Re: __tls_get_addr problem with recent current

On Sun, Aug 31, 2008 at 10:16:18AM +0300, Kostik Belousov wrote:
> On Sat, Aug 30, 2008 at 02:03:00PM -0700, Artem Belevich wrote:
> > With the new patch kernel has crashed as soon as I ran i386 app,
> > though the crash happened within in-kernel thread g_up:
> > 
> > Fatal trap 12: page fault while in kernel mode
> > cpuid = 2; apic id = 02
> > fault virtual address   = 0x20
> > fault code              = supervisor read data, page not present
> > instruction pointer     = 0x8:0xffffffff804a821f
> > stack pointer           = 0x10:0xffffffffac280b60
> > frame pointer           = 0x10:0x0
> > code segment            = base 0x0, limit 0xfffff, type 0x1b
> >                        = DPL 0, pres 1, long 1, def32 0, gran 1
> > processor eflags        = resume, IOPL = 0
> > current process         = 3 (g_up)
> > trap number             = 12
> > panic: page fault
> > cpuid = 2
> > Uptime: 37s
> > Physical memory: 8169 MB
> > Dumping 380 MB: 365 349 333 317 301 285 269 253 237 221 205 189 173
> > 157 141 125 109 93 77 61 45 29 13
> Could you, please, show me the disassembled code around the faulted
> %rip ?

No need, it seems I found the problem. I trashed the %rdx that contains
the third cpu_switch argument. Please, try the updated patch.

Thanks for the testing !

diff --git a/sys/amd64/amd64/cpu_switch.S b/sys/amd64/amd64/cpu_switch.S
index f34b0cc..03f0eca 100644
--- a/sys/amd64/amd64/cpu_switch.S
+++ b/sys/amd64/amd64/cpu_switch.S
_at__at_ -249,6 +249,12 _at__at_ store_seg:
 1:	movl	%ds,PCB_DS(%r8)
 	movl	%es,PCB_ES(%r8)
 	movl	%fs,PCB_FS(%r8)
+	movq	%rdx,%r11
+	movl	$MSR_FSBASE,%ecx
+	rdmsr
+	shlq	$32,%rdx
+	leaq	(%rax,%rdx),%r9
+	movq	%r11,%rdx
 	jmp	done_store_seg
 2:	movq	PCB_GS32P(%r8),%rax
 	movq	(%rax),%rax