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SubjectRe: [PATCH -tip 2/6 V4] x86: add arch-dep register and stack access API to ptrace
Frederic Weisbecker wrote:
> On Thu, Apr 02, 2009 at 01:24:47PM -0400, Masami Hiramatsu wrote:
>> Add following APIs for accessing registers and stack entries from pt_regs.
>> - query_register_offset(const char *name)
>> Query the offset of "name" register.
>>
>> - query_register_name(unsigned offset)
>> Query the name of register by its offset.
>>
>> - get_register(struct pt_regs *regs, unsigned offset)
>> Get the value of a register by its offset.
>>
>> - valid_stack_address(struct pt_regs *regs, unsigned long addr)
>> Check the address is in the stack.
>>
>> - get_stack_nth(struct pt_regs *reg, unsigned nth)
>> Get Nth entry of the stack. (N >= 0)
>>
>> - get_argument_nth(struct pt_regs *reg, unsigned nth)
>> Get Nth argument at function call. (N >= 0)
>>
>> Signed-off-by: Masami Hiramatsu <mhiramat@redhat.com>
>> Cc: Steven Rostedt <rostedt@goodmis.org>
>> Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
>> Cc: Ingo Molnar <mingo@elte.hu>
>> Cc: Frederic Weisbecker <fweisbec@gmail.com>
>> ---
>>
>> arch/x86/include/asm/ptrace.h | 66 +++++++++++++++++++++++++++++++++++++++++
>> arch/x86/kernel/ptrace.c | 59 +++++++++++++++++++++++++++++++++++++
>> 2 files changed, 125 insertions(+), 0 deletions(-)
>>
>>
>> diff --git a/arch/x86/include/asm/ptrace.h b/arch/x86/include/asm/ptrace.h
>> index aed0894..44773b8 100644
>> --- a/arch/x86/include/asm/ptrace.h
>> +++ b/arch/x86/include/asm/ptrace.h
>> @@ -7,6 +7,7 @@
>>
>> #ifdef __KERNEL__
>> #include <asm/segment.h>
>> +#include <asm/page_types.h>
>> #endif
>>
>> #ifndef __ASSEMBLY__
>> @@ -215,6 +216,71 @@ static inline unsigned long user_stack_pointer(struct pt_regs *regs)
>> return regs->sp;
>> }
>>
>> +/* Query offset/name of register from its name/offset */
>> +extern int query_register_offset(const char *name);
>> +extern const char *query_register_name(unsigned offset);
>> +#define MAX_REG_OFFSET (offsetof(struct pt_regs, sp))
>> +
>> +/* Get register value from its offset */
>> +static inline unsigned long get_register(struct pt_regs *regs, unsigned offset)
>> +{
>> + if (unlikely(offset > MAX_REG_OFFSET))
>> + return 0;
>> + return *(unsigned long *)((unsigned long)regs + offset);
>> +}
>> +
>> +/* Check the address in the stack */
>> +static inline int valid_stack_address(struct pt_regs *regs, unsigned long addr)
>> +{
>> + return ((addr & ~(THREAD_SIZE - 1)) ==
>> + (kernel_trap_sp(regs) & ~(THREAD_SIZE - 1)));
>> +}
>> +
>> +/* Get Nth entry of the stack */
>> +static inline unsigned long get_stack_nth(struct pt_regs *regs, unsigned n)
>> +{
>> + unsigned long *addr = (unsigned long *)kernel_trap_sp(regs);
>> + addr += n;
>> + if (valid_stack_address(regs, (unsigned long)addr))
>> + return *addr;
>> + else
>> + return 0;
>> +}
>> +
>> +/* Get Nth argument at function call */
>> +static inline unsigned long get_argument_nth(struct pt_regs *regs, unsigned n)
>> +{
>> +#ifdef CONFIG_X86_32
>> +#define NR_REGPARMS 3
>> + if (n < NR_REGPARMS) {
>> + switch (n) {
>> + case 0: return regs->ax;
>> + case 1: return regs->dx;
>> + case 2: return regs->cx;
>> + }
>> + return 0;
>> +#else /* CONFIG_X86_64 */
>> +#define NR_REGPARMS 6
>> + if (n < NR_REGPARMS) {
>> + switch (n) {
>> + case 0: return regs->di;
>> + case 1: return regs->si;
>> + case 2: return regs->dx;
>> + case 3: return regs->cx;
>> + case 4: return regs->r8;
>> + case 5: return regs->r9;
>> + }
>> + return 0;
>> +#endif
>> + } else {
>> + /*
>> + * The typical case: arg n is on the stack.
>> + * (Note: stack[0] = return address, so skip it)
>> + */
>> + return get_stack_nth(regs, 1 + n - NR_REGPARMS);
>> + }
>> +}
>> +
>> /*
>> * These are defined as per linux/ptrace.h, which see.
>> */
>> diff --git a/arch/x86/kernel/ptrace.c b/arch/x86/kernel/ptrace.c
>> index 5c6e463..8d65dcb 100644
>> --- a/arch/x86/kernel/ptrace.c
>> +++ b/arch/x86/kernel/ptrace.c
>> @@ -46,6 +46,65 @@ enum x86_regset {
>> REGSET_IOPERM32,
>> };
>>
>> +struct pt_regs_offset {
>> + const char *name;
>> + int offset;
>> +};
>> +
>> +#define REG_OFFSET(r) offsetof(struct pt_regs, r)
>> +#define REG_OFFSET_NAME(r) {.name = #r, .offset = REG_OFFSET(r)}
>> +#define REG_OFFSET_END {.name = NULL, .offset = 0}
>> +
>> +static struct pt_regs_offset regoffset_table[] = {
>> +#ifdef CONFIG_X86_64
>> + REG_OFFSET_NAME(r15),
>> + REG_OFFSET_NAME(r14),
>> + REG_OFFSET_NAME(r13),
>> + REG_OFFSET_NAME(r12),
>> + REG_OFFSET_NAME(r11),
>> + REG_OFFSET_NAME(r10),
>> + REG_OFFSET_NAME(r9),
>> + REG_OFFSET_NAME(r8),
>> +#endif
>> + REG_OFFSET_NAME(bx),
>> + REG_OFFSET_NAME(cx),
>> + REG_OFFSET_NAME(dx),
>> + REG_OFFSET_NAME(si),
>> + REG_OFFSET_NAME(di),
>> + REG_OFFSET_NAME(bp),
>> + REG_OFFSET_NAME(ax),
>> +#ifdef CONFIG_X86_32
>> + REG_OFFSET_NAME(ds),
>> + REG_OFFSET_NAME(es),
>> + REG_OFFSET_NAME(fs),
>> + REG_OFFSET_NAME(gs),
>> +#endif
>> + REG_OFFSET_NAME(orig_ax),
>> + REG_OFFSET_NAME(ip),
>> + REG_OFFSET_NAME(cs),
>
>
>
> You seem to have also forgotten ss here.

Oh, I forgot it because ss usually ignored in the kernel...
Anyway, it should be supported.


>> + REG_OFFSET_NAME(flags),
>> + REG_OFFSET_NAME(sp),
>> + REG_OFFSET_END,
>> +};
>> +
>> +int query_register_offset(const char *name)
>> +{
>> + struct pt_regs_offset *roff = regoffset_table;
>> + for (roff = regoffset_table; roff->name != NULL; roff++)
>> + if (!strcmp(roff->name, name))
>> + return (unsigned)roff->offset;
>
>
>
> Tiny thing here: could you set the full (unsigned int) cast?

or, I don't need to cast it...

>> + return -EINVAL;
>> +}
>> +
>> +const char *query_register_name(unsigned offset)
>> +{
>> + struct pt_regs_offset *roff = regoffset_table;
>> + for (roff = regoffset_table; roff->name != NULL; roff++)
>> + if (roff->offset == offset)
>> + return roff->name;
>> + return NULL;
>> +}
>> +
>> /*
>> * does not yet catch signals sent when the child dies.
>> * in exit.c or in signal.c.
>
>
> All in one it looks good!

Thanks!

--
Masami Hiramatsu

Software Engineer
Hitachi Computer Products (America) Inc.
Software Solutions Division

e-mail: mhiramat@redhat.com



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