Well, there's a bug I noticed in this patch, $1 is restored from the
wrong location.
I'm not sure $1 ($at) needs to be restored at all, really. I guess make
this a RFC.
-corey
On 09/16/2014 04:45 PM, minyard@xxxxxxx wrote:
> From: Corey Minyard <cminyard@xxxxxxxxxx>
>
> The MIPS frame save code was just saving a few registers, enough to
> do a backtrace if every function set up a frame. However, this is
> not working if you are using DWARF unwinding, because most of the
> registers are wrong. This was causing kdump backtraces to be short
> or bogus.
>
> So save all the registers.
>
> Signed-off-by: Corey Minyard <cminyard@xxxxxxxxxx>
> ---
> arch/mips/include/asm/stacktrace.h | 64 +++++++++++++++++++++++++++++---------
> 1 file changed, 50 insertions(+), 14 deletions(-)
>
> diff --git a/arch/mips/include/asm/stacktrace.h b/arch/mips/include/asm/stacktrace.h
> index 780ee2c..05a2195 100644
> --- a/arch/mips/include/asm/stacktrace.h
> +++ b/arch/mips/include/asm/stacktrace.h
> @@ -2,6 +2,8 @@
> #define _ASM_STACKTRACE_H
>
> #include <asm/ptrace.h>
> +#include <asm/asm.h>
> +#include <linux/stringify.h>
>
> #ifdef CONFIG_KALLSYMS
> extern int raw_show_trace;
> @@ -20,6 +22,14 @@ static inline unsigned long unwind_stack(struct task_struct *task,
> }
> #endif
>
> +#define STR_PTR_LA __stringify(PTR_LA)
> +#define STR_LONG_S __stringify(LONG_S)
> +#define STR_LONG_L __stringify(LONG_L)
> +#define STR_LONGSIZE __stringify(LONGSIZE)
> +
> +#define STORE_ONE_REG(r) \
> + STR_LONG_S " $" __stringify(r)",("STR_LONGSIZE"*"__stringify(r)")(%1)\n\t"
> +
> static __always_inline void prepare_frametrace(struct pt_regs *regs)
> {
> #ifndef CONFIG_KALLSYMS
> @@ -32,21 +42,47 @@ static __always_inline void prepare_frametrace(struct pt_regs *regs)
> __asm__ __volatile__(
> ".set push\n\t"
> ".set noat\n\t"
> -#ifdef CONFIG_64BIT
> - "1: dla $1, 1b\n\t"
> - "sd $1, %0\n\t"
> - "sd $29, %1\n\t"
> - "sd $31, %2\n\t"
> -#else
> - "1: la $1, 1b\n\t"
> - "sw $1, %0\n\t"
> - "sw $29, %1\n\t"
> - "sw $31, %2\n\t"
> -#endif
> + /* Store $1 so we can use it */
> + STR_LONG_S " $1,"STR_LONGSIZE"(%1)\n\t"
> + /* Store the PC */
> + "1: " STR_PTR_LA " $1, 1b\n\t"
> + STR_LONG_S " $1,%0\n\t"
> + STORE_ONE_REG(2)
> + STORE_ONE_REG(3)
> + STORE_ONE_REG(4)
> + STORE_ONE_REG(5)
> + STORE_ONE_REG(6)
> + STORE_ONE_REG(7)
> + STORE_ONE_REG(8)
> + STORE_ONE_REG(9)
> + STORE_ONE_REG(10)
> + STORE_ONE_REG(11)
> + STORE_ONE_REG(12)
> + STORE_ONE_REG(13)
> + STORE_ONE_REG(14)
> + STORE_ONE_REG(15)
> + STORE_ONE_REG(16)
> + STORE_ONE_REG(17)
> + STORE_ONE_REG(18)
> + STORE_ONE_REG(19)
> + STORE_ONE_REG(20)
> + STORE_ONE_REG(21)
> + STORE_ONE_REG(22)
> + STORE_ONE_REG(23)
> + STORE_ONE_REG(24)
> + STORE_ONE_REG(25)
> + STORE_ONE_REG(26)
> + STORE_ONE_REG(27)
> + STORE_ONE_REG(28)
> + STORE_ONE_REG(29)
> + STORE_ONE_REG(30)
> + STORE_ONE_REG(31)
> + /* Restore $1 */
> + STR_LONG_L " $1,(%1)\n\t"
> ".set pop\n\t"
> - : "=m" (regs->cp0_epc),
> - "=m" (regs->regs[29]), "=m" (regs->regs[31])
> - : : "memory");
> + : "=m" (regs->cp0_epc)
> + : "r" (regs->regs)
> + : "memory");
> }
>
> #endif /* _ASM_STACKTRACE_H */
