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



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