Hey Andy On Fri, Feb 24, 2023 at 05:01:15PM +0000, Andy Chiu wrote: > From: Greentime Hu <greentime.hu@xxxxxxxxxx> > > Early function calls, such as setup_vm, relocate_enable_mmu, Here, and elsewhere in the series, please append the () to functions in commit text. > soc_early_init etc, are free to operate on stack. However, > PT_SIZE_ON_STACK bytes at the head of the kernel stack are purposedly > reserved for the placement of per-task register context pointed by > task_pt_regs(p). Those functions may corrupt task_pt_regs if we overlap > the $sp with it. In fact, we had accidentally corrupted sstatus.VS in some > tests, treating the kernel to save V context before V was actually > allocated, resulting in a kernel panic. > > Thus, we should skip PT_SIZE_ON_STACK for $sp before making C function > calls from the top-level assembly. > > Co-developed-by: ShihPo Hung <shihpo.hung@xxxxxxxxxx> > Signed-off-by: ShihPo Hung <shihpo.hung@xxxxxxxxxx> > Co-developed-by: Vincent Chen <vincent.chen@xxxxxxxxxx> > Signed-off-by: Vincent Chen <vincent.chen@xxxxxxxxxx> > Signed-off-by: Greentime Hu <greentime.hu@xxxxxxxxxx> > Signed-off-by: Andy Chiu <andy.chiu@xxxxxxxxxx> > --- > arch/riscv/kernel/head.S | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/arch/riscv/kernel/head.S b/arch/riscv/kernel/head.S > index e16bb2185d55..11c3b94c4534 100644 > --- a/arch/riscv/kernel/head.S > +++ b/arch/riscv/kernel/head.S > @@ -301,6 +301,7 @@ clear_bss_done: > la tp, init_task > la sp, init_thread_union + THREAD_SIZE > XIP_FIXUP_OFFSET sp > + addi sp, sp, -PT_SIZE_ON_STACK > #ifdef CONFIG_BUILTIN_DTB > la a0, __dtb_start > XIP_FIXUP_OFFSET a0 > @@ -318,6 +319,7 @@ clear_bss_done: > /* Restore C environment */ > la tp, init_task > la sp, init_thread_union + THREAD_SIZE > + addi sp, sp, -PT_SIZE_ON_STACK Reviewed-by: Conor Dooley <conor.dooley@xxxxxxxxxxxxx>
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