Re: [PATCH v13 01/10] arm64: Add HAVE_REGS_AND_STACK_ACCESS_API feature

[Li Bin <huawei.libin@huawei.com>]

on 2016/6/3 11:26, David Long wrote:
> From: "David A. Long" <dave.long@linaro.org>
> 
> Add HAVE_REGS_AND_STACK_ACCESS_API feature for arm64, including supporting
> functions and defines.
> 
> Signed-off-by: David A. Long <dave.long@linaro.org>
> ---
>  arch/arm64/Kconfig              |   1 +
>  arch/arm64/include/asm/ptrace.h |  54 +++++++++++++++++-
>  arch/arm64/kernel/ptrace.c      | 118 ++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 172 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> index 76747d9..0f7a624 100644
> --- a/arch/arm64/Kconfig
> +++ b/arch/arm64/Kconfig
> @@ -85,6 +85,7 @@ 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..c130f2b 100644
> --- a/arch/arm64/include/asm/ptrace.h
> +++ b/arch/arm64/include/asm/ptrace.h
> @@ -74,6 +74,7 @@
>  #define COMPAT_PT_DATA_ADDR		0x10004
>  #define COMPAT_PT_TEXT_END_ADDR		0x10008
>  #ifndef __ASSEMBLY__
> +#include <linux/bug.h>
>  
>  /* sizeof(struct user) for AArch32 */
>  #define COMPAT_USER_SZ	296
> @@ -119,6 +120,8 @@ 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 +150,55 @@ 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 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)
> +{
> +	u64 val = 0;
> +
> +	WARN_ON(offset & 7);
> +
> +	offset >>= 3;

Here, the offset is 3-bits right shifted. So,

> +	switch (offset) {
> +	case	0 ... 30:
> +		val = regs->regs[offset];
> +		break;
> +	case offsetof(struct pt_regs, sp):

here should be shifted too, as

	case offsetof(struct pt_regs, sp) >> 3:


> +		val = regs->sp;
> +		break;
> +	case offsetof(struct pt_regs, pc):

and here,

> +		val = regs->pc;
> +		break;
> +	case offsetof(struct pt_regs, pstate):

and here.

thanks,
Li Bin

> +		val = regs->pstate;
> +		break;
> +	default:
> +		val = 0;
> +	}
> +
> +	return val;
> +}
> +
> +/* Valid only for Kernel mode traps. */
> +static inline unsigned long kernel_stack_pointer(struct pt_regs *regs)
> +{
> +	return regs->sp;
> +}
> +
>  static inline unsigned long regs_return_value(struct pt_regs *regs)
>  {
>  	return regs->regs[0];
> @@ -156,7 +208,7 @@ static inline unsigned long regs_return_value(struct pt_regs *regs)
>  struct task_struct;
>  int valid_user_regs(struct user_pt_regs *regs, struct task_struct *task);
>  
> -#define instruction_pointer(regs)	((unsigned long)(regs)->pc)
> +#define instruction_pointer(regs)	((regs)->pc)
>  
>  extern unsigned long profile_pc(struct pt_regs *regs);
>  
> diff --git a/arch/arm64/kernel/ptrace.c b/arch/arm64/kernel/ptrace.c
> index 3f6cd5c..2c88c33 100644
> --- a/arch/arm64/kernel/ptrace.c
> +++ b/arch/arm64/kernel/ptrace.c
> @@ -48,6 +48,124 @@
>  #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, r)}
> +#define REG_OFFSET_END {.name = NULL, .offset = 0}
> +#define	GPR_OFFSET_NAME(r)	\
> +	{.name = "x" #r, .offset = offsetof(struct pt_regs, regs[r])}
> +
> +static const struct pt_regs_offset regoffset_table[] = {
> +	GPR_OFFSET_NAME(0),
> +	GPR_OFFSET_NAME(1),
> +	GPR_OFFSET_NAME(2),
> +	GPR_OFFSET_NAME(3),
> +	GPR_OFFSET_NAME(4),
> +	GPR_OFFSET_NAME(5),
> +	GPR_OFFSET_NAME(6),
> +	GPR_OFFSET_NAME(7),
> +	GPR_OFFSET_NAME(8),
> +	GPR_OFFSET_NAME(9),
> +	GPR_OFFSET_NAME(10),
> +	GPR_OFFSET_NAME(11),
> +	GPR_OFFSET_NAME(12),
> +	GPR_OFFSET_NAME(13),
> +	GPR_OFFSET_NAME(14),
> +	GPR_OFFSET_NAME(15),
> +	GPR_OFFSET_NAME(16),
> +	GPR_OFFSET_NAME(17),
> +	GPR_OFFSET_NAME(18),
> +	GPR_OFFSET_NAME(19),
> +	GPR_OFFSET_NAME(20),
> +	GPR_OFFSET_NAME(21),
> +	GPR_OFFSET_NAME(22),
> +	GPR_OFFSET_NAME(23),
> +	GPR_OFFSET_NAME(24),
> +	GPR_OFFSET_NAME(25),
> +	GPR_OFFSET_NAME(26),
> +	GPR_OFFSET_NAME(27),
> +	GPR_OFFSET_NAME(28),
> +	GPR_OFFSET_NAME(29),
> +	GPR_OFFSET_NAME(30),
> +	{.name = "lr", .offset = offsetof(struct pt_regs, regs[30])},
> +	REG_OFFSET_NAME(sp),
> +	REG_OFFSET_NAME(pc),
> +	REG_OFFSET_NAME(pstate),
> +	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))) ||
> +		on_irq_stack(addr, raw_smp_processor_id());
> +}
> +
> +/**
> + * 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.
>