kern_exec: Add kern.stacktop sysctl.
ClosedPublic
Actions

Authored by dgr_semihalf.com on Sep 10 2021, 6:14 AM.

Details

Reviewers

mw
emaste
imp
kib
cy

Commits

rG532d925b6f02: kern_exec: Add kern.stacktop sysctl.
rGa97d697122da: kern_exec: Add kern.stacktop sysctl.

Summary

With stack gap enabled top of the stack is moved down by a random
amount of bytes. Because of that some multithreaded applications
which use kern.usrstack sysctl to calculate address of stacks for
their threads can fail. Add kern.stacktop sysctl, which can be used
to retrieve address of the stack after stack gap is applied to it.
Returns value identical to kern.usrstack for processes which have
no stack gap.

Diff Detail

Lint

Lint Skipped

Unit

Tests Skipped

Event Timeline

dgr_semihalf.com requested review of this revision.Sep 10 2021, 6:14 AM

dgr_semihalf.com created this revision.

dgr_semihalf.com mentioned this in D31692: [RFC] Adjust kern.usrstack sysctl by stack gap..Sep 10 2021, 6:17 AM

dgr_semihalf.com added a child revision: D31898: libthr: Use kern.stacktop for thread stack calculation..Sep 10 2021, 6:20 AM

dgr_semihalf.com added a parent revision: D31516: setrlimit: Take stack gap into account..

Ping. Any comments? (Also for D31898)

Hi, do you have any further comments or remarks? If there are no objections, I'm going to merge this patch by EOW.

kib added inline comments.Oct 13 2021, 11:04 AM

sys/kern/kern_exec.c
137	Style: need spaces around binary op '\|'. Ignore other examples in this file, do it right for added code.
199–222	Fix style while there: `return (error);`
236	The op ('-') should be on the previous line, before line split. Also, why not to do single cast, instead of two: val = (unsigned)(p->p_sysent->sv_usrstack - p->p_vmspace->vm_stkgap);
245	`return (error);`