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From:   Ard Biesheuvel <ard.biesheuvel@linaro.org>
Date:   Wed, 7 Mar 2018 19:55:34 +0000
Message-ID: <CAKv+Gu8T6YkP=593PAoNOkz=zNY8ut7SqVt=7HSyCibKUSMaLQ@mail.gmail.com>
Subject: Re: [PATCH 0/2] ESRT fixes for relocatable kexec'd kernel
To:     AKASHI Takahiro <takahiro.akashi@linaro.org>,
        Tyler Baicar <tbaicar@codeaurora.org>,
        Jeffrey Hugo <jhugo@codeaurora.org>,
        Ard Biesheuvel <ard.biesheuvel@linaro.org>,
        linux-efi@vger.kernel.org,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Sameer Goel <sgoel@codeaurora.org>,
        Timur Tabi <timur@codeaurora.org>,
        James Morse <james.morse@arm.com>
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(+ James)

Hello Akashi,

On 6 March 2018 at 09:00, AKASHI Takahiro <takahiro.akashi@linaro.org> wrote:
> Tyler, Jeffrey,
>
> On Fri, Mar 02, 2018 at 08:27:11AM -0500, Tyler Baicar wrote:
>> On 3/2/2018 12:53 AM, AKASHI Takahiro wrote:
>> >Tyler, Jeffrey,
>> >
>> >[Note: This issue takes place in kexec, not kdump. So to be precise,
>> >it is not the same phenomenon as what I addressed in [1],[2]:
>> >   [1] http://lists.infradead.org/pipermail/linux-arm-kernel/2018-February/557254.html
>> >   [2] http://lists.infradead.org/pipermail/linux-arm-kernel/2018-January/553098.html
>> >]
>> >
>> >On Thu, Mar 01, 2018 at 12:56:38PM -0500, Tyler Baicar wrote:
>> >>Hello,
>> >>
>> >>On 2/28/2018 9:50 PM, AKASHI Takahiro wrote:
>> >>>Hi,
>> >>>
>> >>>On Wed, Feb 28, 2018 at 08:39:42AM -0700, Jeffrey Hugo wrote:
>> >>>>On 2/27/2018 11:19 PM, AKASHI Takahiro wrote:
>> >>>>>Tyler,
>> >>>>>
>> >>>>># I missed catching your patch as its subject doesn't contain arm64.
>> >>>>>
>> >>>>>On Fri, Feb 23, 2018 at 12:42:31PM -0700, Tyler Baicar wrote:
>> >>>>>>Currently on arm64 ESRT memory does not appear to be properly blocked off.
>> >>>>>>Upon successful initialization, ESRT prints out the memory region that it
>> >>>>>>exists in like:
>> >>>>>>
>> >>>>>>esrt: Reserving ESRT space from 0x000000000a4c1c18 to 0x000000000a4c1cf0.
>> >>>>>>
>> >>>>>>But then by dumping /proc/iomem this region appears as part of System RAM
>> >>>>>>rather than being reserved:
>> >>>>>>
>> >>>>>>08f10000-0deeffff : System RAM
>> >>>>>>
>> >>>>>>This causes issues when trying to kexec if the kernel is relocatable. When
>> >>>>>>kexec tries to execute, this memory can be selected to relocate the kernel to
>> >>>>>>which then overwrites all the ESRT information. Then when the kexec'd kernel
>> >>>>>>tries to initialize ESRT, it doesn't recognize the ESRT version number and
>> >>>>>>just returns from efi_esrt_init().
>> >>>>>I'm not sure what is the root cause of your problem.
>> >>>>>Do you have good confidence that the kernel (2nd kernel image in this case?)
>> >>>>>really overwrite ESRT region?
>> >>>>According to my debug, yes.
>> >>>>Using JTAG, I was able to determine that the ESRT memory region was getting
>> >>>>overwritten by the secondary kernel in
>> >>>>kernel/arch/arm64/kernel/relocate_kernel.S - specifically the "copy_page"
>> >>>>line of arm64_relocate_new_kernel()
>> >>>>
>> >>>>>To my best knowledge, kexec is carefully designed not to do such a thing
>> >>>>>as it allocates a temporary buffer for kernel image and copies it to the
>> >>>>>final destination at the very end of the 1st kernel.
>> >>>>>
>> >>>>>My guess is that kexec, or rather kexec-tools, tries to load the kernel image
>> >>>>>at 0x8f80000 (or 0x9080000?, not sure) in your case. It may or may not be
>> >>>>>overlapped with ESRT.
>> >>>>>(Try "-d" option when executing kexec command for confirmation.)
>> >>>>With -d, I see
>> >>>>
>> >>>>get_memory_ranges_iomem_cb: 0000000009611000 - 000000000e5fffff : System RAM
>> >>>>
>> >>>>That overlaps the ESRT reservation -
>> >>>>[ 0.000000] esrt: Reserving ESRT space from 0x000000000b708718 to
>> >>>>0x000000000b7087f0
>> >>>>
>> >>>>>Are you using initrd with kexec?
>> >>>>Yes
>> >>>To make the things clear, can you show me, if possible, the followings:
>> >>I have attached all of these:
>> >Many thanks.
>> >According to the data, ESRT was overwritten by initrd, not the kernel image.
>> >It doesn't matter to you though :)
>> >
>> >The solution would be, as Ard suggested, that more information be
>> >added to /proc/iomem.
>> >I'm going to fix the issue as quickly as possible.
>> Great, thank you!! Please add us to the fix and we will gladly test it out.
>
> I have created a workaround patch, attached below, as a kind of PoC.
> Can you give it a go, please?
> You need another patch for kexec-tools, too. See
> https:/git.linaro.org/people/takahiro.akashi/kexecl-tools.git arm64/resv_mem
>

Thanks for putting this together. Some questions below.

> With this patch, extra entries for firmware-reserved memory resources,
> which means any regions that are already reserved before arm64_memblock_init(),
> or specifically efi/acpi tables in this case, are added to /proc/iomem.
>
>  $ cat /proc/iomem (on my qemu+edk2 execution)
>         ...
>         40000000-5871ffff : System RAM
>           40080000-40f1ffff : Kernel code
>           41040000-411e9fff : Kernel data
>           54400000-583fffff : Crash kernel
>           58590000-585effff : reserved
>           58700000-5871ffff : reserved
>         58720000-58b5ffff : reserved
>         58b60000-5be3ffff : System RAM
>           58b61000-58b61fff : reserved
>           59a7b118-59a7b667 : reserved
>         5be40000-5becffff : reserved
>         5bed0000-5bedffff : System RAM
>           5bee0000-5bffffff : reserved
>         5c000000-5fffffff : System RAM
>           5ec00000-5edfffff : reserved
>         8000000000-ffffffffff : PCI Bus 0000:00
>           8000000000-8000003fff : 0000:00:01.0
>             8000000000-8000003fff : virtio-pci-modern
>
> While all the entries are currently marked as just "reserved," we'd better
> give them more specific names for general/extensive use.
> (Then it will require modifying respective fw/drivers.)
>
> Kexec-tools will allocate spaces for kernel, initrd and dtb so that
> they will not be overlapped with "reserved" memory.
>
> As I haven't run extensive tests, please let me know if you find
> any problems.
>
> Thanks,
> -Takahiro AKASHI
>
>>
>> Thanks,
>> Tyler
>>
>> --
>> Qualcomm Datacenter Technologies, Inc. as an affiliate of Qualcomm Technologies, Inc.
>> Qualcomm Technologies, Inc. is a member of the Code Aurora Forum,
>> a Linux Foundation Collaborative Project.
>>
> ===8<===
> From 57d93b89d16b967c913f3949601a5559ddf4aa57 Mon Sep 17 00:00:00 2001
> From: AKASHI Takahiro <takahiro.akashi@linaro.org>
> Date: Fri, 2 Mar 2018 16:39:18 +0900
> Subject: [PATCH] arm64: kexec: set asdie firmware-reserved memory regions
>
> Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org>
> ---
>  arch/arm64/kernel/setup.c | 24 ++++++++++++++++++++----
>  arch/arm64/mm/init.c      | 21 +++++++++++++++++++++
>  2 files changed, 41 insertions(+), 4 deletions(-)
>
> diff --git a/arch/arm64/kernel/setup.c b/arch/arm64/kernel/setup.c
> index 30ad2f085d1f..997f07e86243 100644
> --- a/arch/arm64/kernel/setup.c
> +++ b/arch/arm64/kernel/setup.c
> @@ -87,6 +87,9 @@ static struct resource mem_res[] = {
>  #define kernel_code mem_res[0]
>  #define kernel_data mem_res[1]
>
> +/* TODO: Firmware-reserved memory resources */
> +extern struct memblock_type fw_mem;
> +

Why do you need this intermediate data structure? can't you iterate
over the memblock_reserve'd regions directly?

>  /*
>   * The recorded values of x0 .. x3 upon kernel entry.
>   */
> @@ -206,7 +209,20 @@ static void __init request_standard_resources(void)
>  {
>         struct memblock_region *region;
>         struct resource *res;
> +       int i;
> +
> +       /* add firmware-reserved memory first */
> +       for (i = 1; i < fw_mem.cnt; i++) {
> +               res = alloc_bootmem_low(sizeof(*res));
> +               res->name  = "reserved";
> +               res->flags = IORESOURCE_MEM;
> +               res->start = fw_mem.regions[i].base;
> +               res->end = fw_mem.regions[i].base + fw_mem.regions[i].size - 1;
>
> +               request_resource(&iomem_resource, res);
> +       }
> +
> +       /* add standard resources */
>         kernel_code.start   = __pa_symbol(_text);
>         kernel_code.end     = __pa_symbol(__init_begin - 1);
>         kernel_data.start   = __pa_symbol(_sdata);
> @@ -224,19 +240,19 @@ static void __init request_standard_resources(void)
>                 res->start = __pfn_to_phys(memblock_region_memory_base_pfn(region));
>                 res->end = __pfn_to_phys(memblock_region_memory_end_pfn(region)) - 1;
>
> -               request_resource(&iomem_resource, res);
> +               insert_resource(&iomem_resource, res);
>

I see why you need to switch from request_resource() to
insert_resource(). Could we ever run into the situation where a
memblock_reserved region overlaps the boundary between System RAM and
a NOMAP region? I don't /think/ this is the case, but I am not sure,
and if that happens, this will fail. (I think it should never be
needed to memblock_reserve() NOMAP regions but I am not 100% sure)

>                 if (kernel_code.start >= res->start &&
>                     kernel_code.end <= res->end)
> -                       request_resource(res, &kernel_code);
> +                       insert_resource(res, &kernel_code);
>                 if (kernel_data.start >= res->start &&
>                     kernel_data.end <= res->end)
> -                       request_resource(res, &kernel_data);
> +                       insert_resource(res, &kernel_data);
>  #ifdef CONFIG_KEXEC_CORE
>                 /* Userspace will find "Crash kernel" region in /proc/iomem. */
>                 if (crashk_res.end && crashk_res.start >= res->start &&
>                     crashk_res.end <= res->end)
> -                       request_resource(res, &crashk_res);
> +                       insert_resource(res, &crashk_res);
>  #endif
>         }
>  }
> diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
> index 9f3c47acf8ff..b6f86a7bbfb7 100644
> --- a/arch/arm64/mm/init.c
> +++ b/arch/arm64/mm/init.c
> @@ -62,6 +62,14 @@
>  s64 memstart_addr __ro_after_init = -1;
>  phys_addr_t arm64_dma_phys_limit __ro_after_init;
>
> +static struct memblock_region fw_mem_regions[INIT_MEMBLOCK_REGIONS];
> +struct memblock_type fw_mem = {
> +       .regions        = fw_mem_regions,
> +       .cnt            = 1,    /* empty dummy entry */
> +       .max            = INIT_MEMBLOCK_REGIONS,
> +       .name           = "firmware-reserved memory",
> +};
> +
>  #ifdef CONFIG_BLK_DEV_INITRD
>  static int __init early_initrd(char *p)
>  {
> @@ -362,6 +370,19 @@ static void __init fdt_enforce_memory_region(void)
>  void __init arm64_memblock_init(void)
>  {
>         const s64 linear_region_size = -(s64)PAGE_OFFSET;
> +       struct memblock_region *region;
> +
> +       /*
> +        * Export firmware-reserved memory regions
> +        * TODO: via more generic interface
> +        */
> +       for_each_memblock(reserved, region) {
> +               if (WARN_ON(fw_mem.cnt >= fw_mem.max))
> +                       break;
> +               fw_mem.regions[fw_mem.cnt].base = region->base;
> +               fw_mem.regions[fw_mem.cnt].size = region->size;
> +               fw_mem.cnt++;
> +       }
>
>         /* Handle linux,usable-memory-range property */
>         fdt_enforce_memory_region();
> --
> 2.16.2
>