linux-toradex.git/kernel/module/kallsyms.c, branch v6.16-rc6

module: Use RCU in all users of __module_address().

2025-03-10T10:54:45+00:00

__module_address() can be invoked within a RCU section, there is no
requirement to have preemption disabled.

Replace the preempt_disable() section around __module_address() with
RCU.

Signed-off-by: Sebastian Andrzej Siewior 
Acked-by: Peter Zijlstra (Intel) 
Link: https://lore.kernel.org/r/20250108090457.512198-15-bigeasy@linutronix.de
Signed-off-by: Petr Pavlu

module: Use RCU in module_kallsyms_on_each_symbol().

2025-03-10T10:54:44+00:00

module::kallsyms can be accessed under RCU assumption.

Use rcu_dereference() to access module::kallsyms.
Update callers.

Signed-off-by: Sebastian Andrzej Siewior 
Acked-by: Peter Zijlstra (Intel) 
Link: https://lore.kernel.org/r/20250108090457.512198-9-bigeasy@linutronix.de
Signed-off-by: Petr Pavlu

module: Use RCU in __find_kallsyms_symbol_value().

2025-03-10T10:54:44+00:00

module::kallsyms can be accessed under RCU assumption.

Use rcu_dereference() to access module::kallsyms.
Update callers.

Signed-off-by: Sebastian Andrzej Siewior 
Acked-by: Peter Zijlstra (Intel) 
Link: https://lore.kernel.org/r/20250108090457.512198-8-bigeasy@linutronix.de
Signed-off-by: Petr Pavlu

module: Use RCU in find_module_all().

2025-03-10T10:54:44+00:00

The modules list and module::kallsyms can be accessed under RCU
assumption.

Remove module_assert_mutex_or_preempt() from find_module_all() so it can
be used under RCU protection without warnings. Update its callers to use
RCU protection instead of preempt_disable().

Cc: Jiri Kosina 
Cc: Joe Lawrence 
Cc: Josh Poimboeuf 
Cc: Masami Hiramatsu 
Cc: Mathieu Desnoyers 
Cc: Miroslav Benes 
Cc: Petr Mladek 
Cc: Steven Rostedt 
Cc: linux-trace-kernel@vger.kernel.org
Cc: live-patching@vger.kernel.org
Signed-off-by: Sebastian Andrzej Siewior 
Acked-by: Peter Zijlstra (Intel) 
Reviewed-by: Petr Mladek 
Link: https://lore.kernel.org/r/20250108090457.512198-7-bigeasy@linutronix.de
Signed-off-by: Petr Pavlu

module: Use RCU in module_get_kallsym().

2025-03-10T10:54:44+00:00

The modules list and module::kallsyms can be accessed under RCU
assumption.

Iterate the modules with RCU protection, use rcu_dereference() to access
the kallsyms pointer.

Signed-off-by: Sebastian Andrzej Siewior 
Acked-by: Peter Zijlstra (Intel) 
Link: https://lore.kernel.org/r/20250108090457.512198-6-bigeasy@linutronix.de
Signed-off-by: Petr Pavlu

module: Use RCU in find_kallsyms_symbol().

2025-03-10T10:54:44+00:00

The modules list and module::kallsyms can be accessed under RCU
assumption.

Use rcu_dereference() to reference the kallsyms pointer in
find_kallsyms_symbol().  Use a RCU section instead of preempt_disable in
callers of find_kallsyms_symbol(). Keep the preempt-disable in
module_address_lookup() due to __module_address().

Signed-off-by: Sebastian Andrzej Siewior 
Acked-by: Peter Zijlstra (Intel) 
Link: https://lore.kernel.org/r/20250108090457.512198-5-bigeasy@linutronix.de
Signed-off-by: Petr Pavlu

module: Use proper RCU assignment in add_kallsyms().

2025-03-10T10:54:44+00:00

add_kallsyms() assigns the RCU pointer module::kallsyms and setups the
structures behind it which point to init-data. The module was not
published yet, nothing can see the kallsyms pointer and the data behind
it. Also module's init function was not yet invoked.
There is no need to use rcu_dereference() here, it is just to keep
checkers quiet. The whole RCU read section is also not needed.

Use a local kallsyms pointer and setup the data structures. Assign that
pointer to the data structure at the end via rcu_assign_pointer().

Signed-off-by: Sebastian Andrzej Siewior 
Acked-by: Peter Zijlstra (Intel) 
Link: https://lore.kernel.org/r/20250108090457.512198-4-bigeasy@linutronix.de
Signed-off-by: Petr Pavlu

kallsyms: rework symbol lookup return codes

2024-06-27T15:43:40+00:00

Building with W=1 in some configurations produces a false positive
warning for kallsyms:

kernel/kallsyms.c: In function '__sprint_symbol.isra':
kernel/kallsyms.c:503:17: error: 'strcpy' source argument is the same as destination [-Werror=restrict]
  503 |                 strcpy(buffer, name);
      |                 ^~~~~~~~~~~~~~~~~~~~

This originally showed up while building with -O3, but later started
happening in other configurations as well, depending on inlining
decisions. The underlying issue is that the local 'name' variable is
always initialized to the be the same as 'buffer' in the called functions
that fill the buffer, which gcc notices while inlining, though it could
see that the address check always skips the copy.

The calling conventions here are rather unusual, as all of the internal
lookup functions (bpf_address_lookup, ftrace_mod_address_lookup,
ftrace_func_address_lookup, module_address_lookup and
kallsyms_lookup_buildid) already use the provided buffer and either return
the address of that buffer to indicate success, or NULL for failure,
but the callers are written to also expect an arbitrary other buffer
to be returned.

Rework the calling conventions to return the length of the filled buffer
instead of its address, which is simpler and easier to follow as well
as avoiding the warning. Leave only the kallsyms_lookup() calling conventions
unchanged, since that is called from 16 different functions and
adapting this would be a much bigger change.

Link: https://lore.kernel.org/lkml/20200107214042.855757-1-arnd@arndb.de/
Link: https://lore.kernel.org/lkml/20240326130647.7bfb1d92@gandalf.local.home/
Tested-by: Geert Uytterhoeven 
Reviewed-by: Luis Chamberlain 
Acked-by: Steven Rostedt (Google) 
Signed-off-by: Arnd Bergmann

kallsyms: replace deprecated strncpy with strscpy

2024-05-14T07:31:43+00:00

strncpy() is deprecated for use on NUL-terminated destination strings
[1] and as such we should prefer more robust and less ambiguous string
interfaces. The goal is to remove its use completely [2].

namebuf is eventually cleaned of any trailing llvm suffixes using
strstr(). This hints that namebuf should be NUL-terminated.

static void cleanup_symbol_name(char *s)
{
	char *res;
	...
	res = strstr(s, ".llvm.");
	...
}

Due to this, use strscpy() over strncpy() as it guarantees
NUL-termination on the destination buffer. Drop the -1 from the length
calculation as it is no longer needed to ensure NUL-termination.

Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings [1]
Link: https://manpages.debian.org/testing/linux-manual-4.8/strscpy.9.en.html
Link: https://github.com/KSPP/linux/issues/90 [2]
Cc: linux-hardening@vger.kernel.org
Signed-off-by: Justin Stitt 
Signed-off-by: Luis Chamberlain

kallsyms: remove unsed API lookup_symbol_attrs

2023-05-26T22:10:18+00:00

with commit '7878c231dae0 ("slab: remove /proc/slab_allocators")'
lookup_symbol_attrs usage is removed.

Thus removing redundant API.

Signed-off-by: Maninder Singh 
Reviewed-by: Kees Cook 
Signed-off-by: Luis Chamberlain