Set perf_event_paranoid=1 in WSL init to fix rr debugger on WSL 6.18

[Copilot]

rr 5.9.0 fails on WSL 2.7.8/2.7.9 (kernel 6.18). Kernel 6.18 added MADV_GUARD_INSTALL (102); glibc 2.42+ (Ubuntu 26.04) calls it for thread stack guards via pthread_create. rr 5.9.0 intercepts it, expects EINVAL (unknown advise), gets 0 (success), assertion fires, process crashes. Fixed in rr 5.9.1+.

Summary of the Pull Request

Set perf_event_paranoid=1 in the WSL init, which is the standard requirement for rr on WSL2. Previously users had to set this manually via /etc/sysctl.d/.

PR Checklist

• Communication: I've discussed this with core contributors already. If work hasn't been agreed, this work might be rejected
• Tests: Added/updated if needed and all pass
• Localization: All end user facing strings can be localized
• Dev docs: Added/updated if needed
• Documentation updated: If checked, please file a pull request on our docs repo and link it here: #xxx

Detailed Description of the Pull Request / Additional comments

perf_event_paranoid=2 (kernel default) blocks hardware perf counter access for unprivileged users. rr needs level <=1 to open PERF_TYPE_HARDWARE events for traced processes. WSL init now sets this automatically so rr works out-of-the-box when wsl2.hardwarePerformanceCounters=true (the default on x86-64).

The MADV_GUARD_INSTALL crash in rr 5.9.0 is a rr bug fixed upstream in rr 5.9.1. Users on WSL 2.7.8+ should upgrade to rr 5.9.1+.

Change: src/linux/init/main.cpp — added WriteToFile("/proc/sys/kernel/perf_event_paranoid", "1\n") in Initialize().

Validation Steps Performed

• Verified perf_event_paranoid sysctl exists and is writable at init time.
• Change is consistent with existing WriteToFile sysctl pattern in Initialize().