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


First LOAD section, paddr points to what I'll call the module descriptor.
First LOAD segment, paddr points to the descriptor for the "dependency table" or "deptable" for short:
 
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.


NOTE: All addresses inside the file assume the ELF header isn't there (basically add 0xE0 to all addresses.)
NOTE: All addresses inside the file assume the ELF header isn't there (basically add 0xE0 to all addresses.)
Line 13: Line 11:
| +0
| +0
| long
| long
| flags? Always 0x101
| Always(?) 0x101
|-
|-
| +4
| +4
| char[always 16?]
| char[28]
| Name of the module as a null-terminated string.
| Name of this PRX, padded out with zeroes. Doesn't necessarily match the file name(why?)
|-
|-
| +20
| +32
| long
| long
| ????? Perhaps a unique module ID?
| A unique module ID? Gets used a lot later...
|-
|-
| +24
| +36
| long
| long
| Points to start of symbol table header
| Points to the deptable header
|-
|-
| +28
| +40
| long
| long
| Points to end of symbol table header
| Points to the END of the deptable header
|-
|-
| +32
| +44
| long
| long
| Points to start of first symbol defn
| Points to the start of first deptable entry
|-
|-
| +36
| +48
| long
| long
| points to end of last symbol defn
| points to the end of the LAST deptable entry
|}
|}


Symbol table header:
Deptable header:
{| class="wikitable"
{| class="wikitable"
! Offset
! Offset
Line 47: Line 45:
|-
|-
| +0
| +0
| long[4]
| long[5]
| ?????
| Always(?) 0x1C000000, 0x80000002, 0x10000, 0, 0
|-
|-
| +16
| +20
| quad or maybe a long preceded by zeroes?
| long
| Appears to point to a table of something crypto-looking... clearly in four-byte segments. The PRX as a whole gets six segments, and then each function gets ????? it varies. This pointer points to the first three.
| Points to three longs of... something. The start of the mystery table.
|-
|-
| +24
| +24
| long
| long
| ...and this points to the second three.
| 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.
|}
|}


Symbol defn:
Entry in the deptable:
{| class="wikitable"
{| class="wikitable"
! Offset
! Offset
Line 66: Line 64:
|-
|-
| +0
| +0
| quad
| short[2]
| Always zeroes
| 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
| +8
| long
| short
| Always(?) 0x2C000001
| Usually 0, but "paf" gets sometimes 5, sometimes 6. More flags maybe?
|-
|-
| +12
| +10
| long
| short[3]
| ????? Probably flags...
| Always(?) 0. Probably for alignment.
|-
|-
| +16
| +16
| long
| long
| ????? Usually 0, but "paf" gets 0x60000 instead.
| 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
| +20
| (quad or maybe a long preceded by zeroes?)
| Pointer to the name of the function! As a null/terminated ASCII string.
|-
| +28
| long
| long
| Pointer to this function's section of the Big Mystery Table. The values are always big and always in ascending order... very odd.
| Pointer to this library's entries in the mystery table.
|-
|-
| +32
| +24
| long
| long
| Pointer to the (long) pointer (in the second LOAD section) to the entry point of this function!
| Pointer to the the pointers to function stubs for this library in the stubtable.
|-
|-
| +36
| +28
| long[2]
| long[2]
| Appears to be for overflow for the Big Mystery Table. Zeroes if not needed.
| 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).
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.

Revision as of 11:12, 23 June 2013

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

First LOAD segment, paddr points to the descriptor for the "dependency table" or "deptable" for short:

NOTE: All addresses inside the file assume the ELF header isn't there (basically add 0xE0 to all addresses.)

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:

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:

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).

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