diff options
Diffstat (limited to 'target/linux/generic/backport-6.6/066-v6.10-bpf-Harden-__bpf_kfunc-against-linker-removal.patch')
| -rw-r--r-- | target/linux/generic/backport-6.6/066-v6.10-bpf-Harden-__bpf_kfunc-against-linker-removal.patch | 65 |
1 files changed, 65 insertions, 0 deletions
diff --git a/target/linux/generic/backport-6.6/066-v6.10-bpf-Harden-__bpf_kfunc-against-linker-removal.patch b/target/linux/generic/backport-6.6/066-v6.10-bpf-Harden-__bpf_kfunc-against-linker-removal.patch new file mode 100644 index 0000000000..f7e4f4391d --- /dev/null +++ b/target/linux/generic/backport-6.6/066-v6.10-bpf-Harden-__bpf_kfunc-against-linker-removal.patch @@ -0,0 +1,65 @@ +From ac507ed9882fd91a94657d68fe9ceac04b957103 Mon Sep 17 00:00:00 2001 +From: Tony Ambardar <Tony.Ambardar@gmail.com> +Date: Sat, 1 Jun 2024 00:00:21 -0700 +Subject: [PATCH 2/2] bpf: Harden __bpf_kfunc tag against linker kfunc removal + +BPF kfuncs are often not directly referenced and may be inadvertently +removed by optimization steps during kernel builds, thus the __bpf_kfunc +tag mitigates against this removal by including the __used macro. However, +this macro alone does not prevent removal during linking, and may still +yield build warnings (e.g. on mips64el): + + LD vmlinux + BTFIDS vmlinux + WARN: resolve_btfids: unresolved symbol bpf_verify_pkcs7_signature + WARN: resolve_btfids: unresolved symbol bpf_lookup_user_key + WARN: resolve_btfids: unresolved symbol bpf_lookup_system_key + WARN: resolve_btfids: unresolved symbol bpf_key_put + WARN: resolve_btfids: unresolved symbol bpf_iter_task_next + WARN: resolve_btfids: unresolved symbol bpf_iter_css_task_new + WARN: resolve_btfids: unresolved symbol bpf_get_file_xattr + WARN: resolve_btfids: unresolved symbol bpf_ct_insert_entry + WARN: resolve_btfids: unresolved symbol bpf_cgroup_release + WARN: resolve_btfids: unresolved symbol bpf_cgroup_from_id + WARN: resolve_btfids: unresolved symbol bpf_cgroup_acquire + WARN: resolve_btfids: unresolved symbol bpf_arena_free_pages + NM System.map + SORTTAB vmlinux + OBJCOPY vmlinux.32 + +Update the __bpf_kfunc tag to better guard against linker optimization by +including the new __retain compiler macro, which fixes the warnings above. + +Verify the __retain macro with readelf by checking object flags for 'R': + + $ readelf -Wa kernel/trace/bpf_trace.o + Section Headers: + [Nr] Name Type Address Off Size ES Flg Lk Inf Al + ... + [178] .text.bpf_key_put PROGBITS 00000000 6420 0050 00 AXR 0 0 8 + ... + Key to Flags: + ... + R (retain), D (mbind), p (processor specific) + +Link: https://lore.kernel.org/bpf/ZlmGoT9KiYLZd91S@krava/T/ +Reported-by: kernel test robot <lkp@intel.com> +Closes: https://lore.kernel.org/r/202401211357.OCX9yllM-lkp@intel.com/ +Fixes: 57e7c169cd6a ("bpf: Add __bpf_kfunc tag for marking kernel functions as kfuncs") +Cc: stable@vger.kernel.org # v6.6+ +Signed-off-by: Tony Ambardar <Tony.Ambardar@gmail.com> +--- + include/linux/btf.h | 2 +- + 1 file changed, 1 insertion(+), 1 deletion(-) + +--- a/include/linux/btf.h ++++ b/include/linux/btf.h +@@ -81,7 +81,7 @@ + * as to avoid issues such as the compiler inlining or eliding either a static + * kfunc, or a global kfunc in an LTO build. + */ +-#define __bpf_kfunc __used noinline ++#define __bpf_kfunc __used __retain noinline + + /* + * Return the name of the passed struct, if exists, or halt the build if for |