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-rw-r--r--arch/x86/kernel/unwind_orc.c769
1 files changed, 769 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..7e574cf3b
--- /dev/null
+++ b/arch/x86/kernel/unwind_orc.c
@@ -0,0 +1,769 @@
+// SPDX-License-Identifier: GPL-2.0-only
+#include <linux/objtool.h>
+#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>
+#include <asm/orc_header.h>
+
+ORC_HEADER;
+
+#define orc_warn(fmt, ...) \
+ printk_deferred_once(KERN_WARNING "WARNING: " fmt, ##__VA_ARGS__)
+
+#define orc_warn_current(args...) \
+({ \
+ static bool dumped_before; \
+ if (state->task == current && !state->error) { \
+ orc_warn(args); \
+ if (unwind_debug && !dumped_before) { \
+ dumped_before = true; \
+ unwind_dump(state); \
+ } \
+ } \
+})
+
+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 bool orc_init __ro_after_init;
+static bool unwind_debug __ro_after_init;
+static unsigned int lookup_num_blocks __ro_after_init;
+
+static int __init unwind_debug_cmdline(char *str)
+{
+ unwind_debug = true;
+
+ return 0;
+}
+early_param("unwind_debug", unwind_debug_cmdline);
+
+static void unwind_dump(struct unwind_state *state)
+{
+ static bool dumped_before;
+ unsigned long word, *sp;
+ struct stack_info stack_info = {0};
+ unsigned long visit_mask = 0;
+
+ if (dumped_before)
+ return;
+
+ dumped_before = true;
+
+ printk_deferred("unwind stack type:%d next_sp:%p mask:0x%lx graph_idx:%d\n",
+ state->stack_info.type, state->stack_info.next_sp,
+ state->stack_mask, state->graph_idx);
+
+ for (sp = __builtin_frame_address(0); sp;
+ sp = PTR_ALIGN(stack_info.next_sp, sizeof(long))) {
+ if (get_stack_info(sp, state->task, &stack_info, &visit_mask))
+ break;
+
+ for (; sp < stack_info.end; sp++) {
+
+ word = READ_ONCE_NOCHECK(*sp);
+
+ printk_deferred("%0*lx: %0*lx (%pB)\n", BITS_PER_LONG/4,
+ (unsigned long)sp, BITS_PER_LONG/4,
+ word, (void *)word);
+ }
+ }
+}
+
+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 unwinder comes across a ftrace trampoline, then find the
+ * ftrace function that was used to create it, and use that ftrace
+ * function's orc entry, 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 tramp_addr, offset;
+
+ ops = ftrace_ops_trampoline(ip);
+ if (!ops)
+ return NULL;
+
+ /* Set tramp_addr to the start of the code copied by the trampoline */
+ if (ops->flags & FTRACE_OPS_FL_SAVE_REGS)
+ tramp_addr = (unsigned long)ftrace_regs_caller;
+ else
+ tramp_addr = (unsigned long)ftrace_caller;
+
+ /* Now place tramp_addr to the location within the trampoline ip is at */
+ offset = ip - ops->trampoline;
+ tramp_addr += offset;
+
+ /* Prevent unlikely recursion */
+ if (ip == tramp_addr)
+ return NULL;
+
+ return orc_find(tramp_addr);
+}
+#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
+};
+
+/* Fake frame pointer entry -- used as a fallback for generated code */
+static struct orc_entry orc_fp_entry = {
+ .type = ORC_TYPE_CALL,
+ .sp_reg = ORC_REG_BP,
+ .sp_offset = 16,
+ .bp_reg = ORC_REG_PREV_SP,
+ .bp_offset = -16,
+};
+
+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 (is_kernel_inittext(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);
+}
+
+#ifdef CONFIG_MODULES
+
+static DEFINE_MUTEX(sort_mutex);
+static int *cur_orc_ip_table = __start_orc_unwind_ip;
+static struct orc_entry *cur_orc_table = __start_orc_unwind;
+
+static void orc_sort_swap(void *_a, void *_b, int size)
+{
+ struct orc_entry *orc_a, *orc_b;
+ 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);
+ swap(*orc_a, *orc_b);
+}
+
+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 first
+ * 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->type == ORC_TYPE_UNDEFINED ? -1 : 1;
+}
+
+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;
+ }
+
+ /*
+ * Note, the orc_unwind and orc_unwind_ip tables were already
+ * sorted at build time via the 'sorttable' tool.
+ * It's ready for binary search straight away, no need to sort it.
+ */
+
+ /* 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))
+ return true;
+
+ return !get_stack_info(addr, state->task, info, &state->stack_mask) &&
+ on_stack(info, addr, len);
+}
+
+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 &regs->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) {
+ /*
+ * As a fallback, try to assume this code uses a frame pointer.
+ * This is useful for generated code, like BPF, which ORC
+ * doesn't know about. This is just a guess, so the rest of
+ * the unwind is no longer considered reliable.
+ */
+ orc = &orc_fp_entry;
+ state->error = true;
+ } else {
+ if (orc->type == ORC_TYPE_UNDEFINED)
+ goto err;
+
+ if (orc->type == ORC_TYPE_END_OF_STACK)
+ goto the_end;
+ }
+
+ state->signal = orc->signal;
+
+ /* 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;
+ 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_current("missing R10 value at %pB\n",
+ (void *)state->ip);
+ goto err;
+ }
+ break;
+
+ case ORC_REG_R13:
+ if (!get_reg(state, offsetof(struct pt_regs, r13), &sp)) {
+ orc_warn_current("missing R13 value at %pB\n",
+ (void *)state->ip);
+ goto err;
+ }
+ break;
+
+ case ORC_REG_DI:
+ if (!get_reg(state, offsetof(struct pt_regs, di), &sp)) {
+ orc_warn_current("missing RDI value at %pB\n",
+ (void *)state->ip);
+ goto err;
+ }
+ break;
+
+ case ORC_REG_DX:
+ if (!get_reg(state, offsetof(struct pt_regs, dx), &sp)) {
+ orc_warn_current("missing DX value at %pB\n",
+ (void *)state->ip);
+ goto err;
+ }
+ break;
+
+ default:
+ orc_warn("unknown SP base reg %d at %pB\n",
+ orc->sp_reg, (void *)state->ip);
+ goto err;
+ }
+
+ if (indirect) {
+ if (!deref_stack_reg(state, sp, &sp))
+ goto err;
+
+ if (orc->sp_reg == ORC_REG_SP_INDIRECT)
+ sp += orc->sp_offset;
+ }
+
+ /* 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 = unwind_recover_ret_addr(state, state->ip,
+ (unsigned long *)ip_p);
+ state->sp = sp;
+ state->regs = NULL;
+ state->prev_regs = NULL;
+ break;
+
+ case ORC_TYPE_REGS:
+ if (!deref_stack_regs(state, sp, &state->ip, &state->sp)) {
+ orc_warn_current("can't access registers at %pB\n",
+ (void *)orig_ip);
+ goto err;
+ }
+ /*
+ * There is a small chance to interrupt at the entry of
+ * arch_rethook_trampoline() where the ORC info doesn't exist.
+ * That point is right after the RET to arch_rethook_trampoline()
+ * which was modified return address.
+ * At that point, the @addr_p of the unwind_recover_rethook()
+ * (this has to point the address of the stack entry storing
+ * the modified return address) must be "SP - (a stack entry)"
+ * because SP is incremented by the RET.
+ */
+ state->ip = unwind_recover_rethook(state, state->ip,
+ (unsigned long *)(state->sp - sizeof(long)));
+ state->regs = (struct pt_regs *)sp;
+ state->prev_regs = NULL;
+ state->full_regs = true;
+ break;
+
+ case ORC_TYPE_REGS_PARTIAL:
+ if (!deref_stack_iret_regs(state, sp, &state->ip, &state->sp)) {
+ orc_warn_current("can't access iret registers at %pB\n",
+ (void *)orig_ip);
+ goto err;
+ }
+ /* See ORC_TYPE_REGS case comment. */
+ state->ip = unwind_recover_rethook(state, state->ip,
+ (unsigned long *)(state->sp - sizeof(long)));
+
+ if (state->full_regs)
+ state->prev_regs = state->regs;
+ state->regs = (void *)sp - IRET_FRAME_OFFSET;
+ state->full_regs = false;
+ break;
+
+ default:
+ orc_warn("unknown .orc_unwind entry type %d at %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_current("stack going in the wrong direction? at %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 = regs->sp;
+ 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);
generated by cgit v1.2.3 (git 2.39.1) at 2024-07-19 21:01:11 +0000