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SubjectRe: [PATCH 17/17] riscv: add nommu support
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On 6/10/19 11:16 PM, Christoph Hellwig wrote:
> Most of the patch is just stubbing out code not needed without page
> tables, but there is an interesting detail in the signals implementation:
>
> - The normal RISC-V syscall ABI only implements rt_sigreturn as VDSO
> entry point, but the ELF VDSO is not supported for nommu Linux.
> We instead copy the code to call the syscall onto the stack.

On ARM we perform I/D cache synchronization after stack manipulation.

OTOH, ARM port of uClibc provides SA_RESTORER with intention to avoid
manipulation with stack and cache maintenance operations (yet kernel
still performs such manipulation, IIUC, for backward compatibility)

Cheers
Vladimir

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