module loader dead code removal and cleanups v2

module loader dead code removal and cleanups v2

[Christoph Hellwig]

Hi all,

this series removes support for long term unused export types and
cleans up various loose ends in the module loader.

Changes since v1:
 - move struct symsearch to module.c
 - rework drm to not call find_module at all
 - llow RCU-sched locking for find_module
 - keep find_module as a public API instead of module_loaded
 - update a few comments and commit logs

Diffstat:
 arch/arm/configs/bcm2835_defconfig          |    1 
 arch/arm/configs/mxs_defconfig              |    1 
 arch/mips/configs/nlm_xlp_defconfig         |    1 
 arch/mips/configs/nlm_xlr_defconfig         |    1 
 arch/parisc/configs/generic-32bit_defconfig |    1 
 arch/parisc/configs/generic-64bit_defconfig |    1 
 arch/powerpc/configs/ppc6xx_defconfig       |    1 
 arch/powerpc/platforms/powernv/pci-cxl.c    |   22 -
 arch/s390/configs/debug_defconfig           |    1 
 arch/s390/configs/defconfig                 |    1 
 arch/sh/configs/edosk7760_defconfig         |    1 
 arch/sh/configs/sdk7780_defconfig           |    1 
 arch/x86/configs/i386_defconfig             |    1 
 arch/x86/configs/x86_64_defconfig           |    1 
 arch/x86/tools/relocs.c                     |    4 
 drivers/gpu/drm/drm_crtc_helper_internal.h  |   10 
 drivers/gpu/drm/drm_fb_helper.c             |   21 -
 drivers/gpu/drm/drm_kms_helper_common.c     |   25 +-
 include/asm-generic/vmlinux.lds.h           |   42 ---
 include/linux/export.h                      |    9 
 include/linux/kallsyms.h                    |   17 -
 include/linux/module.h                      |   48 ----
 init/Kconfig                                |   17 -
 kernel/kallsyms.c                           |    8 
 kernel/livepatch/core.c                     |   11 
 kernel/module.c                             |  310 +++++++++-------------------
 kernel/trace/trace_kprobe.c                 |    4 
 lib/bug.c                                   |    3 
 scripts/checkpatch.pl                       |    6 
 scripts/mod/modpost.c                       |   50 ----
 scripts/mod/modpost.h                       |    3 
 scripts/module.lds.S                        |    6 
 tools/include/linux/export.h                |    3 
 33 files changed, 142 insertions(+), 490 deletions(-)

[PATCH 01/13] powerpc/powernv: remove get_cxl_module

[Christoph Hellwig]

The static inline get_cxl_module function is entirely unused since commit
8bf6b91a5125a ("Revert "powerpc/powernv: Add support for the cxl kernel
api on the real phb"), so remove it.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Andrew Donnellan <ajd@linux.ibm.com>
---
 arch/powerpc/platforms/powernv/pci-cxl.c | 22 ----------------------
 1 file changed, 22 deletions(-)

diff --git a/arch/powerpc/platforms/powernv/pci-cxl.c b/arch/powerpc/platforms/powernv/pci-cxl.c
index 8c739c94ed28d6..53172862d23bd3 100644
--- a/arch/powerpc/platforms/powernv/pci-cxl.c
+++ b/arch/powerpc/platforms/powernv/pci-cxl.c
@@ -150,25 +150,3 @@ int pnv_cxl_ioda_msi_setup(struct pci_dev *dev, unsigned int hwirq,
 	return 0;
 }
 EXPORT_SYMBOL(pnv_cxl_ioda_msi_setup);
-
-#if IS_MODULE(CONFIG_CXL)
-static inline int get_cxl_module(void)
-{
-	struct module *cxl_module;
-
-	mutex_lock(&module_mutex);
-
-	cxl_module = find_module("cxl");
-	if (cxl_module)
-		__module_get(cxl_module);
-
-	mutex_unlock(&module_mutex);
-
-	if (!cxl_module)
-		return -ENODEV;
-
-	return 0;
-}
-#else
-static inline int get_cxl_module(void) { return 0; }
-#endif
-- 
2.29.2

[PATCH 03/13] module: unexport find_module and module_mutex

[Christoph Hellwig]

find_module is not used by modular code any more, and random driver code
has no business calling it to start with.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 kernel/module.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/kernel/module.c b/kernel/module.c
index 4bf30e4b3eaaa1..981302f616b411 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -88,7 +88,6 @@
  * (delete and add uses RCU list operations).
  */
 DEFINE_MUTEX(module_mutex);
-EXPORT_SYMBOL_GPL(module_mutex);
 static LIST_HEAD(modules);
 
 /* Work queue for freeing init sections in success case */
@@ -672,7 +671,6 @@ struct module *find_module(const char *name)
 	module_assert_mutex();
 	return find_module_all(name, strlen(name), false);
 }
-EXPORT_SYMBOL_GPL(find_module);
 
 #ifdef CONFIG_SMP
 
-- 
2.29.2

[PATCH 04/13] module: use RCU to synchronize find_module

[Christoph Hellwig]

Allow for a RCU-sched critical section around find_module, following
the lower level find_module_all helper, and switch the two callers
outside of module.c to use such a RCU-sched critical section instead
of module_mutex.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 include/linux/module.h      | 2 +-
 kernel/livepatch/core.c     | 5 +++--
 kernel/module.c             | 1 -
 kernel/trace/trace_kprobe.c | 4 ++--
 4 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/include/linux/module.h b/include/linux/module.h
index 7a0bcb5b1ffccd..a64aa84d1b182c 100644
--- a/include/linux/module.h
+++ b/include/linux/module.h
@@ -586,7 +586,7 @@ static inline bool within_module(unsigned long addr, const struct module *mod)
 	return within_module_init(addr, mod) || within_module_core(addr, mod);
 }
 
-/* Search for module by name: must hold module_mutex. */
+/* Search for module by name: must be in a RCU-sched critical section. */
 struct module *find_module(const char *name);
 
 struct symsearch {
diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c
index f76fdb9255323d..262cd9b003b9f0 100644
--- a/kernel/livepatch/core.c
+++ b/kernel/livepatch/core.c
@@ -19,6 +19,7 @@
 #include <linux/moduleloader.h>
 #include <linux/completion.h>
 #include <linux/memory.h>
+#include <linux/rcupdate.h>
 #include <asm/cacheflush.h>
 #include "core.h"
 #include "patch.h"
@@ -57,7 +58,7 @@ static void klp_find_object_module(struct klp_object *obj)
 	if (!klp_is_module(obj))
 		return;
 
-	mutex_lock(&module_mutex);
+	rcu_read_lock_sched();
 	/*
 	 * We do not want to block removal of patched modules and therefore
 	 * we do not take a reference here. The patches are removed by
@@ -74,7 +75,7 @@ static void klp_find_object_module(struct klp_object *obj)
 	if (mod && mod->klp_alive)
 		obj->mod = mod;
 
-	mutex_unlock(&module_mutex);
+	rcu_read_unlock_sched();
 }
 
 static bool klp_initialized(void)
diff --git a/kernel/module.c b/kernel/module.c
index 981302f616b411..6772fb2680eb3e 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -668,7 +668,6 @@ static struct module *find_module_all(const char *name, size_t len,
 
 struct module *find_module(const char *name)
 {
-	module_assert_mutex();
 	return find_module_all(name, strlen(name), false);
 }
 
diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
index e6fba1798771b4..3137992baa5e7a 100644
--- a/kernel/trace/trace_kprobe.c
+++ b/kernel/trace/trace_kprobe.c
@@ -124,9 +124,9 @@ static nokprobe_inline bool trace_kprobe_module_exist(struct trace_kprobe *tk)
 	if (!p)
 		return true;
 	*p = '\0';
-	mutex_lock(&module_mutex);
+	rcu_read_lock_sched();
 	ret = !!find_module(tk->symbol);
-	mutex_unlock(&module_mutex);
+	rcu_read_unlock_sched();
 	*p = ':';
 
 	return ret;
-- 
2.29.2

Re: [PATCH 04/13] module: use RCU to synchronize find_module

[Thiago Jung Bauermann]

Hi Christoph,

Christoph Hellwig <hch@lst.de> writes:

> diff --git a/kernel/module.c b/kernel/module.c
> index 981302f616b411..6772fb2680eb3e 100644
> --- a/kernel/module.c
> +++ b/kernel/module.c
> @@ -668,7 +668,6 @@ static struct module *find_module_all(const char *name, size_t len,
>  
>  struct module *find_module(const char *name)
>  {
> -	module_assert_mutex();

Does it make sense to replace the assert above with the warn below (untested)?

     RCU_LOCKDEP_WARN(rcu_read_lock_sched_held());

>  	return find_module_all(name, strlen(name), false);
>  }

-- 
Thiago Jung Bauermann
IBM Linux Technology Center

Re: [PATCH 04/13] module: use RCU to synchronize find_module

[Christoph Hellwig]

On Thu, Jan 28, 2021 at 05:50:56PM -0300, Thiago Jung Bauermann wrote:
> >  struct module *find_module(const char *name)
> >  {
> > -	module_assert_mutex();
> 
> Does it make sense to replace the assert above with the warn below (untested)?
> 
>      RCU_LOCKDEP_WARN(rcu_read_lock_sched_held());

One caller actually holds module_mutex still.  And find_module_all,
which implements the actual logic already asserts that either
module_mutex is held or rcu_read_lock, so I don't tink we need an
extra one here.

Re: [PATCH 04/13] module: use RCU to synchronize find_module

[Thiago Jung Bauermann]

Christoph Hellwig <hch@lst.de> writes:

> On Thu, Jan 28, 2021 at 05:50:56PM -0300, Thiago Jung Bauermann wrote:
>> >  struct module *find_module(const char *name)
>> >  {
>> > -	module_assert_mutex();
>> 
>> Does it make sense to replace the assert above with the warn below (untested)?
>> 
>>      RCU_LOCKDEP_WARN(rcu_read_lock_sched_held());
>
> One caller actually holds module_mutex still.  And find_module_all,
> which implements the actual logic already asserts that either
> module_mutex is held or rcu_read_lock, so I don't tink we need an
> extra one here.

Ok, thanks for the clarification.

-- 
Thiago Jung Bauermann
IBM Linux Technology Center

Re: [PATCH 04/13] module: use RCU to synchronize find_module

[Petr Mladek]

On Thu 2021-01-28 19:14:12, Christoph Hellwig wrote:
> Allow for a RCU-sched critical section around find_module, following
> the lower level find_module_all helper, and switch the two callers
> outside of module.c to use such a RCU-sched critical section instead
> of module_mutex.
> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>

It looks good and safe.

Reviewed-by: Petr Mladek <pmladek@suse.com>

Best Regards,
Petr

Re: [PATCH 04/13] module: use RCU to synchronize find_module

[Christoph Hellwig]

On Fri, Jan 29, 2021 at 04:29:02PM +0100, Miroslav Benes wrote:
> >  
> > -	mutex_lock(&module_mutex);
> > +	rcu_read_lock_sched();
> >  	/*
> >  	 * We do not want to block removal of patched modules and therefore
> >  	 * we do not take a reference here. The patches are removed by
> > @@ -74,7 +75,7 @@ static void klp_find_object_module(struct klp_object *obj)
> >  	if (mod && mod->klp_alive)
> 
> RCU always baffles me a bit, so I'll ask. Don't we need 
> rcu_dereference_sched() here? "mod" comes from a RCU-protected list, so I 
> wonder.

rcu_dereference* is only used for dereferencing points where that
reference itself is RCU protected, that is the lookup of mod itself down
in find_module_all in this case.

Re: [PATCH 04/13] module: use RCU to synchronize find_module

[Jessica Yu]

+++ Miroslav Benes [29/01/21 16:29 +0100]:
>On Thu, 28 Jan 2021, Christoph Hellwig wrote:
>
>> Allow for a RCU-sched critical section around find_module, following
>> the lower level find_module_all helper, and switch the two callers
>> outside of module.c to use such a RCU-sched critical section instead
>> of module_mutex.
>
>That's a nice idea.
>
>> @@ -57,7 +58,7 @@ static void klp_find_object_module(struct klp_object *obj)
>>  	if (!klp_is_module(obj))
>>  		return;
>>
>> -	mutex_lock(&module_mutex);
>> +	rcu_read_lock_sched();
>>  	/*
>>  	 * We do not want to block removal of patched modules and therefore
>>  	 * we do not take a reference here. The patches are removed by
>> @@ -74,7 +75,7 @@ static void klp_find_object_module(struct klp_object *obj)
>>  	if (mod && mod->klp_alive)
>
>RCU always baffles me a bit, so I'll ask. Don't we need
>rcu_dereference_sched() here? "mod" comes from a RCU-protected list, so I
>wonder.

Same here :-) I had to double check the RCU documentation. For our
modules list case I believe the rcu list API should take care of that
for us. Worth noting is this snippet from Documentation/RCU/whatisRCU.txt:

    rcu_dereference() is typically used indirectly, via the _rcu
    list-manipulation primitives, such as list_for_each_entry_rcu()

Re: [PATCH 04/13] module: use RCU to synchronize find_module

[Miroslav Benes]

On Mon, 1 Feb 2021, Jessica Yu wrote:

> +++ Miroslav Benes [29/01/21 16:29 +0100]:
> >On Thu, 28 Jan 2021, Christoph Hellwig wrote:
> >
> >> Allow for a RCU-sched critical section around find_module, following
> >> the lower level find_module_all helper, and switch the two callers
> >> outside of module.c to use such a RCU-sched critical section instead
> >> of module_mutex.
> >
> >That's a nice idea.
> >
> >> @@ -57,7 +58,7 @@ static void klp_find_object_module(struct klp_object
> >> *obj)
> >>   if (!klp_is_module(obj))
> >>    return;
> >>
> >> -	mutex_lock(&module_mutex);
> >> +	rcu_read_lock_sched();
> >>   /*
> >>    * We do not want to block removal of patched modules and therefore
> >>    * we do not take a reference here. The patches are removed by
> >> @@ -74,7 +75,7 @@ static void klp_find_object_module(struct klp_object
> >> *obj)
> >>   if (mod && mod->klp_alive)
> >
> >RCU always baffles me a bit, so I'll ask. Don't we need
> >rcu_dereference_sched() here? "mod" comes from a RCU-protected list, so I
> >wonder.
> 
> Same here :-) I had to double check the RCU documentation. For our
> modules list case I believe the rcu list API should take care of that
> for us. Worth noting is this snippet from Documentation/RCU/whatisRCU.txt:
> 
>    rcu_dereference() is typically used indirectly, via the _rcu
>    list-manipulation primitives, such as list_for_each_entry_rcu()

Ok, thanks to both for checking and explanation.

Ack to the patch then.

Miroslav

[PATCH 07/13] module: mark module_mutex static

[Christoph Hellwig]

Except for two lockdep asserts module_mutex is only used in module.c.
Remove the two asserts given that the functions they are in are not
exported and just called from the module code, and mark module_mutex
static.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 include/linux/module.h | 2 --
 kernel/module.c        | 2 +-
 lib/bug.c              | 3 ---
 3 files changed, 1 insertion(+), 6 deletions(-)

diff --git a/include/linux/module.h b/include/linux/module.h
index 3ea4ffae608f97..0f360c48fe92a6 100644
--- a/include/linux/module.h
+++ b/include/linux/module.h
@@ -550,8 +550,6 @@ static inline unsigned long kallsyms_symbol_value(const Elf_Sym *sym)
 }
 #endif
 
-extern struct mutex module_mutex;
-
 /* FIXME: It'd be nice to isolate modules during init, too, so they
    aren't used before they (may) fail.  But presently too much code
    (IDE & SCSI) require entry into the module during init.*/
diff --git a/kernel/module.c b/kernel/module.c
index 856df9e17ff3d0..5152fae1fc9406 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -87,7 +87,7 @@
  * 3) module_addr_min/module_addr_max.
  * (delete and add uses RCU list operations).
  */
-DEFINE_MUTEX(module_mutex);
+static DEFINE_MUTEX(module_mutex);
 static LIST_HEAD(modules);
 
 /* Work queue for freeing init sections in success case */
diff --git a/lib/bug.c b/lib/bug.c
index 7103440c0ee1af..8f9d537bfb2a59 100644
--- a/lib/bug.c
+++ b/lib/bug.c
@@ -91,8 +91,6 @@ void module_bug_finalize(const Elf_Ehdr *hdr, const Elf_Shdr *sechdrs,
 	char *secstrings;
 	unsigned int i;
 
-	lockdep_assert_held(&module_mutex);
-
 	mod->bug_table = NULL;
 	mod->num_bugs = 0;
 
@@ -118,7 +116,6 @@ void module_bug_finalize(const Elf_Ehdr *hdr, const Elf_Shdr *sechdrs,
 
 void module_bug_cleanup(struct module *mod)
 {
-	lockdep_assert_held(&module_mutex);
 	list_del_rcu(&mod->bug_list);
 }
 
-- 
2.29.2

[PATCH 10/13] module: pass struct find_symbol_args to find_symbol

[Christoph Hellwig]

Simplify the calling convention by passing the find_symbol_args structure
to find_symbol instead of initializing it inside the function.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 kernel/module.c | 113 ++++++++++++++++++++++--------------------------
 1 file changed, 52 insertions(+), 61 deletions(-)

diff --git a/kernel/module.c b/kernel/module.c
index ff9045cc984b50..f1441d39c015f5 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -536,12 +536,7 @@ static bool find_exported_symbol_in_section(const struct symsearch *syms,
  * Find an exported symbol and return it, along with, (optional) crc and
  * (optional) module which owns it.  Needs preempt disabled or module_mutex.
  */
-static const struct kernel_symbol *find_symbol(const char *name,
-					struct module **owner,
-					const s32 **crc,
-					enum mod_license *license,
-					bool gplok,
-					bool warn)
+static bool find_symbol(struct find_symbol_arg *fsa)
 {
 	static const struct symsearch arr[] = {
 		{ __start___ksymtab, __stop___ksymtab, __start___kcrctab,
@@ -561,19 +556,14 @@ static const struct kernel_symbol *find_symbol(const char *name,
 		  GPL_ONLY, true },
 #endif
 	};
-	struct find_symbol_arg fsa = {
-		.name = name,
-		.gplok = gplok,
-		.warn = warn,
-	};
 	struct module *mod;
 	unsigned int i;
 
 	module_assert_mutex_or_preempt();
 
 	for (i = 0; i < ARRAY_SIZE(arr); i++)
-		if (find_exported_symbol_in_section(&arr[i], NULL, &fsa))
-			goto found;
+		if (find_exported_symbol_in_section(&arr[i], NULL, fsa))
+			return true;
 
 	list_for_each_entry_rcu(mod, &modules, list,
 				lockdep_is_held(&module_mutex)) {
@@ -603,21 +593,12 @@ static const struct kernel_symbol *find_symbol(const char *name,
 			continue;
 
 		for (i = 0; i < ARRAY_SIZE(arr); i++)
-			if (find_exported_symbol_in_section(&arr[i], mod, &fsa))
-				goto found;
+			if (find_exported_symbol_in_section(&arr[i], mod, fsa))
+				return true;
 	}
 
-	pr_debug("Failed to find symbol %s\n", name);
-	return NULL;
-
-found:
-	if (owner)
-		*owner = fsa.owner;
-	if (crc)
-		*crc = fsa.crc;
-	if (license)
-		*license = fsa.license;
-	return fsa.sym;
+	pr_debug("Failed to find symbol %s\n", fsa->name);
+	return false;
 }
 
 /*
@@ -1079,12 +1060,15 @@ static inline void print_unload_info(struct seq_file *m, struct module *mod)
 
 void __symbol_put(const char *symbol)
 {
-	struct module *owner;
+	struct find_symbol_arg fsa = {
+		.name	= symbol,
+		.gplok	= true,
+	};
 
 	preempt_disable();
-	if (!find_symbol(symbol, &owner, NULL, NULL, true, false))
+	if (!find_symbol(&fsa))
 		BUG();
-	module_put(owner);
+	module_put(fsa.owner);
 	preempt_enable();
 }
 EXPORT_SYMBOL(__symbol_put);
@@ -1353,19 +1337,22 @@ static int check_version(const struct load_info *info,
 static inline int check_modstruct_version(const struct load_info *info,
 					  struct module *mod)
 {
-	const s32 *crc;
+	struct find_symbol_arg fsa = {
+		.name	= "module_layout",
+		.gplok	= true,
+	};
 
 	/*
 	 * Since this should be found in kernel (which can't be removed), no
 	 * locking is necessary -- use preempt_disable() to placate lockdep.
 	 */
 	preempt_disable();
-	if (!find_symbol("module_layout", NULL, &crc, NULL, true, false)) {
+	if (!find_symbol(&fsa)) {
 		preempt_enable();
 		BUG();
 	}
 	preempt_enable();
-	return check_version(info, "module_layout", mod, crc);
+	return check_version(info, "module_layout", mod, fsa.crc);
 }
 
 /* First part is kernel version, which we ignore if module has crcs. */
@@ -1459,10 +1446,11 @@ static const struct kernel_symbol *resolve_symbol(struct module *mod,
 						  const char *name,
 						  char ownername[])
 {
-	struct module *owner;
-	const struct kernel_symbol *sym;
-	const s32 *crc;
-	enum mod_license license;
+	struct find_symbol_arg fsa = {
+		.name	= name,
+		.gplok	= !(mod->taints & (1 << TAINT_PROPRIETARY_MODULE)),
+		.warn	= true,
+	};
 	int err;
 
 	/*
@@ -1472,42 +1460,40 @@ static const struct kernel_symbol *resolve_symbol(struct module *mod,
 	 */
 	sched_annotate_sleep();
 	mutex_lock(&module_mutex);
-	sym = find_symbol(name, &owner, &crc, &license,
-			  !(mod->taints & (1 << TAINT_PROPRIETARY_MODULE)), true);
-	if (!sym)
+	if (!find_symbol(&fsa))
 		goto unlock;
 
-	if (license == GPL_ONLY)
+	if (fsa.license == GPL_ONLY)
 		mod->using_gplonly_symbols = true;
 
-	if (!inherit_taint(mod, owner)) {
-		sym = NULL;
+	if (!inherit_taint(mod, fsa.owner)) {
+		fsa.sym = NULL;
 		goto getname;
 	}
 
-	if (!check_version(info, name, mod, crc)) {
-		sym = ERR_PTR(-EINVAL);
+	if (!check_version(info, name, mod, fsa.crc)) {
+		fsa.sym = ERR_PTR(-EINVAL);
 		goto getname;
 	}
 
-	err = verify_namespace_is_imported(info, sym, mod);
+	err = verify_namespace_is_imported(info, fsa.sym, mod);
 	if (err) {
-		sym = ERR_PTR(err);
+		fsa.sym = ERR_PTR(err);
 		goto getname;
 	}
 
-	err = ref_module(mod, owner);
+	err = ref_module(mod, fsa.owner);
 	if (err) {
-		sym = ERR_PTR(err);
+		fsa.sym = ERR_PTR(err);
 		goto getname;
 	}
 
 getname:
 	/* We must make copy under the lock if we failed to get ref. */
-	strncpy(ownername, module_name(owner), MODULE_NAME_LEN);
+	strncpy(ownername, module_name(fsa.owner), MODULE_NAME_LEN);
 unlock:
 	mutex_unlock(&module_mutex);
-	return sym;
+	return fsa.sym;
 }
 
 static const struct kernel_symbol *
@@ -2268,16 +2254,19 @@ static void free_module(struct module *mod)
 
 void *__symbol_get(const char *symbol)
 {
-	struct module *owner;
-	const struct kernel_symbol *sym;
+	struct find_symbol_arg fsa = {
+		.name	= symbol,
+		.gplok	= true,
+		.warn	= true,
+	};
 
 	preempt_disable();
-	sym = find_symbol(symbol, &owner, NULL, NULL, true, true);
-	if (sym && strong_try_module_get(owner))
-		sym = NULL;
+	if (!find_symbol(&fsa) || !strong_try_module_get(fsa.owner)) {
+		preempt_enable();
+		return NULL;
+	}
 	preempt_enable();
-
-	return sym ? (void *)kernel_symbol_value(sym) : NULL;
+	return (void *)kernel_symbol_value(fsa.sym);
 }
 EXPORT_SYMBOL_GPL(__symbol_get);
 
@@ -2290,7 +2279,6 @@ EXPORT_SYMBOL_GPL(__symbol_get);
 static int verify_exported_symbols(struct module *mod)
 {
 	unsigned int i;
-	struct module *owner;
 	const struct kernel_symbol *s;
 	struct {
 		const struct kernel_symbol *sym;
@@ -2307,12 +2295,15 @@ static int verify_exported_symbols(struct module *mod)
 
 	for (i = 0; i < ARRAY_SIZE(arr); i++) {
 		for (s = arr[i].sym; s < arr[i].sym + arr[i].num; s++) {
-			if (find_symbol(kernel_symbol_name(s), &owner, NULL,
-					NULL, true, false)) {
+			struct find_symbol_arg fsa = {
+				.name	= kernel_symbol_name(s),
+				.gplok	= true,
+			};
+			if (find_symbol(&fsa)) {
 				pr_err("%s: exports duplicate symbol %s"
 				       " (owned by %s)\n",
 				       mod->name, kernel_symbol_name(s),
-				       module_name(owner));
+				       module_name(fsa.owner));
 				return -ENOEXEC;
 			}
 		}
-- 
2.29.2

[PATCH 11/13] module: move struct symsearch to module.c

[Christoph Hellwig]

struct symsearch is only used inside of module.h, so move the definition
out of module.h.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 include/linux/module.h | 11 -----------
 kernel/module.c        | 11 +++++++++++
 2 files changed, 11 insertions(+), 11 deletions(-)

diff --git a/include/linux/module.h b/include/linux/module.h
index 0f360c48fe92a6..da0f5966ee80c9 100644
--- a/include/linux/module.h
+++ b/include/linux/module.h
@@ -587,17 +587,6 @@ static inline bool within_module(unsigned long addr, const struct module *mod)
 /* Search for module by name: must be in a RCU-sched critical section. */
 struct module *find_module(const char *name);
 
-struct symsearch {
-	const struct kernel_symbol *start, *stop;
-	const s32 *crcs;
-	enum mod_license {
-		NOT_GPL_ONLY,
-		GPL_ONLY,
-		WILL_BE_GPL_ONLY,
-	} license;
-	bool unused;
-};
-
 /* Returns 0 and fills in value, defined and namebuf, or -ERANGE if
    symnum out of range. */
 int module_get_kallsym(unsigned int symnum, unsigned long *value, char *type,
diff --git a/kernel/module.c b/kernel/module.c
index f1441d39c015f5..576c780e79c799 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -433,6 +433,17 @@ extern const s32 __start___kcrctab_unused_gpl[];
 #define symversion(base, idx) ((base != NULL) ? ((base) + (idx)) : NULL)
 #endif
 
+struct symsearch {
+	const struct kernel_symbol *start, *stop;
+	const s32 *crcs;
+	enum mod_license {
+		NOT_GPL_ONLY,
+		GPL_ONLY,
+		WILL_BE_GPL_ONLY,
+	} license;
+	bool unused;
+};
+
 struct find_symbol_arg {
 	/* Input */
 	const char *name;
-- 
2.29.2

[PATCH 12/13] module: remove EXPORT_SYMBOL_GPL_FUTURE

[Christoph Hellwig]

As far as I can tell this has never been used at all, and certainly
not any time recently.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 arch/x86/tools/relocs.c           |  4 ++--
 include/asm-generic/vmlinux.lds.h | 14 --------------
 include/linux/export.h            |  1 -
 include/linux/module.h            |  5 -----
 kernel/module.c                   | 29 ++---------------------------
 scripts/mod/modpost.c             | 13 +------------
 scripts/mod/modpost.h             |  1 -
 scripts/module.lds.S              |  2 --
 tools/include/linux/export.h      |  1 -
 9 files changed, 5 insertions(+), 65 deletions(-)

diff --git a/arch/x86/tools/relocs.c b/arch/x86/tools/relocs.c
index ce7188cbdae58a..0d210d0e83e241 100644
--- a/arch/x86/tools/relocs.c
+++ b/arch/x86/tools/relocs.c
@@ -61,8 +61,8 @@ static const char * const sym_regex_kernel[S_NSYMTYPES] = {
 	"(__iommu_table|__apicdrivers|__smp_locks)(|_end)|"
 	"__(start|end)_pci_.*|"
 	"__(start|end)_builtin_fw|"
-	"__(start|stop)___ksymtab(|_gpl|_unused|_unused_gpl|_gpl_future)|"
-	"__(start|stop)___kcrctab(|_gpl|_unused|_unused_gpl|_gpl_future)|"
+	"__(start|stop)___ksymtab(|_gpl|_unused|_unused_gpl)|"
+	"__(start|stop)___kcrctab(|_gpl|_unused|_unused_gpl)|"
 	"__(start|stop)___param|"
 	"__(start|stop)___modver|"
 	"__(start|stop)___bug_table|"
diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index b2b3d81b1535a5..83243506e68b00 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -495,13 +495,6 @@
 		__stop___ksymtab_unused_gpl = .;			\
 	}								\
 									\
-	/* Kernel symbol table: GPL-future-only symbols */		\
-	__ksymtab_gpl_future : AT(ADDR(__ksymtab_gpl_future) - LOAD_OFFSET) { \
-		__start___ksymtab_gpl_future = .;			\
-		KEEP(*(SORT(___ksymtab_gpl_future+*)))			\
-		__stop___ksymtab_gpl_future = .;			\
-	}								\
-									\
 	/* Kernel symbol table: Normal symbols */			\
 	__kcrctab         : AT(ADDR(__kcrctab) - LOAD_OFFSET) {		\
 		__start___kcrctab = .;					\
@@ -530,13 +523,6 @@
 		__stop___kcrctab_unused_gpl = .;			\
 	}								\
 									\
-	/* Kernel symbol table: GPL-future-only symbols */		\
-	__kcrctab_gpl_future : AT(ADDR(__kcrctab_gpl_future) - LOAD_OFFSET) { \
-		__start___kcrctab_gpl_future = .;			\
-		KEEP(*(SORT(___kcrctab_gpl_future+*)))			\
-		__stop___kcrctab_gpl_future = .;			\
-	}								\
-									\
 	/* Kernel symbol table: strings */				\
         __ksymtab_strings : AT(ADDR(__ksymtab_strings) - LOAD_OFFSET) {	\
 		*(__ksymtab_strings)					\
diff --git a/include/linux/export.h b/include/linux/export.h
index fceb5e85571711..362b64f8d4a7c2 100644
--- a/include/linux/export.h
+++ b/include/linux/export.h
@@ -157,7 +157,6 @@ struct kernel_symbol {
 
 #define EXPORT_SYMBOL(sym)		_EXPORT_SYMBOL(sym, "")
 #define EXPORT_SYMBOL_GPL(sym)		_EXPORT_SYMBOL(sym, "_gpl")
-#define EXPORT_SYMBOL_GPL_FUTURE(sym)	_EXPORT_SYMBOL(sym, "_gpl_future")
 #define EXPORT_SYMBOL_NS(sym, ns)	__EXPORT_SYMBOL(sym, "", #ns)
 #define EXPORT_SYMBOL_NS_GPL(sym, ns)	__EXPORT_SYMBOL(sym, "_gpl", #ns)
 
diff --git a/include/linux/module.h b/include/linux/module.h
index da0f5966ee80c9..e6e50ee3041238 100644
--- a/include/linux/module.h
+++ b/include/linux/module.h
@@ -411,11 +411,6 @@ struct module {
 
 	bool async_probe_requested;
 
-	/* symbols that will be GPL-only in the near future. */
-	const struct kernel_symbol *gpl_future_syms;
-	const s32 *gpl_future_crcs;
-	unsigned int num_gpl_future_syms;
-
 	/* Exception table */
 	unsigned int num_exentries;
 	struct exception_table_entry *extable;
diff --git a/kernel/module.c b/kernel/module.c
index 576c780e79c799..492b6fa5a662c8 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -413,11 +413,8 @@ extern const struct kernel_symbol __start___ksymtab[];
 extern const struct kernel_symbol __stop___ksymtab[];
 extern const struct kernel_symbol __start___ksymtab_gpl[];
 extern const struct kernel_symbol __stop___ksymtab_gpl[];
-extern const struct kernel_symbol __start___ksymtab_gpl_future[];
-extern const struct kernel_symbol __stop___ksymtab_gpl_future[];
 extern const s32 __start___kcrctab[];
 extern const s32 __start___kcrctab_gpl[];
-extern const s32 __start___kcrctab_gpl_future[];
 #ifdef CONFIG_UNUSED_SYMBOLS
 extern const struct kernel_symbol __start___ksymtab_unused[];
 extern const struct kernel_symbol __stop___ksymtab_unused[];
@@ -439,7 +436,6 @@ struct symsearch {
 	enum mod_license {
 		NOT_GPL_ONLY,
 		GPL_ONLY,
-		WILL_BE_GPL_ONLY,
 	} license;
 	bool unused;
 };
@@ -463,15 +459,8 @@ static bool check_exported_symbol(const struct symsearch *syms,
 {
 	struct find_symbol_arg *fsa = data;
 
-	if (!fsa->gplok) {
-		if (syms->license == GPL_ONLY)
-			return false;
-		if (syms->license == WILL_BE_GPL_ONLY && fsa->warn) {
-			pr_warn("Symbol %s is being used by a non-GPL module, "
-				"which will not be allowed in the future\n",
-				fsa->name);
-		}
-	}
+	if (!fsa->gplok && syms->license == GPL_ONLY)
+		return false;
 
 #ifdef CONFIG_UNUSED_SYMBOLS
 	if (syms->unused && fsa->warn) {
@@ -555,9 +544,6 @@ static bool find_symbol(struct find_symbol_arg *fsa)
 		{ __start___ksymtab_gpl, __stop___ksymtab_gpl,
 		  __start___kcrctab_gpl,
 		  GPL_ONLY, false },
-		{ __start___ksymtab_gpl_future, __stop___ksymtab_gpl_future,
-		  __start___kcrctab_gpl_future,
-		  WILL_BE_GPL_ONLY, false },
 #ifdef CONFIG_UNUSED_SYMBOLS
 		{ __start___ksymtab_unused, __stop___ksymtab_unused,
 		  __start___kcrctab_unused,
@@ -584,10 +570,6 @@ static bool find_symbol(struct find_symbol_arg *fsa)
 			{ mod->gpl_syms, mod->gpl_syms + mod->num_gpl_syms,
 			  mod->gpl_crcs,
 			  GPL_ONLY, false },
-			{ mod->gpl_future_syms,
-			  mod->gpl_future_syms + mod->num_gpl_future_syms,
-			  mod->gpl_future_crcs,
-			  WILL_BE_GPL_ONLY, false },
 #ifdef CONFIG_UNUSED_SYMBOLS
 			{ mod->unused_syms,
 			  mod->unused_syms + mod->num_unused_syms,
@@ -2297,7 +2279,6 @@ static int verify_exported_symbols(struct module *mod)
 	} arr[] = {
 		{ mod->syms, mod->num_syms },
 		{ mod->gpl_syms, mod->num_gpl_syms },
-		{ mod->gpl_future_syms, mod->num_gpl_future_syms },
 #ifdef CONFIG_UNUSED_SYMBOLS
 		{ mod->unused_syms, mod->num_unused_syms },
 		{ mod->unused_gpl_syms, mod->num_unused_gpl_syms },
@@ -3215,11 +3196,6 @@ static int find_module_sections(struct module *mod, struct load_info *info)
 				     sizeof(*mod->gpl_syms),
 				     &mod->num_gpl_syms);
 	mod->gpl_crcs = section_addr(info, "__kcrctab_gpl");
-	mod->gpl_future_syms = section_objs(info,
-					    "__ksymtab_gpl_future",
-					    sizeof(*mod->gpl_future_syms),
-					    &mod->num_gpl_future_syms);
-	mod->gpl_future_crcs = section_addr(info, "__kcrctab_gpl_future");
 
 #ifdef CONFIG_UNUSED_SYMBOLS
 	mod->unused_syms = section_objs(info, "__ksymtab_unused",
@@ -3413,7 +3389,6 @@ static int check_module_license_and_versions(struct module *mod)
 #ifdef CONFIG_MODVERSIONS
 	if ((mod->num_syms && !mod->crcs)
 	    || (mod->num_gpl_syms && !mod->gpl_crcs)
-	    || (mod->num_gpl_future_syms && !mod->gpl_future_crcs)
 #ifdef CONFIG_UNUSED_SYMBOLS
 	    || (mod->num_unused_syms && !mod->unused_crcs)
 	    || (mod->num_unused_gpl_syms && !mod->unused_gpl_crcs)
diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
index d6c81657d69550..25c1446055d16b 100644
--- a/scripts/mod/modpost.c
+++ b/scripts/mod/modpost.c
@@ -44,7 +44,7 @@ static bool error_occurred;
 
 enum export {
 	export_plain,      export_unused,     export_gpl,
-	export_unused_gpl, export_gpl_future, export_unknown
+	export_unused_gpl, export_unknown
 };
 
 /* In kernel, this size is defined in linux/module.h;
@@ -304,7 +304,6 @@ static const struct {
 	{ .str = "EXPORT_UNUSED_SYMBOL",     .export = export_unused },
 	{ .str = "EXPORT_SYMBOL_GPL",        .export = export_gpl },
 	{ .str = "EXPORT_UNUSED_SYMBOL_GPL", .export = export_unused_gpl },
-	{ .str = "EXPORT_SYMBOL_GPL_FUTURE", .export = export_gpl_future },
 	{ .str = "(unknown)",                .export = export_unknown },
 };
 
@@ -369,8 +368,6 @@ static enum export export_from_secname(struct elf_info *elf, unsigned int sec)
 		return export_gpl;
 	else if (strstarts(secname, "___ksymtab_unused_gpl+"))
 		return export_unused_gpl;
-	else if (strstarts(secname, "___ksymtab_gpl_future+"))
-		return export_gpl_future;
 	else
 		return export_unknown;
 }
@@ -385,8 +382,6 @@ static enum export export_from_sec(struct elf_info *elf, unsigned int sec)
 		return export_gpl;
 	else if (sec == elf->export_unused_gpl_sec)
 		return export_unused_gpl;
-	else if (sec == elf->export_gpl_future_sec)
-		return export_gpl_future;
 	else
 		return export_unknown;
 }
@@ -596,8 +591,6 @@ static int parse_elf(struct elf_info *info, const char *filename)
 			info->export_gpl_sec = i;
 		else if (strcmp(secname, "__ksymtab_unused_gpl") == 0)
 			info->export_unused_gpl_sec = i;
-		else if (strcmp(secname, "__ksymtab_gpl_future") == 0)
-			info->export_gpl_future_sec = i;
 
 		if (sechdrs[i].sh_type == SHT_SYMTAB) {
 			unsigned int sh_link_idx;
@@ -2152,10 +2145,6 @@ static void check_for_gpl_usage(enum export exp, const char *m, const char *s)
 		error("GPL-incompatible module %s.ko uses GPL-only symbol marked UNUSED '%s'\n",
 		      m, s);
 		break;
-	case export_gpl_future:
-		warn("GPL-incompatible module %s.ko uses future GPL-only symbol '%s'\n",
-		     m, s);
-		break;
 	case export_plain:
 	case export_unused:
 	case export_unknown:
diff --git a/scripts/mod/modpost.h b/scripts/mod/modpost.h
index e6f46eee0af02f..834220de002bd1 100644
--- a/scripts/mod/modpost.h
+++ b/scripts/mod/modpost.h
@@ -142,7 +142,6 @@ struct elf_info {
 	Elf_Section  export_unused_sec;
 	Elf_Section  export_gpl_sec;
 	Elf_Section  export_unused_gpl_sec;
-	Elf_Section  export_gpl_future_sec;
 	char         *strtab;
 	char	     *modinfo;
 	unsigned int modinfo_len;
diff --git a/scripts/module.lds.S b/scripts/module.lds.S
index 69b9b71a6a4731..d82b452e8a7168 100644
--- a/scripts/module.lds.S
+++ b/scripts/module.lds.S
@@ -13,12 +13,10 @@ SECTIONS {
 	__ksymtab_gpl		0 : { *(SORT(___ksymtab_gpl+*)) }
 	__ksymtab_unused	0 : { *(SORT(___ksymtab_unused+*)) }
 	__ksymtab_unused_gpl	0 : { *(SORT(___ksymtab_unused_gpl+*)) }
-	__ksymtab_gpl_future	0 : { *(SORT(___ksymtab_gpl_future+*)) }
 	__kcrctab		0 : { *(SORT(___kcrctab+*)) }
 	__kcrctab_gpl		0 : { *(SORT(___kcrctab_gpl+*)) }
 	__kcrctab_unused	0 : { *(SORT(___kcrctab_unused+*)) }
 	__kcrctab_unused_gpl	0 : { *(SORT(___kcrctab_unused_gpl+*)) }
-	__kcrctab_gpl_future	0 : { *(SORT(___kcrctab_gpl_future+*)) }
 
 	.init_array		0 : ALIGN(8) { *(SORT(.init_array.*)) *(.init_array) }
 
diff --git a/tools/include/linux/export.h b/tools/include/linux/export.h
index d07e586b9ba0ec..9f61349a8944e1 100644
--- a/tools/include/linux/export.h
+++ b/tools/include/linux/export.h
@@ -3,7 +3,6 @@
 
 #define EXPORT_SYMBOL(sym)
 #define EXPORT_SYMBOL_GPL(sym)
-#define EXPORT_SYMBOL_GPL_FUTURE(sym)
 #define EXPORT_UNUSED_SYMBOL(sym)
 #define EXPORT_UNUSED_SYMBOL_GPL(sym)
 
-- 
2.29.2

Re: [PATCH 05/13] kallsyms: refactor {,module_}kallsyms_on_each_symbol

[Christoph Hellwig]

On Fri, Jan 29, 2021 at 10:43:36AM +0100, Petr Mladek wrote:
> > --- a/kernel/livepatch/core.c
> > +++ b/kernel/livepatch/core.c
> > @@ -164,12 +164,8 @@ static int klp_find_object_symbol(const char *objname, const char *name,
> >  		.pos = sympos,
> >  	};
> >  
> > -	mutex_lock(&module_mutex);
> > -	if (objname)
> > +	if (objname || !kallsyms_on_each_symbol(klp_find_callback, &args))
> >  		module_kallsyms_on_each_symbol(klp_find_callback, &args);
> > -	else
> > -		kallsyms_on_each_symbol(klp_find_callback, &args);
> > -	mutex_unlock(&module_mutex);
> 
> This change is not needed. (objname == NULL) means that we are
> interested only in symbols in "vmlinux".
> 
> module_kallsyms_on_each_symbol(klp_find_callback, &args)
> will always fail when objname == NULL.

I just tried to keep the old behavior.  I can respin it with your
recommended change noting the change in behavior, though.

Re: [PATCH 05/13] kallsyms: refactor {,module_}kallsyms_on_each_symbol

[Miroslav Benes]

On Mon, 1 Feb 2021, Christoph Hellwig wrote:

> On Fri, Jan 29, 2021 at 10:43:36AM +0100, Petr Mladek wrote:
> > > --- a/kernel/livepatch/core.c
> > > +++ b/kernel/livepatch/core.c
> > > @@ -164,12 +164,8 @@ static int klp_find_object_symbol(const char *objname, const char *name,
> > >  		.pos = sympos,
> > >  	};
> > >  
> > > -	mutex_lock(&module_mutex);
> > > -	if (objname)
> > > +	if (objname || !kallsyms_on_each_symbol(klp_find_callback, &args))
> > >  		module_kallsyms_on_each_symbol(klp_find_callback, &args);
> > > -	else
> > > -		kallsyms_on_each_symbol(klp_find_callback, &args);
> > > -	mutex_unlock(&module_mutex);
> > 
> > This change is not needed. (objname == NULL) means that we are
> > interested only in symbols in "vmlinux".
> > 
> > module_kallsyms_on_each_symbol(klp_find_callback, &args)
> > will always fail when objname == NULL.
> 
> I just tried to keep the old behavior.  I can respin it with your
> recommended change noting the change in behavior, though.

Yes, please. It would be cleaner that way.

Miroslav

Re: [PATCH 05/13] kallsyms: refactor {,module_}kallsyms_on_each_symbol

[Christoph Hellwig]

On Mon, Feb 01, 2021 at 02:37:12PM +0100, Miroslav Benes wrote:
> > > This change is not needed. (objname == NULL) means that we are
> > > interested only in symbols in "vmlinux".
> > > 
> > > module_kallsyms_on_each_symbol(klp_find_callback, &args)
> > > will always fail when objname == NULL.
> > 
> > I just tried to keep the old behavior.  I can respin it with your
> > recommended change noting the change in behavior, though.
> 
> Yes, please. It would be cleaner that way.

Let me know if this works for you:

---
From 18af41e88d088cfb8680d1669fcae2bc2ede5328 Mon Sep 17 00:00:00 2001
From: Christoph Hellwig <hch@lst.de>
Date: Wed, 20 Jan 2021 16:23:16 +0100
Subject: kallsyms: refactor {,module_}kallsyms_on_each_symbol

Require an explicit call to module_kallsyms_on_each_symbol to look
for symbols in modules instead of the call from kallsyms_on_each_symbol,
and acquire module_mutex inside of module_kallsyms_on_each_symbol instead
of leaving that up to the caller.  Note that this slightly changes the
behavior for the livepatch code in that the symbols from vmlinux are not
iterated anymore if objname is set, but that actually is the desired
behavior in this case.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 kernel/kallsyms.c       |  6 +++++-
 kernel/livepatch/core.c |  2 --
 kernel/module.c         | 13 ++++---------
 3 files changed, 9 insertions(+), 12 deletions(-)

diff --git a/kernel/kallsyms.c b/kernel/kallsyms.c
index fe9de067771c34..a0d3f0865916f9 100644
--- a/kernel/kallsyms.c
+++ b/kernel/kallsyms.c
@@ -177,6 +177,10 @@ unsigned long kallsyms_lookup_name(const char *name)
 	return module_kallsyms_lookup_name(name);
 }
 
+/*
+ * Iterate over all symbols in vmlinux.  For symbols from modules use
+ * module_kallsyms_on_each_symbol instead.
+ */
 int kallsyms_on_each_symbol(int (*fn)(void *, const char *, struct module *,
 				      unsigned long),
 			    void *data)
@@ -192,7 +196,7 @@ int kallsyms_on_each_symbol(int (*fn)(void *, const char *, struct module *,
 		if (ret != 0)
 			return ret;
 	}
-	return module_kallsyms_on_each_symbol(fn, data);
+	return 0;
 }
 
 static unsigned long get_symbol_pos(unsigned long addr,
diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c
index 262cd9b003b9f0..335d988bd81117 100644
--- a/kernel/livepatch/core.c
+++ b/kernel/livepatch/core.c
@@ -164,12 +164,10 @@ static int klp_find_object_symbol(const char *objname, const char *name,
 		.pos = sympos,
 	};
 
-	mutex_lock(&module_mutex);
 	if (objname)
 		module_kallsyms_on_each_symbol(klp_find_callback, &args);
 	else
 		kallsyms_on_each_symbol(klp_find_callback, &args);
-	mutex_unlock(&module_mutex);
 
 	/*
 	 * Ensure an address was found. If sympos is 0, ensure symbol is unique;
diff --git a/kernel/module.c b/kernel/module.c
index 6772fb2680eb3e..25345792c770d1 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -255,11 +255,6 @@ static void mod_update_bounds(struct module *mod)
 struct list_head *kdb_modules = &modules; /* kdb needs the list of modules */
 #endif /* CONFIG_KGDB_KDB */
 
-static void module_assert_mutex(void)
-{
-	lockdep_assert_held(&module_mutex);
-}
-
 static void module_assert_mutex_or_preempt(void)
 {
 #ifdef CONFIG_LOCKDEP
@@ -4379,8 +4374,7 @@ int module_kallsyms_on_each_symbol(int (*fn)(void *, const char *,
 	unsigned int i;
 	int ret;
 
-	module_assert_mutex();
-
+	mutex_lock(&module_mutex);
 	list_for_each_entry(mod, &modules, list) {
 		/* We hold module_mutex: no need for rcu_dereference_sched */
 		struct mod_kallsyms *kallsyms = mod->kallsyms;
@@ -4396,10 +4390,11 @@ int module_kallsyms_on_each_symbol(int (*fn)(void *, const char *,
 			ret = fn(data, kallsyms_symbol_name(kallsyms, i),
 				 mod, kallsyms_symbol_value(sym));
 			if (ret != 0)
-				return ret;
+				break;
 		}
 	}
-	return 0;
+	mutex_unlock(&module_mutex);
+	return ret;
 }
 #endif /* CONFIG_KALLSYMS */
 
-- 
2.29.2

Re: [PATCH 05/13] kallsyms: refactor {,module_}kallsyms_on_each_symbol

[Miroslav Benes]

On Mon, 1 Feb 2021, Christoph Hellwig wrote:

> On Mon, Feb 01, 2021 at 02:37:12PM +0100, Miroslav Benes wrote:
> > > > This change is not needed. (objname == NULL) means that we are
> > > > interested only in symbols in "vmlinux".
> > > > 
> > > > module_kallsyms_on_each_symbol(klp_find_callback, &args)
> > > > will always fail when objname == NULL.
> > > 
> > > I just tried to keep the old behavior.  I can respin it with your
> > > recommended change noting the change in behavior, though.
> > 
> > Yes, please. It would be cleaner that way.
> 
> Let me know if this works for you:
> 
> ---
> >From 18af41e88d088cfb8680d1669fcae2bc2ede5328 Mon Sep 17 00:00:00 2001
> From: Christoph Hellwig <hch@lst.de>
> Date: Wed, 20 Jan 2021 16:23:16 +0100
> Subject: kallsyms: refactor {,module_}kallsyms_on_each_symbol
> 
> Require an explicit call to module_kallsyms_on_each_symbol to look
> for symbols in modules instead of the call from kallsyms_on_each_symbol,
> and acquire module_mutex inside of module_kallsyms_on_each_symbol instead
> of leaving that up to the caller.  Note that this slightly changes the
> behavior for the livepatch code in that the symbols from vmlinux are not
> iterated anymore if objname is set, but that actually is the desired
> behavior in this case.
> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>

Acked-by: Miroslav Benes <mbenes@suse.cz>

Thanks Christoph

M

Re: [PATCH 05/13] kallsyms: refactor {,module_}kallsyms_on_each_symbol

[Miroslav Benes]

One more thing...

> @@ -4379,8 +4379,7 @@ int module_kallsyms_on_each_symbol(int (*fn)(void *, const char *,
>  	unsigned int i;
>  	int ret;
>  
> -	module_assert_mutex();
> -
> +	mutex_lock(&module_mutex);
>  	list_for_each_entry(mod, &modules, list) {
>  		/* We hold module_mutex: no need for rcu_dereference_sched */
>  		struct mod_kallsyms *kallsyms = mod->kallsyms;

This was the last user of module_assert_mutex(), which can be removed now.

Miroslav

Re: [PATCH 02/13] drm: remove drm_fb_helper_modinit

[Daniel Vetter]

On Thu, Jan 28, 2021 at 07:14:10PM +0100, Christoph Hellwig wrote:
> drm_fb_helper_modinit has a lot of boilerplate for what is not very
> simple functionality.  Just open code it in the only caller using
> IS_ENABLED and IS_MODULE, and skip the find_module check as a
> request_module is harmless if the module is already loaded (and not
> other caller has this find_module check either).
> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>

Hm I thought I've acked this one already somewhere for merging through
your tree.

Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>

> ---
>  drivers/gpu/drm/drm_crtc_helper_internal.h | 10 ---------
>  drivers/gpu/drm/drm_fb_helper.c            | 21 ------------------
>  drivers/gpu/drm/drm_kms_helper_common.c    | 25 +++++++++++-----------
>  3 files changed, 12 insertions(+), 44 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_crtc_helper_internal.h b/drivers/gpu/drm/drm_crtc_helper_internal.h
> index 25ce42e799952c..61e09f8a8d0ff0 100644
> --- a/drivers/gpu/drm/drm_crtc_helper_internal.h
> +++ b/drivers/gpu/drm/drm_crtc_helper_internal.h
> @@ -32,16 +32,6 @@
>  #include <drm/drm_encoder.h>
>  #include <drm/drm_modes.h>
>  
> -/* drm_fb_helper.c */
> -#ifdef CONFIG_DRM_FBDEV_EMULATION
> -int drm_fb_helper_modinit(void);
> -#else
> -static inline int drm_fb_helper_modinit(void)
> -{
> -	return 0;
> -}
> -#endif
> -
>  /* drm_dp_aux_dev.c */
>  #ifdef CONFIG_DRM_DP_AUX_CHARDEV
>  int drm_dp_aux_dev_init(void);
> diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
> index 4b81195106875d..0b9f1ae1b7864c 100644
> --- a/drivers/gpu/drm/drm_fb_helper.c
> +++ b/drivers/gpu/drm/drm_fb_helper.c
> @@ -2499,24 +2499,3 @@ void drm_fbdev_generic_setup(struct drm_device *dev,
>  	drm_client_register(&fb_helper->client);
>  }
>  EXPORT_SYMBOL(drm_fbdev_generic_setup);
> -
> -/* The Kconfig DRM_KMS_HELPER selects FRAMEBUFFER_CONSOLE (if !EXPERT)
> - * but the module doesn't depend on any fb console symbols.  At least
> - * attempt to load fbcon to avoid leaving the system without a usable console.
> - */
> -int __init drm_fb_helper_modinit(void)
> -{
> -#if defined(CONFIG_FRAMEBUFFER_CONSOLE_MODULE) && !defined(CONFIG_EXPERT)
> -	const char name[] = "fbcon";
> -	struct module *fbcon;
> -
> -	mutex_lock(&module_mutex);
> -	fbcon = find_module(name);
> -	mutex_unlock(&module_mutex);
> -
> -	if (!fbcon)
> -		request_module_nowait(name);
> -#endif
> -	return 0;
> -}
> -EXPORT_SYMBOL(drm_fb_helper_modinit);
> diff --git a/drivers/gpu/drm/drm_kms_helper_common.c b/drivers/gpu/drm/drm_kms_helper_common.c
> index 221a8528c9937a..f933da1656eb52 100644
> --- a/drivers/gpu/drm/drm_kms_helper_common.c
> +++ b/drivers/gpu/drm/drm_kms_helper_common.c
> @@ -64,19 +64,18 @@ MODULE_PARM_DESC(edid_firmware,
>  
>  static int __init drm_kms_helper_init(void)
>  {
> -	int ret;
> -
> -	/* Call init functions from specific kms helpers here */
> -	ret = drm_fb_helper_modinit();
> -	if (ret < 0)
> -		goto out;
> -
> -	ret = drm_dp_aux_dev_init();
> -	if (ret < 0)
> -		goto out;
> -
> -out:
> -	return ret;
> +	/*
> +	 * The Kconfig DRM_KMS_HELPER selects FRAMEBUFFER_CONSOLE (if !EXPERT)
> +	 * but the module doesn't depend on any fb console symbols.  At least
> +	 * attempt to load fbcon to avoid leaving the system without a usable
> +	 * console.
> +	 */
> +	if (IS_ENABLED(CONFIG_DRM_FBDEV_EMULATION) &&
> +	    IS_MODULE(CONFIG_FRAMEBUFFER_CONSOLE) &&
> +	    !IS_ENABLED(CONFIG_EXPERT))
> +		request_module_nowait("fbcon");
> +
> +	return drm_dp_aux_dev_init();
>  }
>  
>  static void __exit drm_kms_helper_exit(void)
> -- 
> 2.29.2
> 

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch

Re: [PATCH 02/13] drm: remove drm_fb_helper_modinit

[Christoph Hellwig]

On Wed, Feb 03, 2021 at 11:34:50AM +0100, Daniel Vetter wrote:
> On Thu, Jan 28, 2021 at 07:14:10PM +0100, Christoph Hellwig wrote:
> > drm_fb_helper_modinit has a lot of boilerplate for what is not very
> > simple functionality.  Just open code it in the only caller using
> > IS_ENABLED and IS_MODULE, and skip the find_module check as a
> > request_module is harmless if the module is already loaded (and not
> > other caller has this find_module check either).
> > 
> > Signed-off-by: Christoph Hellwig <hch@lst.de>
> 
> Hm I thought I've acked this one already somewhere for merging through
> your tree.
> 
> Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>

The difference is that this new version loses the find_module entirely,
while the previous one replaced it with the module_loaded helper that
didn't make it to the second version of the series.

module loader dead code removal and cleanups v3

[Christoph Hellwig]

Hi all,

this series removes support for long term unused export types and
cleans up various loose ends in the module loader.

Changes since v2:
 - clean up klp_find_object_symbol a bit
 - remove the now unused module_assert_mutex helper 

Changes since v1:
 - move struct symsearch to module.c
 - rework drm to not call find_module at all
 - allow RCU-sched locking for find_module
 - keep find_module as a public API instead of module_loaded
 - update a few comments and commit logs

Diffstat:

[PATCH 04/13] module: use RCU to synchronize find_module

[Christoph Hellwig]

Allow for a RCU-sched critical section around find_module, following
the lower level find_module_all helper, and switch the two callers
outside of module.c to use such a RCU-sched critical section instead
of module_mutex.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Acked-by: Miroslav Benes <mbenes@suse.cz>
---
 include/linux/module.h      | 2 +-
 kernel/livepatch/core.c     | 5 +++--
 kernel/module.c             | 1 -
 kernel/trace/trace_kprobe.c | 4 ++--
 4 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/include/linux/module.h b/include/linux/module.h
index 7a0bcb5b1ffccd..a64aa84d1b182c 100644
--- a/include/linux/module.h
+++ b/include/linux/module.h
@@ -586,7 +586,7 @@ static inline bool within_module(unsigned long addr, const struct module *mod)
 	return within_module_init(addr, mod) || within_module_core(addr, mod);
 }
 
-/* Search for module by name: must hold module_mutex. */
+/* Search for module by name: must be in a RCU-sched critical section. */
 struct module *find_module(const char *name);
 
 struct symsearch {
diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c
index f76fdb9255323d..262cd9b003b9f0 100644
--- a/kernel/livepatch/core.c
+++ b/kernel/livepatch/core.c
@@ -19,6 +19,7 @@
 #include <linux/moduleloader.h>
 #include <linux/completion.h>
 #include <linux/memory.h>
+#include <linux/rcupdate.h>
 #include <asm/cacheflush.h>
 #include "core.h"
 #include "patch.h"
@@ -57,7 +58,7 @@ static void klp_find_object_module(struct klp_object *obj)
 	if (!klp_is_module(obj))
 		return;
 
-	mutex_lock(&module_mutex);
+	rcu_read_lock_sched();
 	/*
 	 * We do not want to block removal of patched modules and therefore
 	 * we do not take a reference here. The patches are removed by
@@ -74,7 +75,7 @@ static void klp_find_object_module(struct klp_object *obj)
 	if (mod && mod->klp_alive)
 		obj->mod = mod;
 
-	mutex_unlock(&module_mutex);
+	rcu_read_unlock_sched();
 }
 
 static bool klp_initialized(void)
diff --git a/kernel/module.c b/kernel/module.c
index 981302f616b411..6772fb2680eb3e 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -668,7 +668,6 @@ static struct module *find_module_all(const char *name, size_t len,
 
 struct module *find_module(const char *name)
 {
-	module_assert_mutex();
 	return find_module_all(name, strlen(name), false);
 }
 
diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
index e6fba1798771b4..3137992baa5e7a 100644
--- a/kernel/trace/trace_kprobe.c
+++ b/kernel/trace/trace_kprobe.c
@@ -124,9 +124,9 @@ static nokprobe_inline bool trace_kprobe_module_exist(struct trace_kprobe *tk)
 	if (!p)
 		return true;
 	*p = '\0';
-	mutex_lock(&module_mutex);
+	rcu_read_lock_sched();
 	ret = !!find_module(tk->symbol);
-	mutex_unlock(&module_mutex);
+	rcu_read_unlock_sched();
 	*p = ':';
 
 	return ret;
-- 
2.29.2