Subject: [PATCH v7 1/7] arm64: Add HAVE_REGS_AND_STACK_ACCESS_API feature

From: [email-masked] (David Long)
Date: Mon, 29 Jun 2015 14:36:45 -0400

On 06/29/15 13:23, Steve Capper wrote:
> On 15 June 2015 at 20:07, David Long <[email-masked]> wrote:
>> From: "David A. Long" <[email-masked]>
>>
>> Add HAVE_REGS_AND_STACK_ACCESS_API feature for arm64.
>>
>> Signed-off-by: David A. Long <[email-masked]>
>> ---
>>   arch/arm64/Kconfig              |  1 +
>>   arch/arm64/include/asm/ptrace.h | 25 +++++++++++++
>>   arch/arm64/kernel/ptrace.c      | 77 +++++++++++++++++++++++++++++++++++++++++
>>   3 files changed, 103 insertions(+)
>>
>> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
>> index 7796af4..966091f 100644
>> --- a/arch/arm64/Kconfig
>> +++ b/arch/arm64/Kconfig
>> @@ -68,6 +68,7 @@ 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 d6dd9fd..8f440e9 100644
>> --- a/arch/arm64/include/asm/ptrace.h
>> +++ b/arch/arm64/include/asm/ptrace.h
>> @@ -118,6 +118,8 @@ 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
>> @@ -146,6 +148,29 @@ 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);
>
> Why not:
> return regs->regs[offset];
>

This would not be correct.  The offset is a byte offset and your code 
would index eight times that amount into the structure.  The offset 
needs to remain a byte offset so architecture-independent code does not 
need to know the architecture-specific layout of the structure.

>> +}
>> +
>> +/* 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];
>> diff --git a/arch/arm64/kernel/ptrace.c b/arch/arm64/kernel/ptrace.c
>> index d882b83..f6199a5 100644
>> --- a/arch/arm64/kernel/ptrace.c
>> +++ b/arch/arm64/kernel/ptrace.c
>> @@ -48,6 +48,83 @@
>>   #define CREATE_TRACE_POINTS
>>   #include <trace/events/syscalls.h>
>>
>> +#define ARM_pstate     pstate
>> +#define ARM_pc         pc
>> +#define ARM_sp         sp
>> +#define ARM_x30                regs[30]
>> +#define ARM_x29                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_x17                regs[17]
>> +#define ARM_x16                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 REG_OFFSET_NAME(r) \
>> +       {.name = #r, .offset = offsetof(struct pt_regs, ARM_##r)}
>> +#define REG_OFFSET_END {.name = NULL, .offset = 0}
>> +
>> +const struct pt_regs_offset regs_offset_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(x16),
>> +       REG_OFFSET_NAME(x17),
>> +       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(x29),
>> +       REG_OFFSET_NAME(x30),
>> +       REG_OFFSET_NAME(sp),
>> +       REG_OFFSET_NAME(pc),
>> +       REG_OFFSET_NAME(pstate),
>> +       REG_OFFSET_END,
>> +};
>> +
>>   /*
>>    * TODO: does not yet catch signals sent when the child dies.
>>    * in exit.c or in signal.c.
>> --
>> 1.8.1.2
>>

Thanks,
-dl