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// SPDX-License-Identifier: GPL-2.0
/*
* Generic interfaces for unwinding user space
*/
#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/sched/task_stack.h>
#include <linux/unwind_user.h>
#include <linux/uaccess.h>
#define for_each_user_frame(state) \
for (unwind_user_start(state); !(state)->done; unwind_user_next(state))
static inline int
get_user_word(unsigned long *word, unsigned long base, int off, unsigned int ws)
{
unsigned long __user *addr = (void __user *)base + off;
#ifdef CONFIG_COMPAT
if (ws == sizeof(int)) {
unsigned int data;
int ret = get_user(data, (unsigned int __user *)addr);
*word = data;
return ret;
}
#endif
return get_user(*word, addr);
}
static int unwind_user_next_common(struct unwind_user_state *state,
const struct unwind_user_frame *frame)
{
unsigned long cfa, fp, ra;
if (frame->use_fp) {
if (state->fp < state->sp)
return -EINVAL;
cfa = state->fp;
} else {
cfa = state->sp;
}
/* Get the Canonical Frame Address (CFA) */
cfa += frame->cfa_off;
/* stack going in wrong direction? */
if (cfa <= state->sp)
return -EINVAL;
/* Make sure that the address is word aligned */
if (cfa & (state->ws - 1))
return -EINVAL;
/* Find the Return Address (RA) */
if (get_user_word(&ra, cfa, frame->ra_off, state->ws))
return -EINVAL;
if (frame->fp_off && get_user_word(&fp, cfa, frame->fp_off, state->ws))
return -EINVAL;
state->ip = ra;
state->sp = cfa;
if (frame->fp_off)
state->fp = fp;
state->topmost = false;
return 0;
}
static int unwind_user_next_fp(struct unwind_user_state *state)
{
#ifdef CONFIG_HAVE_UNWIND_USER_FP
struct pt_regs *regs = task_pt_regs(current);
if (state->topmost && unwind_user_at_function_start(regs)) {
const struct unwind_user_frame fp_entry_frame = {
ARCH_INIT_USER_FP_ENTRY_FRAME(state->ws)
};
return unwind_user_next_common(state, &fp_entry_frame);
}
const struct unwind_user_frame fp_frame = {
ARCH_INIT_USER_FP_FRAME(state->ws)
};
return unwind_user_next_common(state, &fp_frame);
#else
return -EINVAL;
#endif
}
static int unwind_user_next(struct unwind_user_state *state)
{
unsigned long iter_mask = state->available_types;
unsigned int bit;
if (state->done)
return -EINVAL;
for_each_set_bit(bit, &iter_mask, NR_UNWIND_USER_TYPE_BITS) {
enum unwind_user_type type = BIT(bit);
state->current_type = type;
switch (type) {
case UNWIND_USER_TYPE_FP:
if (!unwind_user_next_fp(state))
return 0;
continue;
default:
WARN_ONCE(1, "Undefined unwind bit %d", bit);
break;
}
break;
}
/* No successful unwind method. */
state->current_type = UNWIND_USER_TYPE_NONE;
state->done = true;
return -EINVAL;
}
static int unwind_user_start(struct unwind_user_state *state)
{
struct pt_regs *regs = task_pt_regs(current);
memset(state, 0, sizeof(*state));
if ((current->flags & PF_KTHREAD) || !user_mode(regs)) {
state->done = true;
return -EINVAL;
}
if (IS_ENABLED(CONFIG_HAVE_UNWIND_USER_FP))
state->available_types |= UNWIND_USER_TYPE_FP;
state->ip = instruction_pointer(regs);
state->sp = user_stack_pointer(regs);
state->fp = frame_pointer(regs);
state->ws = unwind_user_word_size(regs);
if (!state->ws) {
state->done = true;
return -EINVAL;
}
state->topmost = true;
return 0;
}
int unwind_user(struct unwind_stacktrace *trace, unsigned int max_entries)
{
struct unwind_user_state state;
trace->nr = 0;
if (!max_entries)
return -EINVAL;
if (current->flags & PF_KTHREAD)
return 0;
for_each_user_frame(&state) {
trace->entries[trace->nr++] = state.ip;
if (trace->nr >= max_entries)
break;
}
return 0;
}
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