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I was just reading this answer on StackOverflow, "How can you debug a process using gdb without pausing it?"

The Linux kernel provides some support for this via PTRACE_SEIZE, but gdb doesn't use this yet. There's a bug in bugzilla you can track, "Bug 15250 - use PTRACE_SEIZE and PTRACE_INTERRUPT"

I was able to find PTRACE_SEIZE documented in man ptrace,

PTRACE_SEIZE (since Linux 3.4): Attach to the process specified in pid, making it a tracee of the calling process. Unlike PTRACE_ATTACH, PTRACE_SEIZE does not stop the process. Group- stops are reported as PTRACE_EVENT_STOP and WSTOPSIG(status) returns the stop signal. Automatically attached children stop with PTRACE_EVENT_STOP and WSTOPSIG(status) returns SIGTRAP instead of having SIGSTOP signal delivered to them. execve(2) does not deliver an extra SIGTRAP. Only a PTRACE_SEIZEd process can accept PTRACE_INTERRUPT and PTRACE_LISTEN commands. The "seized" behavior just described is inherited by children that are automatically at‐ tached using PTRACE_O_TRACEFORK, PTRACE_O_TRACEVFORK, and PTRACE_O_TRACECLONE. addr must be zero. data contains a bit mask of ptrace options to activate immediately. Permission to perform a PTRACE_SEIZE is governed by a ptrace access mode PTRACE_MODE_ATTACH_REALCREDS check; see below.

That raises the question if PTRACE_SEIZE isn't supported by gdb, what tooling (if any) does support this functionality on Linux?

Evan Carroll
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