// SPDX-License-Identifier: GPL-2.0#include <string.h>#include "debug.h" #include "demangle-rust.h" /* * Mangled Rust symbols look like this: * *     _$LT$std..sys..fd..FileDesc$u20$as$u20$core..ops..Drop$GT$::drop::hc68340e1baa4987a * * The original symbol is: * *     <std::sys::fd::FileDesc as core::ops::Drop>::drop * * The last component of the path is a 64-bit hash in lowercase hex, prefixed * with "h". Rust does not have a global namespace between crates, an illusion * which Rust maintains by using the hash to distinguish things that would * otherwise have the same symbol. * * Any path component not starting with a XID_Start character is prefixed with * "_". * * The following escape sequences are used: * *     ","  =>  $C$ *     "@"  =>  $SP$ *     "*"  =>  $BP$ *     "&"  =>  $RF$ *     "<"  =>  $LT$ *     ">"  =>  $GT$ *     "("  =>  $LP$ *     ")"  =>  $RP$ *     " "  =>  $u20$ *     "'"  =>  $u27$ *     "["  =>  $u5b$ *     "]"  =>  $u5d$ *     "~"  =>  $u7e$ * * A double ".." means "::" and a single "." means "-". * * The only characters allowed in the mangled symbol are a-zA-Z0-9 and _.:$ */ static const char *hash_prefix = "::h";static const size_t hash_prefix_len = 3;static const size_t hash_len = 16; static bool is_prefixed_hash(const char *start);static bool looks_like_rust(const char *sym, size_t len);static bool unescape(const char **in, char **out, const char *seq, char value); /* * INPUT: *     sym: symbol that has been through BFD-demangling * * This function looks for the following indicators: * *  1. The hash must consist of "h" followed by 16 lowercase hex digits. * *  2. As a sanity check, the hash must use between 5 and 15 of the 16 possible *     hex digits. This is true of 99.9998% of hashes so once in your life you *     may see a false negative. The point is to notice path components that *     could be Rust hashes but are probably not, like "haaaaaaaaaaaaaaaa". In *     this case a false positive (non-Rust symbol has an important path *     component removed because it looks like a Rust hash) is worse than a *     false negative (the rare Rust symbol is not demangled) so this sets the *     balance in favor of false negatives. * *  3. There must be no characters other than a-zA-Z0-9 and _.:$ * *  4. There must be no unrecognized $-sign sequences. * *  5. There must be no sequence of three or more dots in a row ("..."). */boolrust_is_mangled(const char *sym){	size_t len, len_without_hash; 	if (!sym)		return false; 	len = strlen(sym);	if (len <= hash_prefix_len + hash_len)		/* Not long enough to contain "::h" + hash + something else */		return false; 	len_without_hash = len - (hash_prefix_len + hash_len);	if (!is_prefixed_hash(sym + len_without_hash))		return false; 	return looks_like_rust(sym, len_without_hash);} /* * A hash is the prefix "::h" followed by 16 lowercase hex digits. The hex * digits must comprise between 5 and 15 (inclusive) distinct digits. */static bool is_prefixed_hash(const char *str){	const char *end;	bool seen[16];	size_t i;	int count; 	if (strncmp(str, hash_prefix, hash_prefix_len))		return false;	str += hash_prefix_len; 	memset(seen, false, sizeof(seen));	for (end = str + hash_len; str < end; str++)		if (*str >= '0' && *str <= '9')			seen[*str - '0'] = true;		else if (*str >= 'a' && *str <= 'f')			seen[*str - 'a' + 10] = true;		else			return false; 	/* Count how many distinct digits seen */	count = 0;	for (i = 0; i < 16; i++)		if (seen[i])			count++; 	return count >= 5 && count <= 15;} static bool looks_like_rust(const char *str, size_t len){	const char *end = str + len; 	while (str < end)		switch (*str) {		case '$':			if (!strncmp(str, "$C$", 3))				str += 3;			else if (!strncmp(str, "$SP$", 4)					|| !strncmp(str, "$BP$", 4)					|| !strncmp(str, "$RF$", 4)					|| !strncmp(str, "$LT$", 4)					|| !strncmp(str, "$GT$", 4)					|| !strncmp(str, "$LP$", 4)					|| !strncmp(str, "$RP$", 4))				str += 4;			else if (!strncmp(str, "$u20$", 5)					|| !strncmp(str, "$u27$", 5)					|| !strncmp(str, "$u5b$", 5)					|| !strncmp(str, "$u5d$", 5)					|| !strncmp(str, "$u7e$", 5))				str += 5;			else				return false;			break;		case '.':			/* Do not allow three or more consecutive dots */			if (!strncmp(str, "...", 3))				return false;			/* Fall through */		case 'a' ... 'z':		case 'A' ... 'Z':		case '0' ... '9':		case '_':		case ':':			str++;			break;		default:			return false;		} 	return true;} /* * INPUT: *     sym: symbol for which rust_is_mangled(sym) returns true * * The input is demangled in-place because the mangled name is always longer * than the demangled one. */voidrust_demangle_sym(char *sym){	const char *in;	char *out;	const char *end; 	if (!sym)		return; 	in = sym;	out = sym;	end = sym + strlen(sym) - (hash_prefix_len + hash_len); 	while (in < end)		switch (*in) {		case '$':			if (!(unescape(&in, &out, "$C$", ',')					|| unescape(&in, &out, "$SP$", '@')					|| unescape(&in, &out, "$BP$", '*')					|| unescape(&in, &out, "$RF$", '&')					|| unescape(&in, &out, "$LT$", '<')					|| unescape(&in, &out, "$GT$", '>')					|| unescape(&in, &out, "$LP$", '(')					|| unescape(&in, &out, "$RP$", ')')					|| unescape(&in, &out, "$u20$", ' ')					|| unescape(&in, &out, "$u27$", '\'')					|| unescape(&in, &out, "$u5b$", '[')					|| unescape(&in, &out, "$u5d$", ']')					|| unescape(&in, &out, "$u7e$", '~'))) {				pr_err("demangle-rust: unexpected escape sequence");				goto done;			}			break;		case '_':			/*			 * If this is the start of a path component and the next			 * character is an escape sequence, ignore the			 * underscore. The mangler inserts an underscore to make			 * sure the path component begins with a XID_Start			 * character.			 */			if ((in == sym || in[-1] == ':') && in[1] == '$')				in++;			else				*out++ = *in++;			break;		case '.':			if (in[1] == '.') {				/* ".." becomes "::" */				*out++ = ':';				*out++ = ':';				in += 2;			} else {				/* "." becomes "-" */				*out++ = '-';				in++;			}			break;		case 'a' ... 'z':		case 'A' ... 'Z':		case '0' ... '9':		case ':':			*out++ = *in++;			break;		default:			pr_err("demangle-rust: unexpected character '%c' in symbol\n",				*in);			goto done;		} done:	*out = '\0';} static bool unescape(const char **in, char **out, const char *seq, char value){	size_t len = strlen(seq); 	if (strncmp(*in, seq, len))		return false; 	**out = value; 	*in += len;	*out += 1; 	return true;}