Re: [PATCH v6 1/6] arm64: Add HAVE_REGS_AND_STACK_ACCESS_API feature

From: Catalin Marinas
Date: Wed May 20 2015 - 09:40:10 EST


On Mon, Apr 20, 2015 at 04:19:42PM -0400, David Long wrote:
> diff --git a/arch/arm64/include/uapi/asm/ptrace.h b/arch/arm64/include/uapi/asm/ptrace.h
> index 6913643..58c0223 100644
> --- a/arch/arm64/include/uapi/asm/ptrace.h
> +++ b/arch/arm64/include/uapi/asm/ptrace.h
> @@ -61,6 +61,42 @@
>
> #ifndef __ASSEMBLY__
>
> +#define ARM_pstate pstate
> +#define ARM_pc pc
> +#define ARM_sp sp
> +#define ARM_lr regs[30]
> +#define ARM_fp regs[29]
> +#define ARM_x28 regs[28]
> +#define ARM_x27 regs[27]
> +#define ARM_x26 regs[26]
> +#define ARM_x25 regs[25]
> +#define ARM_x24 regs[24]
> +#define ARM_x23 regs[23]
> +#define ARM_x22 regs[22]
> +#define ARM_x21 regs[21]
> +#define ARM_x20 regs[20]
> +#define ARM_x19 regs[19]
> +#define ARM_x18 regs[18]
> +#define ARM_ip1 regs[17]
> +#define ARM_ip0 regs[16]
> +#define ARM_x15 regs[15]
> +#define ARM_x14 regs[14]
> +#define ARM_x13 regs[13]
> +#define ARM_x12 regs[12]
> +#define ARM_x11 regs[11]
> +#define ARM_x10 regs[10]
> +#define ARM_x9 regs[9]
> +#define ARM_x8 regs[8]
> +#define ARM_x7 regs[7]
> +#define ARM_x6 regs[6]
> +#define ARM_x5 regs[5]
> +#define ARM_x4 regs[4]
> +#define ARM_x3 regs[3]
> +#define ARM_x2 regs[2]
> +#define ARM_x1 regs[1]
> +#define ARM_x0 regs[0]
> +#define ARM_ORIG_x0 orig_x0

I replied some time ago on this part. I don't see the point these
macros.

> +
> /*
> * User structures for general purpose, floating point and debug registers.
> */
> diff --git a/arch/arm64/kernel/ptrace.c b/arch/arm64/kernel/ptrace.c
> index d882b83..a889f79 100644
> --- a/arch/arm64/kernel/ptrace.c
> +++ b/arch/arm64/kernel/ptrace.c
> @@ -48,6 +48,122 @@
> #define CREATE_TRACE_POINTS
> #include <trace/events/syscalls.h>
>
> +struct pt_regs_offset {
> + const char *name;
> + int offset;
> +};
> +
> +#define REG_OFFSET_NAME(r) \
> + {.name = #r, .offset = offsetof(struct pt_regs, ARM_##r)}

Can you not just use "offsetof(struct pt_regs, r)" here? That would be
the same as x86, powerpc.

> +#define REG_OFFSET_END {.name = NULL, .offset = 0}
> +
> +static const struct pt_regs_offset regoffset_table[] = {
> + REG_OFFSET_NAME(x0),
> + REG_OFFSET_NAME(x1),
> + REG_OFFSET_NAME(x2),
> + REG_OFFSET_NAME(x3),
> + REG_OFFSET_NAME(x4),
> + REG_OFFSET_NAME(x5),
> + REG_OFFSET_NAME(x6),
> + REG_OFFSET_NAME(x7),
> + REG_OFFSET_NAME(x8),
> + REG_OFFSET_NAME(x9),
> + REG_OFFSET_NAME(x10),
> + REG_OFFSET_NAME(x11),
> + REG_OFFSET_NAME(x12),
> + REG_OFFSET_NAME(x13),
> + REG_OFFSET_NAME(x14),
> + REG_OFFSET_NAME(x15),
> + REG_OFFSET_NAME(ip0),
> + REG_OFFSET_NAME(ip1),
> + REG_OFFSET_NAME(x18),
> + REG_OFFSET_NAME(x19),
> + REG_OFFSET_NAME(x20),
> + REG_OFFSET_NAME(x21),
> + REG_OFFSET_NAME(x22),
> + REG_OFFSET_NAME(x23),
> + REG_OFFSET_NAME(x24),
> + REG_OFFSET_NAME(x25),
> + REG_OFFSET_NAME(x26),
> + REG_OFFSET_NAME(x27),
> + REG_OFFSET_NAME(x28),
> + REG_OFFSET_NAME(fp),
> + REG_OFFSET_NAME(lr),
> + REG_OFFSET_NAME(sp),
> + REG_OFFSET_NAME(pc),

and stick to x16, x17, x29, x30 instead of the ip0 etc.

> + REG_OFFSET_NAME(pstate),
> + REG_OFFSET_NAME(ORIG_x0),
> + REG_OFFSET_END,

Do we need orig_x0 of MAX_REG_OFFSET doesn't include it?

> +};
> +
> +/**
> + * regs_query_register_offset() - query register offset from its name
> + * @name: the name of a register
> + *
> + * regs_query_register_offset() returns the offset of a register in struct
> + * pt_regs from its name. If the name is invalid, this returns -EINVAL;
> + */
> +int regs_query_register_offset(const char *name)
> +{
> + const struct pt_regs_offset *roff;
> +
> + for (roff = regoffset_table; roff->name != NULL; roff++)
> + if (!strcmp(roff->name, name))
> + return roff->offset;
> + return -EINVAL;
> +}
> +
> +/**
> + * regs_query_register_name() - query register name from its offset
> + * @offset: the offset of a register in struct pt_regs.
> + *
> + * regs_query_register_name() returns the name of a register from its
> + * offset in struct pt_regs. If the @offset is invalid, this returns NULL;
> + */
> +const char *regs_query_register_name(unsigned int offset)
> +{
> + const struct pt_regs_offset *roff;
> +
> + for (roff = regoffset_table; roff->name != NULL; roff++)
> + if (roff->offset == offset)
> + return roff->name;
> + return NULL;
> +}

BTW, these functions together with the pt_regs_offset structure look the
same on the other architectures. Can we move them to some common header
to avoid duplication (e.g. linux/ptrace.h)?

> +
> +/**
> + * regs_within_kernel_stack() - check the address in the stack
> + * @regs: pt_regs which contains kernel stack pointer.
> + * @addr: address which is checked.
> + *
> + * regs_within_kernel_stack() checks @addr is within the kernel stack page(s).
> + * If @addr is within the kernel stack, it returns true. If not, returns false.
> + */
> +bool regs_within_kernel_stack(struct pt_regs *regs, unsigned long addr)
> +{
> + return ((addr & ~(THREAD_SIZE - 1)) ==
> + (kernel_stack_pointer(regs) & ~(THREAD_SIZE - 1)));
> +}
> +
> +/**
> + * regs_get_kernel_stack_nth() - get Nth entry of the stack
> + * @regs: pt_regs which contains kernel stack pointer.
> + * @n: stack entry number.
> + *
> + * regs_get_kernel_stack_nth() returns @n th entry of the kernel stack which
> + * is specified by @regs. If the @n th entry is NOT in the kernel stack,
> + * this returns 0.
> + */
> +unsigned long regs_get_kernel_stack_nth(struct pt_regs *regs, unsigned int n)
> +{
> + unsigned long *addr = (unsigned long *)kernel_stack_pointer(regs);
> +
> + addr += n;
> + if (regs_within_kernel_stack(regs, (unsigned long)addr))
> + return *addr;
> + else
> + return 0;
> +}

Same here.

--
Catalin
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