CreateTask patch doesn't work

alvm

123

« on: 08 / October / 2014, 11:06:32 »

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Hi,

Does CreateTask patch work if hook_CreateTask() is placed at ROM?

Thanks,
Alex.

« Last Edit: 08 / October / 2014, 11:08:58 by alvm »

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srsa_4c

4451

Re: CreateTask patch doesn't work

« Reply #1 on: 08 / October / 2014, 13:13:07 »

Quote from: alvm on 08 / October / 2014, 11:06:32

Does CreateTask patch work if hook_CreateTask() is placed at ROM?

I suppose you mean this code snippet:

Code: [Select]

// Install CreateTask patch
"    LDR     R0, =patch_CreateTask\n"   // Patch data
"    LDM     R0, {R1,R2}\n"             // Get two patch instructions
"    LDR     R0, =hook_CreateTask\n"    // Address to patch
"    STM     R0, {R1,R2}\n"             // Store patch instructions

You can't write to the flash ROM directly (and you surely don't want to break the firmware like that), so the answer is no.

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alvm

123

Re: CreateTask patch doesn't work

« Reply #2 on: 09 / October / 2014, 07:38:51 »

Yes, you are right I mean this code. Thanks.

CreateTask() function in SX400 is placed in ROM. So how to create hook for it? Using old hook method like
*(int*)0x1938 = (int)taskCreateHook is not successful.

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srsa_4c

4451

Re: CreateTask patch doesn't work

« Reply #3 on: 09 / October / 2014, 10:48:14 »

Quote from: alvm on 09 / October / 2014, 07:38:51

Yes, you are right I mean this code. Thanks.

CreateTask() function in SX400 is placed in ROM. So how to create hook for it? Using old hook method like
*(int*)0x1938 = (int)taskCreateHook is not successful.

In that case your best choice is to "dig down" to the routines that start the tasks you'd like to replace - as it was done in the first DryOS ports. Can you share the fw dump?

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alvm

123

Re: CreateTask patch doesn't work

« Reply #4 on: 10 / October / 2014, 07:59:33 »

Quote from: srsa_4c on 09 / October / 2014, 10:48:14

Can you share the fw dump?

Yes, sure:

http://chdk.setepontos.com/index.php?topic=11973.0

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srsa_4c

4451

Re: CreateTask patch doesn't work

« Reply #5 on: 10 / October / 2014, 13:04:39 »

Quote from: alvm on 10 / October / 2014, 07:59:33

http://chdk.setepontos.com/index.php?topic=11973.0

Thanks. Fortunately, the DryOS r55+p6 kernel is still located in RAM.
Even though CreateTask() got put back into ROM, you still have the possibility to patch its low level function (let's call it CreateTask_low for example), because that is still in RAM.
CreateTask (0xff824a2c) calls CreateTask_low (0x6b15a4) @ 0xff824abc. Note that the low level function has different arguments and return value, but you'll still be able to replace the task function's pointer.

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