Re: [PATCH V2 0/2] riscv: stack: Fixup independent softirq/irq stack for CONFIG_FRAME_POINTER=n

[Drew Fustini]

On Sat, Jul 15, 2023 at 08:15:04PM -0400, guoren@xxxxxxxxxx wrote:
> From: Guo Ren <guoren@xxxxxxxxxxxxxxxxx>
> 
> The independent softirq/irq stack uses s0 to save & restore sp, but s0
> would be corrupted when CONFIG_FRAME_POINTER=n. So add s0 in the clobber
> list to fix the problem.
> 
> <+0>:     addi    sp,sp,-32
> <+2>:     sd      s0,16(sp)
> <+4>:     sd      s1,8(sp)
> <+6>:     sd      ra,24(sp)
> <+8>:     sd      s2,0(sp)
> <+10>:    mv      s0,a0		--> compiler allocate s0 for a0 when CONFIG_FRAME_POINTER=n
> <+12>:    jal     ra,0xffffffff800bc0ce <irqentry_enter>
> <+16>:    ld      a5,56(tp) # 0x38
> <+20>:    lui     a4,0x4
> <+22>:    mv      s1,a0
> <+24>:    xor     a5,a5,sp
> <+28>:    bgeu    a5,a4,0xffffffff800bc092 <do_irq+88>
> <+32>:    auipc   s2,0x5d
> <+36>:    ld      s2,1118(s2) # 0xffffffff801194b8 <irq_stack_ptr>
> <+40>:    add     s2,s2,a4
> <+42>:    addi    sp,sp,-8
> <+44>:    sd      ra,0(sp)
> <+46>:    addi    sp,sp,-8
> <+48>:    sd      s0,0(sp)
> <+50>:    addi    s0,sp,16	--> our code clobber the s0
> <+52>:    mv      sp,s2
> <+54>:    mv      a0,s0		--> a0 got wrong value for handle_riscv_irq 
> <+56>:    jal     ra,0xffffffff800bbb3a <handle_riscv_irq>
> 
> Changelog:
> V2
>  - Fixup compile error with CONFIG_FRAME_POINTER=y
>  - FIxup stable@xxxxxxxxxxxxxxx tag
> 
> Guo Ren (2):
>   riscv: stack: Fixup independent irq stack for CONFIG_FRAME_POINTER=n
>   riscv: stack: Fixup independent softirq stack for
>     CONFIG_FRAME_POINTER=n
> 
>  arch/riscv/kernel/irq.c   | 3 +++
>  arch/riscv/kernel/traps.c | 3 +++
>  2 files changed, 6 insertions(+)
> 
> -- 
> 2.36.1
> 
> 
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Tested-by: Drew Fustini <dfustini@xxxxxxxxxxxx>

Xi Ruoyao noticed that the mainline kernel crashed when using a kernel
config with CONFIG_FRAME_POINTER=n. I was able to reproduce this [1].
Emil suggested I trying this patche series. I can confirm that this
resolves the kernel crash on the Sipeed Lichee Pi4a [2].

Thanks,
Drew

[1] https://lore.kernel.org/linux-riscv/ZMNojqwLxcG8FcHN@x1/
[2] https://lore.kernel.org/linux-riscv/ZMQAqUfb0y%2FigQs2@x1/