Some Kernel modules use symbol_get() or symbol_request() in order to bind into other drivers. That's the case, for instance, of media dvb drivers that hook the frontend drivers via I2C using dvb_attach() macro.
When such bindings happen, one needs first to unload/unbind the driver that got the symbol before being able to unload/unbind the module that contains the needed symbol.
Add a logic to document it via /proc/modules and via lsmod.
Signed-off-by: Mauro Carvalho Chehab mchehab@kernel.org ---
See [PATCH v6 0/4] at: https://lore.kernel.org/all/cover.1652113087.git.mchehab@kernel.org/
drivers/mtd/chips/gen_probe.c | 4 ++-- include/linux/module.h | 4 ++-- kernel/module/main.c | 3 ++- samples/hw_breakpoint/data_breakpoint.c | 2 +- 4 files changed, 7 insertions(+), 6 deletions(-)
diff --git a/drivers/mtd/chips/gen_probe.c b/drivers/mtd/chips/gen_probe.c index 4d4f97841016..f1e97633ac09 100644 --- a/drivers/mtd/chips/gen_probe.c +++ b/drivers/mtd/chips/gen_probe.c @@ -208,10 +208,10 @@ static inline struct mtd_info *cfi_cmdset_unknown(struct map_info *map, if (!probename) return NULL;
- probe_function = __symbol_get(probename); + probe_function = __symbol_get(probename, THIS_MODULE); if (!probe_function) { request_module("cfi_cmdset_%4.4X", type); - probe_function = __symbol_get(probename); + probe_function = __symbol_get(probename, THIS_MODULE); } kfree(probename);
diff --git a/include/linux/module.h b/include/linux/module.h index a66b9be92ef5..07a77c2618b5 100644 --- a/include/linux/module.h +++ b/include/linux/module.h @@ -298,8 +298,8 @@ struct notifier_block;
extern int modules_disabled; /* for sysctl */ /* Get/put a kernel symbol (calls must be symmetric) */ -void *__symbol_get(const char *symbol); -#define symbol_get(x) ((typeof(&x))(__symbol_get(__stringify(x)))) +void *__symbol_get(const char *symbol, struct module *this); +#define symbol_get(x) ((typeof(&x))(__symbol_get(__stringify(x), THIS_MODULE)))
/* modules using other modules: kdb wants to see this. */ struct module_use { diff --git a/kernel/module/main.c b/kernel/module/main.c index 6044aeba0f18..ec1baa67d6e7 100644 --- a/kernel/module/main.c +++ b/kernel/module/main.c @@ -1259,7 +1259,7 @@ static void free_module(struct module *mod) #endif }
-void *__symbol_get(const char *symbol) +void *__symbol_get(const char *symbol, struct module *this) { struct find_symbol_arg fsa = { .name = symbol, @@ -1273,6 +1273,7 @@ void *__symbol_get(const char *symbol) return NULL; } preempt_enable(); + ref_module_dependency(fsa.owner, this); return (void *)kernel_symbol_value(fsa.sym); } EXPORT_SYMBOL_GPL(__symbol_get); diff --git a/samples/hw_breakpoint/data_breakpoint.c b/samples/hw_breakpoint/data_breakpoint.c index 418c46fe5ffc..30b3261a894b 100644 --- a/samples/hw_breakpoint/data_breakpoint.c +++ b/samples/hw_breakpoint/data_breakpoint.c @@ -41,7 +41,7 @@ static int __init hw_break_module_init(void) { int ret; struct perf_event_attr attr; - void *addr = __symbol_get(ksym_name); + void *addr = __symbol_get(ksym_name, THIS_MODULE);
if (!addr) return -ENXIO;