[PATCH v2 1/2] module: Add module_kallsyms_on_each_addr()
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From: Lawrence Lin via B4 Relay <devnull+deduce.gmail.com@kernel.org>
Date: 2026-10-04 19:51:01
Also in:
b4-sent, linux-trace-kernel, lkml
Subsystem:
module support, the rest · Maintainers:
Luis Chamberlain, Petr Pavlu, Daniel Gomez, Sami Tolvanen, Linus Torvalds
From: Lawrence Lin <redacted> ftrace needs the addresses of the symbols of a module while the module is still being loaded: ftrace_module_init() runs before complete_formation(), while the module is MODULE_STATE_UNFORMED, and module_kallsyms_on_each_symbol() skips unformed modules. It also needs exactly the symbols that find_kallsyms_symbol() may resolve an address to, so that it agrees with kallsyms_lookup(). Factor the symbol filter of find_kallsyms_symbol() into is_lookup_symbol() and add module_kallsyms_on_each_addr(), which calls a function with the address of each such symbol of a given module. Like find_kallsyms_symbol(), it reads mod->kallsyms under RCU, which add_kallsyms() has set up by then. No functional change to find_kallsyms_symbol(). Assisted-by: Claude:claude-opus-5-5 Signed-off-by: Lawrence Lin <redacted> --- include/linux/module.h | 10 ++++++++++ kernel/module/kallsyms.c | 44 +++++++++++++++++++++++++++++++++++--------- 2 files changed, 45 insertions(+), 9 deletions(-)
diff --git a/include/linux/module.h b/include/linux/module.h
index 96cc98568eea..8b1c06d1118c 100644
--- a/include/linux/module.h
+++ b/include/linux/module.h@@ -971,6 +971,10 @@ unsigned long module_kallsyms_lookup_name(const char *name); unsigned long find_kallsyms_symbol_value(struct module *mod, const char *name); +void module_kallsyms_on_each_addr(struct module *mod, + void (*fn)(void *, unsigned long), + void *data); + #else /* CONFIG_MODULES && CONFIG_KALLSYMS */ static inline int module_kallsyms_on_each_symbol(const char *modname,
@@ -1014,6 +1018,12 @@ static inline unsigned long find_kallsyms_symbol_value(struct module *mod, return 0; } +static inline void module_kallsyms_on_each_addr(struct module *mod, + void (*fn)(void *, unsigned long), + void *data) +{ +} + #endif /* CONFIG_MODULES && CONFIG_KALLSYMS */ /* Define __free(module_put) macro for struct module *. */
diff --git a/kernel/module/kallsyms.c b/kernel/module/kallsyms.c
index f23126d804b2..bccee4b8294c 100644
--- a/kernel/module/kallsyms.c
+++ b/kernel/module/kallsyms.c@@ -246,6 +246,18 @@ static const char *kallsyms_symbol_name(struct mod_kallsyms *kallsyms, unsigned return kallsyms->strtab + kallsyms->symtab[symnum].st_name; } +/* + * Whether find_kallsyms_symbol() may resolve an address to symbol @symnum. + * Unnamed symbols are ignored: they're uninformative and inserted at a whim. + */ +static bool is_lookup_symbol(struct mod_kallsyms *kallsyms, unsigned int symnum) +{ + const char *name = kallsyms_symbol_name(kallsyms, symnum); + + return kallsyms->symtab[symnum].st_shndx != SHN_UNDEF && + *name != '\0' && !is_mapping_symbol(name); +} + /* * Given a module and address, find the corresponding symbol and return its name * while providing its size and offset if needed.
@@ -286,15 +298,7 @@ static const char *find_kallsyms_symbol(struct module *mod, const Elf_Sym *sym = &kallsyms->symtab[i]; unsigned long thisval = kallsyms_symbol_value(sym); - if (sym->st_shndx == SHN_UNDEF) - continue; - - /* - * We ignore unnamed symbols: they're uninformative - * and inserted at a whim. - */ - if (*kallsyms_symbol_name(kallsyms, i) == '\0' || - is_mapping_symbol(kallsyms_symbol_name(kallsyms, i))) + if (!is_lookup_symbol(kallsyms, i)) continue; if (thisval <= addr && thisval > bestval) {
@@ -458,6 +462,28 @@ unsigned long find_kallsyms_symbol_value(struct module *mod, const char *name) return __find_kallsyms_symbol_value(mod, name); } +/* + * Call @fn with the address of each symbol of @mod that find_kallsyms_symbol() + * may resolve an address to. Unlike module_kallsyms_on_each_symbol(), this + * also works while @mod is still being loaded. + */ +void module_kallsyms_on_each_addr(struct module *mod, + void (*fn)(void *, unsigned long), + void *data) +{ + struct mod_kallsyms *kallsyms; + unsigned int i; + + guard(rcu)(); + kallsyms = rcu_dereference(mod->kallsyms); + + /* ELF starts real symbols at 1. */ + for (i = 1; i < kallsyms->num_symtab; i++) { + if (is_lookup_symbol(kallsyms, i)) + fn(data, kallsyms_symbol_value(&kallsyms->symtab[i])); + } +} + int module_kallsyms_on_each_symbol(const char *modname, int (*fn)(void *, const char *, unsigned long), void *data)
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2.55.0