bpf: Enable BPF_TRAMP_F_IP_ARG for trampolines with call_get_func_ip

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

diff --git a/include/linux/filter.h b/include/linux/filter.h
index 472f970..ba36989 100644 (file)
--- a/include/linux/filter.h
+++ b/include/linux/filter.h
@@ -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 */

diff --git a/kernel/bpf/trampoline.c b/kernel/bpf/trampoline.c
index 28a3630..b2535ac 100644 (file)
--- a/kernel/bpf/trampoline.c
+++ b/kernel/bpf/trampoline.c
@@ -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);