linux-kernel - Re: [PATCH v2 2/2] amr64: map FDT as RW for early_init_dt

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Date:   Wed, 15 May 2019 18:24:03 +0800
From:   Hsin-Yi Wang <hsinyi@...omium.org>
To:     Mike Rapoport <rppt@...ux.ibm.com>
Cc:     "moderated list:ARM/FREESCALE IMX / MXC ARM ARCHITECTURE" 
        <linux-arm-kernel@...ts.infradead.org>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Frank Rowand <frowand.list@...il.com>,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        Stephen Boyd <swboyd@...omium.org>,
        Kees Cook <keescook@...omium.org>,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        Architecture Mailman List <boot-architecture@...ts.linaro.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Michal Hocko <mhocko@...e.com>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Miles Chen <miles.chen@...iatek.com>,
        James Morse <james.morse@....com>,
        Andrew Murray <andrew.murray@....com>
Subject: Re: [PATCH v2 2/2] amr64: map FDT as RW for early_init_dt_scan()

On Tue, May 14, 2019 at 11:42 PM Mike Rapoport <rppt@...ux.ibm.com> wrote:

> I'm not sure if early console is available at the time kaslr_early_init()
> is called, but if yes, running with memblock=debug may shed some light.
>
> > I didn't trace the real reason causing this. But in this case, maybe
> > don't call memblock_reserve() in kaslr?
>
> My concern that this uncovered a real bug which might hit us later.
>
Hi Mike,
Thanks for the hint. I tried on my device but seems that earlycon
happens after the warning call trace, so can't more information.

Since on my device kaslr will be runned, I tried call
memblock_reserve() in kaslr and not in
setup_machine_fdt()#fixmap_remap_fdt, but got following warning

[    0.000000] memblock_remove:
[0x0001000000000000-0x0000fffffffffffe] arm64_memblock_init+0x28/0x224
[    0.000000] memblock_remove:
[0x0000004040000000-0x000000403ffffffe] arm64_memblock_init+0x64/0x224
[    0.000000] memblock_reserve:
[0x0000000040080000-0x00000000413c3fff]
arm64_memblock_init+0x188/0x224
[    0.000000] WARNING: CPU: 0 PID: 0 at
/mnt/host/source/src/third_party/kernel/v4.19/mm/memblock.c:583
memblock_add_range+0x1bc/0x1c8
[    0.000000] Modules linked in:
[    0.000000] CPU: 0 PID: 0 Comm: swapper Not tainted 4.19.38 #222
[    0.000000] Hardware name: MediaTek kukui rev2 board (DT)
[    0.000000] pstate: 60000085 (nZCv daIf -PAN -UAO)
[    0.000000] pc : memblock_add_range+0x1bc/0x1c8
[    0.000000] lr : memblock_add_range+0x30/0x1c8
[    0.000000] sp : ffffffab68603ea0
[    0.000000] x29: ffffffab68603ef0 x28: 0000000040954324
[    0.000000] x27: 0000000040080000 x26: 0000000000080000
[    0.000000] x25: 0000000080127e4b x24: ffffffab68716000
[    0.000000] x23: ffffffab680b5000 x22: 0000000001344000
[    0.000000] x21: 0000000040080000 x20: 0000000000000000
[    0.000000] x19: ffffffab6864bf00 x18: 00000000fffffc94
[    0.000000] x17: 000000000000003c x16: ffffffab67d49064
[    0.000000] x15: 0000000000000006 x14: 626d656d5f34366d
[    0.000000] x13: 7261205d66666633 x12: 0000000000000000
[    0.000000] x11: 0000000000000000 x10: ffffffffffffffff
[    0.000000] x9 : 0000000000011547 x8 : ffffffab68765690
[    0.000000] x7 : 696e695f6b636f6c x6 : ffffffab6875dd41
[    0.000000] x5 : 0000000000000000 x4 : 0000000000000000
[    0.000000] x3 : ffffffab678a24a0 x2 : 0000000001344000
[    0.000000] x1 : 0000000040080000 x0 : ffffffab6864bf00
[    0.000000] Call trace:
[    0.000000]  memblock_add_range+0x1bc/0x1c8
[    0.000000]  memblock_reserve+0x60/0xac
[    0.000000]  arm64_memblock_init+0x188/0x224
[    0.000000]  setup_arch+0x138/0x19c
[    0.000000]  start_kernel+0x68/0x380
[    0.000000] random: get_random_bytes called from
print_oops_end_marker+0x3c/0x58 with crng_init=0
[    0.000000] ---[ end trace ea99802b425f7adf ]---
[    0.000000] memblock_reserve:
[0x000000005f800000-0x000000005f811536]
early_init_dt_reserve_memory_arch+0x38/0x48
[    0.000000] memblock_reserve:
[0x00000000ffe00000-0x00000000ffffffff]
early_init_dt_reserve_memory_arch+0x38/0x48

So I guess we just can't call memblock_reserve() in kaslr?