[PATCH net] bpf, arm: start flushing icache range from header

[PATCH net] bpf, arm: start flushing icache range from header

[Daniel Borkmann]

During review I noticed that the icache range we're flushing should
start at header already and not at ctx.image.

Reason is that after 55309dd3d4cd ("net: bpf: arm: address randomize
and write protect JIT code"), we also want to make sure to flush the
random-sized trap in front of the start of the actual program (analogous
to x86). No operational differences from user side.

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Tested-by: Nicolas Schichan <nschichan@freebox.fr>
Cc: Alexei Starovoitov <ast@kernel.org>
---
 ( As arm32 fixes usually go via Dave's tree, targeting -net. )

 arch/arm/net/bpf_jit_32.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/arm/net/bpf_jit_32.c b/arch/arm/net/bpf_jit_32.c
index 2f4b14c..591f9db 100644
--- a/arch/arm/net/bpf_jit_32.c
+++ b/arch/arm/net/bpf_jit_32.c
@@ -1061,7 +1061,7 @@ void bpf_jit_compile(struct bpf_prog *fp)
 	}
 	build_epilogue(&ctx);
 
-	flush_icache_range((u32)ctx.target, (u32)(ctx.target + ctx.idx));
+	flush_icache_range((u32)header, (u32)(ctx.target + ctx.idx));
 
 #if __LINUX_ARM_ARCH__ < 7
 	if (ctx.imm_count)
-- 
1.9.3

Re: [PATCH net] bpf, arm: start flushing icache range from header

[Mark Rutland]

On Sat, Nov 14, 2015 at 01:26:53AM +0100, Daniel Borkmann wrote:
> During review I noticed that the icache range we're flushing should
> start at header already and not at ctx.image.
> 
> Reason is that after 55309dd3d4cd ("net: bpf: arm: address randomize
> and write protect JIT code"), we also want to make sure to flush the
> random-sized trap in front of the start of the actual program (analogous
> to x86). No operational differences from user side.
> 
> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
> Tested-by: Nicolas Schichan <nschichan@freebox.fr>
> Cc: Alexei Starovoitov <ast@kernel.org>
> ---
>  ( As arm32 fixes usually go via Dave's tree, targeting -net. )
> 
>  arch/arm/net/bpf_jit_32.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/arm/net/bpf_jit_32.c b/arch/arm/net/bpf_jit_32.c
> index 2f4b14c..591f9db 100644
> --- a/arch/arm/net/bpf_jit_32.c
> +++ b/arch/arm/net/bpf_jit_32.c
> @@ -1061,7 +1061,7 @@ void bpf_jit_compile(struct bpf_prog *fp)
>  	}
>  	build_epilogue(&ctx);
>  
> -	flush_icache_range((u32)ctx.target, (u32)(ctx.target + ctx.idx));
> +	flush_icache_range((u32)header, (u32)(ctx.target + ctx.idx));

As with the arm64 patch, doesn't this prevent us from flushing the end
of the image? ctx.idx doesn't seem to take into account the header size.

Mark.

Re: [PATCH net] bpf, arm: start flushing icache range from header

[Mark Rutland]

On Mon, Nov 16, 2015 at 11:40:55AM +0000, Mark Rutland wrote:
> On Sat, Nov 14, 2015 at 01:26:53AM +0100, Daniel Borkmann wrote:
> > During review I noticed that the icache range we're flushing should
> > start at header already and not at ctx.image.
> > 
> > Reason is that after 55309dd3d4cd ("net: bpf: arm: address randomize
> > and write protect JIT code"), we also want to make sure to flush the
> > random-sized trap in front of the start of the actual program (analogous
> > to x86). No operational differences from user side.
> > 
> > Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
> > Tested-by: Nicolas Schichan <nschichan@freebox.fr>
> > Cc: Alexei Starovoitov <ast@kernel.org>
> > ---
> >  ( As arm32 fixes usually go via Dave's tree, targeting -net. )
> > 
> >  arch/arm/net/bpf_jit_32.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/arch/arm/net/bpf_jit_32.c b/arch/arm/net/bpf_jit_32.c
> > index 2f4b14c..591f9db 100644
> > --- a/arch/arm/net/bpf_jit_32.c
> > +++ b/arch/arm/net/bpf_jit_32.c
> > @@ -1061,7 +1061,7 @@ void bpf_jit_compile(struct bpf_prog *fp)
> >  	}
> >  	build_epilogue(&ctx);
> >  
> > -	flush_icache_range((u32)ctx.target, (u32)(ctx.target + ctx.idx));
> > +	flush_icache_range((u32)header, (u32)(ctx.target + ctx.idx));
> 
> As with the arm64 patch, doesn't this prevent us from flushing the end
> of the image? ctx.idx doesn't seem to take into account the header size.

I'd misread the patch; it is fine.

Sorry for the noise.

Mark.

Re: [PATCH net] bpf, arm: start flushing icache range from header

[David Miller]

From: Daniel Borkmann <daniel@iogearbox.net>
Date: Sat, 14 Nov 2015 01:26:53 +0100

> During review I noticed that the icache range we're flushing should
> start at header already and not at ctx.image.
> 
> Reason is that after 55309dd3d4cd ("net: bpf: arm: address randomize
> and write protect JIT code"), we also want to make sure to flush the
> random-sized trap in front of the start of the actual program (analogous
> to x86). No operational differences from user side.
> 
> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
> Tested-by: Nicolas Schichan <nschichan@freebox.fr>
> Cc: Alexei Starovoitov <ast@kernel.org>

Applied.