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Message-ID: <20200121224718.nu3xh6gmivmt4tj3@kafai-mbp.dhcp.thefacebook.com>
Date: Tue, 21 Jan 2020 22:47:22 +0000
From: Martin Lau <kafai@...com>
To: Daniel Borkmann <daniel@...earbox.net>
CC: "bpf@...r.kernel.org" <bpf@...r.kernel.org>,
Alexei Starovoitov <ast@...nel.org>,
David Miller <davem@...emloft.net>,
Eric Dumazet <edumazet@...gle.com>,
Kernel Team <Kernel-team@...com>,
"netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: [PATCH bpf-next 1/3] bpf: Add BPF_FUNC_jiffies64
On Tue, Jan 21, 2020 at 11:41:06PM +0100, Daniel Borkmann wrote:
> On 1/21/20 8:54 PM, Martin KaFai Lau wrote:
> > This patch adds a helper to read the 64bit jiffies. It will be used
> > in a later patch to implement the bpf_cubic.c.
> >
> > The helper is inlined. "gen_inline" is added to "struct bpf_func_proto"
> > to do that. This helper is available to CAP_SYS_ADMIN.
> >
> > Signed-off-by: Martin KaFai Lau <kafai@...com>
> > ---
> > include/linux/bpf.h | 2 ++
> > include/uapi/linux/bpf.h | 9 ++++++++-
> > kernel/bpf/core.c | 1 +
> > kernel/bpf/helpers.c | 27 +++++++++++++++++++++++++++
> > kernel/bpf/verifier.c | 18 ++++++++++++++++++
> > net/core/filter.c | 2 ++
> > 6 files changed, 58 insertions(+), 1 deletion(-)
> >
> > diff --git a/include/linux/bpf.h b/include/linux/bpf.h
> > index 8e3b8f4ad183..3d85ef44b247 100644
> > --- a/include/linux/bpf.h
> > +++ b/include/linux/bpf.h
> > @@ -258,6 +258,7 @@ enum bpf_return_type {
> > */
> > struct bpf_func_proto {
> > u64 (*func)(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5);
> > + u32 (*gen_inline)(struct bpf_insn *insn_buf);
> > bool gpl_only;
> > bool pkt_access;
> > enum bpf_return_type ret_type;
> > @@ -1406,6 +1407,7 @@ extern const struct bpf_func_proto bpf_get_local_storage_proto;
> > extern const struct bpf_func_proto bpf_strtol_proto;
> > extern const struct bpf_func_proto bpf_strtoul_proto;
> > extern const struct bpf_func_proto bpf_tcp_sock_proto;
> > +extern const struct bpf_func_proto bpf_jiffies64_proto;
> > /* Shared helpers among cBPF and eBPF. */
> > void bpf_user_rnd_init_once(void);
> > diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
> > index 033d90a2282d..d17c6bcd50cd 100644
> > --- a/include/uapi/linux/bpf.h
> > +++ b/include/uapi/linux/bpf.h
> > @@ -2885,6 +2885,12 @@ union bpf_attr {
> > * **-EPERM** if no permission to send the *sig*.
> > *
> > * **-EAGAIN** if bpf program can try again.
> > + *
> > + * u64 bpf_jiffies64(void)
> > + * Description
> > + * Obtain the 64bit jiffies
> > + * Return
> > + * The 64 bit jiffies
> > */
> > #define __BPF_FUNC_MAPPER(FN) \
> > FN(unspec), \
> > @@ -3004,7 +3010,8 @@ union bpf_attr {
> > FN(probe_read_user_str), \
> > FN(probe_read_kernel_str), \
> > FN(tcp_send_ack), \
> > - FN(send_signal_thread),
> > + FN(send_signal_thread), \
> > + FN(jiffies64),
> > /* integer value in 'imm' field of BPF_CALL instruction selects which helper
> > * function eBPF program intends to call
> > diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
> > index 29d47aae0dd1..973a20d49749 100644
> > --- a/kernel/bpf/core.c
> > +++ b/kernel/bpf/core.c
> > @@ -2137,6 +2137,7 @@ const struct bpf_func_proto bpf_map_pop_elem_proto __weak;
> > const struct bpf_func_proto bpf_map_peek_elem_proto __weak;
> > const struct bpf_func_proto bpf_spin_lock_proto __weak;
> > const struct bpf_func_proto bpf_spin_unlock_proto __weak;
> > +const struct bpf_func_proto bpf_jiffies64_proto __weak;
> > const struct bpf_func_proto bpf_get_prandom_u32_proto __weak;
> > const struct bpf_func_proto bpf_get_smp_processor_id_proto __weak;
> > diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
> > index cada974c9f4e..b241cfd350c4 100644
> > --- a/kernel/bpf/helpers.c
> > +++ b/kernel/bpf/helpers.c
> > @@ -11,6 +11,7 @@
> > #include <linux/uidgid.h>
> > #include <linux/filter.h>
> > #include <linux/ctype.h>
> > +#include <linux/jiffies.h>
> > #include "../../lib/kstrtox.h"
> > @@ -312,6 +313,32 @@ void copy_map_value_locked(struct bpf_map *map, void *dst, void *src,
> > preempt_enable();
> > }
> > +static u32 bpf_jiffies64_gen_inline(struct bpf_insn *insn_buf)
> > +{
> > + struct bpf_insn *insn = insn_buf;
> > +#if BITS_PER_LONG == 64
> > + struct bpf_insn ld_jiffies_addr[2] = {
> > + BPF_LD_IMM64(BPF_REG_0, (unsigned long)&jiffies),
> > + };
> > +
> > + BUILD_BUG_ON(sizeof(jiffies) != sizeof(unsigned long));
> > +
> > + *insn++ = ld_jiffies_addr[0];
> > + *insn++ = ld_jiffies_addr[1];
> > + *insn++ = BPF_LDX_MEM(BPF_DW, BPF_REG_0, BPF_REG_0, 0);
> > +#else
> > + *insn++ = BPF_EMIT_CALL(BPF_CAST_CALL(get_jiffies_64));
> > +#endif
> > +
> > + return insn - insn_buf;
> > +}
> > +
> > +const struct bpf_func_proto bpf_jiffies64_proto = {
> > + .gen_inline = bpf_jiffies64_gen_inline,
> > + .gpl_only = false,
> > + .ret_type = RET_INTEGER,
> > +};
> > +
> > #ifdef CONFIG_CGROUPS
> > BPF_CALL_0(bpf_get_current_cgroup_id)
> > {
> > diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
> > index ca17dccc17ba..91818aad2f80 100644
> > --- a/kernel/bpf/verifier.c
> > +++ b/kernel/bpf/verifier.c
> > @@ -9447,6 +9447,24 @@ static int fixup_bpf_calls(struct bpf_verifier_env *env)
> > patch_call_imm:
> > fn = env->ops->get_func_proto(insn->imm, env->prog);
> > + if (fn->gen_inline) {
> > + cnt = fn->gen_inline(insn_buf);
> > + if (cnt == 0 || cnt >= ARRAY_SIZE(insn_buf)) {
> > + verbose(env, "bpf verifier is misconfigured\n");
> > + return -EINVAL;
> > + }
> > +
> > + new_prog = bpf_patch_insn_data(env, i + delta,
> > + insn_buf, cnt);
> > + if (!new_prog)
> > + return -ENOMEM;
> > +
> > + delta += cnt - 1;
> > + env->prog = prog = new_prog;
> > + insn = new_prog->insnsi + i + delta;
> > + continue;
> > + }
>
> We do most of the inlining in fixup_bpf_calls() directly today, why
> breaking with that here with a special callback? (Agree it could probably
> be refactored in general, but such rework should also take the other
> helpers into account.)
Thanks for the review.
I will remove bpf_jiffies64_gen_inline() and move those logic
into fixup_bpf_calls().
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