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Wed, 11 Jan 2023 16:12:47 +0000 From: Gary Guo To: Michael Ellerman , Nicholas Piggin , Christophe Leroy , Luis Chamberlain , Masahiro Yamada , Nathan Chancellor , Nick Desaulniers , Nicolas Schier , Miguel Ojeda , Alex Gaynor , Wedson Almeida Filho , Boqun Feng , Gary Guo , =?utf-8?q?Bj=C3=B6rn_Roy_Baron?= , Kees Cook , Joel Stanley , Julia Lawall , Guo Zhengkui Cc: Wedson Almeida Filho , linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, linux-modules@vger.kernel.org, linux-kbuild@vger.kernel.org, rust-for-linux@vger.kernel.org Subject: [PATCH] modpost: support arbitrary symbol length in modversion Date: Wed, 11 Jan 2023 16:11:51 +0000 Message-Id: <20230111161155.1349375-1-gary@garyguo.net> X-Mailer: git-send-email 2.34.1 X-ClientProxiedBy: LO4P123CA0658.GBRP123.PROD.OUTLOOK.COM (2603:10a6:600:316::7) To LO2P265MB5183.GBRP265.PROD.OUTLOOK.COM (2603:10a6:600:253::10) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: LO2P265MB5183:EE_|CWXP265MB5370:EE_ X-MS-Office365-Filtering-Correlation-Id: f6811b3c-3412-4454-ece1-08daf3eeadba X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0; 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Rust symbols (which encodes crate and module names) can be quite a bit longer. The length limit in kallsyms is increased to 512 for this reason. It's a waste of space to simply expand the fixed array size to 512 in modversion info entries. I therefore make it variably sized, with offset to the next entry indicated by the initial "next" field. In addition to supporting longer-than-56/60 byte symbols, this patch also reduce the size for short symbols by getting rid of excessive 0 paddings. There are still some zero paddings to ensure "next" and "crc" fields are properly aligned. This patch does have a tiny drawback that it makes ".mod.c" files generated a bit less easy to read, as code like "\x08\x00\x00\x00\x78\x56\x34\x12" "symbol\0\0" is generated as opposed to { 0x12345678, "symbol" }, because the structure is now variable-length. But hopefully nobody reads the generated file :) Link: b8a94bfb3395 ("kallsyms: increase maximum kernel symbol length to 512") Link: https://github.com/Rust-for-Linux/linux/pull/379 Signed-off-by: Gary Guo --- arch/powerpc/kernel/module_64.c | 3 ++- include/linux/module.h | 6 ++++-- kernel/module/version.c | 21 +++++++++------------ scripts/export_report.pl | 9 +++++---- scripts/mod/modpost.c | 33 +++++++++++++++++++++++---------- 5 files changed, 43 insertions(+), 29 deletions(-) diff --git a/arch/powerpc/kernel/module_64.c b/arch/powerpc/kernel/module_64.c index ff045644f13f..eac23c11d579 100644 --- a/arch/powerpc/kernel/module_64.c +++ b/arch/powerpc/kernel/module_64.c @@ -236,10 +236,11 @@ static void dedotify_versions(struct modversion_info *vers, { struct modversion_info *end; - for (end = (void *)vers + size; vers < end; vers++) + for (end = (void *)vers + size; vers < end; vers = (void *)vers + vers->next) { if (vers->name[0] == '.') { memmove(vers->name, vers->name+1, strlen(vers->name)); } + } } /* diff --git a/include/linux/module.h b/include/linux/module.h index 8c5909c0076c..37cb25af9099 100644 --- a/include/linux/module.h +++ b/include/linux/module.h @@ -34,8 +34,10 @@ #define MODULE_NAME_LEN MAX_PARAM_PREFIX_LEN struct modversion_info { - unsigned long crc; - char name[MODULE_NAME_LEN]; + /* Offset of the next modversion entry in relation to this one. */ + u32 next; + u32 crc; + char name[0]; }; struct module; diff --git a/kernel/module/version.c b/kernel/module/version.c index 53f43ac5a73e..af7478dcc158 100644 --- a/kernel/module/version.c +++ b/kernel/module/version.c @@ -17,32 +17,29 @@ int check_version(const struct load_info *info, { Elf_Shdr *sechdrs = info->sechdrs; unsigned int versindex = info->index.vers; - unsigned int i, num_versions; - struct modversion_info *versions; + struct modversion_info *versions, *end; + u32 crcval; /* Exporting module didn't supply crcs? OK, we're already tainted. */ if (!crc) return 1; + crcval = *crc; /* No versions at all? modprobe --force does this. */ if (versindex == 0) return try_to_force_load(mod, symname) == 0; versions = (void *)sechdrs[versindex].sh_addr; - num_versions = sechdrs[versindex].sh_size - / sizeof(struct modversion_info); + end = (void *)versions + sechdrs[versindex].sh_size; - for (i = 0; i < num_versions; i++) { - u32 crcval; - - if (strcmp(versions[i].name, symname) != 0) + for (; versions < end; versions = (void *)versions + versions->next) { + if (strcmp(versions->name, symname) != 0) continue; - crcval = *crc; - if (versions[i].crc == crcval) + if (versions->crc == crcval) return 1; - pr_debug("Found checksum %X vs module %lX\n", - crcval, versions[i].crc); + pr_debug("Found checksum %X vs module %X\n", + crcval, versions->crc); goto bad_version; } diff --git a/scripts/export_report.pl b/scripts/export_report.pl index feb3d5542a62..1117646f3141 100755 --- a/scripts/export_report.pl +++ b/scripts/export_report.pl @@ -116,18 +116,19 @@ foreach my $thismod (@allcfiles) { while ( <$module> ) { chomp; if ($state == 0) { - $state = 1 if ($_ =~ /static const struct modversion_info/); + $state = 1 if ($_ =~ /static const char ____versions/); next; } if ($state == 1) { - $state = 2 if ($_ =~ /__attribute__\(\(section\("__versions"\)\)\)/); + $state = 2 if ($_ =~ /__used __section\("__versions"\)/); next; } if ($state == 2) { - if ( $_ !~ /0x[0-9a-f]+,/ ) { + if ( $_ !~ /\\0"/ ) { + last if ($_ =~ /;/); next; } - my $sym = (split /([,"])/,)[4]; + my $sym = (split /(["\\])/,)[2]; my ($module, $value, $symbol, $gpl) = @{$SYMBOL{$sym}}; $SYMBOL{ $sym } = [ $module, $value+1, $symbol, $gpl]; push(@{$MODULE{$thismod}} , $sym); diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c index efff8078e395..334d170de31f 100644 --- a/scripts/mod/modpost.c +++ b/scripts/mod/modpost.c @@ -2046,13 +2046,17 @@ static void add_exported_symbols(struct buffer *buf, struct module *mod) static void add_versions(struct buffer *b, struct module *mod) { struct symbol *s; + unsigned int name_len; + unsigned int name_len_padded; + unsigned int tmp; + unsigned char *tmp_view = (unsigned char *)&tmp; if (!modversions) return; buf_printf(b, "\n"); - buf_printf(b, "static const struct modversion_info ____versions[]\n"); - buf_printf(b, "__used __section(\"__versions\") = {\n"); + buf_printf(b, "static const char ____versions[]\n"); + buf_printf(b, "__used __section(\"__versions\") =\n"); list_for_each_entry(s, &mod->unresolved_symbols, list) { if (!s->module) @@ -2062,16 +2066,25 @@ static void add_versions(struct buffer *b, struct module *mod) s->name, mod->name); continue; } - if (strlen(s->name) >= MODULE_NAME_LEN) { - error("too long symbol \"%s\" [%s.ko]\n", - s->name, mod->name); - break; - } - buf_printf(b, "\t{ %#8x, \"%s\" },\n", - s->crc, s->name); + name_len = strlen(s->name); + name_len_padded = (name_len + 1 + 3) & ~3; + + /* Offset to next entry */ + tmp = TO_NATIVE(8 + name_len_padded); + buf_printf(b, "\t\"\\x%02x\\x%02x\\x%02x\\x%02x", + tmp_view[0], tmp_view[1], tmp_view[2], tmp_view[3]); + + tmp = TO_NATIVE(s->crc); + buf_printf(b, "\\x%02x\\x%02x\\x%02x\\x%02x\"\n", + tmp_view[0], tmp_view[1], tmp_view[2], tmp_view[3]); + + buf_printf(b, "\t\"%s", s->name); + for (; name_len < name_len_padded; name_len++) + buf_printf(b, "\\0"); + buf_printf(b, "\"\n"); } - buf_printf(b, "};\n"); + buf_printf(b, ";\n"); } static void add_depends(struct buffer *b, struct module *mod)