From: Miguel Ojeda ojeda@kernel.org
maillist inclusion category: feature bugzilla: https://gitee.com/openeuler/kernel/issues/I5J75G CVE: NA
Reference: https://lore.kernel.org/rust-for-linux/CANiq72nDcJLSB3pLhkdqGdLitfmqqCUVVfkY...
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Rust symbols can become quite long due to namespacing introduced by modules, types, traits, generics, etc.
Increasing to 255 is not enough in some cases, and therefore we need to introduce longer lengths to the symbol table.
In order to avoid increasing all lengths to 2 bytes (since most of them are small, including many Rust ones), we use ULEB128 to keep smaller symbols in 1 byte, with the rest in 2 bytes.
Reviewed-by: Kees Cook keescook@chromium.org Co-developed-by: Alex Gaynor alex.gaynor@gmail.com Signed-off-by: Alex Gaynor alex.gaynor@gmail.com Co-developed-by: Wedson Almeida Filho wedsonaf@google.com Signed-off-by: Wedson Almeida Filho wedsonaf@google.com Co-developed-by: Gary Guo gary@garyguo.net Signed-off-by: Gary Guo gary@garyguo.net Co-developed-by: Boqun Feng boqun.feng@gmail.com Signed-off-by: Boqun Feng boqun.feng@gmail.com Co-developed-by: Matthew Wilcox willy@infradead.org Signed-off-by: Matthew Wilcox willy@infradead.org Signed-off-by: Miguel Ojeda ojeda@kernel.org Signed-off-by: Weilong Chen chenweilong@huawei.com --- kernel/kallsyms.c | 26 ++++++++++++++++++++++---- scripts/kallsyms.c | 29 ++++++++++++++++++++++++++--- 2 files changed, 48 insertions(+), 7 deletions(-)
diff --git a/kernel/kallsyms.c b/kernel/kallsyms.c index fe9de067771c..ef5f2e5eb1cc 100644 --- a/kernel/kallsyms.c +++ b/kernel/kallsyms.c @@ -66,12 +66,20 @@ 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 @@ -124,7 +132,7 @@ 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, @@ -138,8 +146,18 @@ 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; } diff --git a/scripts/kallsyms.c b/scripts/kallsyms.c index 269927591605..28348f6f5604 100644 --- a/scripts/kallsyms.c +++ b/scripts/kallsyms.c @@ -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");