Returning data from a exported function...

[ne0h]

Hi,
I'm trying to return some data from a function exported from a kernel prx and imported to a user pbp, but it crash every time!
What's the problem?
This is the exported function:

Code: Select all

char* GetBarraInf(void)
{
    char* data="fdsfdsfds";
    return data;
}

And here I try to use it...

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printf("%s",GetBarraInf());

It doesn't work, no one character is printed to screen!
Crash every time!
What I'm trying to do is export a variable ( unsigned char ) that contains a image data ( builted with bin2o )!

[Pirata Nervo]

make sure you allocate pointers.
Also I always need pspSdkSetK1 when exporting functions otherwise it does not work for me

[ne0h]

mmm, is always needed to set K1 to 0? Is not only for "special" operations, or to remove some security protections?
Thanks!

[ne0h]

Doesn't work whit this! ?_?

Code: Select all

char* GetBarraInf(void)
{
    return "asd";
}

EDIT:
Get this exception:

Exception - Address load/inst fetch
EPC - 0889A07C
Location - ra.text + 0009607C
Cause - 10000010
Status - 20008613
BadVAddr - 88217A40

zr:00000000 at:2008FF00 v0:88217A41 v1:0889CB38
a0:88217A40 a1:0BBBFE44 a2:00000073 a3:0BBBFE40
t0:00000068 t1:0000002B t2:00000020 t3:88065244
t4:0BBBFE58 t5:00003E0C t6:0880A5FC t7:20008600
s0:00000000 s1:FFFFFFFF s2:0BBBF63C s3:0BBBF600
s4:08930000 s5:08930000 s6:088AB9E6 s7:08930000
t8:00000000 t9:00000000 k0:0BBBFF00 k1:00000000
gp:08939230 sp:0BBBF5D0 fp:88217A40 ra:0889D7C4

[Badboy_]

Code: Select all

char* GetBarraInf(void)
{
    char* data= (char*) malloc(20);
    strcpy(data, "Hello, world!");
    return data;
}

does this work?

[hlide]

*sigh*, noobish question again...

do you think making a local string in a function is making this string to be... local to this function, don't you ?

didn't it ever occur to you that adding "static" before the local string would turn it into a permanent static string you can return from your function ?

how many times do you think you need to master such a trivial error ?

well, don't answer.

EDIT:

a0:88217A40 <-- hernel address doesn't work with user code. Hint : #define USER_ADDR(x) ({ (typeof(x))(((int)(x))&~0x80000000); }) ==> return USER_ADDR("blahblah");

[ne0h]

Doesn't work!
Got the same exception:

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Exception - Address load/inst fetch
EPC       - 0889A07C
Location  - ra.text + 0009607C
Cause     - 10000010
Status    - 20008613
BadVAddr  - 8002013A

zr:00000000 at:00000000 v0:8002013B v1:0889CB38
a0:8002013A a1:0BBBFE44 a2:00000073 a3:0BBBFE40
t0:00000068 t1:0000002B t2:00000020 t3:88065244
t4:A8028454 t5:00003E0C t6:000000FC t7:880161C8
s0:00000000 s1:FFFFFFFF s2:0BBBF63C s3:0BBBF600
s4:08930000 s5:08930000 s6:088ABA06 s7:08930000
t8:00000000 t9:00000000 k0:0BBBFF00 k1:00000000
gp:08939250 sp:0BBBF5D0 fp:8002013A ra:0889D7C4

EDIT:
hlide, thanks, I'll try!

[hlide]

just look at registers, some registers have kernel addresses when you are running a user code...

[hlide]

replace 0x40000000 into 0x80000000 of course...

[ne0h]

Tryied with this:

Code: Select all

static char data[20];

char* GetBarraInf(void)
{
    k1 = pspSdkSetK1(0);
    strcpy(data, "Hello world!");
    pspSdkSetK1(k1);
    return data;
}

And it doesn't work, crash!
I've also tryied to make it a user prx but it crash!
Get the same exception:

Code: Select all

Exception - Address load/inst fetch
EPC       - 0889A07C
Location  - ra.text + 0009607C
Cause     - 10000010
Status    - 20008613
BadVAddr  - 8002013A

zr:00000000 at:00000000 v0:8002013B v1:0889CB38
a0:8002013A a1:0BBBFE44 a2:00000073 a3:0BBBFE40
t0:00000068 t1:0000002B t2:00000020 t3:88065244
t4:A8028454 t5:00003E0C t6:000000FC t7:880161C8
s0:00000000 s1:FFFFFFFF s2:0BBBF63C s3:0BBBF600
s4:08930000 s5:08930000 s6:088ABA06 s7:08930000
t8:00000000 t9:00000000 k0:0BBBFF00 k1:00000000
gp:08939250 sp:0BBBF5D0 fp:8002013A ra:0889D7C4

just look at registers, some registers have kernel addresses when you are running a user code...

Sorry, doesn't know what mean the content of registers!
Never studied it! ( Have you a tuto about the content of this? )
So kernel address are 0x80000000 like, and user 0x40000000 like this, right?

replace 0x40000000 into 0x80000000 of course...

Sorry, but I've to change the a0 reg value?
EDIT:

nop, maybe I've understand!

[hlide]

Code: Select all

char const * GetBarraInf(void)
{
    return (char const *)(((int)"blahblah")&~0x80000000));
}

[ne0h]

No, I haven't undestrand!
I've writed this:

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#define USER_ADDR(x) ({ (typeof(x))(((int)(x))&~0x80000000); })
    
char* GetBarraInf(void);
intraFontPrintf(ltn8, 20, 20, "%s", USER_ADDR(GetBarraInf()));

But it crash! Get Bus data error...

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Exception - Bus error (data)
EPC       - 0889A084
Location  - ra.text + 00096084
Cause     - 1000001C
Status    - 20008613
BadVAddr  - 01044400

zr:00000000 at:00000000 v0:0002013B v1:0889CB40
a0:0002013A a1:0BBBFE44 a2:00000073 a3:0BBBFE40
t0:00000068 t1:0000002B t2:00000020 t3:88065244
t4:A8028454 t5:00003E0C t6:000000FC t7:880161C8
s0:00000000 s1:FFFFFFFF s2:0BBBF63C s3:0BBBF600
s4:08930000 s5:08930000 s6:088ABA16 s7:08C80000
t8:00000000 t9:00000000 k0:0BBBFF00 k1:00000000
gp:08939260 sp:0BBBF5D0 fp:0002013A ra:0889D7CC

Now I haven't a kernel address, right?
Anyway I've another problem...

[ne0h]

oh my god! I got another kernel address! It crash...

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Exception - Address load/inst fetch
EPC       - 0889A068
Location  - ra.text + 00096068
Cause     - 10000010
Status    - 20008613
BadVAddr  - 8002013A

zr:00000000 at:00000000 v0:8002013B v1:0889CB24
a0:8002013A a1:0BBBFE44 a2:00000073 a3:0BBBFE40
t0:00000068 t1:0000002B t2:00000020 t3:88065244
t4:A8028454 t5:00003E0C t6:000000FC t7:880161C8
s0:00000000 s1:FFFFFFFF s2:0BBBF63C s3:0BBBF600
s4:08930000 s5:08930000 s6:088AB9E6 s7:08930000
t8:00000000 t9:00000000 k0:0BBBFF00 k1:00000000
gp:08939230 sp:0BBBF5D0 fp:8002013A ra:0889D7B0

I'm sorry...

This is the code now:

Code: Select all

static char data[20];

char const * GetBarraInf(void)
{
    strcpy(data, "Hello world!");
    return (char const *)(((int)data)&~0x80000000);
}

[hlide]

Look at BadVAddr values they are abnormal...

[ne0h]

hlide, a question:
EPC, Cause, Status and BadVAddr what means?
To work I've to change the variable addres?
But if I change the address the pointed memory is the same?
Or the kernel mode has a different mode to point a specified memory than the user mode?

[ne0h]

Wow... Finally resolved!

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static char* data = NULL;

char const * GetBarraInf(void)
{
    data = (char*)malloc(20);
    strcpy(data, "Hello World!");
    return (char const *)(((int)data)&~0x80000000); 
}

And before I've commented the loadmodule function, sorry! :(
But the 8002013A of
BadVAddr is == SCE_KERNEL_ERROR_LIBRARY_NOT_YET_LINKED ?

[hlide]

no wonder.

you don't need the malloc stuff. Just be sure the pointer is a user address.

[a_noob]

heh, im too late (please ignore)

[ne0h]

EPC, Cause and Status what means?

[ne0h]

hilde, if I doesn't use malloc it crash!
But the address is a user one...
Maybe I've do something wrong...

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static char* data = "hellooo!!";

char* GetBarraInf(void)
{
    return (char*)(((int)data)&~0x80000000); // USER_ADDR(data);
}

And in the main programm:

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char* GetBarraInf(void);
Init(); // pspDebugScreenInit
printf("%s", GetBarraInf()); // pspDebugScreenPrintf
sleep(2000000); // sceKernelDelayThread

The exception:

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Exception - Bus error (data)
EPC       - 0889A064
Location  - ra.text + 00096064
Cause     - 1000001C
Status    - 20008613
BadVAddr  - 01044410

zr:00000000 at:2008FF00 v0:0824E205 v1:0889CB20
a0:0824E204 a1:0BBBFE48 a2:00000073 a3:0BBBFE44
t0:00000068 t1:0000002B t2:00000020 t3:880E57F0
t4:0BBBFE60 t5:00001E04 t6:0880A4AC t7:20008600
s0:00000000 s1:FFFFFFFF s2:0BBBEF4C s3:0BBBEF10
s4:DEADBEEF s5:DEADBEEF s6:088AB9E6 s7:DEADBEEF
t8:880E5818 t9:00000028 k0:0BBBFF00 k1:00000000
gp:08939230 sp:0BBBEEE0 fp:0824E204 ra:0889D7AC

The problem is not the address I think!
But 0x0824E204 is a strange address, right?

[ne0h]

Work only with this:

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static char* data;

char* GetBarraInf(void)
{
    data = (char*)malloc(20);
    strcpy(data, "Hello World!!!");
    return (char*)(((int)data)&~0x80000000); // USER_ADDR(data);
}

But I can't do that, I've to return a unsiged char array...
( unsigned char data[]; <-- builted with bin2o )

[ne0h]

Resolved with this... but I have to use malloc! Without that it crash!
But I haven't found the malloc function in the kernel libc, where I can find it?
I'll built the prx with the kernel libs and libc to reduce its size!

[Pirata Nervo]

search these forums for a malloc function made by HellCat I think using the sce memory functions.

He made it exactly because kernel libc does not have it