kallsyms: Rust requirements

index 8caabddf817c..880c4404731b 100644
@@ -27,8 +27,18 @@
 
 #define ARRAY_SIZE(arr) (sizeof(arr) / sizeof(arr[0]))
 
+#define _stringify_1(x)	#x
+#define _stringify(x)	_stringify_1(x)
+
 #define KSYM_NAME_LEN		128
 
+/* A substantially bigger size than the current maximum. */
+#define KSYM_NAME_LEN_BUFFER	512
+_Static_assert(
+	KSYM_NAME_LEN_BUFFER == KSYM_NAME_LEN * 4,
+	"Please keep KSYM_NAME_LEN_BUFFER in sync with KSYM_NAME_LEN"
+);
+
 struct sym_entry {
 	unsigned long long addr;
 	unsigned int len;

@@ -197,15 +207,15 @@ static void check_symbol_range(const char *sym, unsigned long long addr,
 
 static struct sym_entry *read_symbol(FILE *in)
 {
-	char name[500], type;
+	char name[KSYM_NAME_LEN_BUFFER+1], type;
 	unsigned long long addr;
 	unsigned int len;
 	struct sym_entry *sym;
 	int rc;
 
-	rc = fscanf(in, "%llx %c %499s\n", &addr, &type, name);
+	rc = fscanf(in, "%llx %c %" _stringify(KSYM_NAME_LEN_BUFFER) "s\n", &addr, &type, name);
 	if (rc != 3) {
-		if (rc != EOF && fgets(name, 500, in) == NULL)
+		if (rc != EOF && fgets(name, KSYM_NAME_LEN_BUFFER + 1, in) == NULL)
 			fprintf(stderr, "Read error or end of file.\n");
 		return NULL;
 	}

index 79f2eb617a62..e8d2262ef2d2 100644
@@ -69,12 +69,20 @@ static unsigned int kallsyms_expand_symbol(unsigned int off,
 	data = &kallsyms_names[off];
 	len = *data;
 	data++;
+	off++;
+
+	/* If MSB is 1, it is a "big" symbol, so needs an additional byte. */
+	if ((len & 0x80) != 0) {
+		len = (len & 0x7F) | (*data << 7);
+		data++;
+		off++;
+	}
 
 	/*
 	 * Update the offset to return the offset for the next symbol on
 	 * the compressed stream.
 	 */
-	off += len + 1;
+	off += len;
 
 	/*
 	 * For every byte on the compressed symbol data, copy the table

@@ -127,7 +135,7 @@ static char kallsyms_get_symbol_type(unsigned int off)
 static unsigned int get_symbol_offset(unsigned long pos)
 {
 	const u8 *name;
-	int i;
+	int i, len;
 
 	/*
 	 * Use the closest marker we have. We have markers every 256 positions,

@@ -141,8 +149,18 @@ static unsigned int get_symbol_offset(unsigned long pos)
 	 * so we just need to add the len to the current pointer for every
 	 * symbol we wish to skip.
 	 */
-	for (i = 0; i < (pos & 0xFF); i++)
-		name = name + (*name) + 1;
+	for (i = 0; i < (pos & 0xFF); i++) {
+		len = *name;
+
+		/*
+		 * If MSB is 1, it is a "big" symbol, so we need to look into
+		 * the next byte (and skip it, too).
+		 */
+		if ((len & 0x80) != 0)
+			len = ((len & 0x7F) | (name[1] << 7)) + 1;
+
+		name = name + len + 1;
+	}
 
 	return name - kallsyms_names;
 }

index 880c4404731b..c4e85eec2b4b 100644
@@ -480,12 +480,35 @@ static void write_src(void)
 		if ((i & 0xFF) == 0)
 			markers[i >> 8] = off;
 
-		printf("\t.byte 0x%02x", table[i]->len);
+		/* There cannot be any symbol of length zero. */
+		if (table[i]->len == 0) {
+			fprintf(stderr, "kallsyms failure: "
+				"unexpected zero symbol length\n");
+			exit(EXIT_FAILURE);
+		}
+
+		/* Only lengths that fit in up-to-two-byte ULEB128 are supported. */
+		if (table[i]->len > 0x3FFF) {
+			fprintf(stderr, "kallsyms failure: "
+				"unexpected huge symbol length\n");
+			exit(EXIT_FAILURE);
+		}
+
+		/* Encode length with ULEB128. */
+		if (table[i]->len <= 0x7F) {
+			/* Most symbols use a single byte for the length. */
+			printf("\t.byte 0x%02x", table[i]->len);
+			off += table[i]->len + 1;
+		} else {
+			/* "Big" symbols use two bytes. */
+			printf("\t.byte 0x%02x, 0x%02x",
+				(table[i]->len & 0x7F) | 0x80,
+				(table[i]->len >> 7) & 0x7F);
+			off += table[i]->len + 2;
+		}
 		for (k = 0; k < table[i]->len; k++)
 			printf(", 0x%02x", table[i]->sym[k]);
 		printf("\n");
-
-		off += table[i]->len + 1;
 	}
 	printf("\n");
 

index ce1bd2fbf23e..e5ad6e31697d 100644
@@ -15,7 +15,7 @@
 
 #include <asm/sections.h>
 
-#define KSYM_NAME_LEN 128
+#define KSYM_NAME_LEN 512
 #define KSYM_SYMBOL_LEN (sizeof("%s+%#lx/%#lx [%s %s]") + \
 			(KSYM_NAME_LEN - 1) + \
 			2*(BITS_PER_LONG*3/10) + (MODULE_NAME_LEN - 1) + \

index bc475e62279d..ec06ce59d728 100644
@@ -213,7 +213,7 @@ static int klp_resolve_symbols(Elf_Shdr *sechdrs, const char *strtab,
 	 * we use the smallest/strictest upper bound possible (56, based on
 	 * the current definition of MODULE_NAME_LEN) to prevent overflows.
 	 */
-	BUILD_BUG_ON(MODULE_NAME_LEN < 56 || KSYM_NAME_LEN != 128);
+	BUILD_BUG_ON(MODULE_NAME_LEN < 56 || KSYM_NAME_LEN != 512);
 
 	relas = (Elf_Rela *) relasec->sh_addr;
 	/* For each rela in this klp relocation section */

@@ -227,7 +227,7 @@ static int klp_resolve_symbols(Elf_Shdr *sechdrs, const char *strtab,
 
 		/* Format: .klp.sym.sym_objname.sym_name,sympos */
 		cnt = sscanf(strtab + sym->st_name,
-			     ".klp.sym.%55[^.].%127[^,],%lu",
+			     ".klp.sym.%55[^.].%511[^,],%lu",
 			     sym_objname, sym_name, &sympos);
 		if (cnt != 3) {
 			pr_err("symbol %s has an incorrectly formatted name\n",

index c4e85eec2b4b..f9d07f9eb709 100644
@@ -30,10 +30,10 @@
 #define _stringify_1(x)	#x
 #define _stringify(x)	_stringify_1(x)
 
-#define KSYM_NAME_LEN		128
+#define KSYM_NAME_LEN		512
 
 /* A substantially bigger size than the current maximum. */
-#define KSYM_NAME_LEN_BUFFER	512
+#define KSYM_NAME_LEN_BUFFER	2048
 _Static_assert(
 	KSYM_NAME_LEN_BUFFER == KSYM_NAME_LEN * 4,
 	"Please keep KSYM_NAME_LEN_BUFFER in sync with KSYM_NAME_LEN"

index efb6c3f5f2a9..5a37ccbec54f 100644
@@ -6,7 +6,7 @@
 #include <stdio.h>
 #include <unistd.h>
 
-#define KSYM_NAME_LEN 128
+#define KSYM_NAME_LEN 512
 
 struct module;
 

index e7758707cadd..116a80c31675 100644
@@ -95,7 +95,7 @@ struct perf_record_throttle {
 };
 
 #ifndef KSYM_NAME_LEN
-#define KSYM_NAME_LEN 256
+#define KSYM_NAME_LEN 512
 #endif
 
 struct perf_record_ksymbol {

index 72ab9870454b..542f9b059c3b 100644
@@ -7,7 +7,7 @@
 #include <linux/types.h>
 
 #ifndef KSYM_NAME_LEN
-#define KSYM_NAME_LEN 256
+#define KSYM_NAME_LEN 512
 #endif
 
 static inline u8 kallsyms2elf_binding(char type)