netdev - Re: [PATCH bpf-next 1/5] bpf: Unify memory address casting operation style

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Date:   Sat, 16 Jul 2022 19:03:54 -0700
From:   Yonghong Song <yhs@...com>
To:     Pu Lehui <pulehui@...wei.com>, bpf@...r.kernel.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Quentin Monnet <quentin@...valent.com>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...nel.org>,
        Jean-Philippe Brucker <jean-philippe@...aro.org>
Subject: Re: [PATCH bpf-next 1/5] bpf: Unify memory address casting operation
 style



On 7/16/22 5:51 AM, Pu Lehui wrote:
> Memory addresses are conceptually unsigned, (unsigned long) casting
> makes more sense, so let's make a change for conceptual uniformity
> and there is no functional change.
> 
> Signed-off-by: Pu Lehui <pulehui@...wei.com>

Only a few in bpf system, agree that we can do the change so in
the future we can recommend 'unsigned long' vs. 'long' casting
based on existing code base.

Acked-by: Yonghong Song <yhs@...com>

> ---
>   kernel/bpf/core.c     | 2 +-
>   kernel/bpf/helpers.c  | 6 +++---
>   kernel/bpf/syscall.c  | 2 +-
>   kernel/bpf/verifier.c | 6 +++---
>   4 files changed, 8 insertions(+), 8 deletions(-)
> 
> diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
> index cfb8a50a9f12..e14b399dd408 100644
> --- a/kernel/bpf/core.c
> +++ b/kernel/bpf/core.c
> @@ -1954,7 +1954,7 @@ static u64 ___bpf_prog_run(u64 *regs, const struct bpf_insn *insn)
>   		CONT;							\
>   	LDX_PROBE_MEM_##SIZEOP:						\
>   		bpf_probe_read_kernel(&DST, sizeof(SIZE),		\
> -				      (const void *)(long) (SRC + insn->off));	\
> +				      (const void *)(unsigned long) (SRC + insn->off));	\
>   		DST = *((SIZE *)&DST);					\
>   		CONT;
>   
> diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
> index a1c84d256f83..92c01dd007a6 100644
> --- a/kernel/bpf/helpers.c
> +++ b/kernel/bpf/helpers.c
> @@ -903,7 +903,7 @@ int bpf_bprintf_prepare(char *fmt, u32 fmt_size, const u64 *raw_args,
>   					err = snprintf(tmp_buf,
>   						       (tmp_buf_end - tmp_buf),
>   						       "%pB",
> -						       (void *)(long)raw_args[num_spec]);
> +						       (void *)(unsigned long)raw_args[num_spec]);
>   					tmp_buf += (err + 1);
>   				}
>   
> @@ -929,7 +929,7 @@ int bpf_bprintf_prepare(char *fmt, u32 fmt_size, const u64 *raw_args,
>   				goto out;
>   			}
>   
> -			unsafe_ptr = (char *)(long)raw_args[num_spec];
> +			unsafe_ptr = (char *)(unsigned long)raw_args[num_spec];
>   			err = copy_from_kernel_nofault(cur_ip, unsafe_ptr,
>   						       sizeof_cur_ip);
>   			if (err < 0)
> @@ -966,7 +966,7 @@ int bpf_bprintf_prepare(char *fmt, u32 fmt_size, const u64 *raw_args,
>   				goto out;
>   			}
>   
> -			unsafe_ptr = (char *)(long)raw_args[num_spec];
> +			unsafe_ptr = (char *)(unsigned long)raw_args[num_spec];
>   			err = bpf_trace_copy_string(tmp_buf, unsafe_ptr,
>   						    fmt_ptype,
>   						    tmp_buf_end - tmp_buf);
> diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
> index 83c7136c5788..d1380473e620 100644
> --- a/kernel/bpf/syscall.c
> +++ b/kernel/bpf/syscall.c
> @@ -5108,7 +5108,7 @@ BPF_CALL_3(bpf_sys_bpf, int, cmd, union bpf_attr *, attr, u32, attr_size)
>   			bpf_prog_put(prog);
>   			return -EBUSY;
>   		}
> -		attr->test.retval = bpf_prog_run(prog, (void *) (long) attr->test.ctx_in);
> +		attr->test.retval = bpf_prog_run(prog, (void *) (unsigned long) attr->test.ctx_in);
>   		__bpf_prog_exit_sleepable(prog, 0 /* bpf_prog_run does runtime stats */, &run_ctx);
>   		bpf_prog_put(prog);
>   		return 0;
> diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
> index c59c3df0fea6..d91f17598833 100644
> --- a/kernel/bpf/verifier.c
> +++ b/kernel/bpf/verifier.c
> @@ -4445,7 +4445,7 @@ static int bpf_map_direct_read(struct bpf_map *map, int off, int size, u64 *val)
>   	err = map->ops->map_direct_value_addr(map, &addr, off);
>   	if (err)
>   		return err;
> -	ptr = (void *)(long)addr + off;
> +	ptr = (void *)(unsigned long)addr + off;
>   
>   	switch (size) {
>   	case sizeof(u8):
> @@ -6113,7 +6113,7 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 arg,
>   			return err;
>   		}
>   
> -		str_ptr = (char *)(long)(map_addr);
> +		str_ptr = (char *)(unsigned long)(map_addr);
>   		if (!strnchr(str_ptr + map_off, map->value_size - map_off, 0)) {
>   			verbose(env, "string is not zero-terminated\n");
>   			return -EINVAL;
> @@ -7099,7 +7099,7 @@ static int check_bpf_snprintf_call(struct bpf_verifier_env *env,
>   		verbose(env, "verifier bug\n");
>   		return -EFAULT;
>   	}
> -	fmt = (char *)(long)fmt_addr + fmt_map_off;
> +	fmt = (char *)(unsigned long)fmt_addr + fmt_map_off;
>   
>   	/* We are also guaranteed that fmt+fmt_map_off is NULL terminated, we
>   	 * can focus on validating the format specifiers.