Re: [PATCH -tip 2/6 V4] x86: add arch-dep register and stack access API to ptrace

[Frederic Weisbecker <fweisbec@gmail.com>]

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.



> +	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?



> +	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!

Frederic.