tools/x86/kcpuid: Parse subleaf ranges if provided

It's a common pattern in cpuid leaves to have the same bitfields format
repeated across a number of subleaves.  Typically, this is used for
enumerating hierarchial structures like cache and TLB levels, CPU
topology levels, etc.

Modify kcpuid.c to handle subleaf ranges in the CSV file subleaves
column.  For example, make it able to parse lines in the form:

 # LEAF, SUBLEAVES,  reg,    bits,    short_name             , ...
    0xb,       1:0,  eax,     4:0,    x2apic_id_shift        , ...
    0xb,       1:0,  ebx,    15:0,    domain_lcpus_count     , ...
    0xb,       1:0,  ecx,     7:0,    domain_nr              , ...

This way, full output can be printed to the user.
Signed-off-by: Ahmed S. Darwish <darwi@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/20240718134755.378115-8-darwi@linutronix.de

tools/arch/x86/kcpuid/kcpuid.c

@@ -305,6 +305,8 @@ static int parse_line(char *line)
 	struct bits_desc *bdesc;
 	int reg_index;
 	char *start, *end;
+	u32 subleaf_start, subleaf_end;
+	unsigned bit_start, bit_end;
 
 	/* Skip comments and NULL line */
 	if (line[0] == '#' || line[0] == '\n')
@@ -343,13 +345,25 @@ static int parse_line(char *line)
 		return 0;
 
 	/* subleaf */
-	sub = strtoul(tokens[1], NULL, 0);
-	if ((int)sub > func->nr)
-		return -1;
+	buf = tokens[1];
+	end = strtok(buf, ":");
+	start = strtok(NULL, ":");
+	subleaf_end = strtoul(end, NULL, 0);
+
+	/* A subleaf range is given? */
+	if (start) {
+		subleaf_start = strtoul(start, NULL, 0);
+		subleaf_end = min(subleaf_end, (u32)(func->nr - 1));
+		if (subleaf_start > subleaf_end)
+			return 0;
+	} else {
+		subleaf_start = subleaf_end;
+		if (subleaf_start > (u32)(func->nr - 1))
+			return 0;
+	}
 
-	leaf = &func->leafs[sub];
+	/* register */
 	buf = tokens[2];
-
 	if (strcasestr(buf, "EAX"))
 		reg_index = R_EAX;
 	else if (strcasestr(buf, "EBX"))
@@ -361,23 +375,23 @@ static int parse_line(char *line)
 	else
 		goto err_exit;
 
-	reg = &leaf->info[reg_index];
-	bdesc = &reg->descs[reg->nr++];
-
 	/* bit flag or bits field */
 	buf = tokens[3];
-
 	end = strtok(buf, ":");
-	bdesc->end = strtoul(end, NULL, 0);
-	bdesc->start = bdesc->end;
-
-	/* start != NULL means it is bit fields */
 	start = strtok(NULL, ":");
-	if (start)
-		bdesc->start = strtoul(start, NULL, 0);
-
-	strcpy(bdesc->simp, strtok(tokens[4], " \t"));
-	strcpy(bdesc->detail, tokens[5]);
+	bit_end = strtoul(end, NULL, 0);
+	bit_start = (start) ? strtoul(start, NULL, 0) : bit_end;
+
+	for (sub = subleaf_start; sub <= subleaf_end; sub++) {
+		leaf = &func->leafs[sub];
+		reg = &leaf->info[reg_index];
+		bdesc = &reg->descs[reg->nr++];
+
+		bdesc->end = bit_end;
+		bdesc->start = bit_start;
+		strcpy(bdesc->simp, strtok(tokens[4], " \t"));
+		strcpy(bdesc->detail, tokens[5]);
+	}
 	return 0;
 
 err_exit: