/**

 * @file backtrace.c

 *

 * @remark Copyright 2002 OProfile authors

 * @remark Read the file COPYING

 *

 * @author John Levon

 * @author David Smith

 * Modified for Xen by Amitabha Roy

 *

 */

#include <xen/types.h>

#include <asm/page.h>

#include <xen/xenoprof.h>

#include <xen/guest_access.h>

struct __packed frame_head {

    struct frame_head * ebp;

    unsigned long ret;

};

typedef struct frame_head frame_head_t;

DEFINE_XEN_GUEST_HANDLE(frame_head_t);

struct __packed frame_head_32bit {

    uint32_t ebp;

    uint32_t ret;

};

typedef struct frame_head_32bit frame_head32_t;

DEFINE_COMPAT_HANDLE(frame_head32_t);

static struct frame_head *

dump_hypervisor_backtrace(struct vcpu *vcpu, const struct frame_head *head,

                          int mode)

{

    if (!xenoprof_add_trace(vcpu, head->ret, mode))

        return 0;

    /* frame pointers should strictly progress back up the stack

     * (towards higher addresses) */

    if (head >= head->ebp)

        return NULL;

    return head->ebp;

}

static inline int is_32bit_vcpu(struct vcpu *vcpu)

{

    if (is_hvm_vcpu(vcpu))

        return !hvm_long_mode_active(vcpu);

    else

        return is_pv_32bit_vcpu(vcpu);

}

static struct frame_head *

dump_guest_backtrace(struct vcpu *vcpu, const struct frame_head *head,

                     int mode)

{

    frame_head_t bufhead;

    if ( is_32bit_vcpu(vcpu) )

    {

        __compat_handle_const_frame_head32_t guest_head =

            { .c = (unsigned long)head };

        frame_head32_t bufhead32;

        /* Also check accessibility of one struct frame_head beyond */

        if (!compat_handle_okay(guest_head, 2))

            return 0;

        if (__copy_from_compat(&bufhead32, guest_head, 1))

            return 0;

        bufhead.ebp = (struct frame_head *)(unsigned long)bufhead32.ebp;

        bufhead.ret = bufhead32.ret;

    }

    else

    {

        XEN_GUEST_HANDLE(const_frame_head_t) guest_head;

        XEN_GUEST_HANDLE_PARAM(const_frame_head_t) guest_head_param =

            const_guest_handle_from_ptr(head, frame_head_t);

        guest_head = guest_handle_from_param(guest_head_param,

               const_frame_head_t);

        /* Also check accessibility of one struct frame_head beyond */

        if (!guest_handle_okay(guest_head, 2))

            return 0;

        if (__copy_from_guest(&bufhead, guest_head, 1))

            return 0;

    }

    if (!xenoprof_add_trace(vcpu, bufhead.ret, mode))

        return 0;

    /* frame pointers should strictly progress back up the stack

     * (towards higher addresses) */

    if (head >= bufhead.ebp)

        return NULL;

    return bufhead.ebp;

}

/*

 * |             | /\ Higher addresses

 * |             |

 * --------------- stack base (address of current_thread_info)

 * | thread info |

 * .             .

 * |    stack    |

 * --------------- saved regs->ebp value if valid (frame_head address)

 * .             .

 * --------------- saved regs->rsp value if x86_64

 * |             |

 * --------------- struct pt_regs * stored on stack if 32-bit

 * |             |

 * .             .

 * |             |

 * --------------- %esp

 * |             |

 * |             | \/ Lower addresses

 *

 * Thus, regs (or regs->rsp for x86_64) <-> stack base restricts the

 * valid(ish) ebp values. Note: (1) for x86_64, NMI and several other

 * exceptions use special stacks, maintained by the interrupt stack table

 * (IST). These stacks are set up in trap_init() in

 * arch/x86_64/kernel/traps.c. Thus, for x86_64, regs now does not point

 * to the kernel stack; instead, it points to some location on the NMI

 * stack. On the other hand, regs->rsp is the stack pointer saved when the

 * NMI occurred. (2) For 32-bit, regs->esp is not valid because the

 * processor does not save %esp on the kernel stack when interrupts occur

 * in the kernel mode.

 */

#if defined(CONFIG_FRAME_POINTER)

static int valid_hypervisor_stack(const struct frame_head *head,

          const struct cpu_user_regs *regs)

{

    unsigned long headaddr = (unsigned long)head;

    unsigned long stack = (unsigned long)regs->rsp;

    unsigned long stack_base = (stack & ~(STACK_SIZE - 1)) + STACK_SIZE;

    return headaddr > stack && headaddr < stack_base;

}

#else

/* without fp, it's just junk */

static int valid_hypervisor_stack(const struct frame_head *head,

          const struct cpu_user_regs *regs)

{

    return 0;

}

#endif

void xenoprof_backtrace(struct vcpu *vcpu, const struct cpu_user_regs *regs,

      unsigned long depth, int mode)

{

    const struct frame_head *head = (void *)regs->rbp;

    if (mode > 1) {

        while (depth-- && valid_hypervisor_stack(head, regs))

            head = dump_hypervisor_backtrace(vcpu, head, mode);

        return;

    }

    while (depth-- && head)

        head = dump_guest_backtrace(vcpu, head, mode);

}