Date: Sun, 4 Jun 2017 22:07:51 -0700 From: Mark Millard <markmi@dsl-only.net> To: Justin Hibbits <jhibbits@FreeBSD.org>, Nathan Whitehorn <nwhitehorn@freebsd.org>, FreeBSD PowerPC ML <freebsd-ppc@freebsd.org>, freebsd-hackers@freebsd.org Subject: 32-bit powerpc FreeBSD address 0x0-0xff content (physical addresses): What is the explanation? Message-ID: <C47C6470-40CF-47D2-9E51-976FE240CCFA@dsl-only.net>
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I've been trying to get evidence for periodic/random panics in the likes of head -r317820 for 32-bit powerpc FreeBSD used on an old PowerMac G5 so-called "Quad Core". One thing that I've noticed that looks odd is that the vmcore.* files (debug.minidump=0) show content that looks like the following for physical address range 0x0..0xff (via a hacked-to-work-a-little kgdb for physical address access to such a vmcore.* file): (kgdb) x/128wx 0x0 0x0: 0x00000000 0x00000000 0x00000000 0x00000000 0x10: 0x00000000 0xffa35e50 0xffa35ee8 0x00000000 0x20: 0x00000000 0x00000000 0x00000000 0x00000000 0x30: 0x00000000 0x00000000 0x00000000 0x00000000 0x40: 0x00000000 0x00000000 0x00000000 0x00000000 0x50: 0x00000000 0x00000000 0x00000000 0x00000000 0x60: 0x00000000 0x00000000 0x00000000 0x00000000 0x70: 0x00000000 0x00000000 0x00000000 0x00000000 0x80: 0x00000090 0x7ff7c080 0x7fc9e7c8 0x00000000 0x90: 0x3c007ff7 0x6000c100 0x7c0903a6 0x4e800421 0xa0: 0x00000000 0x00000000 0x00000000 0x00000000 0xb0: 0x00000000 0x00000000 0x00000000 0x00000000 0xc0: 0x00000000 0x00000000 0x00000000 0x00000000 0xd0: 0x00000000 0x00000000 0x00000000 0x00000000 0xe0: 0x00000000 0x00000000 0x00000000 0x00000000 0xf0: 0x00000000 0x00000000 0x00000000 0x00000000 . . . Or viewed as instructions when the bit patterns fit such (with added NOTE's): (kgdb) x/128i 0x0 0x0: .long 0x0 0x4: .long 0x0 0x8: .long 0x0 0xc: .long 0x0 0x10: .long 0x0 0x14: .long 0xffa35e50 0x18: .long 0xffa35ee8 0x1c: .long 0x0 0x20: .long 0x0 0x24: .long 0x0 0x28: .long 0x0 0x2c: .long 0x0 0x30: .long 0x0 0x34: .long 0x0 0x38: .long 0x0 0x3c: .long 0x0 0x40: .long 0x0 0x44: .long 0x0 0x48: .long 0x0 0x4c: .long 0x0 0x50: .long 0x0 0x54: .long 0x0 0x58: .long 0x0 0x5c: .long 0x0 0x60: .long 0x0 0x64: .long 0x0 0x68: .long 0x0 0x6c: .long 0x0 0x70: .long 0x0 0x74: .long 0x0 0x78: .long 0x0 0x7c: .long 0x0 0x80: .long 0x90 0x84: .long 0x7ff7c080 0x88: .long 0x7fc9e7c8 0x8c: .long 0x0 0x90: lis r0,32759 (NOTE: 32759==0x7ff7) 0x94: ori r0,r0,49408 (NOTE: 49408==0xC100) 0x98: mtctr r0 (NOTE: So ctr==r0==0x7ff7C100) 0x9c: bctrl (NOTE: So to 0x7ff7C100 virtual address) 0xa0: .long 0x0 (NOTE: lr would end up pointing here.) 0xa4: .long 0x0 0xa8: .long 0x0 0xac: .long 0x0 0xb0: .long 0x0 0xb4: .long 0x0 0xb8: .long 0x0 0xbc: .long 0x0 0xc0: .long 0x0 0xc4: .long 0x0 0xc8: .long 0x0 0xcc: .long 0x0 0xd0: .long 0x0 0xd4: .long 0x0 0xd8: .long 0x0 0xdc: .long 0x0 0xe0: .long 0x0 0xe4: .long 0x0 0xe8: .long 0x0 0xec: .long 0x0 0xf0: .long 0x0 0xf4: .long 0x0 0xf8: .long 0x0 0xfc: .long 0x0 . . . Is this deliberate? If yes: What is it for? (I've not found what writes those bytes.) I do not make the claim that the above is tied to the periodic/random panics. It just seems unusual. === Mark Millard markmi at dsl-only.net
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