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

From: Steve Capper
Date: Tue Jun 30 2015 - 06:51:27 EST

On 29 June 2015 at 19:36, David Long <dave.long@xxxxxxxxxx> wrote:
> On 06/29/15 13:23, Steve Capper wrote:
>>
>> On 15 June 2015 at 20:07, David Long <dave.long@xxxxxxxxxx> 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 | 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.

Ahh, apologies. Thank you, I substituted offset as index in my head.

>
>
>>> +}
>>> +
>>> +/* 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
>
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