[PATCH] riscv: additional crash information

[Sean Anderson]

On 7/29/20 4:36 PM, Heinrich Schuchardt wrote:
> If an exception occurs, the relocated program counter and return address
> are required for an analysis.

Thanks for putting together a patch for this. I realized after I added
the feature originally that I had left out RA from the default error
info, but I never got around to fixing it.

> 
> With this patch you get:
> 
>     => exception undefined
> 
>     Unhandled exception: Illegal instruction
>     EPC: 0000000080595908 RA: 000000008059c0c6 TVAL: 000000008030c01e
>     EPC: 0000000080007908 RA: 000000008000e0c6 reloc
> 
> We can use the relocated addresses to find the involved functions in
> u.boot.map:
> 
>     .text.do_undefined
>                 0x0000000080007908        0x8 cmd/built-in.o
>     .text.cmd_process
>                 0x000000008000dfcc      0x11a common/built-in.o
>                 0x000000008000dfcc                cmd_process
> 
> If an exception occurs in an UEFI binary additionally the load addresses of
> the UEFI binaries are needed. With this patch:
> 
>     => setenv efi_selftest exception
>     => bootefi selftest
> 
>     Unhandled exception: Illegal instruction
>     EPC: 000000008042e18a RA: 000000008042e18a TVAL: 000000008030c01e
>     EPC: 000000007fea018a RA: 000000007fea018a reloc
> 
>     UEFI image [0x0000000000000000:0xffffffffffffffff] '/\selftest'
>     UEFI image [0x000000008042e000:0x000000008042e43f] pc=0x18a '/bug.efi'
> 
> The value pc=0x18a matches the position of the illegal instruction in
> efi_selftest_miniapp_exception.efi (loaded as /bug.efi);
> 
>     asm volatile (".word 0xffffffff\n");
> 
>     00000180   93 85 C5 11  1C 64 22 85  82 97 FF FF  FF FF 1C 64
> 
> Signed-off-by: Heinrich Schuchardt <xypron.glpk at gmx.de>
> ---
>  arch/riscv/lib/interrupts.c | 57 +++++++++++++++++++++++--------------
>  1 file changed, 35 insertions(+), 22 deletions(-)
> 
> diff --git a/arch/riscv/lib/interrupts.c b/arch/riscv/lib/interrupts.c
> index 074c70ee77..bcdfc5ea3a 100644
> --- a/arch/riscv/lib/interrupts.c
> +++ b/arch/riscv/lib/interrupts.c
> @@ -10,36 +10,43 @@
>   */
> 
>  #include <common.h>
> +#include <efi_loader.h>
>  #include <hang.h>
>  #include <irq_func.h>
>  #include <asm/ptrace.h>
>  #include <asm/system.h>
>  #include <asm/encoding.h>
> 
> +DECLARE_GLOBAL_DATA_PTR;
> +
> +static void show_efi_loaded_images(uintptr_t epc)
> +{
> +	efi_print_image_infos((void *)epc);
> +}
> +
>  static void show_regs(struct pt_regs *regs)
>  {
>  #ifdef CONFIG_SHOW_REGS
> -	printf("RA: " REG_FMT " SP:  " REG_FMT " GP:  " REG_FMT "\n",
> -	       regs->ra, regs->sp, regs->gp);
> -	printf("TP: " REG_FMT " T0:  " REG_FMT " T1:  " REG_FMT "\n",
> -	       regs->tp, regs->t0, regs->t1);
> -	printf("T2: " REG_FMT " S0:  " REG_FMT " S1:  " REG_FMT "\n",
> -	       regs->t2, regs->s0, regs->s1);
> -	printf("A0: " REG_FMT " A1:  " REG_FMT " A2:  " REG_FMT "\n",
> -	       regs->a0, regs->a1, regs->a2);
> -	printf("A3: " REG_FMT " A4:  " REG_FMT " A5:  " REG_FMT "\n",
> -	       regs->a3, regs->a4, regs->a5);
> -	printf("A6: " REG_FMT " A7:  " REG_FMT " S2:  " REG_FMT "\n",
> -	       regs->a6, regs->a7, regs->s2);
> -	printf("S3: " REG_FMT " S4:  " REG_FMT " S5:  " REG_FMT "\n",
> -	       regs->s3, regs->s4, regs->s5);
> -	printf("S6: " REG_FMT " S7:  " REG_FMT " S8:  " REG_FMT "\n",
> -	       regs->s6, regs->s7, regs->s8);
> -	printf("S9: " REG_FMT " S10: " REG_FMT " S11: " REG_FMT "\n",
> -	       regs->s9, regs->s10, regs->s11);
> -	printf("T3: " REG_FMT " T4:  " REG_FMT " T5:  " REG_FMT "\n",
> -	       regs->t3, regs->t4, regs->t5);
> -	printf("T6: " REG_FMT "\n", regs->t6);
> +	printf("SP:  " REG_FMT " GP:  " REG_FMT " TP:  " REG_FMT "\n",
> +	       regs->sp, regs->gp, regs->tp);
> +	printf("T0:  " REG_FMT " T1:  " REG_FMT " T2:  " REG_FMT "\n",
> +	       regs->t0, regs->t1, regs->t2);
> +	printf("S0:  " REG_FMT " S1:  " REG_FMT " A0:  " REG_FMT "\n",
> +	       regs->s0, regs->s1, regs->a0);
> +	printf("A1:  " REG_FMT " A2:  " REG_FMT " A3:  " REG_FMT "\n",
> +	       regs->a1, regs->a2, regs->a3);
> +	printf("A4:  " REG_FMT " A5:  " REG_FMT " A6:  " REG_FMT "\n",
> +	       regs->a4, regs->a5, regs->a6);
> +	printf("A7:  " REG_FMT " S2:  " REG_FMT " S3:  " REG_FMT "\n",
> +	       regs->a7, regs->s2, regs->s3);
> +	printf("S4:  " REG_FMT " S5:  " REG_FMT " S6:  " REG_FMT "\n",
> +	       regs->s4, regs->s5, regs->s6);
> +	printf("S7:  " REG_FMT " S8:  " REG_FMT " S9:  " REG_FMT "\n",
> +	       regs->s7, regs->s8, regs->s9);
> +	printf("S10: " REG_FMT " S11: " REG_FMT " T3:  " REG_FMT "\n",
> +	       regs->s10, regs->s11, regs->t3);
> +	printf("T4:  " REG_FMT " T5:  " REG_FMT " T6:  " REG_FMT "\n\n",
> +	       regs->t4, regs->t5, regs->t6);
>  #endif
>  }
> 
> @@ -69,8 +76,14 @@ static void _exit_trap(ulong code, ulong epc, ulong tval, struct pt_regs *regs)
>  	else
>  		printf("Unhandled exception code: %ld\n", code);
> 
> -	printf("EPC: " REG_FMT " TVAL: " REG_FMT "\n", epc, tval);
> +	printf("EPC: " REG_FMT " RA: " REG_FMT " TVAL: " REG_FMT "\n",
> +	       epc, regs->ra, tval);
> +	if (gd->flags & GD_FLG_RELOC)
> +		printf("EPC: " REG_FMT " RA: " REG_FMT " reloc\n\n",

I'm not so sure about the wording of this last line. Perhaps we could
reword this to something like "EPC: ... RA: ... (adjusted for relocation
offset)"? That's a bit wordy for my taste, but I think it's less
ambiguous than what you have now.

> +		       epc - gd->reloc_off, regs->ra - gd->reloc_off);
> +
>  	show_regs(regs);
> +	show_efi_loaded_images(epc);
>  	hang();
>  }
> 
> --
> 2.27.0
> 

--Sean