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compel: clear a breakpoint right after it's been triggered

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Breakpoints are used to stop as close as possible to a target system call.

First, we don't need it after this point.
Second, PTRACE_CONT can't pass through a breakpoint on arm64.

Signed-off-by: Andrei Vagin <avagin@gmail.com>
This commit is contained in:
Andrei Vagin 2022-08-07 16:36:15 -07:00
parent d7477dac03
commit 719fea2fc9
2 changed files with 11 additions and 25 deletions
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15
compel/src/lib/infect.c
View file

@ -1418,9 +1418,6 @@ static int parasite_fini_seized(struct parasite_ctl *ctl)
if (compel_stop_on_syscall(1, __NR(rt_sigreturn, 0), __NR(rt_sigreturn, 1)))
return -1;
if (ptrace_flush_breakpoints(pid))
return -1;
/*
* All signals are unblocked now. The kernel notifies about leaving
* syscall before starting to deliver signals. All parasite code are
@ -1650,8 +1647,18 @@ int compel_stop_on_syscall(int tasks, const int sys_nr, const int sys_nr_compat)
pr_debug("%d was trapped\n", pid);
if ((WSTOPSIG(status) & PTRACE_SYSCALL_TRAP) == 0)
if ((WSTOPSIG(status) & PTRACE_SYSCALL_TRAP) == 0) {
/*
* On some platforms such as ARM64, it is impossible to
* pass through a breakpoint, so let's clear it right
* after it has been triggered.
*/
if (ptrace_flush_breakpoints(pid)) {
pr_err("Unable to clear breakpoints\n");
return -1;
}
goto goon;
}
if (trace == TRACE_EXIT) {
trace = TRACE_ENTER;
pr_debug("`- Expecting exit\n");

21
criu/cr-restore.c
View file

@ -2071,24 +2071,6 @@ static int catch_tasks(bool root_seized)
return 0;
}
static int clear_breakpoints(void)
{
struct pstree_item *item;
int ret = 0, i;
if (fault_injected(FI_NO_BREAKPOINTS))
return 0;
for_each_pstree_item(item) {
if (!task_alive(item))
continue;
for (i = 0; i < item->nr_threads; i++)
ret |= ptrace_flush_breakpoints(item->threads[i].real);
}
return ret;
}
static void finalize_restore(void)
{
struct pstree_item *item;
@ -2459,9 +2441,6 @@ skip_ns_bouncing:
goto out_kill_network_unlocked;
}
if (clear_breakpoints())
pr_err("Unable to flush breakpoints\n");
finalize_restore();
/*
* Some external devices such as GPUs might need a very late