Require an explicit cll 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.
Signed-off-by: Christoph Hellwig <[email protected]>
---
kernel/kallsyms.c | 6 +++++-
kernel/livepatch/core.c | 6 +-----
kernel/module.c | 8 ++++----
3 files changed, 10 insertions(+), 10 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 878759baadd81c..8063b9089bd2f8 100644
--- a/kernel/livepatch/core.c
+++ b/kernel/livepatch/core.c
@@ -135,12 +135,8 @@ 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);
/*
* Ensure an address was found. If sympos is 0, ensure symbol is unique;
diff --git a/kernel/module.c b/kernel/module.c
index 299cbac0775cf2..885feec64c1b6f 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -4407,8 +4407,7 @@ 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;
@@ -4424,10 +4423,11 @@ 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
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.
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
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
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 <[email protected]>
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 <[email protected]>
---
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
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 <[email protected]>
> 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 <[email protected]>
Acked-by: Miroslav Benes <[email protected]>
Thanks Christoph
M