[PATCH] [2.6.16] powerpc: Fix OOPS in lparcfg on G5

[Nathan Lynch]

Olof Johansson wrote:
> Hi,
> 
> Bugfix, so please consider for 2.6.16:
> 
> 
> Hit the following with LTP with a ppc64_defconfig kernel on a G5:
> 
> Unable to handle kernel paging request for data at address 0x00000030
> Faulting instruction address: 0xc00000000001f6d0
> Oops: Kernel access of bad area, sig: 11 [#1]
> SMP NR_CPUS=32 POWERMAC
> Modules linked in:
> NIP: C00000000001F6D0 LR: C00000000001F6CC CTR: 0000000000000000
> REGS: c000000054853790 TRAP: 0300   Not tainted  (2.6.16-rc3-mm1)
> MSR: 9000000000009032 <EE,ME,IR,DR>  CR: 24000444  XER: 00000000
> DAR: 0000000000000030, DSISR: 0000000040000000
> TASK = c00000005fb65810[4820] 'proc01' THREAD: c000000054850000 CPU: 1
> GPR00: C00000000001F6CC C000000054853A10 C00000000079FBB0 C0000000007A32E8
> GPR04: C0000000004AE220 0000000000000000 0000000000000020 0000000000000000
> GPR08: C000000000610178 0000000000000072 C00000005FFFEE62 0000000000000092
> GPR12: 0000000000000002 C0000000005BA100 00000000100D0000 0000000010116C88
> GPR16: 00000000100D0000 00000000FFFF9008 0000000000000000 0000000000000000
> GPR20: 000000001001B5D8 000000000FF58224 C000000054853E08 C00000000F44A330
> GPR24: C00000005E47B700 0000000010016FB4 0000000000000000 C00000000F44A300
> GPR28: 0000000000000000 0000000000000000 C0000000004AE220 0000000000000000
> NIP [C00000000001F6D0] .of_find_property+0x30/0xa8
> LR [C00000000001F6CC] .of_find_property+0x2c/0xa8
> Call Trace:
> [C000000054853A10] [C00000000001F6CC] .of_find_property+0x2c/0xa8 (unreliable)
> [C000000054853AA0] [C00000000001F758] .get_property+0x10/0x34
> [C000000054853B10] [C00000000001D3C8] .lparcfg_data+0x11c/0x6c8
> [C000000054853C20] [C0000000000DC78C] .seq_read+0x198/0x418
> [C000000054853CF0] [C0000000000B2634] .vfs_read+0xd0/0x1b0
> [C000000054853D90] [C0000000000B32FC] .sys_read+0x4c/0x8c
> [C000000054853E30] [C0000000000086F8] syscall_exit+0x0/0x40
> 
> 
> It happens since the lookup of the /rtas device node is never checked for
> success and just passed into get_property.
> 
> It doesn't make sense to create the lparcfg proc entry on non-LPAR
> systems at all.

Despite the lparcfg name, I think there are apps which depend on it
even on non-lpar systems; we should still create the file on non-lpar
Power4, for example.