On 11/26/18 9:44 PM, Russell King - ARM Linux wrote:
On Mon, Nov 26, 2018 at 11:41:11PM +0000, Russell King - ARM Linux wrote:
On Mon, Nov 26, 2018 at 11:33:03PM +0000, Russell King - ARM Linux wrote:
On Mon, Nov 26, 2018 at 08:53:35PM -0200, Rafael David Tinoco wrote:
Right now, only way for task->thread_info->syscall to be updated is if
if _TIF_SYSCALL_WORK is set in current's task thread_info->flags
(similar to what has_syscall_work() checks for arm64).
This means that "->syscall" will only be updated if we are tracing the
syscalls through ptrace, for example. This is NOT the same behavior as
arm64, when pt_regs->syscallno is updated in the beginning of svc0
handler for *every* syscall entry.
So when was it decided that the syscall number will always be required
(we need it to know how far back this has to be backported).
PS, I rather object to the fact that the required behaviour seems to
change, arch maintainers aren't told about it until... some test is
created at some random point in the future which then fails.
Surely there's a better way to communicate changes in requirements
than discovery-by-random-bug-report ?
Final comment for tonight - the commit introducing /proc/*/syscall says:
This adds /proc/PID/syscall and /proc/PID/task/TID/syscall magic files.
These use task_current_syscall() to show the task's current system call
number and argument registers, stack pointer and PC. For a task blocked
but not in a syscall, the file shows "-1" in place of the syscall number,
followed by only the SP and PC. For a task that's not blocked, it shows
"running".
Please validate that a blocked task does indeed show -1 with your patch
applied.
Will do. This is done in an upper level (collect_syscall <-
task_current_syscall <- proc_pid_syscall):
if (!try_get_task_stack(target)) {
/* Task has no stack, so the task isn't in a syscall. */
*sp = *pc = 0;
*callno = -1;
return 0;
}
I think only missing part for arm was that one, but will confirm, after
fixing usage of "r7" for obtaining "scno". Will send a v2 in this thread.
Thanks!
--
Rafael D. Tinoco
Linaro Kernel Validation
