From: Jakub Sitnicki <jakub@cloudflare.com>
To: Xu Kuohai <xukuohai@huawei.com>
Cc: bpf@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org, netdev@vger.kernel.org,
linux-kselftest@vger.kernel.org,
Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will@kernel.org>,
Steven Rostedt <rostedt@goodmis.org>,
Ingo Molnar <mingo@redhat.com>,
Daniel Borkmann <daniel@iogearbox.net>,
Alexei Starovoitov <ast@kernel.org>,
Zi Shen Lim <zlim.lnx@gmail.com>,
Andrii Nakryiko <andrii@kernel.org>,
Martin KaFai Lau <kafai@fb.com>, Song Liu <songliubraving@fb.com>,
Yonghong Song <yhs@fb.com>,
John Fastabend <john.fastabend@gmail.com>,
KP Singh <kpsingh@kernel.org>,
"David S . Miller" <davem@davemloft.net>,
Hideaki YOSHIFUJI <yoshfuji@linux-ipv6.org>,
David Ahern <dsahern@kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
Borislav Petkov <bp@alien8.de>,
Dave Hansen <dave.hansen@linux.intel.com>,
x86@kernel.org, hpa@zytor.com, Shuah Khan <shuah@kernel.org>,
Jakub Kicinski <kuba@kernel.org>,
Jesper Dangaard Brouer <hawk@kernel.org>,
Mark Rutland <mark.rutland@arm.com>,
Pasha Tatashin <pasha.tatashin@soleen.com>,
Ard Biesheuvel <ardb@kernel.org>,
Daniel Kiss <daniel.kiss@arm.com>,
Steven Price <steven.price@arm.com>,
Sudeep Holla <sudeep.holla@arm.com>,
Marc Zyngier <maz@kernel.org>,
Peter Collingbourne <pcc@google.com>,
Mark Brown <broonie@kernel.org>, Delyan Kratunov <delyank@fb.com>,
Kumar Kartikeya Dwivedi <memxor@gmail.com>
Subject: Re: [PATCH bpf-next v3 4/7] bpf, arm64: Impelment bpf_arch_text_poke() for arm64
Date: Tue, 10 May 2022 13:45:38 +0200 [thread overview]
Message-ID: <87ee11obih.fsf@cloudflare.com> (raw)
In-Reply-To: <20220424154028.1698685-5-xukuohai@huawei.com>
On Sun, Apr 24, 2022 at 11:40 AM -04, Xu Kuohai wrote:
> Impelment bpf_arch_text_poke() for arm64, so bpf trampoline code can use
> it to replace nop with jump, or replace jump with nop.
>
> Signed-off-by: Xu Kuohai <xukuohai@huawei.com>
> Acked-by: Song Liu <songliubraving@fb.com>
> ---
> arch/arm64/net/bpf_jit_comp.c | 63 +++++++++++++++++++++++++++++++++++
> 1 file changed, 63 insertions(+)
>
> diff --git a/arch/arm64/net/bpf_jit_comp.c b/arch/arm64/net/bpf_jit_comp.c
> index 8ab4035dea27..3f9bdfec54c4 100644
> --- a/arch/arm64/net/bpf_jit_comp.c
> +++ b/arch/arm64/net/bpf_jit_comp.c
> @@ -9,6 +9,7 @@
>
> #include <linux/bitfield.h>
> #include <linux/bpf.h>
> +#include <linux/memory.h>
> #include <linux/filter.h>
> #include <linux/printk.h>
> #include <linux/slab.h>
> @@ -18,6 +19,7 @@
> #include <asm/cacheflush.h>
> #include <asm/debug-monitors.h>
> #include <asm/insn.h>
> +#include <asm/patching.h>
> #include <asm/set_memory.h>
>
> #include "bpf_jit.h"
> @@ -1529,3 +1531,64 @@ void bpf_jit_free_exec(void *addr)
> {
> return vfree(addr);
> }
> +
> +static int gen_branch_or_nop(enum aarch64_insn_branch_type type, void *ip,
> + void *addr, u32 *insn)
> +{
> + if (!addr)
> + *insn = aarch64_insn_gen_nop();
> + else
> + *insn = aarch64_insn_gen_branch_imm((unsigned long)ip,
> + (unsigned long)addr,
> + type);
> +
> + return *insn != AARCH64_BREAK_FAULT ? 0 : -EFAULT;
> +}
> +
> +int bpf_arch_text_poke(void *ip, enum bpf_text_poke_type poke_type,
> + void *old_addr, void *new_addr)
> +{
> + int ret;
> + u32 old_insn;
> + u32 new_insn;
> + u32 replaced;
> + enum aarch64_insn_branch_type branch_type;
> +
> + if (!is_bpf_text_address((long)ip))
> + /* Only poking bpf text is supported. Since kernel function
> + * entry is set up by ftrace, we reply on ftrace to poke kernel
> + * functions. For kernel funcitons, bpf_arch_text_poke() is only
Nit: s/funcitons/functions/
> + * called after a failed poke with ftrace. In this case, there
> + * is probably something wrong with fentry, so there is nothing
> + * we can do here. See register_fentry, unregister_fentry and
> + * modify_fentry for details.
> + */
> + return -EINVAL;
> +
> + if (poke_type == BPF_MOD_CALL)
> + branch_type = AARCH64_INSN_BRANCH_LINK;
> + else
> + branch_type = AARCH64_INSN_BRANCH_NOLINK;
> +
> + if (gen_branch_or_nop(branch_type, ip, old_addr, &old_insn) < 0)
> + return -EFAULT;
> +
> + if (gen_branch_or_nop(branch_type, ip, new_addr, &new_insn) < 0)
> + return -EFAULT;
> +
> + mutex_lock(&text_mutex);
> + if (aarch64_insn_read(ip, &replaced)) {
> + ret = -EFAULT;
> + goto out;
> + }
> +
> + if (replaced != old_insn) {
> + ret = -EFAULT;
> + goto out;
> + }
> +
> + ret = aarch64_insn_patch_text_nosync((void *)ip, new_insn);
Nit: No need for the explicit cast to void *. Type already matches.
> +out:
> + mutex_unlock(&text_mutex);
> + return ret;
> +}
next prev parent reply other threads:[~2022-05-10 11:47 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-04-24 15:40 [PATCH bpf-next v3 0/7] bpf trampoline for arm64 Xu Kuohai
2022-04-24 15:40 ` [PATCH bpf-next v3 1/7] arm64: ftrace: Add ftrace direct call support Xu Kuohai
2022-04-24 15:40 ` [PATCH bpf-next v3 2/7] ftrace: Fix deadloop caused by direct call in ftrace selftest Xu Kuohai
2022-04-25 15:05 ` Steven Rostedt
2022-04-26 7:36 ` Xu Kuohai
2022-04-24 15:40 ` [PATCH bpf-next v3 3/7] bpf: Move is_valid_bpf_tramp_flags() to the public trampoline code Xu Kuohai
2022-04-24 15:40 ` [PATCH bpf-next v3 4/7] bpf, arm64: Impelment bpf_arch_text_poke() for arm64 Xu Kuohai
2022-05-10 11:45 ` Jakub Sitnicki [this message]
2022-05-11 3:18 ` Xu Kuohai
2022-05-13 14:59 ` Mark Rutland
2022-05-16 6:55 ` Xu Kuohai
2022-05-16 7:18 ` Mark Rutland
2022-05-16 7:58 ` Xu Kuohai
2022-04-24 15:40 ` [PATCH bpf-next v3 5/7] bpf, arm64: Support to poke bpf prog Xu Kuohai
2022-05-10 9:36 ` Jakub Sitnicki
2022-05-11 3:12 ` Xu Kuohai
2022-05-12 10:54 ` Jakub Sitnicki
2022-04-24 15:40 ` [PATCH bpf-next v3 6/7] bpf, arm64: bpf trampoline for arm64 Xu Kuohai
2022-04-24 15:40 ` [PATCH bpf-next v3 7/7] selftests/bpf: Fix trivial typo in fentry_fexit.c Xu Kuohai
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