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Date:   Wed, 13 Feb 2019 17:56:36 +0800
From:   Nicolas Boichat <drinkcat@...omium.org>
To:     Prateek Patel <prpatel@...dia.com>
Cc:     Rob Herring <robh+dt@...nel.org>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Will Deacon <will.deacon@....com>, matt@...eblueprint.co.uk,
        Catalin Marinas <catalin.marinas@....com>,
        Frank Rowand <frowand.list@...il.com>,
        devicetree@...r.kernel.org,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        linux-tegra@...r.kernel.org, talho@...dia.com,
        Stephen Warren <swarren@...dia.com>, vdumpa@...dia.com,
        snikam@...dia.com
Subject: Re: [PATCH] of: reserved_mem: disable kmemleak scan on removed memory blocks

On Tue, Jan 22, 2019 at 4:46 PM Prateek Patel <prpatel@...dia.com> wrote:
>
>
> On 11/10/2018 2:58 AM, Rob Herring wrote:
> > On Fri, Nov 9, 2018 at 1:09 AM Prateek Patel <prpatel@...dia.com> wrote:
> >> From: Sri Krishna chowdary <schowdary@...dia.com>
> >>
> >> Memory reserved with "nomap" DT property in of_reserved_mem.c
> >> removes the memory block. The removed memory blocks don't have
> >> VA to PA mapping created in kernel page table. Kmemleak scan on
> >> removed memory blocks is causing page faults and leading to
> >> kernel panic. So, Disable kmemleak scan on the removed memory
> >> blocks.
> >>
> >> Following is the observed crash log:
> >> [  154.846370] Unable to handle kernel paging request at virtual address ffffffc070a00000
> >> <1>[  154.846576] Mem abort info:
> >> <1>[  154.846635]   Exception class = DABT (current EL), IL = 32 bits
> >> <1>[  154.846737]   SET = 0, FnV = 0
> >> <1>[  154.846796]   EA = 0, S1PTW = 0
> >> <1>[  154.846859] Data abort info:
> >> <1>[  154.846913]   ISV = 0, ISS = 0x00000006
> >> <1>[  154.846983]   CM = 0, WnR = 0
> >> <1>[  154.847053] swapper pgtable: 4k pages, 39-bit VAs, pgd = ffffff8009df7000
> >> <1>[  154.847228] [ffffffc070a00000] *pgd=000000087fff5803, *pud=000000087fff5803, *pmd=0000000000000000
> >> <0>[  154.847408] Internal error: Oops: 96000006 [#1] PREEMPT SMP
> >> <4>[  154.847511] Modules linked in: nvs_led_test nvs_bmi160 nvs_cm3218 nvs_bh1730fvc nvi_bmpX80 nvi_ak89xx nvi_mpu cdc_acm uas lr388k7_ts imx268 imx318 imx204 imx274 imx185 lc898212 ov23850 ov10823 ov9281 ov5693 tc358840 pca9570 nvs snd_soc_tegra_machine_driver_mobile lp855x_bl spidev input_cfboost pwm_tegra tegra_cryptodev tegra_se_nvhost tegra_se_elp tegra_se ghash_ce sha2_ce sha1_ce aes_ce_ccm cryptd nvgpu cpufreq_userspace snd_soc_tegra186_alt_dspk snd_soc_tegra186_alt_asrc snd_soc_tegra186_alt_arad snd_soc_tegra210_alt_ope snd_soc_tegra210_alt_mvc snd_soc_tegra210_alt_dmic snd_soc_tegra210_alt_amx snd_soc_tegra210_alt_adx snd_soc_tegra210_alt_afc snd_soc_tegra210_alt_mixer snd_soc_tegra210_alt_i2s snd_soc_tegra210_alt_sfc snd_soc_tegra210_alt_adsp snd_soc_tegra210_alt_admaif snd_soc_tegra210_alt_xbar
> >> <4>[  154.882606]  snd_soc_tegra_alt_utils snd_hda_tegra
> >> <4>[  154.888133] CPU: 2 PID: 8079 Comm: sh Not tainted 4.14.53-tegra-05132-g9c33465 #2
> >> <4>[  154.895983] Hardware name: e3360_1099 (DT)
> >> <4>[  154.900447] task: ffffffc7d62dda00 task.stack: ffffff800e2b0000
> >> <4>[  154.906502] PC is at scan_block+0x7c/0x148
> >> <4>[  154.911234] LR is at scan_block+0x78/0x148
> >> <4>[  154.915689] pc : [<ffffff8008271724>] lr : [<ffffff8008271720>] pstate: 804000c9
> >> <4>[  154.923290] sp : ffffff800e2b3b80
> >> <4>[  154.927228] x29: ffffff800e2b3b80 x28: ffffffc7d62dda00
> >> <4>[  154.932999] x27: ffffff8009aaa000 x26: ffffffc070c00000
> >> <4>[  154.938769] x25: 00000000000000c0 x24: ffffff8009d90608
> >> <4>[  154.944287] x23: ffffffc7dc6c6000 x22: ffffff8009d90000
> >> <4>[  154.950320] x21: ffffff8009aeb320 x20: ffffffc070a00ff9
> >> <4>[  154.955919] x19: ffffffc070a00000 x18: 00000000bec4c3f2
> >> <4>[  154.961438] x17: 0000002224777924 x16: ffffff80080bb0e0
> >> <4>[  154.967124] x15: 0000000000000000 x14: 0000000000000f75
> >> <4>[  154.973069] x13: 000fffffffffffff x12: ffffffbf1e9f4240
> >> <4>[  154.978670] x11: 0000000000000040 x10: 0000000000000ad0
> >> <4>[  154.984107] x9 : ffffff800e2b3ab0 x8 : ffffffc7d62de530
> >> <4>[  154.989958] x7 : 0000000780000000 x6 : 0000000000000018
> >> <4>[  154.995645] x5 : 0000000000000000 x4 : 0000000000000000
> >> <4>[  155.001245] x3 : ffffff8009aaa000 x2 : 00000047f6712000
> >> <4>[  155.006846] x1 : ffffffc7d1ae6900 x0 : 0000000000000000
> >>
> >> Signed-off-by: Sri Krishna chowdary <schowdary@...dia.com>
> >> Signed-off-by: Prateek <prpatel@...dia.com>
> >> ---
> >>   drivers/of/of_reserved_mem.c | 5 ++++-
> >>   1 file changed, 4 insertions(+), 1 deletion(-)
> >>
> >> diff --git a/drivers/of/of_reserved_mem.c b/drivers/of/of_reserved_mem.c
> >> index 1977ee0..ac8f377 100644
> >> --- a/drivers/of/of_reserved_mem.c
> >> +++ b/drivers/of/of_reserved_mem.c
> >> @@ -21,6 +21,7 @@
> >>   #include <linux/sort.h>
> >>   #include <linux/slab.h>
> >>   #include <linux/memblock.h>
> >> +#include <linux/kmemleak.h>
> >>
> >>   #define MAX_RESERVED_REGIONS   32
> >>   static struct reserved_mem reserved_mem[MAX_RESERVED_REGIONS];
> >> @@ -50,8 +51,10 @@ int __init __weak early_init_dt_alloc_reserved_memory_arch(phys_addr_t size,
> >>          }
> >>
> >>          *res_base = base;
> >> -       if (nomap)
> >> +       if (nomap) {
> >> +               kmemleak_no_scan(__va(base));
> >>                  return memblock_remove(base, size);
> > I'm curious how I can't find any other similar example in the kernel.
> > Please Cc some kmemleak folks.
> >
> > Perhaps we should be using memblock_mark_nomap() for nomap areas?
> >
> > Rob
>
> Sorry for this late reply.
>
> Yes, memblock_mark_nomap() can be used here but if I understand
> correctly, memblock_mark_nomap() is used to indicate marked parts of
> memory should not be covered by the kernel direct mapping and
> memblock_remove() here is doing that by removing a given memory from the
> "memblock.memory" list to prevent the memory from CPU accessing by the
> linear address. I am not 100% sure what will be the side effects of
> using memblock_mark_nomap(). Adding folks to help me here on
> MEMBLOCK_NOMAP and kmemleak.

I have no idea about your question: memblock_mark_nomap seems
reasonable though, but I think this is orthogonal to this patch, whose
main purpose is to add kmemleak_no_scan?

In any case, I tested both the original patch, and the hunk below on a
different platform (with some no-map reserved_memory as well), and
they fix the issue.

Tested-by: Nicolas Boichat <drinkcat@...omium.org>

> I checked and verified with following and I didn't find any errors on my
> local setup:
>
> diff --git a/drivers/of/of_reserved_mem.c b/drivers/of/of_reserved_mem.c
> index 1977ee0..f77cde0 100644
> --- a/drivers/of/of_reserved_mem.c
> +++ b/drivers/of/of_reserved_mem.c
> @@ -50,8 +50,10 @@ int __init __weak
> early_init_dt_alloc_reserved_memory_arch(phys_addr_t size,
>          }
>
>          *res_base = base;
> -       if (nomap)
> -               return memblock_remove(base, size);
> +       if (nomap) {
> +               kmemleak_no_scan(__va(base));
> +               return memblock_mark_nomap(base, size);
> +       }
>          return 0;
>   }

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