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ARM binaries (view source)

Revision as of 08:02, 23 September 2022

311 bytes removed ,  08:02, 23 September 2022
→‎ELF format: updated descriptions to not be as outdated
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'''ARM binaries''' are contained inside .wad files in update partitions. The .wad format and how to decrypt it is described in [[WAD_Files]].
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'''ARM binaries''' are contained inside .wad files in update partitions. The .wad format and how to decrypt it is described in [[WAD Files]].
    
== ELF format ==
 
== ELF format ==
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IOS modules, at least, use bare ELF files. The files seem to be compiled with GCC 3.4.3, and they are EABI compliant.
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Individual IOS modules use bare [[ELF]] files. The files seem to be compiled with GCC 3.4.3, and they are EABI compliant. The file is in big endian format. All ELF files are stripped and don't include function names or symbols.
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=== ELF Note Structure ===
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IOS modules in the main binary are loaded by the main kernel thread according to an ELF note. There are exactly as many IOSELFNoteData as process main threads in IOS.
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<source lang="c">
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struct IOSELFNoteData
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{
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  u32 version_maybe; // always 0x0b?
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  u32 pid;
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  u32 unk2; // unused
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  u32 entry_point;
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  u32 unk4; // unused
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  u32 priority;
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  u32 unk6; // unused
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  u32 stack_size;
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  u32 unk8; // unused
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  u32 stack_top;
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};
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struct IOSELFNote
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{
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  // Standard ELF note header
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  u32 name_size; // always 0x0
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  u32 descriptor_size;
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  u32 note_type; // always 0x6
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  // IOS specific data
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  IOSELFNoteData data[];
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};
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</source>
    
== ELFLOADER format ==
 
== ELFLOADER format ==
 
The ELFLOADER ARM binary format is used for the "bootup" files, including the IOS kernel (or the entirety of the IOS in earlier versions which are monolithic) and BOOT2. Once decrypted, the data has the following format:
 
The ELFLOADER ARM binary format is used for the "bootup" files, including the IOS kernel (or the entirety of the IOS in earlier versions which are monolithic) and BOOT2. Once decrypted, the data has the following format:
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{| style="border-collapse: collapse; padding: 0.2em 0.2em 0.2em 0.2em;"
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{| class="wikitable"
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|- style="background-color: #ddd;"
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| style="border: 1px solid #ccc; padding: 0.2em; background-color: #ded;" | '''Start'''
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| style="border: 1px solid #ccc; padding: 0.2em; background-color: #dde;" | '''End'''
  −
| style="border: 1px solid #ccc; padding: 0.2em; background-color: #ddd;" | '''Length'''
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| style="border: 1px solid #ccc; padding: 0.2em; background-color: #edd;" | '''Description'''
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|- style="background-color: #ddd;"
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| style="border: 1px solid #ccc; padding: 0.2em; background-color: #ded;" | 0x000
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| style="border: 1px solid #ccc; padding: 0.2em; background-color: #dde;" | 0x004
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| style="border: 1px solid #ccc; padding: 0.2em; background-color: #ddd;" | 0x004
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| style="border: 1px solid #ccc; padding: 0.2em; background-color: #edd;" | Header size = 0x0010
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|- style="background-color: #ddd;"
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| style="border: 1px solid #ccc; padding: 0.2em; background-color: #ded;" | 0x004
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| style="border: 1px solid #ccc; padding: 0.2em; background-color: #dde;" | 0x008
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| style="border: 1px solid #ccc; padding: 0.2em; background-color: #ddd;" | 0x004
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| style="border: 1px solid #ccc; padding: 0.2em; background-color: #edd;" | Offset to ELF file after header
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|- style="background-color: #ddd;"
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| style="border: 1px solid #ccc; padding: 0.2em; background-color: #ded;" | 0x008
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| style="border: 1px solid #ccc; padding: 0.2em; background-color: #dde;" | 0x00C
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| style="border: 1px solid #ccc; padding: 0.2em; background-color: #ddd;" | 0x004
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| style="border: 1px solid #ccc; padding: 0.2em; background-color: #edd;" | Size of ELF file
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|- style="background-color: #ddd;"
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| style="border: 1px solid #ccc; padding: 0.2em; background-color: #ded;" | 0x00C
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| style="border: 1px solid #ccc; padding: 0.2em; background-color: #dde;" | 0x010
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| style="border: 1px solid #ccc; padding: 0.2em; background-color: #ddd;" | 0x004
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| style="border: 1px solid #ccc; padding: 0.2em; background-color: #edd;" | 0x00 padding / unused
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|- style="background-color: #ddd;"
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| style="border: 1px solid #ccc; padding: 0.2em; background-color: #ded;" | 0x010
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| style="border: 1px solid #ccc; padding: 0.2em; background-color: #dde;" | variable
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| style="border: 1px solid #ccc; padding: 0.2em; background-color: #ddd;" | variable
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| style="border: 1px solid #ccc; padding: 0.2em; background-color: #edd;" | ELF file stub loader binary
   
|-
 
|-
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| style="border: 1px solid #ccc; padding: 0.2em; background-color: #ded;" | variable
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! Start
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| style="border: 1px solid #ccc; padding: 0.2em; background-color: #dde;" | variable
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! End
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| style="border: 1px solid #ccc; padding: 0.2em; background-color: #ddd;" | variable
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! Length
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| style="border: 1px solid #ccc; padding: 0.2em; background-color: #edd;" | ELF file
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! Description
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|-
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| 0x000
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| 0x004
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| 0x004
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| Header size = 0x0010
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|-
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| 0x004
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| 0x008
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| 0x004
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| Offset to ELF file after header
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|-
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| 0x008
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| 0x00C
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| 0x004
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| Size of ELF file
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|-
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| 0x00C
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| 0x010
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| 0x004
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| Unknown "ddrInit", set to 0 on boot
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|-
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| 0x010
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| variable
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| variable
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| ELF file stub loader binary
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|-
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| variable
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| variable
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| variable
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| ELF file
 
|}
 
|}
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=== BOOT2 elf loader ===
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=== Official ELF loaders ===
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The [[boot2]] and [[IOS]] elf stub loaders seem to be position-independent: they can be loaded at any address and will still work, as long as it doesn't overlap with the destination of the ELF load.
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The BOOT2 elf stub loader sets up a stack, calculates its own address, and switches to THUMB mode. Then it does the following:
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The official ELF loaders set up a stack and calculate their own address, switches to THUMB mode, and then they do the following:
    
<source lang="c">
 
<source lang="c">
Line 55: Line 86:  
</source>
 
</source>
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0xD800000 seems to be the start of the (a?) hardware register space.
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This sets the [[Hollywood/Registers#HW_SRNPROT|HW_SRNPROT]] register to enable the [[Starlet/Main Memory|SRAM]] mirror at 0xFFFE0000.
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After this, it loads the ELF file, and then '''zeroes out the memory area where most of the ELF loader resides'''. Then it goes back to ARM mode and vectors to 0xFFFF0000 (the entrypoint of the ARM / vector table). The entire BOOT2 file cleartext is loaded and then the loader is called, so the loader can calculate the offset of the header simply by subtracting 0x10 from the PC at its entrypoint.
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=== Embedded Broadway Code ===
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Some ARM binaries include PowerPC code for the Broadway. For example MIOS include code at address 0x00003400 and 0x01300000. The first code sets the BATs up, initializes the powerpc and vectors to the second code (which can be addressed at 0x81300000 then) then. This code is executed by writing a small stub to the EXI boot buffer and setting a bit in another register then.
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After this, it loads the ELF file, and then '''zeroes out the memory area where the ELF file resides'''. Then it goes back to ARM mode and vectors to 0xFFFF0000 (the entrypoint of the ARM / vector table). The entire BOOT2 code seems to be position-independent: it can be loaded at any address and will still work, as long as it doesn't overlap with the destination of the ELF load. The entire BOOT2 file cleartext is loaded and then the loader is called, so the loader can calculate the offset of the header simply by subtracting 0x10 from the PC at its entrypoint.
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=== Dynamic Linker ===
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In later IOS versions ([[IOS28]] and later) the single monolithic IOS ARM binary was split into individual dynamically loaded modules. The main kernel is the only file to include the ELFLOADER header and stub; each individual module is a regular ELF file, loaded dynamically by the kernel to a fixed address specified in the ELF header. No functions are called directly between modules - [[IOS/Syscalls#Syscalls_.28via_undefined_instructions.29|Syscalls]] are used for individual modules to communicate with the main kernel, and resource managers are used for modules to communicate between each other (such as [[:/dev/di|DI]] interfacing with [[:/dev/es]] for ticket verification)
    
=== Extract ELF file ===
 
=== Extract ELF file ===
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#include <stdio.h>
 
#include <stdio.h>
 
#include <stdint.h>
 
#include <stdint.h>
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#include <malloc.h>
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#include <stdlib.h>
 
#include <netinet/in.h>
 
#include <netinet/in.h>
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}
 
}
 
fclose(fout);
 
fclose(fout);
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free(buffer);
 
return 0;
 
return 0;
 
}
 
}
 
</source>
 
</source>
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 +
[[Category:File formats]]
Hallowizer
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