Problem with my BOOTx64.efi application [Solved]

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Fulgurance

Joined: 27 Nov 2017
Posts: 276

Fulgurance 04 Apr 2020, 18:40

Hello, i have problem. I have coded BOOTx64.efi application to test EFI Programming. I have formatted one of my USB to GPT partition schema, and fat32 format. I have made /BOOT/EFI directories and put my BOOTx64.efi program into this directories.

But when i choose my USB into VirtualBox, nothing append.

Is it not the good way ?

Code:

format pe64 dll efi
entry Main

section '.text' code executable readable

Main:
sub rsp,0x20
mov [Handle],rcx
mov [SystemTable],rdx
lea rdx,[Message]
mov rcx,[SystemTable]
add rcx,[EFISystemTable.ConOut]
call rcx
add rsp,0x20
mov eax,0x0
retn

include "EFIVariables/EFISystemTable.fasm"

section '.data' data readable writeable

Handle:      dq ?
SystemTable: dq ?
Message:     db "* Fulgurance: Test UEFI Ok",13,10,0

section '.reloc' fixups data discardable

(I have made custom library with official UEFI documentattion: https://uefi.org/specifications)

Last edited by Fulgurance on 08 Apr 2020, 22:55; edited 1 time in total

04 Apr 2020, 18:40

Feryno

Joined: 23 Mar 2005
Posts: 514
Location: Czech republic, Slovak republic

Feryno 05 Apr 2020, 20:43

pls check with disassembler how is this line assembled into binary:

Code:

add rcx,[EFISystemTable.ConOut]

it seems like something is added from some position in memory [...]
when correct it should assemble into something like add rcx,value where value is the offset of ConOut in EFISystemTable which is hexadecimal 40h so it should be add rcx,40h

05 Apr 2020, 20:43

Fulgurance

Joined: 27 Nov 2017
Posts: 276

Fulgurance 08 Apr 2020, 22:59

Can you remove this post please ?

08 Apr 2020, 22:59

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 20445
Location: In your JS exploiting you and your system

revolution 08 Apr 2020, 23:03

Fulgurance wrote:

Can you remove this post please ?

Why? It might help someone else in the future.

08 Apr 2020, 23:03

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