bpftool: Add ability to dump LOC_PARAM, LOC_PROTO and LOCSEC

In raw mode ensure we can dump new BTF kinds in normal/json format.
BTF_KIND_LOC_PARAMs are rendered as strings, for example a
const value of 0x2a and a dereference of %r10 + 0x20:

  [12] LOC_PARAM '(anon)' size=4 flags=0x2 vlen=1 values='0x2a'
  [13] LOC_PARAM '(anon)' size=8 flags=0x38 vlen=2 values='*(reg10 + 0x20)'

LOC_PROTOs render the associated values of each of their
LOC_PARAMs for easier readability:

  [14] LOC_PROTO '(anon)' vlen=2
  	type_id=12 value='0x2a'
  	type_id=13 value='*(reg10 + 0x20)'

and LOCSEC shows function name associated with site:

  [15] LOCSEC 'inline.text' vlen=1
  	name='foo' func_type_id=5 loc_proto_type_id=14 offset=64

Registers are displayed in an architecture-neutral form;
'regN' where N is the DWARF register number, or 'fbreg'
for the stack frame base.

Signed-off-by: Alan Maguire <alan.maguire@oracle.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://patch.msgid.link/20260924111428.75957-10-alan.maguire@oracle.com

tools/bpf/bpftool/btf.c

@@ -29,6 +29,7 @@
 
 #define MAX_ROOT_IDS		16
 #define MAX_BTF_FILES		64
+#define MAX_LOC_PARAM_WORDS	8
 
 static const char * const btf_kind_str[NR_BTF_KINDS] = {
 	[BTF_KIND_UNKN]		= "UNKNOWN",
@@ -51,6 +52,9 @@ static const char * const btf_kind_str[NR_BTF_KINDS] = {
 	[BTF_KIND_DECL_TAG]	= "DECL_TAG",
 	[BTF_KIND_TYPE_TAG]	= "TYPE_TAG",
 	[BTF_KIND_ENUM64]	= "ENUM64",
+	[BTF_KIND_LOC_PARAM]	= "LOC_PARAM",
+	[BTF_KIND_LOC_PROTO]	= "LOC_PROTO",
+	[BTF_KIND_LOCSEC]	= "LOCSEC",
 };
 
 struct sort_datum {
@@ -117,6 +121,137 @@ static int btf_kind_safe(int kind)
 	return kind <= BTF_KIND_MAX ? kind : BTF_KIND_UNKN;
 }
 
+static void btf_loc_param_reg_str(__u32 reg, char *str, size_t sz)
+{
+	if (reg == BTF_LOC_PARAM_FBREG)
+		snprintf(str, sz, "fbreg");
+	else
+		snprintf(str, sz, "reg%u", reg);
+}
+
+static void btf_loc_param_raw_str(const struct btf_loc_param *p, __u32 vlen,
+				  char *str, size_t sz)
+{
+	__u32 i, nr_words = min(vlen, (__u32)MAX_LOC_PARAM_WORDS);
+	size_t off = 0;
+
+	if (!sz)
+		return;
+
+	off += snprintf(str + off, sz - off, "raw=[");
+	for (i = 0; i < nr_words && off < sz; i++)
+		off += snprintf(str + off, sz - off, "%s0x%08x",
+				i ? ", " : "", p->values[i]);
+	if (vlen > nr_words && off < sz)
+		off += snprintf(str + off, sz - off, ", ...");
+	if (off < sz)
+		snprintf(str + off, sz - off, "]");
+}
+
+static void btf_loc_param_str(const struct btf_type *t, char *str, size_t sz)
+{
+	const struct btf_loc_param *p;
+	__u32 i = 0, vlen;
+	__u64 value;
+	__u32 value_size;
+	bool negative = false;
+	char regs[32] = {};
+	char num[32] = {};
+	const char *op = "";
+
+	if (!t || !btf_is_loc_param(t)) {
+		snprintf(str, sz, "<invalid>");
+		return;
+	}
+
+	p = btf_loc_param(t);
+	vlen = btf_vlen(t);
+
+	if (p->flags & BTF_LOC_PARAM_REG) {
+		__u32 nregs = (p->flags == BTF_LOC_PARAM_REG) ? vlen : 1;
+
+		if (nregs > vlen) {
+			btf_loc_param_raw_str(p, vlen, str, sz);
+			return;
+		}
+
+		switch (nregs) {
+		case 2:
+			btf_loc_param_reg_str(p->values[0], regs, sizeof(regs));
+			snprintf(regs + strlen(regs), sizeof(regs) - strlen(regs),
+				 ", ");
+			btf_loc_param_reg_str(p->values[1],
+					      regs + strlen(regs),
+					      sizeof(regs) - strlen(regs));
+			break;
+		case 1:
+			btf_loc_param_reg_str(p->values[0], regs, sizeof(regs));
+			break;
+		default:
+			btf_loc_param_raw_str(p, vlen, str, sz);
+			return;
+		}
+		i += nregs;
+	}
+	if (p->flags & (BTF_LOC_PARAM_CONST|BTF_LOC_PARAM_OFFSET)) {
+		switch (vlen - i) {
+		case 1:
+			value_size = sizeof(p->values[0]);
+			value = p->values[i];
+			break;
+		case 2:
+			value_size = 2 * sizeof(p->values[0]);
+			value = ((__u64)p->values[i + 1] << 32) | p->values[i];
+			break;
+		default:
+			btf_loc_param_raw_str(p, vlen, str, sz);
+			return;
+		}
+		i = vlen;
+		if (p->flags & BTF_LOC_PARAM_SIGNED) {
+			/*
+			 * size describes the represented parameter, so it
+			 * describes a constant's signed width. An offset
+			 * is determined by its value words after the register
+			 * number.
+			 */
+			__u32 size = p->flags & BTF_LOC_PARAM_OFFSET ?
+				     value_size : t->size;
+			__u32 bits = size * 8;
+
+			/*
+			 * Since we represent constant values in hex, we
+			 * need to determine if the value is negative so
+			 * we can prepend a "-", and also fix the value
+			 * to be positive so we can have - 0x<value>.
+			 */
+			if (size && size <= sizeof(value)) {
+				if (size < sizeof(value))
+					value &= (1ULL << bits) - 1;
+				negative = value & (1ULL << (bits - 1));
+				if (negative)
+					value = size == sizeof(value) ? -value :
+						(1ULL << bits) - value;
+			}
+		}
+		snprintf(num, sizeof(num), "0x%llx%s", (unsigned long long)value,
+			 p->flags & BTF_LOC_PARAM_ADDR ? " (addr)" : "");
+	}
+	if (i != vlen) {
+		btf_loc_param_raw_str(p, vlen, str, sz);
+		return;
+	}
+	if (num[0])
+		op = regs[0] ? (negative ? " - " : " + ") : negative ? "-" : "";
+
+	snprintf(str, sz, "%s%s%s%s%s",
+		 p->flags & BTF_LOC_PARAM_DEREF ? "*(" : "",
+		 regs,
+		 op,
+		 num,
+		 p->flags & BTF_LOC_PARAM_DEREF ? ")" : "");
+}
+
 static int dump_btf_type(const struct btf *btf, __u32 id,
 			 const struct btf_type *t)
 {
@@ -415,6 +550,95 @@ static int dump_btf_type(const struct btf *btf, __u32 id,
 		}
 		break;
 	}
+	case BTF_KIND_LOC_PARAM: {
+		const struct btf_loc_param *p = btf_loc_param(t);
+		__u32 vlen = btf_vlen(t);
+		char param_str[256] = {};
+
+		btf_loc_param_str(t, param_str, sizeof(param_str));
+
+		if (json_output) {
+			jsonw_uint_field(w, "size", t->size);
+			jsonw_uint_field(w, "flags", p->flags);
+			jsonw_uint_field(w, "vlen", vlen);
+			jsonw_string_field(w, "values", param_str);
+		} else {
+			printf(" size=%u flags=0x%x vlen=%u values='%s'",
+			       t->size, p->flags, vlen, param_str);
+		}
+		break;
+	}
+	case BTF_KIND_LOC_PROTO: {
+		__u32 *params = btf_loc_proto_params(t);
+		__u32 i, vlen = btf_vlen(t);
+
+		if (json_output) {
+			jsonw_uint_field(w, "vlen", vlen);
+			jsonw_name(w, "params");
+			jsonw_start_array(w);
+		} else {
+			printf(" vlen=%u", vlen);
+		}
+
+		for (i = 0; i < vlen; i++, params++) {
+			const struct btf_type *p;
+			char param_str[256] = {};
+
+			if (*params) {
+				p = btf__type_by_id(btf, *params);
+				btf_loc_param_str(p, param_str, sizeof(param_str));
+			} else {
+				snprintf(param_str, sizeof(param_str), "<unavailable>");
+			}
+			if (json_output) {
+				jsonw_start_object(w);
+				jsonw_uint_field(w, "type_id", *params);
+				jsonw_string_field(w, "value", param_str);
+				jsonw_end_object(w);
+			} else {
+				printf("\n\ttype_id=%u value='%s'", *params, param_str);
+			}
+		}
+		if (json_output)
+			jsonw_end_array(w);
+		break;
+	}
+
+	case BTF_KIND_LOCSEC: {
+		struct btf_loc *locs = btf_locsec_locs(t);
+		__u32 i, vlen = btf_vlen(t);
+
+		if (json_output) {
+			jsonw_uint_field(w, "vlen", vlen);
+			jsonw_name(w, "locs");
+			jsonw_start_array(w);
+		} else {
+			printf(" vlen=%u", vlen);
+		}
+
+		for (i = 0; i < vlen; i++, locs++) {
+			const struct btf_type *f = btf__type_by_id(btf, locs->func);
+			const char *name = "<invalid>";
+
+			if (f && btf_is_func(f))
+				name = btf_str(btf, f->name_off);
+
+			if (json_output) {
+				jsonw_start_object(w);
+				jsonw_uint_field(w, "func_type_id", locs->func);
+				jsonw_string_field(w, "name", name);
+				jsonw_uint_field(w, "loc_proto_type_id", locs->loc_proto);
+				jsonw_uint_field(w, "offset", locs->offset);
+				jsonw_end_object(w);
+			} else {
+				printf("\n\tname='%s' func_type_id=%u loc_proto_type_id=%u offset=%u",
+				       name, locs->func, locs->loc_proto, locs->offset);
+			}
+		}
+		if (json_output)
+			jsonw_end_array(w);
+		break;
+	}
 	default:
 		break;
 	}