path: root/arch/x86/kernel/unwind_orc.c

// SPDX-License-Identifier: GPL-2.0-only
#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 "WARNING: " fmt, ##__VA_ARGS__)

#define orc_warn_current(args...)					\
({									\
	if (state->task == current)					\
		orc_warn(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 bool orc_init __ro_after_init;
static unsigned int lookup_num_blocks __ro_after_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 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 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
};

/* 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,
	.end		= 0,
};

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);
}

#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;
	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 +