[PATCH -next v17 14/20] riscv: signal: Report signal frame size to userspace via auxv

[Heiko Stübner]

Am Montag, 27. März 2023, 18:49:34 CEST schrieb Andy Chiu:
> From: Vincent Chen <vincent.chen at sifive.com>
> 
> The vector register belongs to the signal context. They need to be stored
> and restored as entering and leaving the signal handler. According to the
> V-extension specification, the maximum length of the vector registers can
> be 2^16. Hence, if userspace refers to the MINSIGSTKSZ to create a
> sigframe, it may not be enough. To resolve this problem, this patch refers
> to the commit 94b07c1f8c39c
> ("arm64: signal: Report signal frame size to userspace via auxv") to enable
> userspace to know the minimum required sigframe size through the auxiliary
> vector and use it to allocate enough memory for signal context.
> 
> Note that auxv always reports size of the sigframe as if V exists for
> all starting processes, whenever the kernel has CONFIG_RISCV_ISA_V. The
> reason is that users usually reference this value to allocate an
> alternative signal stack, and the user may use V anytime. So the user
> must reserve a space for V-context in sigframe in case that the signal
> handler invokes after the kernel allocating V.
> 
> Signed-off-by: Greentime Hu <greentime.hu at sifive.com>
> Signed-off-by: Vincent Chen <vincent.chen at sifive.com>
> Signed-off-by: Andy Chiu <andy.chiu at sifive.com>
> Acked-by: Conor Dooley <conor.dooley at microchip.com>
> Reviewed-by: Björn Töpel <bjorn at rivosinc.com>
> Reviewed-by: Guo Ren <guoren at kernel.org>

Reviewed-by: Heiko Stuebner <heiko.stuebner at vrull.eu>
Tested-by: Heiko Stuebner <heiko.stuebner at vrull.eu>