Re: [PATCH bpf-next v2] bpf: fix warning for crash_kexec

[Yonghong Song]

On 3/19/24 3:56 PM, Andrii Nakryiko wrote:

On Tue, Mar 19, 2024 at 1:02 AM Hari Bathini  wrote:

With [1], crash dump specific code is moved out of CONFIG_KEXEC_CORE
and placed under CONFIG_CRASH_DUMP, where it is more appropriate.
And since CONFIG_KEXEC & !CONFIG_CRASH_DUMP build option is supported
with that, it led to the below warning:

   "WARN: resolve_btfids: unresolved symbol crash_kexec"

Fix it by using the appropriate #ifdef.

[1] https://lore.kernel.org/all/20240124051254.67105-1-...@redhat.com/

Acked-by: Baoquan He 
Fixes: 29fd9ae62910 ("crash: split crash dumping code out from kexec_core.c")

I don't think either bpf or bpf-next have this commit just yet, so
landing it in the bpf/bpf-next tree doesn't make much sense. It
probably would be best to land it through the tree which does the
CONFIG_KEXEC_CORE -> CONFIG_CRASH_DUMP change in kernel/Makefile.


With bpf-next, I found the config at kernel/Kconfig.kexec:

config CRASH_DUMP
    bool "kernel crash dumps"
    depends on ARCH_SUPPORTS_CRASH_DUMP
    select CRASH_CORE
    select KEXEC_CORE
    help

...


pw-bot: cr


Acked-by: Jiri Olsa 
Acked-by: Stanislav Fomichev 
Signed-off-by: Hari Bathini 
---

Changes in v2:
* Updated changelog.
* Added Fixes and Acked-by tags.


  kernel/bpf/helpers.c | 2 +-
  1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
index a89587859571..449b9a5d3fe3 100644
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -2548,7 +2548,7 @@ __bpf_kfunc void bpf_throw(u64 cookie)
  __bpf_kfunc_end_defs();

  BTF_KFUNCS_START(generic_btf_ids)
-#ifdef CONFIG_KEXEC_CORE
+#ifdef CONFIG_CRASH_DUMP
  BTF_ID_FLAGS(func, crash_kexec, KF_DESTRUCTIVE)
  #endif
  BTF_ID_FLAGS(func, bpf_obj_new_impl, KF_ACQUIRE | KF_RET_NULL)
--
2.44.0



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Re: [PATCH linux-next] bpf: fix warning for crash_kexec

[Yonghong Song]

On 3/17/24 11:52 PM, Hari Bathini wrote:

Just checking on whether this will go via bpf or mm tree?


Sending to bpf-next should be okay.
Could you resubmit the patch as CONFIG_CRASH_DUMP probably not
available to bpf-next when you initially submitted the patch.



On 09/02/24 6:05 pm, Hari Bathini wrote:

With [1], CONFIG_KEXEC & !CONFIG_CRASH_DUMP is supported but that led
to the below warning:

   "WARN: resolve_btfids: unresolved symbol crash_kexec"

Fix it by using the appropriate #ifdef.

[1] https://lore.kernel.org/all/20240124051254.67105-1-...@redhat.com/

Signed-off-by: Hari Bathini 
---
  kernel/bpf/helpers.c | 2 +-
  1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
index 4db1c658254c..e408d1115e26 100644
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -2545,7 +2545,7 @@ __bpf_kfunc void bpf_throw(u64 cookie)
  __bpf_kfunc_end_defs();
    BTF_KFUNCS_START(generic_btf_ids)
-#ifdef CONFIG_KEXEC_CORE
+#ifdef CONFIG_CRASH_DUMP
  BTF_ID_FLAGS(func, crash_kexec, KF_DESTRUCTIVE)
  #endif
  BTF_ID_FLAGS(func, bpf_obj_new_impl, KF_ACQUIRE | KF_RET_NULL)




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