Re: [PATCH v2] RISC-V: vDSO: Correct inline assembly constraints in the getrandom syscall wrapper

From: patchwork-bot+linux-riscv
Date: Thu Jun 12 2025 - 16:10:26 EST


Hello:

This patch was applied to riscv/linux.git (fixes)
by Palmer Dabbelt <palmer@xxxxxxxxxxx>:

On Fri, 6 Jun 2025 17:24:44 +0800 you wrote:
> As recently pointed out by Thomas, if a register is forced for two
> different register variables, among them one is used as "+" (both input
> and output) and another is only used as input, Clang would treat the
> conflicting input parameters as undefined behaviour and optimize away
> the argument assignment.
>
> Per an example in the GCC documentation, for this purpose we can use "="
> (only output) for the output, and "0" for the input for that we must
> reuse the same register as the output. And GCC developers have
> confirmed using a simple "r" (that we use for most vDSO implementations)
> instead of "0" is also fine.
>
> [...]

Here is the summary with links:
- [v2] RISC-V: vDSO: Correct inline assembly constraints in the getrandom syscall wrapper
https://git.kernel.org/riscv/c/2b9518684f85

You are awesome, thank you!
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