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    Subject[PATCH -tip v7 5/6] x86: add pt_regs register and stack access APIs
    Date
    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.

    - within_kernel_stack(struct pt_regs *regs, unsigned long addr)
    Check the address is in the kernel stack.

    - get_kernel_stack_nth(struct pt_regs *reg, unsigned nth)
    Get Nth entry of the kernel stack. (N >= 0)

    - get_argument_nth(struct pt_regs *reg, unsigned nth)
    Get Nth argument at function call. (N >= 0)

    Changes from v5:
    - Rename valid_stack_address to within_kernel_stack.
    - Rename get_stack_nth to get_kernel_stack_nth.

    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>
    Cc: Roland McGrath <roland@redhat.com>
    ---

    arch/x86/include/asm/ptrace.h | 67 +++++++++++++++++++++++++++++++++++++++++
    arch/x86/kernel/ptrace.c | 60 +++++++++++++++++++++++++++++++++++++
    2 files changed, 127 insertions(+), 0 deletions(-)

    diff --git a/arch/x86/include/asm/ptrace.h b/arch/x86/include/asm/ptrace.h
    index 0f0d908..577d625 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__
    @@ -216,6 +217,72 @@ 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, ss))
    +
    +/* 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 within_kernel_stack(struct pt_regs *regs, unsigned long addr)
    +{
    + return ((addr & ~(THREAD_SIZE - 1)) ==
    + (kernel_stack_pointer(regs) & ~(THREAD_SIZE - 1)));
    +}
    +
    +/* Get Nth entry of the stack */
    +static inline unsigned long get_kernel_stack_nth(struct pt_regs *regs,
    + unsigned n)
    +{
    + unsigned long *addr = (unsigned long *)kernel_stack_pointer(regs);
    + addr += n;
    + if (within_kernel_stack(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_kernel_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 09ecbde..00eb9d7 100644
    --- a/arch/x86/kernel/ptrace.c
    +++ b/arch/x86/kernel/ptrace.c
    @@ -48,6 +48,66 @@ 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 const 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),
    + REG_OFFSET_NAME(flags),
    + REG_OFFSET_NAME(sp),
    + REG_OFFSET_NAME(ss),
    + REG_OFFSET_END,
    +};
    +
    +int query_register_offset(const char *name)
    +{
    + const struct pt_regs_offset *roff;
    + for (roff = regoffset_table; roff->name != NULL; roff++)
    + if (!strcmp(roff->name, name))
    + return roff->offset;
    + return -EINVAL;
    +}
    +
    +const char *query_register_name(unsigned offset)
    +{
    + const struct pt_regs_offset *roff;
    + 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.

    --
    Masami Hiramatsu

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

    e-mail: mhiramat@redhat.com


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