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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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