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