From: Jean-Philippe Brucker <jean-philippe@linaro.org>
To: Xu Kuohai <xukuohai@huawei.com>
Cc: bpf@vger.kernel.org, linux-kernel@vger.kernel.org, lkp@intel.com,
kbuild-all@lists.01.org, Daniel Borkmann <daniel@iogearbox.net>,
catalin.marinas@arm.com, will@kernel.org
Subject: Re: [PATCH bpf] bpf, arm64: Fix bpf trampoline instruction endianness
Date: Tue, 9 Aug 2022 11:33:58 +0100 [thread overview]
Message-ID: <YvI4FqZ91e2+0sBA@myrica> (raw)
In-Reply-To: <20220808040735.1232002-1-xukuohai@huawei.com>
[+ arm64 maintainers]
On Mon, Aug 08, 2022 at 12:07:35AM -0400, Xu Kuohai wrote:
> The sparse tool complains as follows:
>
> arch/arm64/net/bpf_jit_comp.c:1684:16:
> warning: incorrect type in assignment (different base types)
> arch/arm64/net/bpf_jit_comp.c:1684:16:
> expected unsigned int [usertype] *branch
> arch/arm64/net/bpf_jit_comp.c:1684:16:
> got restricted __le32 [usertype] *
> arch/arm64/net/bpf_jit_comp.c:1700:52:
> error: subtraction of different types can't work (different base
> types)
> arch/arm64/net/bpf_jit_comp.c:1734:29:
> warning: incorrect type in assignment (different base types)
> arch/arm64/net/bpf_jit_comp.c:1734:29:
> expected unsigned int [usertype] *
> arch/arm64/net/bpf_jit_comp.c:1734:29:
> got restricted __le32 [usertype] *
> arch/arm64/net/bpf_jit_comp.c:1918:52:
> error: subtraction of different types can't work (different base
> types)
>
> This is because the variable branch in function invoke_bpf_prog and the
> variable branches in function prepare_trampoline are defined as type
> u32 *, which conflicts with ctx->image's type __le32 *, so sparse complains
> when assignment or arithmetic operation are performed on these two
> variables and ctx->image.
>
> Since arm64 instructions are always little-endian, change the type of
> these two variables to __le32 * and call cpu_to_le32 to convert
> instruction to little-endian before writing it to memory.
>
> Reported-by: kernel test robot <lkp@intel.com>
> Fixes: efc9909fdce0 ("bpf, arm64: Add bpf trampoline for arm64")
> Signed-off-by: Xu Kuohai <xukuohai@huawei.com>
Reviewed-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
> ---
> arch/arm64/net/bpf_jit_comp.c | 12 ++++++------
> 1 file changed, 6 insertions(+), 6 deletions(-)
>
> diff --git a/arch/arm64/net/bpf_jit_comp.c b/arch/arm64/net/bpf_jit_comp.c
> index 7ca8779ae34f..29dc55da2476 100644
> --- a/arch/arm64/net/bpf_jit_comp.c
> +++ b/arch/arm64/net/bpf_jit_comp.c
> @@ -1643,7 +1643,7 @@ static void invoke_bpf_prog(struct jit_ctx *ctx, struct bpf_tramp_link *l,
> int args_off, int retval_off, int run_ctx_off,
> bool save_ret)
> {
> - u32 *branch;
> + __le32 *branch;
> u64 enter_prog;
> u64 exit_prog;
> struct bpf_prog *p = l->link.prog;
> @@ -1698,7 +1698,7 @@ static void invoke_bpf_prog(struct jit_ctx *ctx, struct bpf_tramp_link *l,
>
> if (ctx->image) {
> int offset = &ctx->image[ctx->idx] - branch;
> - *branch = A64_CBZ(1, A64_R(0), offset);
> + *branch = cpu_to_le32(A64_CBZ(1, A64_R(0), offset));
> }
>
> /* arg1: prog */
> @@ -1713,7 +1713,7 @@ static void invoke_bpf_prog(struct jit_ctx *ctx, struct bpf_tramp_link *l,
>
> static void invoke_bpf_mod_ret(struct jit_ctx *ctx, struct bpf_tramp_links *tl,
> int args_off, int retval_off, int run_ctx_off,
> - u32 **branches)
> + __le32 **branches)
> {
> int i;
>
> @@ -1784,7 +1784,7 @@ static int prepare_trampoline(struct jit_ctx *ctx, struct bpf_tramp_image *im,
> struct bpf_tramp_links *fexit = &tlinks[BPF_TRAMP_FEXIT];
> struct bpf_tramp_links *fmod_ret = &tlinks[BPF_TRAMP_MODIFY_RETURN];
> bool save_ret;
> - u32 **branches = NULL;
> + __le32 **branches = NULL;
>
> /* trampoline stack layout:
> * [ parent ip ]
> @@ -1892,7 +1892,7 @@ static int prepare_trampoline(struct jit_ctx *ctx, struct bpf_tramp_image *im,
> flags & BPF_TRAMP_F_RET_FENTRY_RET);
>
> if (fmod_ret->nr_links) {
> - branches = kcalloc(fmod_ret->nr_links, sizeof(u32 *),
> + branches = kcalloc(fmod_ret->nr_links, sizeof(__le32 *),
> GFP_KERNEL);
> if (!branches)
> return -ENOMEM;
> @@ -1916,7 +1916,7 @@ static int prepare_trampoline(struct jit_ctx *ctx, struct bpf_tramp_image *im,
> /* update the branches saved in invoke_bpf_mod_ret with cbnz */
> for (i = 0; i < fmod_ret->nr_links && ctx->image != NULL; i++) {
> int offset = &ctx->image[ctx->idx] - branches[i];
> - *branches[i] = A64_CBNZ(1, A64_R(10), offset);
> + *branches[i] = cpu_to_le32(A64_CBNZ(1, A64_R(10), offset));
> }
>
> for (i = 0; i < fexit->nr_links; i++)
> --
> 2.30.2
>
next prev parent reply other threads:[~2022-08-09 10:34 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-08-08 4:07 [PATCH bpf] bpf, arm64: Fix bpf trampoline instruction endianness Xu Kuohai
2022-08-09 10:33 ` Jean-Philippe Brucker [this message]
2022-08-10 14:53 ` Daniel Borkmann
2022-08-10 15:00 ` patchwork-bot+netdevbpf
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