linux-kernel - [PATCH v2 09/10] riscv: Initialize thread pointer before calling C functions

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Date:   Wed, 29 Sep 2021 16:51:12 +0200
From:   Alexandre Ghiti <alexandre.ghiti@...onical.com>
To:     Jonathan Corbet <corbet@....net>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        Zong Li <zong.li@...ive.com>, Anup Patel <anup@...infault.org>,
        Atish Patra <Atish.Patra@....com>,
        Christoph Hellwig <hch@....de>,
        Andrey Ryabinin <ryabinin.a.a@...il.com>,
        Alexander Potapenko <glider@...gle.com>,
        Andrey Konovalov <andreyknvl@...il.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Ard Biesheuvel <ardb@...nel.org>,
        Arnd Bergmann <arnd@...db.de>,
        Kees Cook <keescook@...omium.org>,
        Guo Ren <guoren@...ux.alibaba.com>,
        Heinrich Schuchardt <heinrich.schuchardt@...onical.com>,
        Mayuresh Chitale <mchitale@...tanamicro.com>,
        linux-doc@...r.kernel.org, linux-riscv@...ts.infradead.org,
        linux-kernel@...r.kernel.org, kasan-dev@...glegroups.com,
        linux-efi@...r.kernel.org, linux-arch@...r.kernel.org
Cc:     Alexandre Ghiti <alexandre.ghiti@...onical.com>
Subject: [PATCH v2 09/10] riscv: Initialize thread pointer before calling C functions

Because of the stack canary feature that reads from the current task
structure the stack canary value, the thread pointer register "tp" must
be set before calling any C function from head.S: by chance, setup_vm
and all the functions that it calls does not seem to be part of the
functions where the canary check is done, but in the following commits,
some functions will.

Fixes: f2c9699f65557a31 ("riscv: Add STACKPROTECTOR supported")
Signed-off-by: Alexandre Ghiti <alexandre.ghiti@...onical.com>
---
 arch/riscv/kernel/head.S | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/riscv/kernel/head.S b/arch/riscv/kernel/head.S
index 8f21ef339c68..892a25c6079d 100644
--- a/arch/riscv/kernel/head.S
+++ b/arch/riscv/kernel/head.S
@@ -301,6 +301,7 @@ clear_bss_done:
 	REG_S a0, (a2)
 
 	/* Initialize page tables and relocate to virtual addresses */
+	la tp, init_task
 	la sp, init_thread_union + THREAD_SIZE
 	XIP_FIXUP_OFFSET sp
 #ifdef CONFIG_BUILTIN_DTB
-- 
2.30.2