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SubjectRe: [PATCHv3 2/2] x86/vdso: Add build salt to the vDSO
On Wed, May 23, 2018 at 3:53 PM Laura Abbott <labbott@redhat.com> wrote:

> Actually I remember now why this is necessary: there is not a simple way
> to encode a string into a linker file as it has to be spit out byte
> by byte.

I think you can use the "fill" thing to basically add any random data to a
section.

So you can do something like

. = ALIGN(16);
.salt : AT(ADDR(.salt) - LOAD_OFFSET) {
LONG(0xffaa5500);
. = ALIGN(16);
} =0x01234567890abcdef

in the lds file, and you'll get a section that looks like this:

[torvalds@i7 linux]$ objdump -h vmlinux -j .salt -s

vmlinux: file format elf64-x86-64

Sections:
Idx Name Size VMA LMA File off
Algn
15 .salt 00000010 ffffffff8432b000 000000000432b000 0352b000
2**0
CONTENTS, ALLOC, LOAD, DATA
Contents of section .salt:
ffffffff8432b000 0055aaff 00123456 7890abcd ef001234 .U....4Vx......4

Now whether that is sufficient for your needs, I dunno.

Linus

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