Re: [PATCH v4 1/6] arm64: Add HAVE_REGS_AND_STACK_ACCESS_API feature

[Steve Capper]

On Sat, Jan 10, 2015 at 11:03:16PM -0500, David Long wrote:
> From: "David A. Long" <dave.long@xxxxxxxxxx>
> 
> Add HAVE_REGS_AND_STACK_ACCESS_API feature for arm64.
> 
> Signed-off-by: David A. Long <dave.long@xxxxxxxxxx>
> ---
>  arch/arm64/Kconfig                   |   1 +
>  arch/arm64/include/asm/ptrace.h      |  29 +++++++++
>  arch/arm64/include/uapi/asm/ptrace.h |  36 +++++++++++
>  arch/arm64/kernel/ptrace.c           | 119 +++++++++++++++++++++++++++++++++++
>  4 files changed, 185 insertions(+)
> 
> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> index b1f9a20..12b3fd6 100644
> --- a/arch/arm64/Kconfig
> +++ b/arch/arm64/Kconfig
> @@ -64,6 +64,7 @@ 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 IRQ_DOMAIN
> diff --git a/arch/arm64/include/asm/ptrace.h b/arch/arm64/include/asm/ptrace.h
> index 41ed9e1..3613e49 100644
> --- a/arch/arm64/include/asm/ptrace.h
> +++ b/arch/arm64/include/asm/ptrace.h
> @@ -111,6 +111,8 @@ struct pt_regs {
>  	u64 syscallno;
>  };
>  
> +#define MAX_REG_OFFSET (sizeof(struct user_pt_regs) - sizeof(u64))
> +
>  #define arch_has_single_step()	(1)
>  
>  #ifdef CONFIG_COMPAT
> @@ -139,11 +141,38 @@ struct pt_regs {
>  #define user_stack_pointer(regs) \
>  	(!compat_user_mode(regs) ? (regs)->sp : (regs)->compat_sp)
>  
> +/**
> + * regs_get_register() - get register value from its offset
> + * @regs:	   pt_regs from which register value is gotten
> + * @offset:    offset number of the register.
> + *
> + * 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);
> +}
> +
> +/* Valid only for Kernel mode traps. */
> +static inline unsigned long kernel_stack_pointer(struct pt_regs *regs)
> +{
> +	return regs->ARM_sp;
> +}
> +
>  static inline unsigned long regs_return_value(struct pt_regs *regs)
>  {
>  	return regs->regs[0];
>  }
>  
> +extern int regs_query_register_offset(const char *name);
> +extern unsigned long regs_get_kernel_stack_nth(struct pt_regs *regs,
> +					       unsigned int n);
> +
>  /*
>   * Are the current registers suitable for user mode? (used to maintain
>   * security in signal handlers)
> diff --git a/arch/arm64/include/uapi/asm/ptrace.h b/arch/arm64/include/uapi/asm/ptrace.h
> index 6913643..700d28b 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_cpsr	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
> +
>  /*
>   * 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..9115b25 100644
> --- a/arch/arm64/kernel/ptrace.c
> +++ b/arch/arm64/kernel/ptrace.c
> @@ -48,6 +48,125 @@
>  #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)}
> +#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(ip),
> +*/

Should this comment block be removed?

> +	REG_OFFSET_NAME(sp),
> +	REG_OFFSET_NAME(pc),
> +	REG_OFFSET_NAME(cpsr),
> +	REG_OFFSET_NAME(ORIG_x0),
> +	REG_OFFSET_END,
> +};
> +
> +/**
> + * 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;
> +}
> +
> +/**
> + * 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;
> +}
> +
>  /*
>   * TODO: does not yet catch signals sent when the child dies.
>   * in exit.c or in signal.c.
> -- 
> 1.8.1.2
> 
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