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[2001:1ae9:1c2:4c00:726e:c10f:8833:ff22]) by smtp.gmail.com with ESMTPSA id la1-20020a170907780100b00787f91a6b16sm6048721ejc.26.2022.11.22.05.48.08 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 22 Nov 2022 05:48:09 -0800 (PST) From: Jiri Olsa X-Google-Original-From: Jiri Olsa Date: Tue, 22 Nov 2022 14:48:07 +0100 To: Chen Hu Cc: jpoimboe@kernel.org, memxor@gmail.com, bpf@vger.kernel.org, Pengfei Xu , Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Martin KaFai Lau , Song Liu , Yonghong Song , John Fastabend , KP Singh , Stanislav Fomichev , Hao Luo , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , linux-kernel@vger.kernel.org, netdev@vger.kernel.org, Peter Zijlstra Subject: Re: [PATCH bpf v2] selftests/bpf: Fix "missing ENDBR" BUG for destructor kfunc Message-ID: References: <20221122073244.21279-1-hu1.chen@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20221122073244.21279-1-hu1.chen@intel.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Nov 21, 2022 at 11:32:43PM -0800, Chen Hu wrote: > With CONFIG_X86_KERNEL_IBT enabled, the test_verifier triggers the > following BUG: > > traps: Missing ENDBR: bpf_kfunc_call_test_release+0x0/0x30 > ------------[ cut here ]------------ > kernel BUG at arch/x86/kernel/traps.c:254! > invalid opcode: 0000 [#1] PREEMPT SMP > > asm_exc_control_protection+0x26/0x50 > RIP: 0010:bpf_kfunc_call_test_release+0x0/0x30 > Code: 00 48 c7 c7 18 f2 e1 b4 e8 0d ca 8c ff 48 c7 c0 00 f2 e1 b4 c3 > 0f 1f 44 00 00 66 0f 1f 00 0f 1f 44 00 00 0f 0b 31 c0 c3 66 90 > <66> 0f 1f 00 0f 1f 44 00 00 48 85 ff 74 13 4c 8d 47 18 b8 ff ff ff > bpf_map_free_kptrs+0x2e/0x70 > array_map_free+0x57/0x140 > process_one_work+0x194/0x3a0 > worker_thread+0x54/0x3a0 > ? rescuer_thread+0x390/0x390 > kthread+0xe9/0x110 > ? kthread_complete_and_exit+0x20/0x20 > > This is because there are no compile-time references to the destructor > kfuncs, bpf_kfunc_call_test_release() for example. So objtool marked > them sealable and ENDBR in the functions were sealed (converted to NOP) > by apply_ibt_endbr(). > > This fix creates dummy compile-time references to destructor kfuncs so > ENDBR stay there. > > Fixes: 05a945deefaa ("selftests/bpf: Add verifier tests for kptr") > Signed-off-by: Chen Hu > Tested-by: Pengfei Xu > --- > v2: > - Use generic macro name and place the macro after function body as > - suggested by Jiri Olsa > > v1: https://lore.kernel.org/all/20221121085113.611504-1-hu1.chen@intel.com/ > > include/linux/btf_ids.h | 7 +++++++ > net/bpf/test_run.c | 4 ++++ > 2 files changed, 11 insertions(+) > > diff --git a/include/linux/btf_ids.h b/include/linux/btf_ids.h > index 2aea877d644f..db02691b506d 100644 > --- a/include/linux/btf_ids.h > +++ b/include/linux/btf_ids.h > @@ -266,4 +266,11 @@ MAX_BTF_TRACING_TYPE, > > extern u32 btf_tracing_ids[]; > > +#if defined(CONFIG_X86_KERNEL_IBT) && !defined(__DISABLE_EXPORTS) > +#define FUNC_IBT_NOSEAL(name) \ > + asm(IBT_NOSEAL(#name)); > +#else > +#define FUNC_IBT_NOSEAL(name) > +#endif /* CONFIG_X86_KERNEL_IBT */ hum, IBT_NOSEAL is x86 specific, so this will probably fail build on other archs.. I think we could ifdef it with CONFIG_X86, but it should go to some IBT related header? surely not to btf_ids.h cc-ing Peter and Josh thanks, jirka > + > #endif > diff --git a/net/bpf/test_run.c b/net/bpf/test_run.c > index 13d578ce2a09..07263b7cc12d 100644 > --- a/net/bpf/test_run.c > +++ b/net/bpf/test_run.c > @@ -597,10 +597,14 @@ noinline void bpf_kfunc_call_test_release(struct prog_test_ref_kfunc *p) > refcount_dec(&p->cnt); > } > > +FUNC_IBT_NOSEAL(bpf_kfunc_call_test_release) > + > noinline void bpf_kfunc_call_memb_release(struct prog_test_member *p) > { > } > > +FUNC_IBT_NOSEAL(bpf_kfunc_call_memb_release) > + > noinline void bpf_kfunc_call_memb1_release(struct prog_test_member1 *p) > { > WARN_ON_ONCE(1); > -- > 2.34.1 >