path: root/arch/arm64/kernel/signal.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 * Based on arch/arm/kernel/signal.c
 *
 * Copyright (C) 1995-2009 Russell King
 * Copyright (C) 2012 ARM Ltd.
 */

#include <linux/cache.h>
#include <linux/compat.h>
#include <linux/errno.h>
#include <linux/kernel.h>
#include <linux/signal.h>
#include <linux/freezer.h>
#include <linux/stddef.h>
#include <linux/uaccess.h>
#include <linux/sizes.h>
#include <linux/string.h>
#include <linux/resume_user_mode.h>
#include <linux/ratelimit.h>
#include <linux/syscalls.h>

#include <asm/daifflags.h>
#include <asm/debug-monitors.h>
#include <asm/elf.h>
#include <asm/cacheflush.h>
#include <asm/ucontext.h>
#include <asm/unistd.h>
#include <asm/fpsimd.h>
#include <asm/ptrace.h>
#include <asm/syscall.h>
#include <asm/signal32.h>
#include <asm/traps.h>
#include <asm/vdso.h>

/*
 * Do a signal return; undo the signal stack. These are aligned to 128-bit.
 */
struct rt_sigframe {
	struct siginfo info;
	struct ucontext uc;
};

struct frame_record {
	u64 fp;
	u64 lr;
};

struct rt_sigframe_user_layout {
	struct rt_sigframe __user *sigframe;
	struct frame_record __user *next_frame;

	unsigned long size;	/* size of allocated sigframe data */
	unsigned long limit;	/* largest allowed size */

	unsigned long fpsimd_offset;
	unsigned long esr_offset;
	unsigned long sve_offset;
	unsigned long za_offset;
	unsigned long extra_offset;
	unsigned long end_offset;
};

#define BASE_SIGFRAME_SIZE round_up(sizeof(struct rt_sigframe), 16)
#define TERMINATOR_SIZE round_up(sizeof(struct _aarch64_ctx), 16)
#define EXTRA_CONTEXT_SIZE round_up(sizeof(struct extra_context), 16)

static void init_user_layout(struct rt_sigframe_user_layout *user)
{
	const size_t reserved_size =
		sizeof(user->sigframe->uc.uc_mcontext.__reserved);

	memset(user, 0, sizeof(*user));
	user->size = offsetof(struct rt_sigframe, uc.uc_mcontext.__reserved);

	user->limit = user->size + reserved_size;

	user->limit -= TERMINATOR_SIZE;
	user->limit -= EXTRA_CONTEXT_SIZE;
	/* Reserve space for extension and terminator ^ */
}

static size_t sigframe_size(struct rt_sigframe_user_layout const *user)
{
	return round_up(max(user->size, sizeof(struct rt_sigframe)), 16);
}

/*
 * Sanity limit on the approximate maximum size of signal frame we'll
 * try to generate.  Stack alignment padding and the frame record are
 * not taken into account.  This limit is not a guarantee and is
 * NOT ABI.
 */
#define SIGFRAME_MAXSZ SZ_64K

static int __sigframe_alloc(struct rt_sigframe_user_layout *user,
			    unsigned long *offset, size_t size, bool extend)
{
	size_t padded_size = round_up(size, 16);

	if (padded_size > user->limit - user->size &&
	    !user->extra_offset &&
	    extend) {
		int ret;

		user->limit += EXTRA_CONTEXT_SIZE;
		ret = __sigframe_alloc(user, &user->extra_offset,
				       sizeof(struct extra_context), false);
		if (ret) {
			user->limit -= EXTRA_CONTEXT_SIZE;
			return ret;
		}

		/* Reserve space for the __reserved[] terminator */
		user->size += TERMINATOR_SIZE;

		/*
		 * Allow expansion up to SIGFRAME_MAXSZ, ensuring space for
		 * the terminator:
		 */
		user->limit = SIGFRAME_MAXSZ - TERMINATOR_SIZE;
	}

	/* Still not enough space?  Bad luck! */
	if (padded_size > user->limit - user->size)
		return -ENOMEM;

	*offset = user->size;
	user->size += padded_size;

	return 0;
}

/*
 * Allocate space for an optional record of <size> bytes in the user
 * signal frame.  The offset from the signal frame base address to the
 * allocated block is assigned to *offset.
 */
static int sigframe_alloc(struct rt_sigframe_user_layout *user,
			  unsigned long *offset, size_t size)
{
	return __sigframe_alloc(user, offset, size, true);
}

/* Allocate the null terminator record and prevent further allocations */
static int sigframe_alloc_end(struct rt_sigframe_user_layout *user)
{
	int ret;

	/* Un-reserve the space reserved for the terminator: */
	user->limit += TERMINATOR_SIZE;

	ret = sigframe_alloc(user, &user->end_offset,
			     sizeof