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bpf: Allow to resolve bpf trampoline and dispatcher in unwind

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When unwinding the stack we need to identify each address
to successfully continue. Adding latch tree to keep trampolines
for quick lookup during the unwind.

The patch uses first 48 bytes for latch tree node, leaving 4048
bytes from the rest of the page for trampoline or dispatcher
generated code.

It's still enough not to affect trampoline and dispatcher progs
maximum counts.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200123161508.915203-3-jolsa@kernel.org
This commit is contained in:
Jiri Olsa
2020-01-23 17:15:07 +01:00
committed by Alexei Starovoitov
parent 84ad7a7ab6
commit e9b4e606c2
4 changed files with 90 additions and 13 deletions
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4
kernel/bpf/dispatcher.c
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@@ -113,7 +113,7 @@ static void bpf_dispatcher_update(struct bpf_dispatcher *d, int prev_num_progs)
noff = 0;
} else {
old = d->image + d->image_off;
noff = d->image_off ^ (PAGE_SIZE / 2);
noff = d->image_off ^ (BPF_IMAGE_SIZE / 2);
}
new = d->num_progs ? d->image + noff : NULL;
@@ -140,7 +140,7 @@ void bpf_dispatcher_change_prog(struct bpf_dispatcher *d, struct bpf_prog *from,
mutex_lock(&d->mutex);
if (!d->image) {
d->image = bpf_jit_alloc_exec_page();
d->image = bpf_image_alloc();
if (!d->image)
goto out;
}