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bpf: Remove bpf trampoline selector

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After commit e21aa34178 ("bpf: Fix fexit trampoline."), the selector is only
used to indicate how many times the bpf trampoline image are updated and been
displayed in the trampoline ksym name. After the trampoline is freed, the
selector will start from 0 again. So the selector is a useless value to the
user. We can remove it.

If the user want to check whether the bpf trampoline image has been updated
or not, the user can compare the address. Each time the trampoline image is
updated, the address will change consequently. Jiri also pointed out another
issue that perf is still using the old name "bpf_trampoline_%lu", so this
change can fix the issue in perf.

Fixes: e21aa34178 ("bpf: Fix fexit trampoline.")
Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Song Liu <song@kernel.org>
Cc: Jiri Olsa <olsajiri@gmail.com>
Link: https://lore.kernel.org/bpf/ZFvOOlrmHiY9AgXE@krava
Link: https://lore.kernel.org/bpf/20230515130849.57502-3-laoar.shao@gmail.com
This commit is contained in:
Yafang Shao 2023-05-15 13:08:48 +00:00 committed by Daniel Borkmann
parent 90564f1e3d
commit 47e79cbeea
2 changed files with 4 additions and 8 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
include/linux/bpf.h
View File

@ -1125,7 +1125,6 @@ struct bpf_trampoline {
int progs_cnt[BPF_TRAMP_MAX];
/* Executable image of trampoline */
struct bpf_tramp_image *cur_image;
u64 selector;
struct module *mod;
};

11
kernel/bpf/trampoline.c
View File

@ -344,7 +344,7 @@ static void bpf_tramp_image_put(struct bpf_tramp_image *im)
call_rcu_tasks_trace(&im->rcu, __bpf_tramp_image_put_rcu_tasks);
}
static struct bpf_tramp_image *bpf_tramp_image_alloc(u64 key, u32 idx)
static struct bpf_tramp_image *bpf_tramp_image_alloc(u64 key)
{
struct bpf_tramp_image *im;
struct bpf_ksym *ksym;
@ -371,7 +371,7 @@ static struct bpf_tramp_image *bpf_tramp_image_alloc(u64 key, u32 idx)
ksym = &im->ksym;
INIT_LIST_HEAD_RCU(&ksym->lnode);
snprintf(ksym->name, KSYM_NAME_LEN, "bpf_trampoline_%llu_%u", key, idx);
snprintf(ksym->name, KSYM_NAME_LEN, "bpf_trampoline_%llu", key);
bpf_image_ksym_add(image, ksym);
return im;
@ -401,11 +401,10 @@ static int bpf_trampoline_update(struct bpf_trampoline *tr, bool lock_direct_mut
err = unregister_fentry(tr, tr->cur_image->image);
bpf_tramp_image_put(tr->cur_image);
tr->cur_image = NULL;
tr->selector = 0;
goto out;
}
im = bpf_tramp_image_alloc(tr->key, tr->selector);
im = bpf_tramp_image_alloc(tr->key);
if (IS_ERR(im)) {
err = PTR_ERR(im);
goto out;
@ -442,8 +441,7 @@ again:
set_memory_rox((long)im->image, 1);
WARN_ON(tr->cur_image && tr->selector == 0);
WARN_ON(!tr->cur_image && tr->selector);
WARN_ON(tr->cur_image && total == 0);
if (tr->cur_image)
/* progs already running at this address */
err = modify_fentry(tr, tr->cur_image->image, im->image, lock_direct_mutex);
@ -473,7 +471,6 @@ again:
if (tr->cur_image)
bpf_tramp_image_put(tr->cur_image);
tr->cur_image = im;
tr->selector++;
out:
/* If any error happens, restore previous flags */
if (err)