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SubjectRe: [PATCH v12 01/10] arm64: Add HAVE_REGS_AND_STACK_ACCESS_API feature
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On 27/04/16 19:52, David Long wrote:
> From: "David A. Long" <dave.long@linaro.org>
>
> Add HAVE_REGS_AND_STACK_ACCESS_API feature for arm64.

And clearly a lot more.

>
> Signed-off-by: David A. Long <dave.long@linaro.org>
> ---
> arch/arm64/Kconfig | 1 +
> arch/arm64/include/asm/ptrace.h | 33 ++++++++++-
> arch/arm64/kernel/ptrace.c | 118 ++++++++++++++++++++++++++++++++++++++++
> 3 files changed, 151 insertions(+), 1 deletion(-)
>
> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> index 4f43622..8f662fd 100644
> --- a/arch/arm64/Kconfig
> +++ b/arch/arm64/Kconfig
> @@ -80,6 +80,7 @@ config ARM64
> select HAVE_PERF_EVENTS
> select HAVE_PERF_REGS
> select HAVE_PERF_USER_STACK_DUMP
> + select HAVE_REGS_AND_STACK_ACCESS_API
> select HAVE_RCU_TABLE_FREE
> select HAVE_SYSCALL_TRACEPOINTS
> select IOMMU_DMA if IOMMU_SUPPORT
> diff --git a/arch/arm64/include/asm/ptrace.h b/arch/arm64/include/asm/ptrace.h
> index a307eb6..ee02637 100644
> --- a/arch/arm64/include/asm/ptrace.h
> +++ b/arch/arm64/include/asm/ptrace.h
> @@ -119,6 +119,8 @@ struct pt_regs {
> u64 syscallno;
> };
>
> +#define MAX_REG_OFFSET offsetof(struct pt_regs, pstate)
> +
> #define arch_has_single_step() (1)
>
> #ifdef CONFIG_COMPAT
> @@ -147,6 +149,35 @@ struct pt_regs {
> #define user_stack_pointer(regs) \
> (!compat_user_mode(regs) ? (regs)->sp : (regs)->compat_sp)
>
> +extern int regs_query_register_offset(const char *name);
> +extern const char *regs_query_register_name(unsigned int offset);
> +extern bool regs_within_kernel_stack(struct pt_regs *regs, unsigned long addr);
> +extern unsigned long regs_get_kernel_stack_nth(struct pt_regs *regs,
> + unsigned int n);
> +
> +/**
> + * regs_get_register() - get register value from its offset
> + * @regs: pt_regs from which register value is gotten
> + * @offset: offset number of the register.

Is it the offset? or the number?

> + *
> + * regs_get_register returns the value of a register whose offset from @regs.
> + * The @offset is the offset of the register in struct pt_regs.
> + * If @offset is bigger than MAX_REG_OFFSET, this returns 0.
> + */
> +static inline u64 regs_get_register(struct pt_regs *regs,
> + unsigned int offset)
> +{
> + if (unlikely(offset > MAX_REG_OFFSET))
> + return 0;
> + return *(u64 *)((u64)regs + offset);

So clearly it is the offset. But is 3 a valid value? I don't think so.
How about something slightly more type safe:

u64 val = 0;

WARN_ON(offset & 7);

offset >>= 3;
switch (offset) {
case 0 ... 30:
val = regs->reg[offset];
break;
case 31:
val = regs->sp;
break;
case 32:
val = regs->pc;
break;
case 33:
val = regs->pstate;
break;
}

return val;

I'm pretty sure you could replace 31/32/33 with macros using offsetof().
The compiler may even optimize this to something similar to what you
already have.

Thanks,

M.
--
Jazz is not dead. It just smells funny...

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