129 lines
3.8 KiB
Diff
129 lines
3.8 KiB
Diff
From 73bbb94466fd3f8b313eeb0b0467314a262dddb3 Mon Sep 17 00:00:00 2001
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From: Miguel Ojeda <ojeda@kernel.org>
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Date: Mon, 5 Apr 2021 04:58:39 +0200
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Subject: [PATCH] kallsyms: support "big" kernel symbols
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Rust symbols can become quite long due to namespacing introduced
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by modules, types, traits, generics, etc.
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Increasing to 255 is not enough in some cases, therefore
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introduce longer lengths to the symbol table.
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In order to avoid increasing all lengths to 2 bytes (since most
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of them are small, including many Rust ones), use ULEB128 to
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keep smaller symbols in 1 byte, with the rest in 2 bytes.
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Reviewed-by: Kees Cook <keescook@chromium.org>
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Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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Co-developed-by: Alex Gaynor <alex.gaynor@gmail.com>
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Signed-off-by: Alex Gaynor <alex.gaynor@gmail.com>
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Co-developed-by: Wedson Almeida Filho <wedsonaf@google.com>
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Signed-off-by: Wedson Almeida Filho <wedsonaf@google.com>
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Co-developed-by: Gary Guo <gary@garyguo.net>
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Signed-off-by: Gary Guo <gary@garyguo.net>
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Co-developed-by: Boqun Feng <boqun.feng@gmail.com>
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Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
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Co-developed-by: Matthew Wilcox <willy@infradead.org>
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Signed-off-by: Matthew Wilcox <willy@infradead.org>
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Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
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---
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kernel/kallsyms.c | 26 ++++++++++++++++++++++----
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scripts/kallsyms.c | 29 ++++++++++++++++++++++++++---
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2 files changed, 48 insertions(+), 7 deletions(-)
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--- a/kernel/kallsyms.c
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+++ b/kernel/kallsyms.c
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@@ -69,12 +69,20 @@ static unsigned int kallsyms_expand_symb
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data = &kallsyms_names[off];
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len = *data;
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data++;
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+ off++;
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+
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+ /* If MSB is 1, it is a "big" symbol, so needs an additional byte. */
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+ if ((len & 0x80) != 0) {
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+ len = (len & 0x7F) | (*data << 7);
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+ data++;
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+ off++;
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+ }
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/*
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* Update the offset to return the offset for the next symbol on
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* the compressed stream.
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*/
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- off += len + 1;
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+ off += len;
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/*
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* For every byte on the compressed symbol data, copy the table
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@@ -127,7 +135,7 @@ static char kallsyms_get_symbol_type(uns
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static unsigned int get_symbol_offset(unsigned long pos)
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{
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const u8 *name;
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- int i;
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+ int i, len;
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/*
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* Use the closest marker we have. We have markers every 256 positions,
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@@ -141,8 +149,18 @@ static unsigned int get_symbol_offset(un
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* so we just need to add the len to the current pointer for every
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* symbol we wish to skip.
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*/
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- for (i = 0; i < (pos & 0xFF); i++)
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- name = name + (*name) + 1;
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+ for (i = 0; i < (pos & 0xFF); i++) {
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+ len = *name;
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+
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+ /*
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+ * If MSB is 1, it is a "big" symbol, so we need to look into
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+ * the next byte (and skip it, too).
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+ */
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+ if ((len & 0x80) != 0)
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+ len = ((len & 0x7F) | (name[1] << 7)) + 1;
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+
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+ name = name + len + 1;
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+ }
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return name - kallsyms_names;
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}
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--- a/scripts/kallsyms.c
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+++ b/scripts/kallsyms.c
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@@ -470,12 +470,35 @@ static void write_src(void)
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if ((i & 0xFF) == 0)
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markers[i >> 8] = off;
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- printf("\t.byte 0x%02x", table[i]->len);
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+ /* There cannot be any symbol of length zero. */
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+ if (table[i]->len == 0) {
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+ fprintf(stderr, "kallsyms failure: "
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+ "unexpected zero symbol length\n");
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+ exit(EXIT_FAILURE);
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+ }
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+
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+ /* Only lengths that fit in up-to-two-byte ULEB128 are supported. */
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+ if (table[i]->len > 0x3FFF) {
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+ fprintf(stderr, "kallsyms failure: "
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+ "unexpected huge symbol length\n");
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+ exit(EXIT_FAILURE);
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+ }
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+
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+ /* Encode length with ULEB128. */
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+ if (table[i]->len <= 0x7F) {
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+ /* Most symbols use a single byte for the length. */
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+ printf("\t.byte 0x%02x", table[i]->len);
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+ off += table[i]->len + 1;
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+ } else {
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+ /* "Big" symbols use two bytes. */
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+ printf("\t.byte 0x%02x, 0x%02x",
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+ (table[i]->len & 0x7F) | 0x80,
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+ (table[i]->len >> 7) & 0x7F);
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+ off += table[i]->len + 2;
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+ }
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for (k = 0; k < table[i]->len; k++)
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printf(", 0x%02x", table[i]->sym[k]);
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printf("\n");
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-
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- off += table[i]->len + 1;
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}
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printf("\n");
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