[PATCH bpf-next v3 0/2] bpf, btf: Add DEBUG_INFO_BTF checks for __register_bpf_struct_ops

[PATCH bpf-next v3 0/2] bpf, btf: Add DEBUG_INFO_BTF checks for __register_bpf_struct_ops

[Geliang Tang]

From: Geliang Tang <tanggeliang@kylinos.cn>

v3:
 - fix this build error:
kernel/bpf/btf.c:7750:11: error: incomplete definition of type 'struct module'

Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202402040934.Fph0XeEo-lkp@intel.com/

v2:
 - add register_check_missing_btf helper as Jiri suggested.

Geliang Tang (2):
  bpf, btf: Add register_check_missing_btf helper
  bpf, btf: Check btf for register_bpf_struct_ops

 kernel/bpf/btf.c | 47 ++++++++++++++++++++++++++---------------------
 1 file changed, 26 insertions(+), 21 deletions(-)

-- 
2.40.1

[PATCH bpf-next v3 1/2] bpf, btf: Add register_check_missing_btf helper

[Geliang Tang]

From: Geliang Tang <tanggeliang@kylinos.cn>

This patch extracts duplicate code on error path when btf_get_module_btf()
returns NULL from the functions __register_btf_kfunc_id_set() and
register_btf_id_dtor_kfuncs() into a new helper named
register_check_missing_btf() to check CONFIG_DEBUG_INFO_BTF,
CONFIG_DEBUG_INFO_BTF_MODULES and CONFIG_MODULE_ALLOW_BTF_MISMATCH in it.

Signed-off-by: Geliang Tang <tanggeliang@kylinos.cn>
---
 kernel/bpf/btf.c | 43 +++++++++++++++++++++++--------------------
 1 file changed, 23 insertions(+), 20 deletions(-)

diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index f7725cb6e564..d166c12206ea 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -26,6 +26,7 @@
 #include <linux/bsearch.h>
 #include <linux/kobject.h>
 #include <linux/sysfs.h>
+#include <linux/module.h>
 
 #include <net/netfilter/nf_bpf_link.h>
 
@@ -7738,6 +7739,24 @@ static struct btf *btf_get_module_btf(const struct module *module)
 	return btf;
 }
 
+static int register_check_missing_btf(const struct module *module, const char *msg)
+{
+	if (!module && IS_ENABLED(CONFIG_DEBUG_INFO_BTF)) {
+		pr_err("missing vmlinux BTF, cannot register %s\n", msg);
+		return -ENOENT;
+	}
+	if (module && IS_ENABLED(CONFIG_DEBUG_INFO_BTF_MODULES)) {
+		if (IS_ENABLED(CONFIG_MODULE_ALLOW_BTF_MISMATCH)) {
+			pr_warn("allow module %s BTF mismatch, skip register %s\n",
+				module->name, msg);
+			return 0;
+		}
+		pr_err("missing module %s BTF, cannot register %s\n", module->name, msg);
+		return -ENOENT;
+	}
+	return 0;
+}
+
 BPF_CALL_4(bpf_btf_find_by_name_kind, char *, name, int, name_sz, u32, kind, int, flags)
 {
 	struct btf *btf = NULL;
@@ -8098,15 +8117,8 @@ static int __register_btf_kfunc_id_set(enum btf_kfunc_hook hook,
 	int ret, i;
 
 	btf = btf_get_module_btf(kset->owner);
-	if (!btf) {
-		if (!kset->owner && IS_ENABLED(CONFIG_DEBUG_INFO_BTF)) {
-			pr_err("missing vmlinux BTF, cannot register kfuncs\n");
-			return -ENOENT;
-		}
-		if (kset->owner && IS_ENABLED(CONFIG_DEBUG_INFO_BTF_MODULES))
-			pr_warn("missing module BTF, cannot register kfuncs\n");
-		return 0;
-	}
+	if (!btf)
+		return register_check_missing_btf(kset->owner, "kfuncs");
 	if (IS_ERR(btf))
 		return PTR_ERR(btf);
 
@@ -8214,17 +8226,8 @@ int register_btf_id_dtor_kfuncs(const struct btf_id_dtor_kfunc *dtors, u32 add_c
 	int ret;
 
 	btf = btf_get_module_btf(owner);
-	if (!btf) {
-		if (!owner && IS_ENABLED(CONFIG_DEBUG_INFO_BTF)) {
-			pr_err("missing vmlinux BTF, cannot register dtor kfuncs\n");
-			return -ENOENT;
-		}
-		if (owner && IS_ENABLED(CONFIG_DEBUG_INFO_BTF_MODULES)) {
-			pr_err("missing module BTF, cannot register dtor kfuncs\n");
-			return -ENOENT;
-		}
-		return 0;
-	}
+	if (!btf)
+		return register_check_missing_btf(owner, "dtor kfuncs");
 	if (IS_ERR(btf))
 		return PTR_ERR(btf);
 
-- 
2.40.1

Re: [PATCH bpf-next v3 1/2] bpf, btf: Add register_check_missing_btf helper

[kernel test robot]

Hi Geliang,

kernel test robot noticed the following build errors:

[auto build test ERROR on bpf-next/master]

url:    https://github.com/intel-lab-lkp/linux/commits/Geliang-Tang/bpf-btf-Add-register_check_missing_btf-helper/20240204-150130
base:   https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next.git master
patch link:    https://lore.kernel.org/r/6dfe28c4045e1a3d31b3ba60dde31c7650ac66df.1707029682.git.tanggeliang%40kylinos.cn
patch subject: [PATCH bpf-next v3 1/2] bpf, btf: Add register_check_missing_btf helper
config: x86_64-buildonly-randconfig-004-20240209 (https://download.01.org/0day-ci/archive/20240209/202402091146.VUsU5iPl-lkp@intel.com/config)
compiler: gcc-9 (Debian 9.3.0-22) 9.3.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20240209/202402091146.VUsU5iPl-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202402091146.VUsU5iPl-lkp@intel.com/

All errors (new ones prefixed by >>):

   kernel/bpf/btf.c: In function 'btf_seq_show':
   kernel/bpf/btf.c:7287:22: warning: function 'btf_seq_show' might be a candidate for 'gnu_printf' format attribute [-Wsuggest-attribute=format]
    7287 |  seq_vprintf((struct seq_file *)show->target, fmt, args);
         |                      ^~~~~~~~
   kernel/bpf/btf.c: In function 'btf_snprintf_show':
   kernel/bpf/btf.c:7324:2: warning: function 'btf_snprintf_show' might be a candidate for 'gnu_printf' format attribute [-Wsuggest-attribute=format]
    7324 |  len = vsnprintf(show->target, ssnprintf->len_left, fmt, args);
         |  ^~~
   In file included from include/asm-generic/bug.h:22,
                    from arch/x86/include/asm/bug.h:87,
                    from include/linux/bug.h:5,
                    from arch/x86/include/asm/paravirt.h:19,
                    from arch/x86/include/asm/cpuid.h:62,
                    from arch/x86/include/asm/processor.h:19,
                    from include/linux/sched.h:13,
                    from include/linux/ptrace.h:6,
                    from include/uapi/asm-generic/bpf_perf_event.h:4,
                    from ./arch/x86/include/generated/uapi/asm/bpf_perf_event.h:1,
                    from include/uapi/linux/bpf_perf_event.h:11,
                    from kernel/bpf/btf.c:6:
   kernel/bpf/btf.c: In function 'register_check_missing_btf':
>> kernel/bpf/btf.c:7751:11: error: dereferencing pointer to incomplete type 'const struct module'
    7751 |     module->name, msg);
         |           ^~
   include/linux/printk.h:427:19: note: in definition of macro 'printk_index_wrap'
     427 |   _p_func(_fmt, ##__VA_ARGS__);    \
         |                   ^~~~~~~~~~~
   include/linux/printk.h:508:2: note: in expansion of macro 'printk'
     508 |  printk(KERN_WARNING pr_fmt(fmt), ##__VA_ARGS__)
         |  ^~~~~~
   kernel/bpf/btf.c:7750:4: note: in expansion of macro 'pr_warn'
    7750 |    pr_warn("allow module %s BTF mismatch, skip register %s\n",
         |    ^~~~~~~


vim +7751 kernel/bpf/btf.c

  7741	
  7742	static int register_check_missing_btf(const struct module *module, const char *msg)
  7743	{
  7744		if (!module && IS_ENABLED(CONFIG_DEBUG_INFO_BTF)) {
  7745			pr_err("missing vmlinux BTF, cannot register %s\n", msg);
  7746			return -ENOENT;
  7747		}
  7748		if (module && IS_ENABLED(CONFIG_DEBUG_INFO_BTF_MODULES)) {
  7749			if (IS_ENABLED(CONFIG_MODULE_ALLOW_BTF_MISMATCH)) {
  7750				pr_warn("allow module %s BTF mismatch, skip register %s\n",
> 7751					module->name, msg);
  7752				return 0;
  7753			}
  7754			pr_err("missing module %s BTF, cannot register %s\n", module->name, msg);
  7755			return -ENOENT;
  7756		}
  7757		return 0;
  7758	}
  7759	

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki

[PATCH bpf-next v3 2/2] bpf, btf: Check btf for register_bpf_struct_ops

[Geliang Tang]

From: Geliang Tang <tanggeliang@kylinos.cn>

Similar to the handling in the functions __register_btf_kfunc_id_set()
and register_btf_id_dtor_kfuncs(), this patch uses the newly added
helper register_check_missing_btf() and IS_ERR() to check the return
value of btf_get_module_btf().

Signed-off-by: Geliang Tang <tanggeliang@kylinos.cn>
---
 kernel/bpf/btf.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index d166c12206ea..714f13121f1c 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -8890,7 +8890,9 @@ int __register_bpf_struct_ops(struct bpf_struct_ops *st_ops)
 
 	btf = btf_get_module_btf(st_ops->owner);
 	if (!btf)
-		return -EINVAL;
+		return register_check_missing_btf(st_ops->owner, "structs");
+	if (IS_ERR(btf))
+		return PTR_ERR(btf);
 
 	log = kzalloc(sizeof(*log), GFP_KERNEL | __GFP_NOWARN);
 	if (!log) {
-- 
2.40.1