Subject: Re: [PATCH] efi/arm: fix allocation failure when reserving the kernel base

From: Chester Lin <[email-masked]>
Date: Thu, 15 Aug 2019 11:16:11 +0000

Hi Ard,

On Thu, Aug 15, 2019 at 10:59:43AM +0300, Ard Biesheuvel wrote:
> On Sun, 4 Aug 2019 at 10:57, Ard Biesheuvel <[email-masked]> wrote:
> >
> > Hello Chester,
> >
> > On Fri, 2 Aug 2019 at 08:40, Chester Lin <[email-masked]> wrote:
> > >
> > > In some cases the arm32 efistub could fail to allocate memory for
> > > uncompressed kernel. For example, we got the following error message when
> > > verifying EFI stub on Raspberry Pi-2 [kernel-5.2.1 + grub-2.04] :
> > >
> > >   EFI stub: Booting Linux Kernel...
> > >   EFI stub: ERROR: Unable to allocate memory for uncompressed kernel.
> > >   EFI stub: ERROR: Failed to relocate kernel
> > >
> > > After checking the EFI memory map we found that the first page [0 - 0xfff]
> > > had been reserved by Raspberry Pi-2's firmware, and the efistub tried to
> > > set the dram base at 0, which was actually in a reserved region.
> > >
> >
> > This by itself is a violation of the Linux boot protocol for 32-bit
> > ARM when using the decompressor. The decompressor rounds down its own
> > base address to a multiple of 128 MB, and assumes the whole area is
> > available for the decompressed kernel and related data structures.
> > (The first TEXT_OFFSET bytes are no longer used in practice, which is
> > why putting a reserved region of 4 KB bytes works at the moment, but
> > this is fragile). Note that the decompressor does not look at any DT
> > or EFI provided memory maps *at all*.
> >
> > So unfortunately, this is not something we can fix in the kernel, but
> > we should fix it in the bootloader or in GRUB, so it does not put any
> > reserved regions in the first 128 MB of memory,
> >
> 
> OK, perhaps we can fix this by taking TEXT_OFFSET into account. The
> ARM boot protocol docs are unclear about whether this memory should be
> used or not, but it is no longer used for its original purpose (page
> tables), and the RPi loader already keeps data there.
> 
> Can you check whether the following patch works for you?
> 
> diff --git a/drivers/firmware/efi/libstub/Makefile
> b/drivers/firmware/efi/libstub/Makefile
> index 0460c7581220..ee0661ddb25b 100644
> --- a/drivers/firmware/efi/libstub/Makefile
> +++ b/drivers/firmware/efi/libstub/Makefile
> @@ -52,6 +52,7 @@ lib-$(CONFIG_EFI_ARMSTUB)     += arm-stub.o fdt.o
> string.o random.o \
> 
>  lib-$(CONFIG_ARM)              += arm32-stub.o
>  lib-$(CONFIG_ARM64)            += arm64-stub.o
> +CFLAGS_arm32-stub.o            := -DTEXT_OFFSET=$(TEXT_OFFSET)
>  CFLAGS_arm64-stub.o            := -DTEXT_OFFSET=$(TEXT_OFFSET)
> 
>  #
> diff --git a/drivers/firmware/efi/libstub/arm32-stub.c
> b/drivers/firmware/efi/libstub/arm32-stub.c
> index e8f7aefb6813..66ff0c8ec269 100644
> --- a/drivers/firmware/efi/libstub/arm32-stub.c
> +++ b/drivers/firmware/efi/libstub/arm32-stub.c
> @@ -204,7 +204,7 @@ efi_status_t
> handle_kernel_image(efi_system_table_t *sys_table,
>          * loaded. These assumptions are made by the decompressor,
>          * before any memory map is available.
>          */
> -       dram_base = round_up(dram_base, SZ_128M);
> +       dram_base = round_up(dram_base, SZ_128M) + TEXT_OFFSET;
> 
>         status = reserve_kernel_base(sys_table, dram_base, reserve_addr,
>                                      reserve_size);
> 

I tried your patch on rpi2 and got the following panic. Just a reminder that I
have replaced some log messages with "......" since it might be too long to
post all.

In this case the kernel failed to reserve cma, which should hit the issue of
memblock_limit=0x1000 as I had mentioned in my patch description. The first
block [0-0xfff] was scanned in adjust_lowmem_bounds(), but it did not align
with PMD_SIZE so the cma reservation failed because the memblock.current_limit
was extremely low. That's why I expand the first reservation from 1 PAGESIZE to
1 PMD_SIZE in my patch in order to avoid this issue. Please kindly let me know
if any suggestion, thank you.

boot-log:
--------

Loading Linux test ...
EFI stub: Booting Linux Kernel...
EFI stub: Using DTB from configuration table
EFI stub: Exiting boot services and installing virtual address map...
Uncompressing Linux... done, booting the kernel.
[    0.000000] Booting Linux on physical CPU 0xf00
[    0.000000] Linux version 5.2.1-lpae (chester@linux-8mug) (......)
[    0.000000] CPU: ARMv7 Processor [410fc075] revision 5 (ARMv7), cr=30c5387d
[    0.000000] CPU: div instructions available: patching division code
[    0.000000] CPU: PIPT / VIPT nonaliasing data cache, VIPT aliasing instruction cache
[    0.000000] OF: fdt: Machine model: Raspberry Pi 2 Model B Rev 1.1
[    0.000000] printk: bootconsole [earlycon0] enabled
[    0.000000] Memory policy: Data cache writealloc
[    0.000000] efi: Getting EFI parameters from FDT:
[    0.000000] efi:   System Table: 0x000000003df757c0
[    0.000000] efi:   MemMap Address: 0x000000002c1c5040
[    0.000000] efi:   MemMap Size: 0x000003c0
[    0.000000] efi:   MemMap Desc. Size: 0x00000028
[    0.000000] efi:   MemMap Desc. Version: 0x00000001
[    0.000000] efi: EFI v2.70 by Das U-Boot
[    0.000000] efi:  SMBIOS=0x3cb62000  MEMRESERVE=0x3cb3d040
[    0.000000] memblock_reserve: [0x000000003cb3d040-0x000000003cb3d04f] efi_config_parse_tables+0x25c/0x2d8
[    0.000000] efi: Processing EFI memory map:
[    0.000000] MEMBLOCK configuration:
[    0.000000]  memory size = 0x000000003e000000 reserved size = 0x0000000000000010
[    0.000000]  memory.cnt  = 0x1
[    0.000000]  memory[0x0]     [0x0000000000000000-0x000000003dffffff], 0x000000003e000000 bytes flags: 0x0
[    0.000000]  reserved.cnt  = 0x1
[    0.000000]  reserved[0x0]   [0x000000003cb3d040-0x000000003cb3d04f], 0x0000000000000010 bytes flags: 0x0
[    0.000000] memblock_remove: [0x0000000000000000-0xfffffffffffffffe] reserve_regions+0x68/0x23c
[    0.000000] efi:   0x000000000000-0x000000000fff [Reserved           |   |  |  |  |  |  |  |   |WB|  |  |  ]
[    0.000000] memblock_add: [0x0000000000000000-0x0000000000000fff] early_init_dt_add_memory_arch+0x164/0x178
[    0.000000] efi:   0x000000001000-0x000000307fff [Conventional Memory|   |  |  |  |  |  |  |   |WB|  |  |  ]
[    0.000000] memblock_add: [0x0000000000001000-0x0000000000307fff] early_init_dt_add_memory_arch+0x164/0x178
[    0.000000] efi:   0x000000308000-0x000002307fff [Boot Data          |   |  |  |  |  |  |  |   |WB|  |  |  ]
[    0.000000] memblock_add: [0x0000000000308000-0x0000000002307fff] early_init_dt_add_memory_arch+0x164/0x178
[    0.000000] efi:   0x000002308000-0x000002a93fff [Loader Data        |   |  |  |  |  |  |  |   |WB|  |  |  ]
[    0.000000] memblock_add: [0x0000000002308000-0x0000000002a93fff] early_init_dt_add_memory_arch+0x164/0x178
[    0.000000] efi:   0x000002a94000-0x000007cf5fff [Conventional Memory|   |  |  |  |  |  |  |   |WB|  |  |  ]
[    0.000000] memblock_add: [0x0000000002a94000-0x0000000007cf5fff] early_init_dt_add_memory_arch+0x164/0x178
......
......
[    0.000000] memblock_add: [0x000000003df76000-0x000000003dffffff] early_init_dt_add_memory_arch+0x164/0x178
[    0.000000] efi:   0x00003f100000-0x00003f100fff [Memory Mapped I/O  |RUN|  |  |  |  |  |  |   |  |  |  |  ]
[    0.000000] memblock_reserve: [0x000000002c1c5000-0x000000002c1c5fff] efi_init+0xd8/0x1c8
[    0.000000] memblock_reserve: [0x0000000000400000-0x0000000001df2cef] arm_memblock_init+0x44/0x19c
[    0.000000] memblock_reserve: [0x0000000000303000-0x0000000000307fff] arm_mm_memblock_reserve+0x30/0x38
[    0.000000] memblock_reserve: [0x0000000007cf6000-0x0000000007cfc5c4] early_init_dt_reserve_memory_arch+0x2c/0x30
[    0.000000] cma: Failed to reserve 64 MiB
[    0.000000] MEMBLOCK configuration:
[    0.000000]  memory size = 0x000000003e000000 reserved size = 0x00000000019ff2c5
[    0.000000]  memory.cnt  = 0xa
[    0.000000]  memory[0x0]     [0x0000000000000000-0x0000000000000fff], 0x0000000000001000 bytes flags: 0x4
[    0.000000]  memory[0x1]     [0x0000000000001000-0x0000000007ef5fff], 0x0000000007ef5000 bytes flags: 0x0
[    0.000000]  memory[0x2]     [0x0000000007ef6000-0x0000000007f09fff], 0x0000000000014000 bytes flags: 0x4
[    0.000000]  memory[0x3]     [0x0000000007f0a000-0x000000003cb3efff], 0x0000000034c35000 bytes flags: 0x0
[    0.000000]  memory[0x4]     [0x000000003cb3f000-0x000000003cb3ffff], 0x0000000000001000 bytes flags: 0x4
[    0.000000]  memory[0x5]     [0x000000003cb40000-0x000000003cb5ffff], 0x0000000000020000 bytes flags: 0x0
[    0.000000]  memory[0x6]     [0x000000003cb60000-0x000000003cb68fff], 0x0000000000009000 bytes flags: 0x4
[    0.000000]  memory[0x7]     [0x000000003cb69000-0x000000003df74fff], 0x000000000140c000 bytes flags: 0x0
[    0.000000]  memory[0x8]     [0x000000003df75000-0x000000003df75fff], 0x0000000000001000 bytes flags: 0x4
[    0.000000]  memory[0x9]     [0x000000003df76000-0x000000003dffffff], 0x000000000008a000 bytes flags: 0x0
[    0.000000]  reserved.cnt  = 0x5
[    0.000000]  reserved[0x0]   [0x0000000000303000-0x0000000000307fff], 0x0000000000005000 bytes flags: 0x0
[    0.000000]  reserved[0x1]   [0x0000000000400000-0x0000000001df2cef], 0x00000000019f2cf0 bytes flags: 0x0
[    0.000000]  reserved[0x2]   [0x0000000007cf6000-0x0000000007cfc5c4], 0x00000000000065c5 bytes flags: 0x0
[    0.000000]  reserved[0x3]   [0x000000002c1c5000-0x000000002c1c5fff], 0x0000000000001000 bytes flags: 0x0
[    0.000000]  reserved[0x4]   [0x000000003cb3d040-0x000000003cb3d04f], 0x0000000000000010 bytes flags: 0x0
[    0.000000] memblock_alloc_try_nid: 4096 bytes align=0x1000 nid=-1 from=0x0000000000000000 max_addr=0x0000000000000000 early_alloc+0x44/0x70
[    0.000000] Kernel panic - not syncing: early_alloc: Failed to allocate 4096 bytes align=0x1000
[    0.000000] CPU: 0 PID: 0 Comm: swapper Not tainted 5.2.1-lpae #1 openSUSE Tumbleweed (unreleased)
[    0.000000] Hardware name: BCM2835
[    0.000000] Backtrace:
[    0.000000] [<c043fafc>] (dump_backtrace) from [<c043fd84>] (show_stack+0x20/0x24)
[    0.000000]  r7:c1800000 r6:00000000 r5:600001d3 r4:c1901ba0
[    0.000000] [<c043fd64>] (show_stack) from [<c0df9400>] (dump_stack+0xd0/0x104)
[    0.000000] [<c0df9330>] (dump_stack) from [<c048061c>] (panic+0xf8/0x32c)
[    0.000000]  r10:c0307000 r9:c0001000 r8:00000003 r7:00000000 r6:00000000 r5:c181df04
[    0.000000]  r4:c192b8d8 r3:00000001
[    0.000000] [<c0480528>] (panic) from [<c1609728>] (early_alloc+0x60/0x70)
[    0.000000]  r3:00001000 r2:00001000 r1:c10037e8 r0:c12fe64c
[    0.000000]  r7:00000000
[    0.000000] [<c16096c8>] (early_alloc) from [<c1609114>] (arm_pte_alloc+0x34/0x94)
[    0.000000]  r7:00000000 r6:00000000 r4:c0307000
[    0.000000] [<c16090e0>] (arm_pte_alloc) from [<c1609384>] (__create_mapping+0x210/0x2c0)
[    0.000000]  r9:c0001000 r8:c0001000 r7:00000001 r6:c13f22e0 r5:c0200000 r4:c0400000
[    0.000000] [<c1609174>] (__create_mapping) from [<c160951c>] (create_mapping+0xe8/0x108)
[    0.000000]  r10:c0400000 r9:c16a2110 r8:c19c7a80 r7:00000000 r6:00400000 r5:c13f2000
[    0.000000]  r4:c1801ef0
[    0.000000] [<c1609434>] (create_mapping) from [<c1609f50>] (paging_init+0x350/0x75c)
[    0.000000]  r4:c1842d40

> >
> > >   grub> lsefimmap
> > >   Type      Physical start  - end             #Pages        Size Attributes
> > >   reserved  0000000000000000-0000000000000fff 00000001      4KiB WB
> > >   conv-mem  0000000000001000-0000000007ef5fff 00007ef5 130004KiB WB
> > >   RT-data   0000000007ef6000-0000000007f09fff 00000014     80KiB RT WB
> > >   conv-mem  0000000007f0a000-000000002d871fff 00025968 615840KiB WB
> > >   .....
> > >
> > > To avoid a reserved address, we have to ignore the memory regions which are
> > > marked as EFI_RESERVED_TYPE, and only conventional memory regions can be
> > > chosen. If the region before the kernel base is unaligned, it will be
> > > marked as EFI_RESERVED_TYPE and let kernel ignore it so that memblock_limit
> > > will not be sticked with a very low address such as 0x1000.
> > >
> 
> This is a separate issue, so it should be handled in a separate patch.
> 
> > > Signed-off-by: Chester Lin <[email-masked]>
> > > ---
> > >  arch/arm/mm/mmu.c                         |  3 ++
> > >  drivers/firmware/efi/libstub/arm32-stub.c | 43 ++++++++++++++++++-----
> > >  2 files changed, 37 insertions(+), 9 deletions(-)
> > >
> > > diff --git a/arch/arm/mm/mmu.c b/arch/arm/mm/mmu.c
> > > index f3ce34113f89..909b11ba48d8 100644
> > > --- a/arch/arm/mm/mmu.c
> > > +++ b/arch/arm/mm/mmu.c
> > > @@ -1184,6 +1184,9 @@ void __init adjust_lowmem_bounds(void)
> > >                 phys_addr_t block_start = reg->base;
> > >                 phys_addr_t block_end = reg->base + reg->size;
> > >
> > > +               if (memblock_is_nomap(reg))
> > > +                       continue;
> > > +
> > >                 if (reg->base < vmalloc_limit) {
> > >                         if (block_end > lowmem_limit)
> > >                                 /*
> > > diff --git a/drivers/firmware/efi/libstub/arm32-stub.c b/drivers/firmware/efi/libstub/arm32-stub.c
> > > index e8f7aefb6813..10d33d36df00 100644
> > > --- a/drivers/firmware/efi/libstub/arm32-stub.c
> > > +++ b/drivers/firmware/efi/libstub/arm32-stub.c
> > > @@ -128,7 +128,7 @@ static efi_status_t reserve_kernel_base(efi_system_table_t *sys_table_arg,
> > >
> > >         for (l = 0; l < map_size; l += desc_size) {
> > >                 efi_memory_desc_t *desc;
> > > -               u64 start, end;
> > > +               u64 start, end, spare, kernel_base;
> > >
> > >                 desc = (void *)memory_map + l;
> > >                 start = desc->phys_addr;
> > > @@ -144,27 +144,52 @@ static efi_status_t reserve_kernel_base(efi_system_table_t *sys_table_arg,
> > >                 case EFI_BOOT_SERVICES_DATA:
> > >                         /* Ignore types that are released to the OS anyway */
> > >                         continue;
> > > -
> > > +               case EFI_RESERVED_TYPE:
> > > +                       /* Ignore reserved regions */
> > > +                       continue;
> > >                 case EFI_CONVENTIONAL_MEMORY:
> > >                         /*
> > >                          * Reserve the intersection between this entry and the
> > >                          * region.
> > >                          */
> > >                         start = max(start, (u64)dram_base);
> > > -                       end = min(end, (u64)dram_base + MAX_UNCOMP_KERNEL_SIZE);
> > > +                       kernel_base = round_up(start, PMD_SIZE);
> > > +                       spare = kernel_base - start;
> > > +                       end = min(end, kernel_base + MAX_UNCOMP_KERNEL_SIZE);
> > > +
> > > +                       status = efi_call_early(allocate_pages,
> > > +                                       EFI_ALLOCATE_ADDRESS,
> > > +                                       EFI_LOADER_DATA,
> > > +                                       MAX_UNCOMP_KERNEL_SIZE / EFI_PAGE_SIZE,
> > > +                                       &kernel_base);
> > > +                       if (status != EFI_SUCCESS) {
> > > +                               pr_efi_err(sys_table_arg,
> > > +                                       "reserve_kernel_base: alloc failed.\n");
> > > +                               goto out;
> > > +                       }
> > > +                       *reserve_addr = kernel_base;
> > >
> > > +                       if (!spare)
> > > +                               break;
> > > +                       /*
> > > +                        * If there's a gap between start and kernel_base,
> > > +                        * it needs be reserved so that the memblock_limit
> > > +                        * will not fall on a very low address when running
> > > +                        * adjust_lowmem_bounds(), wchich could eventually
> > > +                        * cause CMA reservation issue.
> > > +                        */
> > >                         status = efi_call_early(allocate_pages,
> > >                                                 EFI_ALLOCATE_ADDRESS,
> > > -                                               EFI_LOADER_DATA,
> > > -                                               (end - start) / EFI_PAGE_SIZE,
> > > +                                               EFI_RESERVED_TYPE,
> > > +                                               spare / EFI_PAGE_SIZE,
> > >                                                 &start);
> > >                         if (status != EFI_SUCCESS) {
> > >                                 pr_efi_err(sys_table_arg,
> > > -                                       "reserve_kernel_base(): alloc failed.\n");
> > > +                                       "reserve spare-region failed\n");
> > >                                 goto out;
> > >                         }
> > > -                       break;
> > >
> > > +                       break;
> > >                 case EFI_LOADER_CODE:
> > >                 case EFI_LOADER_DATA:
> > >                         /*
> > > @@ -220,7 +245,7 @@ efi_status_t handle_kernel_image(efi_system_table_t *sys_table,
> > >         *image_size = image->image_size;
> > >         status = efi_relocate_kernel(sys_table, image_addr, *image_size,
> > >                                      *image_size,
> > > -                                    dram_base + MAX_UNCOMP_KERNEL_SIZE, 0);
> > > +                                    *reserve_addr + MAX_UNCOMP_KERNEL_SIZE, 0);
> > >         if (status != EFI_SUCCESS) {
> > >                 pr_efi_err(sys_table, "Failed to relocate kernel.\n");
> > >                 efi_free(sys_table, *reserve_size, *reserve_addr);
> > > @@ -233,7 +258,7 @@ efi_status_t handle_kernel_image(efi_system_table_t *sys_table,
> > >          * in memory. The kernel determines the base of DRAM from the
> > >          * address at which the zImage is loaded.
> > >          */
> > > -       if (*image_addr + *image_size > dram_base + ZIMAGE_OFFSET_LIMIT) {
> > > +       if (*image_addr + *image_size > *reserve_addr + ZIMAGE_OFFSET_LIMIT) {
> > >                 pr_efi_err(sys_table, "Failed to relocate kernel, no low memory available.\n");
> > >                 efi_free(sys_table, *reserve_size, *reserve_addr);
> > >                 *reserve_size = 0;
> > > --
> > > 2.22.0
> > >
> 

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