Re: [PATCH 0/2] ESRT fixes for relocatable kexec'd kernel

From: Ard Biesheuvel
Date: Wed Mar 07 2018 - 14:55:45 EST

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(+ James)

Hello Akashi,

On 6 March 2018 at 09:00, AKASHI Takahiro <takahiro.akashi@xxxxxxxxxx> 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@xxxxxxxxxx>
> 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@xxxxxxxxxx>
> ---
> 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
>

Next message: Greg Kroah-Hartman: "[PATCH 4.14 088/110] KVM: s390: consider epoch index on hotplugged CPUs"
Previous message: Ivan Gorinov: "[PATCH v4 4/4] x86/devicetree: Enable multiprocessing in DT"
In reply to: Tyler Baicar: "Re: [PATCH 0/2] ESRT fixes for relocatable kexec'd kernel"
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