PRX: Difference between revisions

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(Correcting what I had. Total overhaul.)
 
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scetool can decrypt SPRX's, producing an ELF... or is it? Not really. It has an ELF header but...
= Overview =


First LOAD segment, paddr points to the descriptor for the "dependency table" or "deptable" for short:
'''P'''laystation '''R'''elocatable E'''x'''ecutable (PRX)


NOTE: All addresses inside the file assume the ELF header isn't there (basically add 0xE0 to all addresses.)
= PRX2 =
{| class="wikitable"
! Offset
! Type
! Description
|-
| +0
| long
| Always(?) 0x101
|-
| +4
| char[28]
| Name of this PRX, padded out with zeroes. Doesn't necessarily match the file name(why?)
|-
| +32
| long
| A unique module ID? Gets used a lot later...
|-
| +36
| long
| Points to the deptable header
|-
| +40
| long
| Points to the END of the deptable header
|-
| +44
| long
| Points to the start of first deptable entry
|-
| +48
| long
| points to the end of the LAST deptable entry
|}


Deptable header:
PRX2 is only present on PSVita. PSP and PS3 use PRX version 1.
{| class="wikitable"
! Offset
! Type
! Description
|-
| +0
| long[5]
| Always(?) 0x1C000000, 0x80000002, 0x10000, 0, 0
|-
| +20
| long
| Points to three longs of... something. The start of the mystery table.
|-
| +24
| long
| Points to three pointers in the mystery table. Two go to pointers to subroutines in the funcpointer table, the third goes back to the deptable descriptor.
|}


Entry in the deptable:
== Recognition ==
{| class="wikitable"
! Offset
! Type
! Description
|-
| +0
| short[2]
| Always(?) 0x2C00, 1
|-
| +4
| short
| Flags? 0x1 is always set, 0x8 often, 0x2000 seems to indicate a non-PRX library (like "stdc" or "allocator") that comes from somewhere else (LV2?)
|-
| +6
| short
| The number of functions the depending PRX needs from the depended PRX. There's this many entries in the Mystery Table for that PRX, and there is this many function pointers in the stubtable (see below).
|-
| +8
| short
| Usually 0, but "paf" gets sometimes 5, sometimes 6. More flags maybe?
|-
| +10
| short[3]
| Always(?) 0. Probably for alignment.
|-
| +16
| long
| Pointer to the ASCII string of the depended PRX's name. These don't seem to consistently map with the PRX's file name in dev_flash.
|-
| +20
| long
| Pointer to this library's entries in the mystery table.
|-
| +24
| long
| Pointer to the the pointers to function stubs for this library in the stubtable.
|-
| +28
| long[2]
| 0, 0 for every PRX except paf, which gets two more sets in the mystery table, pointed to by these. I suspect that +8 is somehow connected to this.
|}


Second LOAD segment 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).
A PRX module is PRX2 format only if ehdr.e_type is ET_SCE_EXEC or ET_SCE_RELEXEC.
 
A Program Segment is PRX2 format only if p_type is PT_SCE_RELA or PT_SCE_COMMENT.
 
= Module Info =
 
PS3 and PSP PRX embed Module Info version 0.
 
== Location ==
 
For PS3 (?and PSP?), it is located in text segment (first LOAD segment) at offset Elf32_Phdrs[text_seg_id].p_paddr - Elf32_Phdrs[text_seg_id].p_offset. Or more simply: at offset Elf32_Phdrs[text_seg_id].p_paddr in the ELF file.
 
== Structure ==
 
<source lang="C">
#define MODULE_NAME_MAX_LEN 27
 
typedef struct sceModuleInfo_common { // size is 0x20
  unsigned short modattr;
  unsigned char modver[2];
  char modname[MODULE_NAME_MAX_LEN];
  unsigned char infover;
} sceModuleInfo_common;
 
typedef struct sceModuleInfo_v0 { // size is 0x34
  sceModuleInfo_common c;
  Elf32_Addr gp_value;
  Elf32_Addr libent_top;
  Elf32_Addr libent_btm;
  Elf32_Addr libstub_top;
  Elf32_Addr libstub_btm;
} sceModuleInfo_v0;
</source>
 
= Exports =
 
PS3 uses exports structure of size 0x1C ?or 0x28 in 64bits?.
 
<source lang="C">
typedef struct _scelibent_common { // size is 0x10
unsigned char size;
unsigned char auxattribute;
unsigned short version;
unsigned short attribute;
unsigned short nfunc;
unsigned short nvar;
unsigned short ntls;
unsigned char hashinfo;
unsigned char hashinfotls;
unsigned char reserved;
unsigned char nidaltsets;
} sceKernelLibraryEntryTable_common;
 
typedef struct _scelibent_1C { // size is 0x1C
sceKernelLibraryEntryTable_common c;
Elf32_Addr libname;
Elf32_Addr nid_table;
Elf32_Addr entry_table;
} sceKernelLibraryEntryTable_1C;
</source>
 
= Imports =
 
PS3 use imports structures of size 0x2C.
 
<source lang="C">
typedef struct _scelibstub_common { // size is 0xC
unsigned short size;
unsigned short version;
unsigned short attribute;
unsigned short nfunc;
unsigned short nvar;
unsigned short ntls;
} sceKernelLibraryStubTable_common;
 
typedef struct _scelibstub_2C { // size is 0x2C
sceKernelLibraryStubTable_common c;
unsigned char reserved[4];
Elf32_Addr libname;
Elf32_Addr func_nid_table;
Elf32_Addr func_entry_table;
Elf32_Addr var_nid_table;
Elf32_Addr var_entry_table;
Elf32_Addr tls_nid_table;
Elf32_Addr tls_entry_table;
} sceKernelLibraryStubTable_2C;
</source>
 
= Relocations =
 
== PS3 ==
 
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 PRXs but it is currently unknown what it is used for.
 
 
 
{{File Formats}}
<noinclude>[[Category:Main]]</noinclude>

Latest revision as of 22:05, 19 January 2020

Overview[edit | edit source]

Playstation Relocatable Executable (PRX)

PRX2[edit | edit source]

PRX2 is only present on PSVita. PSP and PS3 use PRX version 1.

Recognition[edit | edit source]

A PRX module is PRX2 format only if ehdr.e_type is ET_SCE_EXEC or ET_SCE_RELEXEC.

A Program Segment is PRX2 format only if p_type is PT_SCE_RELA or PT_SCE_COMMENT.

Module Info[edit | edit source]

PS3 and PSP PRX embed Module Info version 0.

Location[edit | edit source]

For PS3 (?and PSP?), it is located in text segment (first LOAD segment) at offset Elf32_Phdrs[text_seg_id].p_paddr - Elf32_Phdrs[text_seg_id].p_offset. Or more simply: at offset Elf32_Phdrs[text_seg_id].p_paddr in the ELF file.

Structure[edit | edit source]

#define MODULE_NAME_MAX_LEN 27

typedef struct sceModuleInfo_common { // size is 0x20
  unsigned short modattr;
  unsigned char modver[2];
  char modname[MODULE_NAME_MAX_LEN];
  unsigned char infover;
} sceModuleInfo_common;

typedef struct sceModuleInfo_v0 { // size is 0x34
  sceModuleInfo_common c;
  Elf32_Addr gp_value;
  Elf32_Addr libent_top;
  Elf32_Addr libent_btm;
  Elf32_Addr libstub_top;
  Elf32_Addr libstub_btm;
} sceModuleInfo_v0;

Exports[edit | edit source]

PS3 uses exports structure of size 0x1C ?or 0x28 in 64bits?. 

typedef struct _scelibent_common { // size is 0x10
	unsigned char size;
	unsigned char auxattribute;
	unsigned short version;
	unsigned short attribute;
	unsigned short nfunc;
	unsigned short nvar;
	unsigned short ntls;
	unsigned char hashinfo;
	unsigned char hashinfotls;
	unsigned char reserved;
	unsigned char nidaltsets;
} sceKernelLibraryEntryTable_common;

typedef struct _scelibent_1C { // size is 0x1C
	sceKernelLibraryEntryTable_common c;
	Elf32_Addr libname;
	Elf32_Addr nid_table;
	Elf32_Addr entry_table;
} sceKernelLibraryEntryTable_1C;

Imports[edit | edit source]

PS3 use imports structures of size 0x2C. 

typedef struct _scelibstub_common { // size is 0xC
	unsigned short size;
	unsigned short version;
	unsigned short attribute;
	unsigned short nfunc;
	unsigned short nvar;
	unsigned short ntls;
} sceKernelLibraryStubTable_common;

typedef struct _scelibstub_2C { // size is 0x2C
	sceKernelLibraryStubTable_common c;
	unsigned char reserved[4];
	Elf32_Addr libname;
	Elf32_Addr func_nid_table;
	Elf32_Addr func_entry_table;
	Elf32_Addr var_nid_table;
	Elf32_Addr var_entry_table;
	Elf32_Addr tls_nid_table;
	Elf32_Addr tls_entry_table;
} sceKernelLibraryStubTable_2C;

Relocations[edit | edit source]

PS3[edit | edit source]

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 PRXs but it is currently unknown what it is used for.


SCE File Types
Certified File
NPDRM
NPDRM · App Types · ACT.DAT · RIF
PKG
EDAT
RCOXML
CXML
XMBML
XMB Config
DB Config
Databases
System Data
XMB Preload
Licences
 ·
Games/Apps
PS3
Emulators
Web
Unsorted
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