Commit 0f861992 authored by Alan Maguire's avatar Alan Maguire Committed by Andrii Nakryiko
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libbpf: Usdt aarch64 arg parsing support 



Parsing of USDT arguments is architecture-specific. On aarch64 it is
relatively easy since registers used are x[0-31] and sp. Format is
slightly different compared to x86_64. Possible forms are:

- "size@[reg[,offset]]" for dereferences, e.g. "-8@[sp,76]" and "-4@[sp]";
- "size@reg" for register values, e.g. "-4@x0";
- "size@value" for raw values, e.g. "-8@1".

Signed-off-by: default avatarAlan Maguire <alan.maguire@oracle.com>
Signed-off-by: default avatarAndrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/1649690496-1902-2-git-send-email-alan.maguire@oracle.com
parent aa1b02e6

tools/lib/bpf/usdt.c

+76 −0
Original line number Diff line number Diff line
@@ -1324,6 +1324,82 @@ static int parse_usdt_arg(const char *arg_str, int arg_num, struct usdt_arg_spec 
	return len;

}



#elif defined(__aarch64__)



static int calc_pt_regs_off(const char *reg_name)

{

	int reg_num;



	if (sscanf(reg_name, "x%d", &reg_num) == 1) {

		if (reg_num >= 0 && reg_num < 31)

			return offsetof(struct user_pt_regs, regs[reg_num]);

	} else if (strcmp(reg_name, "sp") == 0) {

		return offsetof(struct user_pt_regs, sp);

	}

	pr_warn("usdt: unrecognized register '%s'\n", reg_name);

	return -ENOENT;

}



static int parse_usdt_arg(const char *arg_str, int arg_num, struct usdt_arg_spec *arg)

{

	char *reg_name = NULL;

	int arg_sz, len, reg_off;

	long off;



	if (sscanf(arg_str, " %d @ \[ %m[a-z0-9], %ld ] %n", &arg_sz, &reg_name, &off, &len) == 3) {

		/* Memory dereference case, e.g., -4@[sp, 96] */

		arg->arg_type = USDT_ARG_REG_DEREF;

		arg->val_off = off;

		reg_off = calc_pt_regs_off(reg_name);

		free(reg_name);

		if (reg_off < 0)

			return reg_off;

		arg->reg_off = reg_off;

	} else if (sscanf(arg_str, " %d @ \[ %m[a-z0-9] ] %n", &arg_sz, &reg_name, &len) == 2) {

		/* Memory dereference case, e.g., -4@[sp] */

		arg->arg_type = USDT_ARG_REG_DEREF;

		arg->val_off = 0;

		reg_off = calc_pt_regs_off(reg_name);

		free(reg_name);

		if (reg_off < 0)

			return reg_off;

		arg->reg_off = reg_off;

	} else if (sscanf(arg_str, " %d @ %ld %n", &arg_sz, &off, &len) == 2) {

		/* Constant value case, e.g., 4@5 */

		arg->arg_type = USDT_ARG_CONST;

		arg->val_off = off;

		arg->reg_off = 0;

	} else if (sscanf(arg_str, " %d @ %m[a-z0-9] %n", &arg_sz, &reg_name, &len) == 2) {

		/* Register read case, e.g., -8@x4 */

		arg->arg_type = USDT_ARG_REG;

		arg->val_off = 0;

		reg_off = calc_pt_regs_off(reg_name);

		free(reg_name);

		if (reg_off < 0)

			return reg_off;

		arg->reg_off = reg_off;

	} else {

		pr_warn("usdt: unrecognized arg #%d spec '%s'\n", arg_num, arg_str);

		return -EINVAL;

	}



	arg->arg_signed = arg_sz < 0;

	if (arg_sz < 0)

		arg_sz = -arg_sz;



	switch (arg_sz) {

	case 1: case 2: case 4: case 8:

		arg->arg_bitshift = 64 - arg_sz * 8;

		break;

	default:

		pr_warn("usdt: unsupported arg #%d (spec '%s') size: %d\n",

			arg_num, arg_str, arg_sz);

		return -EINVAL;

	}



	return len;

}



#else



static int parse_usdt_arg(const char *arg_str, int arg_num, struct usdt_arg_spec *arg)