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Message-ID: <ba838451-1a96-2c83-9188-a994f45d7523@huawei.com> Date: Fri, 15 Apr 2022 10:34:47 +0800 From: Hou Tao <houtao1@...wei.com> To: Xu Kuohai <xukuohai@...wei.com>, <bpf@...r.kernel.org>, <linux-arm-kernel@...ts.infradead.org>, <linux-kernel@...r.kernel.org>, <netdev@...r.kernel.org>, <linux-kselftest@...r.kernel.org> CC: Catalin Marinas <catalin.marinas@....com>, Will Deacon <will@...nel.org>, Steven Rostedt <rostedt@...dmis.org>, Ingo Molnar <mingo@...hat.com>, Daniel Borkmann <daniel@...earbox.net>, Alexei Starovoitov <ast@...nel.org>, Zi Shen Lim <zlim.lnx@...il.com>, Andrii Nakryiko <andrii@...nel.org>, Martin KaFai Lau <kafai@...com>, Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>, John Fastabend <john.fastabend@...il.com>, KP Singh <kpsingh@...nel.org>, "David S . Miller" <davem@...emloft.net>, Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>, David Ahern <dsahern@...nel.org>, Thomas Gleixner <tglx@...utronix.de>, Borislav Petkov <bp@...en8.de>, Dave Hansen <dave.hansen@...ux.intel.com>, <x86@...nel.org>, <hpa@...or.com>, Shuah Khan <shuah@...nel.org>, Mark Rutland <mark.rutland@....com>, Ard Biesheuvel <ardb@...nel.org>, Pasha Tatashin <pasha.tatashin@...een.com>, Peter Collingbourne <pcc@...gle.com>, Daniel Kiss <daniel.kiss@....com>, Sudeep Holla <sudeep.holla@....com>, Steven Price <steven.price@....com>, Marc Zyngier <maz@...nel.org>, Mark Brown <broonie@...nel.org>, Kumar Kartikeya Dwivedi <memxor@...il.com>, Delyan Kratunov <delyank@...com> Subject: Re: [PATCH bpf-next v2 4/6] bpf, arm64: Impelment bpf_arch_text_poke() for arm64 Hi, On 4/15/2022 12:22 AM, 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@...wei.com> > Acked-by: Song Liu <songliubraving@...com> > --- > arch/arm64/net/bpf_jit_comp.c | 52 +++++++++++++++++++++++++++++++++++ > 1 file changed, 52 insertions(+) > > diff --git a/arch/arm64/net/bpf_jit_comp.c b/arch/arm64/net/bpf_jit_comp.c > index 8ab4035dea27..1a1c3ea75ee2 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 +1531,53 @@ 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; > + In bpf_arch_text_poke() of x86, it disables the poking of kernel module, can you explain why it is OK to do so in arm64 ? Because there is no test cases for fentry on linux kernel module, could you please add some tests for it ? > + 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); > +out: > + mutex_unlock(&text_mutex); > + return ret; > +}
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