From mboxrd@z Thu Jan 1 00:00:00 1970 From: daniel@iogearbox.net (Daniel Borkmann) Date: Mon, 16 Nov 2015 12:48:08 +0100 Subject: [PATCH] bpf, arm64: start flushing icache range from header In-Reply-To: <20151116113912.GB20696@leverpostej> References: <41c4a481eb665a492c3b2df16af219b1250224a0.1447446460.git.daniel@iogearbox.net> <20151116113912.GB20696@leverpostej> Message-ID: <5649C278.2030803@iogearbox.net> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On 11/16/2015 12:39 PM, Mark Rutland wrote: > On Sat, Nov 14, 2015 at 01:16:18AM +0100, Daniel Borkmann wrote: >> While recently going over ARM64's BPF code, I noticed that the icache >> range we're flushing should start at header already and not at ctx.image. >> >> Reason is that after b569c1c622c5 ("net: bpf: arm64: 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 >> Acked-by: Zi Shen Lim >> Cc: Alexei Starovoitov >> --- >> ( As arm64 jit fixes seem to go via arm64 tree, sending them here. ) >> >> arch/arm64/net/bpf_jit_comp.c | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/arch/arm64/net/bpf_jit_comp.c b/arch/arm64/net/bpf_jit_comp.c >> index a44e529..ee06570 100644 >> --- a/arch/arm64/net/bpf_jit_comp.c >> +++ b/arch/arm64/net/bpf_jit_comp.c >> @@ -740,7 +740,7 @@ void bpf_int_jit_compile(struct bpf_prog *prog) >> if (bpf_jit_enable > 1) >> bpf_jit_dump(prog->len, image_size, 2, ctx.image); >> >> - bpf_flush_icache(ctx.image, ctx.image + ctx.idx); >> + bpf_flush_icache(header, ctx.image + ctx.idx); > > As far as I can see, ctx.idx doesn't take into account the size of the > header, given we zero it after bpf_jit_binary_alloc, and increment it > for each instruction. > > So won't this prevent us from flushing the end of the image? Or did I > miss something? Nope, bpf_flush_icache() takes start and end pointer ... header starts before ctx.image on the linear buffer. Why should this prevent us from flushing the end of the image?