riscv: Initialize thread pointer before calling C functions

stable inclusion
from stable-v5.10.121
commit 4a5c7a61ff506a7cc385cd952038183a2d095880
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I5L6CQ

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=4a5c7a61ff506a7cc385cd952038183a2d095880

--------------------------------

commit 35d33c76 upstream.

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: f2c9699f ("riscv: Add STACKPROTECTOR supported")
Signed-off-by: NAlexandre Ghiti <alexandre.ghiti@canonical.com>
Cc: stable@vger.kernel.org
Signed-off-by: NPalmer Dabbelt <palmer@rivosinc.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>
Acked-by: NXie XiuQi <xiexiuqi@huawei.com>

arch/riscv/kernel/head.S

@@ -261,6 +261,7 @@ 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
 	mv a0, s1
 	call setup_vm