[PATCH v3] powerpc: implement CONFIG_DEBUG_VIRTUAL

[Michael Ellerman]

Christophe Leroy <christophe.leroy at c-s.fr> writes:

> This patch implements CONFIG_DEBUG_VIRTUAL to warn about
> incorrect use of virt_to_phys() and page_to_phys()

This commit is breaking my p5020ds booting a 32-bit kernel with:

  smp: Bringing up secondary CPUs ...
  __ioremap(): phys addr 0x7fef5000 is RAM lr ioremap_coherent
  Unable to handle kernel paging request for data at address 0x00000000
  Faulting instruction address: 0xc002e950
  Oops: Kernel access of bad area, sig: 11 [#1]
  BE SMP NR_CPUS=24 CoreNet Generic
  Modules linked in:
  CPU: 0 PID: 1 Comm: swapper/0 Not tainted 4.20.0-rc2-gcc-7.0.1-00138-g9a0380d299e9 #148
  NIP:  c002e950 LR: c002eb20 CTR: 00000001
  REGS: e804bd20 TRAP: 0300   Not tainted  (4.20.0-rc2-gcc-7.0.1-00138-g9a0380d299e9)
  MSR:  00021002 <CE,ME>  CR: 28004222  XER: 00000000
  DEAR: 00000000 ESR: 00000000 
  GPR00: c002eb20 e804bdd0 e8050000 00000000 00021002 00000000 00000050 00021002 
  GPR08: 2d3f0000 00000001 00000000 00000004 24000842 00000000 c00026d0 00000000 
  GPR16: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000001 
  GPR24: 00029002 7fef5140 30000000 00000000 00000000 00000040 00000001 00000000 
  NIP [c002e950] smp_85xx_kick_cpu+0x120/0x410
  LR [c002eb20] smp_85xx_kick_cpu+0x2f0/0x410
  Call Trace:
  [e804bdd0] [c002eb20] smp_85xx_kick_cpu+0x2f0/0x410 (unreliable)
  [e804be20] [c0012e38] __cpu_up+0xc8/0x230
  [e804be50] [c0040b34] bringup_cpu+0x34/0x110
  [e804be70] [c00418a8] cpu_up+0x128/0x250
  [e804beb0] [c0b84b14] smp_init+0xc4/0x10c
  [e804bee0] [c0b75c1c] kernel_init_freeable+0xc8/0x250
  [e804bf20] [c00026e8] kernel_init+0x18/0x120
  [e804bf40] [c0011298] ret_from_kernel_thread+0x14/0x1c
  Instruction dump:
  7fb3e850 57bdd1be 2e1d0000 41d20250 57bd3032 393dffc0 7e6a9b78 5529d1be 
  39290001 7d2903a6 60000000 60000000 <7c0050ac> 394a0040 4200fff8 7c0004ac 
  ---[ end trace edcab2a1dfd5b38c ]---


Which is obviously this hunk:

> diff --git a/arch/powerpc/mm/pgtable_32.c b/arch/powerpc/mm/pgtable_32.c
> index 4fc77a99c9bf..68d204a45cd0 100644
> --- a/arch/powerpc/mm/pgtable_32.c
> +++ b/arch/powerpc/mm/pgtable_32.c
> @@ -143,7 +143,7 @@ __ioremap_caller(phys_addr_t addr, unsigned long size, pgprot_t prot, void *call
>  	 * Don't allow anybody to remap normal RAM that we're using.
>  	 * mem_init() sets high_memory so only do the check after that.
>  	 */
> -	if (slab_is_available() && (p < virt_to_phys(high_memory)) &&
> +	if (slab_is_available() && virt_addr_valid(p) &&
>  	    page_is_ram(__phys_to_pfn(p))) {
>  		printk("__ioremap(): phys addr 0x%llx is RAM lr %ps\n",
>  		       (unsigned long long)p, __builtin_return_address(0));


I'll try and come up with a fix tomorrow.

cheers