Date: Sun, 3 Oct 2010 03:10:04 GMT From: Zhouyi Zhou <zhouzhouyi@gmail.com> To: freebsd-gnats-submit@FreeBSD.org Subject: amd64/151167: amd64 remote debug fails Message-ID: <201010030310.o933A41i095896@www.freebsd.org> Resent-Message-ID: <201010030320.o933K3EY010561@freefall.freebsd.org>
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>Number: 151167
>Category: amd64
>Synopsis: amd64 remote debug fails
>Confidential: no
>Severity: non-critical
>Priority: medium
>Responsible: freebsd-amd64
>State: open
>Quarter:
>Keywords:
>Date-Required:
>Class: sw-bug
>Submitter-Id: current-users
>Arrival-Date: Sun Oct 03 03:20:02 UTC 2010
>Closed-Date:
>Last-Modified:
>Originator: Zhouyi Zhou
>Release: FreeBSD 8.0
>Organization:
Institute of Computing Technology, CAS
>Environment:
FreeBSD zzy 8.0-RELEASE FreeBSD 8.0-RELEASE #137: Sun Oct 3 14:25:54 UTC 2010 root@zzy:/usr/src/sys/amd64/compile/GENERIC amd64
>Description:
When remote debug FreeBSD 8.0 using gdb on a Intel x86_64 machine, the next command will cause kernel panic.
>How-To-Repeat:
use next command to step over a function all will cause kernel panic
for example:
Breakpoint 1, fork1 (td=0xffffff0002fce390, flags=20, pages=4, procp=0xffffff804a0afaf0) at ../../../kern/kern_fork.c:283
283 newproc = uma_zalloc(proc_zone, M_WAITOK);
(gdb) n
>Fix:
The problems is in some intel x86_64 machines, the computing the rsp from trap frame is not correct.
void
makectx(struct trapframe *tf, struct pcb *pcb)
{
pcb->pcb_r12 = tf->tf_r12;
pcb->pcb_r13 = tf->tf_r13;
pcb->pcb_r14 = tf->tf_r14;
pcb->pcb_r15 = tf->tf_r15;
pcb->pcb_rbp = tf->tf_rbp;
pcb->pcb_rbx = tf->tf_rbx;
pcb->pcb_rip = tf->tf_rip;
pcb->pcb_rsp = (ISPL(tf->tf_cs)) ? tf->tf_rsp : (long)(tf + 1) - 8;
}
But according to <Intel 64 and IA-32 Architecutres Software Developer's Manual Volume 3A: System Programming Guide, Part 1> section 5.14.2: (64-bit mode also pushes SS:RSP unconditionally, rather than only on a CPL change).
So the function makectx in sys/amd64/amd64/machdep.c should be modified as
void
makectx(struct trapframe *tf, struct pcb *pcb)
{
pcb->pcb_r12 = tf->tf_r12;
pcb->pcb_r13 = tf->tf_r13;
pcb->pcb_r14 = tf->tf_r14;
pcb->pcb_r15 = tf->tf_r15;
pcb->pcb_rbp = tf->tf_rbp;
pcb->pcb_rbx = tf->tf_rbx;
pcb->pcb_rip = tf->tf_rip;
pcb->pcb_rsp = tf->tf_rsp;
}
>Release-Note:
>Audit-Trail:
>Unformatted:
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