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= Overview =
scetool can decrypt SPRX's, producing an ELF... or is it? Not really. It has an ELF header but...


'''P'''laystation '''R'''elocatable E'''x'''ecutable (PRX)
First LOAD section, paddr points to what I'll call the module descriptor.


= PRX2 =
Second LOAD section starts off with a list of the entry points for all the exposed functions and then some (more on that later). The remainder is garbage/padding.


PRX2 is only present on PSVita. PSP and PS3 use PRX version 1.
NOTE: All addresses inside the file assume the ELF header isn't there (basically add 0xE0 to all addresses.)


== Recognition ==
{|
! Offset
! Type
! Description
|-
| +0
| long
| flags? Always 0x101
|-
| +4
| char[always 16?]
| Name of the module as a null-terminated string.
|-
| +20
| long
| ????? Perhaps a unique module ID?
|-
| +24
| long
| Points to start of symbol table header
|-
| +28
| long
| Points to end of symbol table header
|-
| +32
| long
| Points to start of first symbol defn
|-
| +36
| long
| points to end of last symbol defn
|}


A PRX module is PRX2 format only if ehdr.e_type is ET_SCE_EXEC or ET_SCE_RELEXEC.
Symbol table header:
{|
! Offset
! Type
! Description
|-
| +0
| long[4]
| ?????
|-
| +16
| quad or maybe a long preceded by zeroes?
| Appears to point to a table of something crypto-looking... definitely intended to be an array of longs. The whole library gets six, and then each function gets ????? it varies. This pointer points to the first three.
|-
| +24
| long
| ...and this points to the second three.
|}


A Program Segment is PRX2 format only if p_type is PT_SCE_RELA or PT_SCE_COMMENT.
Symbol defn:
{|
! Offset
! Type
! Description
|-
| +0
| quad
| Always zeroes
|-
| +8
| long
| Always(?) 0x2C000001
|-
| +12
| long
| ????? Probably flags...
|-
| +16
| long
| ????? Usually 0, but "paf" gets 0x60000 instead.
|-
| +20
| (quad or maybe a long preceded by zeroes?)
| Pointer to the name of the function! As a null/terminated ASCII string.
|-
| +28
| long
| Pointer to this function's section of the Big Mystery Table. The values are always big and always in ascending order... very odd.
|-
| +32
| long
| Pointer to the (long) pointer (in the second LOAD section) to the entry point of this function!
|-
| +36
| long[2]
| Appears to be for overflow for the Big Mystery Table. Zeroes if not needed.
|}


= Module Info =


PS3 and PSP PRX embed Module Info version 0.
Two functions are ALWAYS present: "paf" and "SysPrxForUser". What do they do? Not sure. They are real functions with legitimate entry points, so they can't be some kind of metadata. Hm.
 
== 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.
 
 
 
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