[PATCH] ARM: compressed: discard ksym/kcrctab input section

[Russell King - ARM Linux]

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?

What does objdump -h arch/arm/boot/vmlinux say?

Thanks.

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