)state->ip == ret_from_fork; + } + + if (get_stack_info((unsigned long *)state->sp, state->task, + &state->stack_info, &state->stack_mask)) { + /* + * We weren't on a valid stack. It's possible that + * we overflowed a valid stack into a guard page. + * See if the next page up is valid so that we can + * generate some kind of backtrace if this happens. + */ + void *next_page = (void *)PAGE_ALIGN((unsigned long)state->sp); + state->error = true; + if (get_stack_info(next_page, state->task, &state->stack_info, + &state->stack_mask)) + return; + } + + /* + * The caller can provide the address of the first frame directly + * (first_frame) or indirectly (regs->sp) to indicate which stack frame + * to start unwinding at. Skip ahead until we reach it. + */ + + /* When starting from regs, skip the regs frame: */ + if (regs) { + unwind_next_frame(state); + return; + } + + /* Otherwise, skip ahead to the user-specified starting frame: */ + while (!unwind_done(state) && + (!on_stack(&state->stack_info, first_frame, sizeof(long)) || + state->sp < (unsigned long)first_frame)) + unwind_next_frame(state); + + return; + +err: + state->error = true; +the_end: + state->stack_info.type = STACK_TYPE_UNKNOWN; +} +EXPORT_SYMBOL_GPL(__unwind_start); |