[PATCH] ARM: compressed: discard ksym/kcrctab input section
Matthias Brugger
matthias.bgg at gmail.com
Mon Oct 23 14:15:18 PDT 2017
On 10/23/2017 11:29 AM, Russell King - ARM Linux wrote:
> On Mon, Oct 23, 2017 at 12:00:46AM +0200, Matthias Brugger wrote:
>> Hi Ard,
>>
>> On 10/21/2017 10:14 AM, Ard Biesheuvel wrote:
>>> On 21 October 2017 at 08:56, Matthias Brugger <mbrugger at suse.com> wrote:
>>>> On 09/08/2017 05:31 PM, Ard Biesheuvel wrote:
>>>>> As it turns out, building the ARM kernel with EFI support pulls in
>>>>> a couple of sections that we don't really need in the decompressor.
>>>>> This is due to the fact the the UEFI stub uses sort() to sort the UEFI
>>>>> memory map, which is an exported symbol pulled in from lib/sort.c.
>>>>>
>>>>> Before commit e4bae4d0b5f3 ("arm/efi: Split zImage code and data into
>>>>> separate PE/COFF sections"), this resulted in the following layout
>>>>> for the decompressor ELF binary.
>>>>>
>>>>> [Nr] Name Type Addr Off Size ES Flg Lk Inf Al
>>>>> [ 0] NULL 00000000 000000 000000 00 0 0 0
>>>>> [ 1] .text PROGBITS 00000000 010000 009b3c 00 AX 0 0 512
>>>>> [ 2] .rodata PROGBITS 00009b3c 019b3c 001684 00 A 0 0 4
>>>>> [ 3] __ksymtab_strings PROGBITS 0000b1c0 01b1c0 000005 00 A 0 0 1
>>>>> [ 4] .data PROGBITS 0000b1c8 01b1c8 000020 00 WA 0 0 8
>>>>> [ 5] ___ksymtab+sort PROGBITS 0000b1e8 01b1e8 000008 00 WA 0 0 4
>>>>> [ 6] .piggydata PROGBITS 0000b1f0 01b1f0 77ac38 00 A 0 0 1
>>>>> [ 7] .got.plt PROGBITS 00785e28 795e28 00000c 04 WA 0 0 4
>>>>> [ 8] .got PROGBITS 00785e34 795e34 000028 00 WA 0 0 4
>>>>> [ 9] .pad PROGBITS 00785e5c 795e5c 000004 00 WA 0 0 1
>>>>> [10] .bss NOBITS 00785e60 795e60 00001c 00 WA 0 0 4
>>>>> [11] .stack NOBITS 00785e80 795e60 001000 00 WA 0 0 1
>>>>>
>>>>> Commit e4bae4d0b5f3 made some changes to the linker script to allow the
>>>>> UEFI firmware to map the decompressor with strict R-X/RW- permissions
>>>>> before invoking it. Unfortunately, this turns out to break the boot on
>>>>> some systems, because the linker now also moves the ksymtab/kcrctab
>>>>> sections around, resulting in .piggydata to appear misaligned.
>>>>>
>>>>> [Nr] Name Type Addr Off Size ES Flg Lk Inf Al
>>>>> [ 0] NULL 00000000 000000 000000 00 0 0 0
>>>>> [ 1] .text PROGBITS 00000000 010000 00a93c 00 AX 0 0 4096
>>>>> [ 2] .rodata PROGBITS 0000a93c 01a93c 001684 00 A 0 0 4
>>>>> [ 3] __ksymtab_strings PROGBITS 0000bfc0 01bfc0 000005 00 A 0 0 1
>>>>> [ 4] .piggydata PROGBITS 0000bfc5 01bfc5 77ac47 00 A 0 0 1
>>>>> [ 5] .got.plt PROGBITS 00786c0c 796c0c 00000c 04 WA 0 0 4
>>>>> [ 6] .got PROGBITS 00786c18 796c18 000028 00 WA 0 0 4
>>>>> [ 7] .pad PROGBITS 00786c40 796c40 000008 00 WA 0 0 1
>>>>> [ 8] .data PROGBITS 00787000 797000 000200 00 WA 0 0 4096
>>>>> [ 9] ___ksymtab+sort PROGBITS 00787200 797200 000008 00 WA 0 0 4
>>>>> [10] .bss NOBITS 00787208 797208 00001c 00 WA 0 0 4
>>>>> [11] .stack NOBITS 00787228 797208 001000 00 WA 0 0 1
>>>>>
>>>>> So let's align piggydata explicitly, and discard these sections from the
>>>>> binary.
>>>>>
>>>>> Cc: Russell King <linux at armlinux.org.uk>
>>>>> Fixes: e4bae4d0b5f3 ("arm/efi: Split zImage code and data into separate ...")
>>>>> Tested-by: Gregory CLEMENT <gregory.clement at free-electrons.com>
>>>>> Signed-off-by: Ard Biesheuvel <ard.biesheuvel at linaro.org>
>>>>> ---
>>>>> arch/arm/boot/compressed/piggy.S | 1 +
>>>>> arch/arm/boot/compressed/vmlinux.lds.S | 1 +
>>>>> 2 files changed, 2 insertions(+)
>>>>>
>>>>
>>>> This fixes the boot regression on bananapi-r2.
>>>> Thanks! Feel free to add:
>>>>
>>>> Tested-by: Matthias Brugger <mbrugger at suse.com>
>>>>
>>>
>>> Thanks for confirming Matthias. Could you please check whether this
>>> patch from Arnd
>>>
>>> https://marc.info/?l=linux-kernel&m=150852980119217&w=2
>>>
>>> fixes the issue as well? (after reverting this one)
>>>
>>
>> After only applying this patch on top of v4.14-rc5 I was not able to boot.
>
> Which decompression method are you using?
uImage/zImage
>
> What does objdump -h arch/arm/boot/vmlinux say?
>
arch/arm/boot/compressed/vmlinux: file format elf32-littlearm
Sections:
Idx Name Size VMA LMA File off Algn
0 .text 0000b06c 00000000 00000000 00010000 2**12
CONTENTS, ALLOC, LOAD, READONLY, CODE
1 .rodata 000016cc 0000b06c 0000b06c 0001b06c 2**2
CONTENTS, ALLOC, LOAD, READONLY, DATA
2 __ksymtab_strings 00000005 0000c738 0000c738 0001c738 2**0
CONTENTS, ALLOC, LOAD, READONLY, DATA
3 .piggydata 007ce9c5 0000c73d 0000c73d 0001c73d 2**0
CONTENTS, ALLOC, LOAD, READONLY, DATA
4 .got.plt 0000000c 007db104 007db104 007eb104 2**2
CONTENTS, ALLOC, LOAD, DATA
5 .got 00000028 007db110 007db110 007eb110 2**2
CONTENTS, ALLOC, LOAD, DATA
6 .pad 00000008 007db138 007db138 007eb138 2**0
CONTENTS, ALLOC, LOAD, DATA
7 .data 00000200 007dc000 007dc000 007ec000 2**12
CONTENTS, ALLOC, LOAD, DATA
8 ___ksymtab+sort 00000008 007dc200 007dc200 007ec200 2**2
CONTENTS, ALLOC, LOAD, DATA
9 .bss 0000001c 007dc208 007dc208 007ec208 2**2
ALLOC
10 .stack 00001000 007dc228 007dc228 007ec208 2**0
ALLOC
11 .comment 0000002d 00000000 00000000 007ec208 2**0
CONTENTS, READONLY
12 .ARM.attributes 0000002d 00000000 00000000 007ec235 2**0
CONTENTS, READONLY
13 .debug_line 00007088 00000000 00000000 007ec262 2**0
CONTENTS, READONLY, DEBUGGING
14 .debug_info 00057677 00000000 00000000 007f32ea 2**0
CONTENTS, READONLY, DEBUGGING
15 .debug_abbrev 00003bc2 00000000 00000000 0084a961 2**0
CONTENTS, READONLY, DEBUGGING
16 .debug_aranges 00000308 00000000 00000000 0084e528 2**3
CONTENTS, READONLY, DEBUGGING
17 .debug_ranges 00000e78 00000000 00000000 0084e830 2**3
CONTENTS, READONLY, DEBUGGING
18 .debug_frame 00002228 00000000 00000000 0084f6a8 2**2
CONTENTS, READONLY, DEBUGGING
19 .debug_loc 00005bff 00000000 00000000 008518d0 2**0
CONTENTS, READONLY, DEBUGGING
20 .debug_str 00008c41 00000000 00000000 008574cf 2**0
CONTENTS, READONLY, DEBUGGING
This objdump is with Arnd Bergmans patch applied on top of v4.14-rc5.
Beware that Ard provided a patch against efi/libstub which independently fixes
the boot regression:
"efi/libstub: arm: omit sorting of the UEFI memory map"
Regards,
Matthias
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