linux_kernel/kernel/trace/trace_probe_tmpl.h

/* SPDX-License-Identifier: GPL-2.0 */
/*
 * Traceprobe fetch helper inlines
 */

static nokprobe_inline void
fetch_store_raw(unsigned long val, struct fetch_insn *code, void *buf)
{
	switch (code->size) {
	case 1:
		*(u8 *)buf = (u8)val;
		break;
	case 2:
		*(u16 *)buf = (u16)val;
		break;
	case 4:
		*(u32 *)buf = (u32)val;
		break;
	case 8:
		//TBD: 32bit signed
		*(u64 *)buf = (u64)val;
		break;
	default:
		*(unsigned long *)buf = val;
	}
}

static nokprobe_inline void
fetch_apply_bitfield(struct fetch_insn *code, void *buf)
{
	switch (code->basesize) {
	case 1:
		*(u8 *)buf <<= code->lshift;
		*(u8 *)buf >>= code->rshift;
		break;
	case 2:
		*(u16 *)buf <<= code->lshift;
		*(u16 *)buf >>= code->rshift;
		break;
	case 4:
		*(u32 *)buf <<= code->lshift;
		*(u32 *)buf >>= code->rshift;
		break;
	case 8:
		*(u64 *)buf <<= code->lshift;
		*(u64 *)buf >>= code->rshift;
		break;
	}
}

/*
 * These functions must be defined for each callsite.
 * Return consumed dynamic data size (>= 0), or error (< 0).
 * If dest is NULL, don't store result and return required dynamic data size.
 */
static int
process_fetch_insn(struct fetch_insn *code, struct pt_regs *regs,
		   void *dest, void *base);
static nokprobe_inline int fetch_store_strlen(unsigned long addr);
static nokprobe_inline int
fetch_store_string(unsigned long addr, void *dest, void *base);
static nokprobe_inline int
probe_mem_read(void *dest, void *src, size_t size);

/* From the 2nd stage, routine is same */
static nokprobe_inline int
process_fetch_insn_bottom(struct fetch_insn *code, unsigned long val,
			   void *dest, void *base)
{
	struct fetch_insn *s3 = NULL;
	int total = 0, ret = 0, i = 0;
	u32 loc = 0;
	unsigned long lval = val;

stage2:
	/* 2nd stage: dereference memory if needed */
	while (code->op == FETCH_OP_DEREF) {
		lval = val;
		ret = probe_mem_read(&val, (void *)val + code->offset,
					sizeof(val));
		if (ret)
			return ret;
		code++;
	}

	s3 = code;
stage3:
	/* 3rd stage: store value to buffer */
	if (unlikely(!dest)) {
		if (code->op == FETCH_OP_ST_STRING) {
			ret += fetch_store_strlen(val + code->offset);
			code++;
			goto array;
		} else
			return -EILSEQ;
	}

	switch (code->op) {
	case FETCH_OP_ST_RAW:
		fetch_store_raw(val, code, dest);
		break;
	case FETCH_OP_ST_MEM:
		probe_mem_read(dest, (void *)val + code->offset, code->size);
		break;
	case FETCH_OP_ST_STRING:
		loc = *(u32 *)dest;
		ret = fetch_store_string(val + code->offset, dest, base);
		break;
	default:
		return -EILSEQ;
	}
	code++;

	/* 4th stage: modify stored value if needed */
	if (code->op == FETCH_OP_MOD_BF) {
		fetch_apply_bitfield(code, dest);
		code++;
	}

array:
	/* the last stage: Loop on array */
	if (code->op == FETCH_OP_LP_ARRAY) {
		total += ret;
		if (++i < code->param) {
			code = s3;
			if (s3->op != FETCH_OP_ST_STRING) {
				dest += s3->size;
				val += s3->size;
				goto stage3;
			}
			code--;
			val = lval + sizeof(char *);
			if (dest) {
				dest += sizeof(u32);
				*(u32 *)dest = update_data_loc(loc, ret);
			}
			goto stage2;
		}
		code++;
		ret = total;
	}

	return code->op == FETCH_OP_END ? ret : -EILSEQ;
}

/* Sum up total data length for dynamic arraies (strings) */
static nokprobe_inline int
__get_data_size(struct trace_probe *tp, struct pt_regs *regs)
{
	struct probe_arg *arg;
	int i, len, ret = 0;

	for (i = 0; i < tp->nr_args; i++) {
		arg = tp->args + i;
		if (unlikely(arg->dynamic)) {
			len = process_fetch_insn(arg->code, regs, NULL, NULL);
			if (len > 0)
				ret += len;
		}
	}

	return ret;
}

/* Store the value of each argument */
static nokprobe_inline void
store_trace_args(void *data, struct trace_probe *tp, struct pt_regs *regs,
		 int header_size, int maxlen)
{
	struct probe_arg *arg;
	void *base = data - header_size;
	void *dyndata = data + tp->size;
	u32 *dl;	/* Data location */
	int ret, i;

	for (i = 0; i < tp->nr_args; i++) {
		arg = tp->args + i;
		dl = data + arg->offset;
		/* Point the dynamic data area if needed */
		if (unlikely(arg->dynamic))
			*dl = make_data_loc(maxlen, dyndata - base);
		ret = process_fetch_insn(arg->code, regs, dl, base);
		if (unlikely(ret < 0 && arg->dynamic))
			*dl = make_data_loc(0, dyndata - base);
		else
			dyndata += ret;
	}
}

static inline int
print_probe_args(struct trace_seq *s, struct probe_arg *args, int nr_args,
		 u8 *data, void *field)
{
	void *p;
	int i, j;

	for (i = 0; i < nr_args; i++) {
		struct probe_arg *a = args + i;

		trace_seq_printf(s, " %s=", a->name);
		if (likely(!a->count)) {
			if (!a->type->print(s, data + a->offset, field))
				return -ENOMEM;
			continue;
		}
		trace_seq_putc(s, '{');
		p = data + a->offset;
		for (j = 0; j < a->count; j++) {
			if (!a->type->print(s, p, field))
				return -ENOMEM;
			trace_seq_putc(s, j == a->count - 1 ? '}' : ',');
			p += a->type->size;
		}
	}
	return 0;
}