Need help implementing text_patch for JUMP_LABEL

Need help implementing text_patch for JUMP_LABEL

[Miao Chen]

Hi,

As part of my participation in GSOC, I am currently working on
implementing the jump_label mechanism for OpenRISC. I have already
implemented the basic functionality of jump_label, but when working on
the arch_jump_label_transform_queue function, I need to perform
instruction replacement and writing. In the implementations for the
ARM64 architecture [1] and RISC-V architecture [2], this is achieved
using text_patch [3].

By the way, ftrace also relies on this functionality for writing
instructions [4].

However, after reviewing the OpenRISC architecture code, I found that
the text_patch functionality is missing. Since you previously worked
on ftrace, I wanted to ask if you have already made progress on the
text_patch part? If not, I might start working on it myself.

Best regards,
Chen Miao

[1] https://github.com/torvalds/linux/blob/a5806cd506af5a7c19bcd596e4708b5c464bfd21/arch/arm64/kernel/jump_label.c#L28
[2] https://github.com/torvalds/linux/blob/a5806cd506af5a7c19bcd596e4708b5c464bfd21/arch/riscv/kernel/jump_label.c#L45
[3] https://github.com/torvalds/linux/blob/master/arch/riscv/include/asm/text-patching.h
[4] https://github.com/torvalds/linux/blob/a5806cd506af5a7c19bcd596e4708b5c464bfd21/arch/riscv/kernel/ftrace.c#L91

Re: Need help implementing text_patch for JUMP_LABEL

[Sahil Siddiq]

Hi,

On 5/20/25 1:08 PM, Miao Chen wrote:
> As part of my participation in GSOC, I am currently working on
> implementing the jump_label mechanism for OpenRISC. I have already
> implemented the basic functionality of jump_label, but when working on
> the arch_jump_label_transform_queue function, I need to perform
> instruction replacement and writing. In the implementations for the
> ARM64 architecture [1] and RISC-V architecture [2], this is achieved
> using text_patch [3].
> 
> By the way, ftrace also relies on this functionality for writing
> instructions [4].
> 
> However, after reviewing the OpenRISC architecture code, I found that
> the text_patch functionality is missing. Since you previously worked
> on ftrace, I wanted to ask if you have already made progress on the
> text_patch part? If not, I might start working on it myself.
> 

I haven't started implementing ftrace for OpenRISC. In my previous email
thread [1] with Stafford, we had decided to focus on implementing data
sources (e.g. kprobes, uprobes, etc.) first before moving to data consumers
such as ftrace.

Feel free to start working on implementing text_patch.

Thanks,
Sahil

[1] https://lore.kernel.org/openrisc/51b89c55-ee58-461d-a2a0-5c8dd8ba77e7@gmail.com/T/#m196b35b073dc133522a49a7a31caa5dd16cc0187