linux-kernel - Re: [PATCH v2 2/5] LoongArch: Use la.pcrel instead of la.abs for exception handlers

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Date:   Tue, 07 Feb 2023 22:39:39 +0800
From:   Xi Ruoyao <xry111@...111.site>
To:     Youling Tang <tangyouling@...ngson.cn>,
        Huacai Chen <chenhuacai@...nel.org>,
        Jinyang He <hejinyang@...ngson.cn>
Cc:     Xuerui Wang <kernel@...0n.name>, loongarch@...ts.linux.dev,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/5] LoongArch: Use la.pcrel instead of la.abs for
 exception handlers

On Tue, 2023-02-07 at 22:28 +0800, Xi Ruoyao wrote:
> +struct handler_reloc *eentry_reloc[128] = {
> +       [0] = NULL, /* merr handler */

Self review:

This is actually incorrect.  Currently the merr handler (except_vec_cex)
is coded as:

SYM_FUNC_START(except_vec_cex)
        b       cache_parity_error
SYM_FUNC_END(except_vec_cex)

Once this is copied into the per-cpu handler page, the offset (coded in
the b instruction) will be absolutely wrong.  But it's already incorrect
in the current mainline, and I'm not familiar with CSR.CRMD.DA=1
configuration so I'm not sure how to fix it.

-- 
Xi Ruoyao <xry111@...111.site>
School of Aerospace Science and Technology, Xidian University