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Date: Sun, 18 Nov 2018 07:47:27 +0000
From: Y Song <ys114321@...il.com>
To: ard.biesheuvel@...aro.org
Cc: LKML <linux-kernel@...r.kernel.org>,
Daniel Borkmann <daniel@...earbox.net>,
Alexei Starovoitov <ast@...nel.org>,
rick.p.edgecombe@...el.com, eric.dumazet@...il.com,
jannh@...gle.com, Kees Cook <keescook@...omium.org>,
jeyu@...nel.org, arnd@...db.de, catalin.marinas@....com,
will.deacon@....com, mark.rutland@....com, ralf@...ux-mips.org,
paul.burton@...s.com, jhogan@...nel.org, benh@...nel.crashing.org,
paulus@...ba.org, mpe@...erman.id.au,
David Miller <davem@...emloft.net>,
linux-arm-kernel@...ts.infradead.org, linux-mips@...ux-mips.org,
linuxppc-dev@...ts.ozlabs.org, sparclinux@...r.kernel.org,
netdev <netdev@...r.kernel.org>
Subject: Re: [PATCH 2/4] net/bpf: refactor freeing of executable allocations
On Sat, Nov 17, 2018 at 6:58 PM Ard Biesheuvel
<ard.biesheuvel@...aro.org> wrote:
>
> All arch overrides of the __weak bpf_jit_free() amount to the same
> thing: the allocated memory was never mapped read-only, and so
> it does not have to be remapped to read-write before being freed.
>
> So in preparation of permitting arches to serve allocations for BPF
> JIT programs from other regions than the module region, refactor
> the existing bpf_jit_free() implementations to use the shared code
> where possible, and only specialize the remap and free operations.
>
> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@...aro.org>
> ---
> arch/mips/net/bpf_jit.c | 7 ++-----
> arch/powerpc/net/bpf_jit_comp.c | 7 ++-----
> arch/powerpc/net/bpf_jit_comp64.c | 9 +++------
> arch/sparc/net/bpf_jit_comp_32.c | 7 ++-----
> kernel/bpf/core.c | 15 +++++----------
> 5 files changed, 14 insertions(+), 31 deletions(-)
>
> diff --git a/arch/mips/net/bpf_jit.c b/arch/mips/net/bpf_jit.c
> index 1b69897274a1..5696bd7dccc7 100644
> --- a/arch/mips/net/bpf_jit.c
> +++ b/arch/mips/net/bpf_jit.c
> @@ -1261,10 +1261,7 @@ void bpf_jit_compile(struct bpf_prog *fp)
> kfree(ctx.offsets);
> }
>
> -void bpf_jit_free(struct bpf_prog *fp)
> +void bpf_jit_binary_free(struct bpf_binary_header *hdr)
> {
> - if (fp->jited)
> - bpf_jit_binary_free(bpf_jit_binary_hdr(fp));
> -
> - bpf_prog_unlock_free(fp);
> + module_memfree(hdr);
> }
> diff --git a/arch/powerpc/net/bpf_jit_comp.c b/arch/powerpc/net/bpf_jit_comp.c
> index a1ea1ea6b40d..5b5ce4a1b44b 100644
> --- a/arch/powerpc/net/bpf_jit_comp.c
> +++ b/arch/powerpc/net/bpf_jit_comp.c
> @@ -680,10 +680,7 @@ void bpf_jit_compile(struct bpf_prog *fp)
> return;
> }
>
> -void bpf_jit_free(struct bpf_prog *fp)
> +void bpf_jit_binary_free(struct bpf_binary_header *hdr)
> {
> - if (fp->jited)
> - bpf_jit_binary_free(bpf_jit_binary_hdr(fp));
> -
> - bpf_prog_unlock_free(fp);
> + module_memfree(hdr);
> }
> diff --git a/arch/powerpc/net/bpf_jit_comp64.c b/arch/powerpc/net/bpf_jit_comp64.c
> index 84c8f013a6c6..f64f1294bd62 100644
> --- a/arch/powerpc/net/bpf_jit_comp64.c
> +++ b/arch/powerpc/net/bpf_jit_comp64.c
> @@ -1021,11 +1021,8 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *fp)
> return fp;
> }
>
> -/* Overriding bpf_jit_free() as we don't set images read-only. */
> -void bpf_jit_free(struct bpf_prog *fp)
> +/* Overriding bpf_jit_binary_free() as we don't set images read-only. */
> +void bpf_jit_binary_free(struct bpf_binary_header *hdr)
> {
> - if (fp->jited)
> - bpf_jit_binary_free(bpf_jit_binary_hdr(fp));
> -
> - bpf_prog_unlock_free(fp);
> + module_memfree(hdr);
> }
> diff --git a/arch/sparc/net/bpf_jit_comp_32.c b/arch/sparc/net/bpf_jit_comp_32.c
> index 01bda6bc9e7f..589950d152cc 100644
> --- a/arch/sparc/net/bpf_jit_comp_32.c
> +++ b/arch/sparc/net/bpf_jit_comp_32.c
> @@ -756,10 +756,7 @@ cond_branch: f_offset = addrs[i + filter[i].jf];
> return;
> }
>
> -void bpf_jit_free(struct bpf_prog *fp)
> +void bpf_jit_binary_free(struct bpf_binary_header *hdr)
> {
> - if (fp->jited)
> - bpf_jit_binary_free(bpf_jit_binary_hdr(fp));
> -
> - bpf_prog_unlock_free(fp);
> + module_memfree(hdr);
> }
> diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
> index 1a796e0799ec..29f766dac203 100644
> --- a/kernel/bpf/core.c
> +++ b/kernel/bpf/core.c
> @@ -646,25 +646,20 @@ bpf_jit_binary_alloc(unsigned int proglen, u8 **image_ptr,
> return hdr;
> }
>
> -void bpf_jit_binary_free(struct bpf_binary_header *hdr)
> +void __weak bpf_jit_binary_free(struct bpf_binary_header *hdr)
> {
> - u32 pages = hdr->pages;
> -
> + bpf_jit_binary_unlock_ro(hdr);
> module_memfree(hdr);
> - bpf_jit_uncharge_modmem(pages);
> }
>
> -/* This symbol is only overridden by archs that have different
> - * requirements than the usual eBPF JITs, f.e. when they only
> - * implement cBPF JIT, do not set images read-only, etc.
> - */
Do you want to move the above comments to
new weak function bpf_jit_binary_free?
> -void __weak bpf_jit_free(struct bpf_prog *fp)
> +void bpf_jit_free(struct bpf_prog *fp)
> {
> if (fp->jited) {
> struct bpf_binary_header *hdr = bpf_jit_binary_hdr(fp);
> + u32 pages = hdr->pages;
>
> - bpf_jit_binary_unlock_ro(hdr);
> bpf_jit_binary_free(hdr);
> + bpf_jit_uncharge_modmem(pages);
>
> WARN_ON_ONCE(!bpf_prog_kallsyms_verify_off(fp));
> }
> --
> 2.17.1
>
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