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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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