Re: [PATCH v3] powerpc: implement CONFIG_DEBUG_VIRTUAL

[Michael Ellerman]

Christophe Leroy <christophe.leroy@xxxxxx> writes:

> This patch implements CONFIG_DEBUG_VIRTUAL to warn about
> incorrect use of virt_to_phys() and page_to_phys()
>
> Below is the result of test_debug_virtual:
>
> [    1.438746] WARNING: CPU: 0 PID: 1 at ./arch/powerpc/include/asm/io.h:808 test_debug_virtual_init+0x3c/0xd4
> [    1.448156] CPU: 0 PID: 1 Comm: swapper Not tainted 4.20.0-rc5-00560-g6bfb52e23a00-dirty #532
> [    1.457259] NIP:  c066c550 LR: c0650ccc CTR: c066c514
> [    1.462257] REGS: c900bdb0 TRAP: 0700   Not tainted  (4.20.0-rc5-00560-g6bfb52e23a00-dirty)
> [    1.471184] MSR:  00029032 <EE,ME,IR,DR,RI>  CR: 48000422  XER: 20000000
> [    1.477811]
> [    1.477811] GPR00: c0650ccc c900be60 c60d0000 00000000 006000c0 c9000000 00009032 c7fa0020
> [    1.477811] GPR08: 00002400 00000001 09000000 00000000 c07b5d04 00000000 c00037d8 00000000
> [    1.477811] GPR16: 00000000 00000000 00000000 00000000 c0760000 c0740000 00000092 c0685bb0
> [    1.477811] GPR24: c065042c c068a734 c0685b8c 00000006 00000000 c0760000 c075c3c0 ffffffff
> [    1.512711] NIP [c066c550] test_debug_virtual_init+0x3c/0xd4
> [    1.518315] LR [c0650ccc] do_one_initcall+0x8c/0x1cc
> [    1.523163] Call Trace:
> [    1.525595] [c900be60] [c0567340] 0xc0567340 (unreliable)
> [    1.530954] [c900be90] [c0650ccc] do_one_initcall+0x8c/0x1cc
> [    1.536551] [c900bef0] [c0651000] kernel_init_freeable+0x1f4/0x2cc
> [    1.542658] [c900bf30] [c00037ec] kernel_init+0x14/0x110
> [    1.547913] [c900bf40] [c000e1d0] ret_from_kernel_thread+0x14/0x1c
> [    1.553971] Instruction dump:
> [    1.556909] 3ca50100 bfa10024 54a5000e 3fa0c076 7c0802a6 3d454000 813dc204 554893be
> [    1.564566] 7d294010 7d294910 90010034 39290001 <0f090000> 7c3e0b78 955e0008 3fe0c062
> [    1.572425] ---[ end trace 6f6984225b280ad6 ]---
> [    1.577467] PA: 0x09000000 for VA: 0xc9000000
> [    1.581799] PA: 0x061e8f50 for VA: 0xc61e8f50
>
> Signed-off-by: Christophe Leroy <christophe.leroy@xxxxxx>
> ---
>  v3: Added missing linux/mm.h
>      I realised that a driver may use DMA on stack after checking with virt_addr_valid(), so the new
>      verification might induce false positives. I remove it for now, will add it again later in a more
>      controled way.

What is this comment referring to?

I can't see any difference to v2 except the linux/mm.h include.

cheers