PRX: Difference between revisions

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(The headers are not ignored, the addresses are just relative)
(more info, second load segment is nothing special (maps to .data, .opd, .toc, etc). nothing new.)
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=Structure=
=Structure=
 
First LOAD segment p_paddr points to module info.
==First LOAD segment==
==Module Info==
paddr points to the descriptor for the "dependency table" or "deptable" for short:
 
*Notes:
**All addresses are relative to the offset where this segment starts, which is specified in the program header. In other words, you have to add phdr.p_offset to these addresses. Since the first program header corresponds to the first LOAD segment, this offset is usually the same as the size of the ELF Header (0x40) + the size of the program headers combined.
 
===Module Info===
{| class="wikitable"
{| class="wikitable"
! Offset
! Offset
Line 124: Line 118:
| +4
| +4
| short
| short
| Attributes. 0x1 is always set, 0x8 often, 0x2000 seems to indicate a non-PRX library (like "stdc" or "allocator") that comes from somewhere else (LV2?)
| Attributes. AUTO_EXPORT=0x0001, WEAK_EXPORT=0x0002, NOLINK_EXPORT=0x0004, WEAK_IMPORT=0x0008, 0x2000 seems to indicate a non-PRX library (like "stdc" or "allocator") that comes from somewhere else (LV2?)
|-
|-
| +6
| +6
| short
| short
| The number of functions the depending PRX needs from the depended PRX. There is this many function pointers in the stubtable (see below) for this PRX. Most of the time, there's also this many entries in the Mystery Table for that PRX. But not always? "allocator" in particular seems to get strange stuff.
| Number of functions
|-
|-
| +8
| +8
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| +20
| +20
| long
| long
| Pointer to this library's entries in the mystery table.
| Pointer to the list of NID's for the exported functions.
|-
|-
| +24
| +24
| long
| long
| Pointer to the the pointers to function wrappers for this library in the wrapper list.
| Pointer to the list of exported functions.
|-
|-
| +28
| +28
| long
| long
| ver_nid_table
| var_nid_table
|-
|-
| +32
| +32
| long
| long
| ver_entry_table
| var_entry_table
|-
|-
| +36
| +36
Line 171: Line 165:
|}
|}


==Second LOAD segment==
== Relocations ==
Is all the relocation and symbol data, save for the names (as ASCII strings) of the exposed functions (which are in the first LOAD segment along with all the other strings the PRX uses).
Relocations can be found in either PT_SCE_PPURELA segments or SHT_SCE_PPURELA / SHT_RELA sections. RELA relocations are standard relocations while PPURELA relocations have 2 segment (program header) indexes stored in r_sym of r_info.
 
*The first index can be extracted with 0x7FFFFF00 as a mask and is used as a base address for r_addend. This sum will be the value applied to the patch.  
At the start of this section is the wrapper list, just a flat array of pointers to subroutines that appear to be wrappers for calling functions in other PRXes. This combined with the deptable maps those wrappers to PRXes.
*The second index can be extracted with 0x000000FF as a mask and is used as a base address for the target segment to patch and is added to r_offset.
*The first bit (0x80000000) is also set on earlier PRX's but it is currently unknown what it is used for.


At EOF-20 is a pointer to the start of the funcpointer table. After 0xFFFFFFFF and a handful of pointers into itself, it goes into a list of pointers to subroutines (as longs) each followed by a long containing the unique ID from the deptable descriptor.


Table number two: All longs(?) The very first is a pointer to the very start of the funcpointer table.
There is a table that's a listing of the functions exposed to apps/other PRXes. This table is usually referenced by a function; how exactly it is reached remains to be seen.
{| class="wikitable"
! Offset
! Type
! Description
|-
| +12n
| long
| Pointer to the ASCII string name of this function
|-
| +12n +4
| long
| Pointer to this function's entry in the funcpointer table.
|-
| +12n +8
| long
| Always(?) zero.
|}


= FNID generation =
= FNID generation =
Line 215: Line 189:
_Mbstatet>, std::_Iosb<int>::_Openmode)')) = FNID('_ZNSt13basic_filebufIwSt11char_traitsIwEE7seekposESt4fposISt9_MbstatetENSt5_IosbIiE9_OpenmodeE') = '''0xB6A4D760'''
_Mbstatet>, std::_Iosb<int>::_Openmode)')) = FNID('_ZNSt13basic_filebufIwSt11char_traitsIwEE7seekposESt4fposISt9_MbstatetENSt5_IosbIiE9_OpenmodeE') = '''0xB6A4D760'''


 
noname_nid_suffix: 0xbc5eba9e042504905b64274994d9c41f
 
For import stub's with no names, you must use SHA1 over concatenation of symbol's name and noname_nid_suffix as an ascii string. Some examples of noname imports are module_start, module_info, and module_stop.
  ''SHA1''('module_info' + '0xbc5eba9e042504905b64274994d9c41f') = '''1630f4d7'''0bf3df419db9d481983411fd3130482a = '''0xD7F43016'''


{{File Formats}}
{{File Formats}}
<noinclude>[[Category:Main]]</noinclude>
<noinclude>[[Category:Main]]</noinclude>

Revision as of 15:09, 23 February 2017

Overview

Signed PPU Relocatable Executable (SPRX)

Structure

First LOAD segment p_paddr points to module info.

Module Info

Offset Type Description
+0 short Module attributes
+2 char[2] Module version
+4 char[28] Module name
+32 long TOC address
+36 long Pointer to the start of exports section
+40 long Pointer to end of exports section
+44 long Points to the start of imports section
+48 long Points to the end of imports section

Exports

Offset Type Description
+0 char[2] Structure size (0x1C 32-bit or 0x28 64-bit), padding
+2 short Version
+4 short Attributes
+6 short Number of functions
+8 short Number of variables
+10 short Number of thread local storage variables
+12 char Hash info
+13 char Thread local storage hash info
+14 char[2] Reserved
+16 long Pointer to exported library name
+20 long Pointer to function NID table
+24 long Pointer to function stub table

Imports

Offset Type Description
+0 char Structure size (0x2C)
+1 char Unused
+2 short Version
+4 short Attributes. AUTO_EXPORT=0x0001, WEAK_EXPORT=0x0002, NOLINK_EXPORT=0x0004, WEAK_IMPORT=0x0008, 0x2000 seems to indicate a non-PRX library (like "stdc" or "allocator") that comes from somewhere else (LV2?)
+6 short Number of functions
+8 short Number of variables
+10 short Number of thread local storage variables
+12 byte[4] reserved
+16 long Pointer to imported library name.
+20 long Pointer to the list of NID's for the exported functions.
+24 long Pointer to the list of exported functions.
+28 long var_nid_table
+32 long var_entry_table
+36 long tls_nid_table
+40 long tls_entry_table

Relocations

Relocations can be found in either PT_SCE_PPURELA segments or SHT_SCE_PPURELA / SHT_RELA sections. RELA relocations are standard relocations while PPURELA relocations have 2 segment (program header) indexes stored in r_sym of r_info.

  • The first index can be extracted with 0x7FFFFF00 as a mask and is used as a base address for r_addend. This sum will be the value applied to the patch.
  • The second index can be extracted with 0x000000FF as a mask and is used as a base address for the target segment to patch and is added to r_offset.
  • The first bit (0x80000000) is also set on earlier PRX's but it is currently unknown what it is used for.


FNID generation

symbol name suffix

symbol_name_suffix: 6759659904250490566427499489741A

To calculate FNID value of exported/imported symbol from .PRX you need to take SHA-1 hash over concatenation of symbol's name and symbol_name_suffix and then grab first 4 bytes from it and reverse these bytes (because of little-endian). Let's take, for example, _sys_sprintf: 

 SHA1('_sys_sprintf' + '\x67\x59\x65\x99\x04\x25\x04\x90\x56\x64\x27\x49\x94\x89\x74\x1A') = FEEAF9A123D7D1A7619B40CD52500F9735A852A4
 FNID('_sys_sprintf') = swap_uint32(0xFEEAF9A1) = 0xA1F9EAFE.

For C++ functions you should use mangled representation of symbol's name. For example, mangled name of std::runtime_error::what() const is _ZNKSt13runtime_error4whatEv and FNID('_ZNKSt13runtime_error4whatEv') = 0x5333BDC9. More complex example: FNID(mangle('std::basic_filebuf<wchar_t, std::char_traits<wchar_t> >::seekpos(std::fpos<std:: _Mbstatet>, std::_Iosb<int>::_Openmode)')) = FNID('_ZNSt13basic_filebufIwSt11char_traitsIwEE7seekposESt4fposISt9_MbstatetENSt5_IosbIiE9_OpenmodeE') = 0xB6A4D760 

noname_nid_suffix: 0xbc5eba9e042504905b64274994d9c41f

For import stub's with no names, you must use SHA1 over concatenation of symbol's name and noname_nid_suffix as an ascii string. Some examples of noname imports are module_start, module_info, and module_stop. 

 SHA1('module_info' + '0xbc5eba9e042504905b64274994d9c41f') = 1630f4d70bf3df419db9d481983411fd3130482a = 0xD7F43016
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