Re: current now panics when starting VBox VM

On Wed, Nov 03, 2021 at 11:05:11AM -0400, Michael Butler via freebsd-emulation wrote:
> On 11/3/21 10:36, Ed Maste wrote:
> The kgdb back-trace isn't any more enlightening to me :-(
> 
> __curthread () at /usr/src/sys/amd64/include/pcpu_aux.h:55
> 55              __asm("movq %%gs:%P1,%0" : "=r" (td) : "n" (offsetof(struct
> pcpu,
> (kgdb) bt
> #0  __curthread () at /usr/src/sys/amd64/include/pcpu_aux.h:55
> #1  doadump (textdump=<optimized out>) at
> /usr/src/sys/kern/kern_shutdown.c:399
> #2  0xffffffff808cbac5 in kern_reboot (howto=260) at
> /usr/src/sys/kern/kern_shutdown.c:487
> #3  0xffffffff808cbedb in vpanic (fmt=<optimized out>,
> ap=0xfffffe0129a6a8d0) at /usr/src/sys/kern/kern_shutdown.c:920
> #4  0xffffffff808cbd33 in panic (fmt=<unavailable>) at
> /usr/src/sys/kern/kern_shutdown.c:844
> #5  0xffffffff80ca920c in trap_fatal (frame=frame@entry=0xfffffe0129a6aac0,
> eva=0) at /usr/src/sys/amd64/amd64/trap.c:946
> #6  0xffffffff80ca95af in trap_pfault (frame=frame@entry=0xfffffe0129a6aac0,
> usermode=false, signo=<optimized out>, signo@entry=0x0, ucode=<optimized
> out>, ucode@entry=0x0)
>     at /usr/src/sys/amd64/include/cpufunc.h:417
> #7  0xffffffff80ca89bc in trap (frame=0xfffffe0129a6aac0) at
> /usr/src/sys/amd64/amd64/trap.c:443
> #8  <signal handler called>
> #9  strlen () at /usr/src/sys/amd64/amd64/support.S:751
> #10 0xffffffff808b4d79 in sysctl_kern_proc_pathname (oidp=<optimized out>,
> arg1=0xfffffe0129a6ad8c, arg2=<optimized out>, req=0xfffffe0129a6acc0) at
> /usr/src/sys/kern/kern_proc.c:2330
> #11 0xffffffff808dc331 in sysctl_root_handler_locked
> (oid=oid@entry=0xffffffff810cf0e0 <sysctl___kern_proc_pathname>,
> arg1=arg1@entry=0xfffffe0129a6ad8c, arg2=arg2@entry=1,
>     req=0xfffffe0129a6acc0, tracker=tracker@entry=0xfffffe0129a6ac38) at
> /usr/src/sys/kern/kern_sysctl.c:185
> #12 0xffffffff808db88b in sysctl_root (oidp=<optimized out>,
> arg1=0xfffffe0129a6ad8c, arg1@entry=0xfffffe0129a6ad80, arg2=1,
> arg2@entry=4, req=req@entry=0xfffffe0129a6acc0)
>     at /usr/src/sys/kern/kern_sysctl.c:2305
> #13 0xffffffff808dbdf3 in userland_sysctl (td=td@entry=0xfffffe012991a000,
> name=name@entry=0xfffffe0129a6ad80, namelen=4, old=<optimized out>,
> oldlenp=<optimized out>,
>     inkernel=<optimized out>, inkernel@entry=0, new=0x0, newlen=0,
> retval=0xfffffe0129a6ade8, flags=0) at /usr/src/sys/kern/kern_sysctl.c:2462
> #14 0xffffffff808dbc3c in sys___sysctl (td=0xfffffe012991a000,
> uap=0xfffffe012991a3f0) at /usr/src/sys/kern/kern_sysctl.c:2335
> #15 0xffffffff80ca9b5c in syscallenter (td=0xfffffe012991a000) at
> /usr/src/sys/amd64/amd64/../../kern/subr_syscall.c:189
> #16 amd64_syscall (td=0xfffffe012991a000, traced=0) at
> /usr/src/sys/amd64/amd64/trap.c:1191
> #17 <signal handler called>
> #18 0x000000080315a71a in ?? ()
> Backtrace stopped: Cannot access memory at address 0x7fffffffc778
> (kgdb)
> 

Try this

commit 2d3f95bd1fd4f71769f60b8037c1ff27c75d8258
Author: Konstantin Belousov <kib@FreeBSD.org>
Date:   Wed Nov 3 17:11:33 2021 +0200

    proc_get_binpath(): return empty string instead of NULL
    
    for strange case where process does not have text.
    
    Sponsored by:   The FreeBSD Foundation
    MFC after:      3 days

diff --git a/sys/kern/kern_proc.c b/sys/kern/kern_proc.c
index 2156c5c465ba..d11f651960c0 100644
--- a/sys/kern/kern_proc.c
+++ b/sys/kern/kern_proc.c
@@ -2252,7 +2252,7 @@ proc_get_binpath(struct proc *p, char *binname, char **retbuf,
 	vp = p->p_textvp;
 	if (vp == NULL) {
 		PROC_UNLOCK(p);
-		*retbuf = NULL;
+		*retbuf = "";
 		*freebuf = NULL;
 		return (0);
 	}