* Kevin O'Connor ([email protected]) wrote: > On Fri, Jan 20, 2017 at 06:40:44PM +0000, Dr. David Alan Gilbert wrote: > > Hi, > > I turned the debug level up to 4 on our smaller (128k) ROM downstream > > build and seem to have hit a case where it's been layed out so that the > > 'ExtraStack' is at the same location as some code (display_uuid) which > > was causing some very random behaviour; > > > > from an objdump disassemble of the rom.o that was produced: > > > > ef79d: f3 ab rep stos %eax,%es:(%edi) > > ef79f: 8d 43 08 lea 0x8(%ebx),%eax > > ef7a2: b1 10 mov $0x10,%cl > > ef7a4: 8d 54 24 74 lea 0x74(%esp),%edx > > ef7a8: e8 50 46 ff ff call e3dfd <memcmp> > > ef7ad: 85 c0 test %eax,%eax > > ef7af: 0f 84 33 01 00 00 je ef8e8 <ExtraStack+0x110> > > ef7b5: 8b 15 0c 23 0f 00 mov 0xf230c,%edx > > ef7bb: 80 7a 06 02 cmpb $0x2,0x6(%edx) > > ef7bf: 0f b6 43 17 movzbl 0x17(%ebx),%eax > > ef7c3: 77 0c ja ef7d1 <StackPos+0x1> > > ef7c5: 0f 85 80 00 00 00 jne ef84b <ExtraStack+0x73> > > ef7cb: 80 7a 07 05 cmpb $0x5,0x7(%edx) > > ef7cf: 76 7a jbe ef84b <ExtraStack+0x73> > > > > Note the 'ExtraStack+...' where as a few lines before it's maininit > > for other jumps, then looking at a sorted output of the rom.o.objdump: > > > > 000eddf2 l F .text 000000e0 virtio_scsi_add_lun.constprop.113 > > 000eded2 l F .text 0000080d device_hardware_setup > > 000ee6df l F .text 00001a17 maininit > > <------------- > > 000ef790 g *ABS* 00000000 final_varlow_start > > 000ef790 g O *ABS* 00000004 BootSequence > > 000ef794 g O *ABS* 00000001 FloppyDOR > > 000ef798 g O *ABS* 00000008 LastUSBkey > > 000ef7a0 g O *ABS* 00000001 Ps2ctr > > 000ef7a4 g O *ABS* 00000004 RTCusers > > 000ef7a8 g O *ABS* 00000004 TimerLast > > 000ef7ac g O *ABS* 00000001 HaveAttemptedReboot > > 000ef7ad g O *ABS* 00000001 Century > > 000ef7b0 g O *ABS* 00000010 CDRom_locks > > 000ef7c0 g O *ABS* 00000010 DefaultDPTE > > 000ef7d0 g O *ABS* 00000004 StackPos > > 000ef7d8 g O *ABS* 00000801 ExtraStack > > <------------- > > 000effdc g O *ABS* 00000018 Call16Data > > 000f0000 g *ABS* 00000000 final_readonly_start > > 000f0000 g *ABS* 00000000 zonefseg_start > > 000f00f6 g F .text 0000038b dopost > > 000f0481 g F .text 000001c2 handle_pmm > > 000f0644 l O .text 00000014 CSWTCH.1353 > > 000f0658 l O .text 00000014 __func__.14607 > > 000f066c l O .text 00000011 __func__.14624 > > 000f0680 l O .text 00000010 __func__.14549 > > 000f0690 l O .text 0000000b __func__.14497 > > What I think you're seeing here is an artifact of seabios' code > self-relocation. The objdump stores the final location of "varlow" > variables, and not the location of their pre-relocation initial > values. After the code is self-relocated (in post.c:reloc_preinit() ) > it's malloc.c:malloc_init() (see memmove call) that copies over that > area of memory.
OK, I'll try and trace that. > > What's supposed to stop that happening? > > The code in scripts/layoutrom.py is supposed to layout the rom without > conflicts. It's not clear to me if that's malfunctioning or if the > underlying issue is something else - what is the "very random > behaviour" you are seeing? Hangs, typically after/in display_uuid or kvm entry exceptions where the EIP is totally bogus; they only happen sometimes on reboot, and adding some debug can make them totally disappear. So the thought of the code beign scribbled over by a stack sounded like a reasonable explanation. > > I'd chosen a debug level of 4 since that was the largest it would go > > without the build complaining it wouldn't fit, so I thought I was > > safe since something did complain if it got way too big. > > It should have been safe - something must not be right. Hmm OK. Dve > -Kevin -- Dr. David Alan Gilbert / [email protected] / Manchester, UK _______________________________________________ SeaBIOS mailing list [email protected] https://www.coreboot.org/mailman/listinfo/seabios
