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compel: flush caches after parasite injection

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After the CRIU process saves the parasite code for the target thread in
the shared mmap, it is necessary to call __clear_cache before the target
thread executes the code.

Without this step, the target thread may not see the correct code to
execute, which can result in a SIGILL signal.

For the specific arm64 case. this is important so that the newly copied
code is flushed from d-cache to RAM, so that the target thread sees the
new code.

The change is based on commit 6be10a2 by @fu.lin and on input received
from @adrianreber.

[ avagin: tweak code comment ]

Signed-off-by: Ignacio Moreno Gonzalez <Ignacio.MorenoGonzalez@kuka.com>
Signed-off-by: Andrei Vagin <avagin@gmail.com>
This commit is contained in:
Ignacio Moreno Gonzalez 2025-07-16 16:32:25 +02:00 committed by Andrei Vagin
parent 59970a606d
commit 04012eac7f
1 changed files with 10 additions and 0 deletions
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10
compel/src/lib/infect.c
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@ -1054,6 +1054,16 @@ int compel_infect_no_daemon(struct parasite_ctl *ctl, unsigned long nr_threads,
memcpy(ctl->local_map, ctl->pblob.hdr.mem, ctl->pblob.hdr.bsize);
compel_relocs_apply(ctl->local_map, ctl->remote_map, &ctl->pblob);
/*
* Ensure the infected thread sees the updated code.
*
* On architectures like ARM64, the Data Cache (D-cache) and
* Instruction Cache (I-cache) are not automatically coherent.
* Modifications land in the D-cache, so we must flush (clean) the
* D-cache to push changes to RAM to ensure the CPU fetches the updated
* instructions.
*/
__builtin___clear_cache(ctl->local_map, ctl->local_map + ctl->pblob.hdr.bsize);
p = parasite_size;