From 47346e96f004eca07720e1e2b24fc7f0b0df4092 Mon Sep 17 00:00:00 2001 From: Masahiro Yamada Date: Tue, 24 Sep 2019 21:07:40 +0900 Subject: modpost: fix static EXPORT_SYMBOL warnings for UML build Johannes Berg reports lots of modpost warnings on ARCH=um builds: WARNING: "rename" [vmlinux] is a static EXPORT_SYMBOL WARNING: "lseek" [vmlinux] is a static EXPORT_SYMBOL WARNING: "ftruncate64" [vmlinux] is a static EXPORT_SYMBOL WARNING: "getuid" [vmlinux] is a static EXPORT_SYMBOL WARNING: "lseek64" [vmlinux] is a static EXPORT_SYMBOL WARNING: "unlink" [vmlinux] is a static EXPORT_SYMBOL WARNING: "pwrite64" [vmlinux] is a static EXPORT_SYMBOL WARNING: "close" [vmlinux] is a static EXPORT_SYMBOL WARNING: "opendir" [vmlinux] is a static EXPORT_SYMBOL WARNING: "pread64" [vmlinux] is a static EXPORT_SYMBOL WARNING: "syscall" [vmlinux] is a static EXPORT_SYMBOL WARNING: "readdir" [vmlinux] is a static EXPORT_SYMBOL WARNING: "readdir64" [vmlinux] is a static EXPORT_SYMBOL WARNING: "futimes" [vmlinux] is a static EXPORT_SYMBOL WARNING: "__lxstat" [vmlinux] is a static EXPORT_SYMBOL WARNING: "write" [vmlinux] is a static EXPORT_SYMBOL WARNING: "closedir" [vmlinux] is a static EXPORT_SYMBOL WARNING: "__xstat" [vmlinux] is a static EXPORT_SYMBOL WARNING: "fsync" [vmlinux] is a static EXPORT_SYMBOL WARNING: "__lxstat64" [vmlinux] is a static EXPORT_SYMBOL WARNING: "__fxstat64" [vmlinux] is a static EXPORT_SYMBOL WARNING: "telldir" [vmlinux] is a static EXPORT_SYMBOL WARNING: "printf" [vmlinux] is a static EXPORT_SYMBOL WARNING: "readlink" [vmlinux] is a static EXPORT_SYMBOL WARNING: "__sprintf_chk" [vmlinux] is a static EXPORT_SYMBOL WARNING: "link" [vmlinux] is a static EXPORT_SYMBOL WARNING: "rmdir" [vmlinux] is a static EXPORT_SYMBOL WARNING: "fdatasync" [vmlinux] is a static EXPORT_SYMBOL WARNING: "truncate" [vmlinux] is a static EXPORT_SYMBOL WARNING: "statfs" [vmlinux] is a static EXPORT_SYMBOL WARNING: "__errno_location" [vmlinux] is a static EXPORT_SYMBOL WARNING: "__xmknod" [vmlinux] is a static EXPORT_SYMBOL WARNING: "open64" [vmlinux] is a static EXPORT_SYMBOL WARNING: "truncate64" [vmlinux] is a static EXPORT_SYMBOL WARNING: "open" [vmlinux] is a static EXPORT_SYMBOL WARNING: "read" [vmlinux] is a static EXPORT_SYMBOL WARNING: "chown" [vmlinux] is a static EXPORT_SYMBOL WARNING: "chmod" [vmlinux] is a static EXPORT_SYMBOL WARNING: "utime" [vmlinux] is a static EXPORT_SYMBOL WARNING: "fchmod" [vmlinux] is a static EXPORT_SYMBOL WARNING: "seekdir" [vmlinux] is a static EXPORT_SYMBOL WARNING: "ioctl" [vmlinux] is a static EXPORT_SYMBOL WARNING: "dup2" [vmlinux] is a static EXPORT_SYMBOL WARNING: "statfs64" [vmlinux] is a static EXPORT_SYMBOL WARNING: "utimes" [vmlinux] is a static EXPORT_SYMBOL WARNING: "mkdir" [vmlinux] is a static EXPORT_SYMBOL WARNING: "fchown" [vmlinux] is a static EXPORT_SYMBOL WARNING: "__guard" [vmlinux] is a static EXPORT_SYMBOL WARNING: "symlink" [vmlinux] is a static EXPORT_SYMBOL WARNING: "access" [vmlinux] is a static EXPORT_SYMBOL WARNING: "__stack_smash_handler" [vmlinux] is a static EXPORT_SYMBOL When you run "make", the modpost is run twice; before linking vmlinux, and before building modules. All the warnings above are from the second modpost. The offending symbols are defined not in vmlinux, but in the C library. The first modpost is run against the relocatable vmlinux.o, and those warnings are nicely suppressed because the SH_UNDEF entries from the symbol table clear the ->is_static flag. The second modpost is run against the executable vmlinux (+ modules), where those symbols have been resolved, but the definitions do not exist. This commit fixes it in a straightforward way; suppress the static EXPORT_SYMBOL warnings from "vmlinux". Without this commit, we see valid warnings twice anyway. For example, ARCH=arm64 defconfig shows the following warning twice: WARNING: "HYPERVISOR_platform_op" [vmlinux] is a static EXPORT_SYMBOL_GPL So, it is reasonable to suppress the second one. Fixes: 15bfc2348d54 ("modpost: check for static EXPORT_SYMBOL* functions") Reported-by: Johannes Berg Signed-off-by: Masahiro Yamada Tested-by: Johannes Berg Tested-by: Denis Efremov --- scripts/mod/modpost.c | 13 +++++++++---- 1 file changed, 9 insertions(+), 4 deletions(-) (limited to 'scripts/mod') diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c index 3961941e8e7a..442d5e2ad688 100644 --- a/scripts/mod/modpost.c +++ b/scripts/mod/modpost.c @@ -2652,15 +2652,20 @@ int main(int argc, char **argv) fatal("modpost: Section mismatches detected.\n" "Set CONFIG_SECTION_MISMATCH_WARN_ONLY=y to allow them.\n"); for (n = 0; n < SYMBOL_HASH_SIZE; n++) { - struct symbol *s = symbolhash[n]; + struct symbol *s; + + for (s = symbolhash[n]; s; s = s->next) { + /* + * Do not check "vmlinux". This avoids the same warnings + * shown twice, and false-positives for ARCH=um. + */ + if (is_vmlinux(s->module->name) && !s->module->is_dot_o) + continue; - while (s) { if (s->is_static) warn("\"%s\" [%s] is a static %s\n", s->name, s->module->name, export_str(s->export)); - - s = s->next; } } -- cgit v1.2.3 From bf70b0503abd19194dba25fe383d143d0229dc6a Mon Sep 17 00:00:00 2001 From: Masahiro Yamada Date: Thu, 3 Oct 2019 16:58:21 +0900 Subject: module: swap the order of symbol.namespace Currently, EXPORT_SYMBOL_NS(_GPL) constructs the kernel symbol as follows: __ksymtab_SYMBOL.NAMESPACE The sym_extract_namespace() in modpost allocates memory for the part SYMBOL.NAMESPACE when '.' is contained. One problem is that the pointer returned by strdup() is lost because the symbol name will be copied to malloc'ed memory by alloc_symbol(). No one will keep track of the pointer of strdup'ed memory. sym->namespace still points to the NAMESPACE part. So, you can free it with complicated code like this: free(sym->namespace - strlen(sym->name) - 1); It complicates memory free. To fix it elegantly, I swapped the order of the symbol and the namespace as follows: __ksymtab_NAMESPACE.SYMBOL then, simplified sym_extract_namespace() so that it allocates memory only for the NAMESPACE part. I prefer this order because it is intuitive and also matches to major languages. For example, NAMESPACE::NAME in C++, MODULE.NAME in Python. Reviewed-by: Matthias Maennich Signed-off-by: Masahiro Yamada Signed-off-by: Jessica Yu --- scripts/mod/modpost.c | 16 +++++++--------- 1 file changed, 7 insertions(+), 9 deletions(-) (limited to 'scripts/mod') diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c index 3961941e8e7a..c4b536ac1327 100644 --- a/scripts/mod/modpost.c +++ b/scripts/mod/modpost.c @@ -350,18 +350,16 @@ static enum export export_from_sec(struct elf_info *elf, unsigned int sec) static const char *sym_extract_namespace(const char **symname) { - size_t n; - char *dupsymname; + char *namespace = NULL; + char *ns_separator; - n = strcspn(*symname, "."); - if (n < strlen(*symname) - 1) { - dupsymname = NOFAIL(strdup(*symname)); - dupsymname[n] = '\0'; - *symname = dupsymname; - return dupsymname + n + 1; + ns_separator = strchr(*symname, '.'); + if (ns_separator) { + namespace = NOFAIL(strndup(*symname, ns_separator - *symname)); + *symname = ns_separator + 1; } - return NULL; + return namespace; } /** -- cgit v1.2.3 From 389eb3f5f4abbdb9810458ac9b87427336ba5b91 Mon Sep 17 00:00:00 2001 From: Masahiro Yamada Date: Thu, 3 Oct 2019 16:58:22 +0900 Subject: modpost: fix broken sym->namespace for external module builds Currently, external module builds produce tons of false-positives: WARNING: module uses symbol from namespace , but does not import it. Here, the part shows a random string. When you build external modules, the symbol info of vmlinux and in-kernel modules are read from $(objtree)/Module.symvers, but read_dump() is buggy in multiple ways: [1] When the modpost is run for vmlinux and in-kernel modules, sym_extract_namespace() allocates memory for the namespace. On the other hand, read_dump() does not, then sym->namespace will point to somewhere in the line buffer of get_next_line(). The data in the buffer will be replaced soon, and sym->namespace will end up with pointing to unrelated data. As a result, check_exports() will show random strings in the warning messages. [2] When there is no namespace, sym_extract_namespace() returns NULL. On the other hand, read_dump() sets namespace to an empty string "". (but, it will be later replaced with unrelated data due to bug [1].) The check_exports() shows a warning unless exp->namespace is NULL, so every symbol read from read_dump() emits the warning, which is mostly false positive. To address [1], sym_add_exported() calls strdup() for s->namespace. The namespace from sym_extract_namespace() must be freed to avoid memory leak. For [2], I changed the if-conditional in check_exports(). This commit also fixes sym_add_exported() to set s->namespace correctly when the symbol is preloaded. Reviewed-by: Matthias Maennich Signed-off-by: Masahiro Yamada Signed-off-by: Jessica Yu --- scripts/mod/modpost.c | 13 ++++++++----- 1 file changed, 8 insertions(+), 5 deletions(-) (limited to 'scripts/mod') diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c index c4b536ac1327..4d2cdb4d71e3 100644 --- a/scripts/mod/modpost.c +++ b/scripts/mod/modpost.c @@ -166,7 +166,7 @@ struct symbol { struct module *module; unsigned int crc; int crc_valid; - const char *namespace; + char *namespace; unsigned int weak:1; unsigned int vmlinux:1; /* 1 if symbol is defined in vmlinux */ unsigned int kernel:1; /* 1 if symbol is from kernel @@ -348,7 +348,7 @@ static enum export export_from_sec(struct elf_info *elf, unsigned int sec) return export_unknown; } -static const char *sym_extract_namespace(const char **symname) +static char *sym_extract_namespace(const char **symname) { char *namespace = NULL; char *ns_separator; @@ -373,7 +373,6 @@ static struct symbol *sym_add_exported(const char *name, const char *namespace, if (!s) { s = new_symbol(name, mod, export); - s->namespace = namespace; } else { if (!s->preloaded) { warn("%s: '%s' exported twice. Previous export was in %s%s\n", @@ -384,6 +383,8 @@ static struct symbol *sym_add_exported(const char *name, const char *namespace, s->module = mod; } } + free(s->namespace); + s->namespace = namespace ? strdup(namespace) : NULL; s->preloaded = 0; s->vmlinux = is_vmlinux(mod->name); s->kernel = 0; @@ -670,7 +671,8 @@ static void handle_modversions(struct module *mod, struct elf_info *info, unsigned int crc; enum export export; bool is_crc = false; - const char *name, *namespace; + const char *name; + char *namespace; if ((!is_vmlinux(mod->name) || mod->is_dot_o) && strstarts(symname, "__ksymtab")) @@ -745,6 +747,7 @@ static void handle_modversions(struct module *mod, struct elf_info *info, name = symname + strlen("__ksymtab_"); namespace = sym_extract_namespace(&name); sym_add_exported(name, namespace, mod, export); + free(namespace); } if (strcmp(symname, "init_module") == 0) mod->has_init = 1; @@ -2193,7 +2196,7 @@ static int check_exports(struct module *mod) else basename = mod->name; - if (exp->namespace) { + if (exp->namespace && exp->namespace[0]) { add_namespace(&mod->required_namespaces, exp->namespace); -- cgit v1.2.3