Userspace may configure rseq cs abort policy by
setting RSEQ_CS_FLAG_NO_RESTART_ON_* flags.
In ("cr-dump: fixup thread IP when inside rseq cs") we have supported
the case when process was caught by CRIU during rseq cs execution by
fixing up IP to abort_ip. Thats a common case, but there is special flag
called RSEQ_CS_FLAG_NO_RESTART_ON_SIGNAL, in this case we have to leave
process IP as it was before CRIU seized it. Unfortunately, that's not
all that we need here. We also must preserve (struct rseq)->rseq_cs field.
You may ask like "why we need to preserve it by hands? CRIU is dumping
all process memory and restores it". That's true. But not so easy. The problem
here is that the kernel performs this field cleanup when it realized that
the process gets out of rseq cs. But during dump/restore procedures we are
executing parasite/restorer from the process context. It means that process
will get out of rseq cs in any case and (struct rseq)->rseq_cs will be cleared
by the kernel. So we need to restore this field by hands at the *last* stage
of restore just before releasing processes.
Signed-off-by: Alexander Mikhalitsyn <alexander.mikhalitsyn@virtuozzo.com>
Support basic rseq C/R scenario. Assume that:
- there are no processes with IP inside the rseq critical section (CS)
- kernel has ptrace(PTRACE_GET_RSEQ_CONFIGURATION) support
On dump:
1. use ptrace(PTRACE_GET_RSEQ_CONFIGURATION) to get
struct rseq pointer, rseq size and signature from the kernel.
2. save to the image
On restore:
1. get rseq ptr, size, signature from the image
2. register it back using rseq() from the restorer parasite
Fixes: #1696
Reported-by: Radostin Stoyanov <radostin@redhat.com>
Suggested-by: Florian Weimer <fweimer@redhat.com>
Signed-off-by: Alexander Mikhalitsyn <alexander.mikhalitsyn@virtuozzo.com>
