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bpf: Enable BPF_TRAMP_F_IP_ARG for trampolines with call_get_func_ip

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Enabling BPF_TRAMP_F_IP_ARG for trampolines that actually need it.

The BPF_TRAMP_F_IP_ARG adds extra 3 instructions to trampoline code
and is used only by programs with bpf_get_func_ip helper, which is
added in following patch and sets call_get_func_ip bit.

This patch ensures that BPF_TRAMP_F_IP_ARG flag is used only for
trampolines that have programs with call_get_func_ip set.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20210714094400.396467-3-jolsa@kernel.org
This commit is contained in:
Jiri Olsa 2021-07-14 11:43:54 +02:00 committed by Alexei Starovoitov
parent 7e6f3cd89f
commit 1e37392ccc
2 changed files with 11 additions and 4 deletions
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3
include/linux/filter.h
View file

@ -559,7 +559,8 @@ struct bpf_prog {
kprobe_override:1, /* Do we override a kprobe? */
has_callchain_buf:1, /* callchain buffer allocated? */
enforce_expected_attach_type:1, /* Enforce expected_attach_type checking at attach time */
call_get_stack:1; /* Do we call bpf_get_stack() or bpf_get_stackid() */
call_get_stack:1, /* Do we call bpf_get_stack() or bpf_get_stackid() */
call_get_func_ip:1; /* Do we call get_func_ip() */
enum bpf_prog_type type; /* Type of BPF program */
enum bpf_attach_type expected_attach_type; /* For some prog types */
u32 len; /* Number of filter blocks */

12
kernel/bpf/trampoline.c
View file

@ -172,7 +172,7 @@ static int register_fentry(struct bpf_trampoline *tr, void *new_addr)
}
static struct bpf_tramp_progs *
bpf_trampoline_get_progs(const struct bpf_trampoline *tr, int *total)
bpf_trampoline_get_progs(const struct bpf_trampoline *tr, int *total, bool *ip_arg)
{
const struct bpf_prog_aux *aux;
struct bpf_tramp_progs *tprogs;
@ -189,8 +189,10 @@ bpf_trampoline_get_progs(const struct bpf_trampoline *tr, int *total)
*total += tr->progs_cnt[kind];
progs = tprogs[kind].progs;
hlist_for_each_entry(aux, &tr->progs_hlist[kind], tramp_hlist)
hlist_for_each_entry(aux, &tr->progs_hlist[kind], tramp_hlist) {
*ip_arg |= aux->prog->call_get_func_ip;
*progs++ = aux->prog;
}
}
return tprogs;
}
@ -333,9 +335,10 @@ static int bpf_trampoline_update(struct bpf_trampoline *tr)
struct bpf_tramp_image *im;
struct bpf_tramp_progs *tprogs;
u32 flags = BPF_TRAMP_F_RESTORE_REGS;
bool ip_arg = false;
int err, total;
tprogs = bpf_trampoline_get_progs(tr, &total);
tprogs = bpf_trampoline_get_progs(tr, &total, &ip_arg);
if (IS_ERR(tprogs))
return PTR_ERR(tprogs);
@ -357,6 +360,9 @@ static int bpf_trampoline_update(struct bpf_trampoline *tr)
tprogs[BPF_TRAMP_MODIFY_RETURN].nr_progs)
flags = BPF_TRAMP_F_CALL_ORIG | BPF_TRAMP_F_SKIP_FRAME;
if (ip_arg)
flags |= BPF_TRAMP_F_IP_ARG;
err = arch_prepare_bpf_trampoline(im, im->image, im->image + PAGE_SIZE,
&tr->func.model, flags, tprogs,
tr->func.addr);