Commit c79dd946 authored by Peter Zijlstra's avatar Peter Zijlstra
Browse files

unwind: Implement compat fp unwind 



It is important to be able to unwind compat tasks too.

Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Link: https://patch.msgid.link/20250924080119.613695709@infradead.org
parent 5578534e

include/linux/unwind_user_types.h

+1 −0
Original line number Diff line number Diff line
@@ -36,6 +36,7 @@ struct unwind_user_state { 
	unsigned long				ip;

	unsigned long				sp;

	unsigned long				fp;

	unsigned int				ws;

	enum unwind_user_type			current_type;

	unsigned int				available_types;

	bool					done;

kernel/unwind/user.c

+29 −11
Original line number Diff line number Diff line
@@ -8,19 +8,32 @@ 
#include <linux/unwind_user.h>

#include <linux/uaccess.h>



static const struct unwind_user_frame fp_frame = {

	ARCH_INIT_USER_FP_FRAME

};



#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_fp(struct unwind_user_state *state)

{

	const struct unwind_user_frame *frame = &fp_frame;

	const struct unwind_user_frame frame = {

		ARCH_INIT_USER_FP_FRAME(state->ws)

	};

	unsigned long cfa, fp, ra;



	if (frame->use_fp) {

	if (frame.use_fp) {

		if (state->fp < state->sp)

			return -EINVAL;

		cfa = state->fp;
@@ -29,26 +42,26 @@ static int unwind_user_next_fp(struct unwind_user_state *state) 
	}



	/* Get the Canonical Frame Address (CFA) */

	cfa += frame->cfa_off;

	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 & (sizeof(long) - 1))

	if (cfa & (state->ws - 1))

		return -EINVAL;



	/* Find the Return Address (RA) */

	if (get_user(ra, (unsigned long *)(cfa + frame->ra_off)))

	if (get_user_word(&ra, cfa, frame.ra_off, state->ws))

		return -EINVAL;



	if (frame->fp_off && get_user(fp, (unsigned long __user *)(cfa + frame->fp_off)))

	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)

	if (frame.fp_off)

		state->fp = fp;

	return 0;

}
@@ -100,6 +113,11 @@ static int unwind_user_start(struct unwind_user_state *state) 
	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;

	}



	return 0;

}