amd64/unwind/unwind.c

/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License (the "License").
 * You may not use this file except in compliance with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */

/*
 * Copyright 2008 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 * Copyright 2012 Milan Jurik. All rights reserved.
 */

/*
 * UNWIND - Unwind library
 */

/*
 * ===================== stack walk ====================
 *
 * Stack walk-back starts with the user code at the top of the stack
 * calling a language specific support routine which calls the generic
 * unwind code. The unwind code captures
 * information which can be used to partially build an _Unwind_Context
 * for the user code containing:
 *
 *    callee saves registers <current values>
 *    PC
 *    %rbp
 *    %rsp
 *
 * Using that pc location the unwind info for the function is found.
 * Then the CFA operations encoded in the unwind info are interepreted to get
 *
 *    callee saves registers <values on entry>
 *    the return address
 *    cannonical frame address
 *
 * completing the context for the user function (See
 * _Unw_Rollback_Registers()) .
 *
 * The values computed above are equivalent to the info which would have been
 * captured from the caller and are used to initialize the callers context
 * (see _Unw_Propagate_Registers()) which can be completed.
 *
 * Using the same two-step procedure
 * context records for each frame down the stack may be constructed
 * in turn.  The ABI defined interface to _Unwind_Context provides
 * access to
 *
 *    callee saves registers <current values>
 *    current PC
 *    frame pointer
 *
 * and allows changing
 *
 *    PC
 *    values of integer argument registers
 *
 * (changed values take effect if context is "installed" - think
 * setcontext(2))
 *
 */

/*
 *
 * |                              |
 * | local storage for start()    | <FP == 0>
 * |                              |
 * --------------------------------.
 * |                              |
 * |     ..........               |
 * |                              | <-  CFA for bar()
 * --------------------------------.
 * |                              |
 * | local storage for bar()      |
 * |                              | <-  SP for bar(), CFA for foo()
 * ................................
 * |  pc for bar()                |
 * --------------------------------
 * |                              |
 * | local storage for foo()      |
 * |                              | <-  SP for foo(), CFA for ex_throw()
 * ................................
 * | pc for foo() - PC3           |
 * ................................
 * | saved RBP from foo() - BP3   | <-  FP for ex_throw() == FP2
 * --------------------------------
 * |                              |
 * | local storage for ex_throw() |
 * |                              | <- SP for ex_throw(), CFA for Unw()
 * ................................
 * | pc for ex_throw() - PC2      |
 * ................................
 * | saved RBP from ex_throw()    | <- FP for Unw() == FP1
 * --------------------------------
 * |                              |
 * | local storage for Unw()      |
 * |                              | <- SP for Unw() == SP1
 *
 * We know that Unw() and ex_throw save and have an FP
 *
 */

#ifdef _LIBCRUN_
#define _Unwind_DeleteException  _SUNW_Unwind_DeleteException
#define _Unwind_ForcedUnwind  _SUNW_Unwind_ForcedUnwind
#define _Unwind_GetCFA  _SUNW_Unwind_GetCFA
#define _Unwind_GetGR  _SUNW_Unwind_GetGR
#define _Unwind_GetIP  _SUNW_Unwind_GetIP
#define _Unwind_GetLanguageSpecificData _SUNW_Unwind_GetLanguageSpecificData
#define _Unwind_GetRegionStart  _SUNW_Unwind_GetRegionStart
#define _Unwind_RaiseException  _SUNW_Unwind_RaiseException
#define _Unwind_Resume  _SUNW_Unwind_Resume
#define _Unwind_SetGR  _SUNW_Unwind_SetGR
#define _Unwind_SetIP  _SUNW_Unwind_SetIP
#else
#pragma weak _SUNW_Unwind_DeleteException = _Unwind_DeleteException
#pragma weak _SUNW_Unwind_ForcedUnwind = _Unwind_ForcedUnwind
#pragma weak _SUNW_Unwind_GetCFA = _Unwind_GetCFA
#pragma weak _SUNW_Unwind_GetGR = _Unwind_GetGR
#pragma weak _SUNW_Unwind_GetIP = _Unwind_GetIP
#pragma weak _SUNW_Unwind_GetLanguageSpecificData = \
        _Unwind_GetLanguageSpecificData
#pragma weak _SUNW_Unwind_GetRegionStart = _Unwind_GetRegionStart
#pragma weak _SUNW_Unwind_RaiseException = _Unwind_RaiseException
#pragma weak _SUNW_Unwind_Resume = _Unwind_Resume
#pragma weak _SUNW_Unwind_SetGR = _Unwind_SetGR
#pragma weak _SUNW_Unwind_SetIP = _Unwind_SetIP
#endif

#include "lint.h"
#include <string.h>
#include "stack_unwind.h"
#include "reg_num.h"
#include "unwind_context.h"

const _Unwind_Action _UA_SEARCH_PHASE = 1;
const _Unwind_Action _UA_CLEANUP_PHASE = 2;
const _Unwind_Action _UA_HANDLER_FRAME = 4;
const _Unwind_Action _UA_FORCE_UNWIND = 8;

void _Unw_capture_regs(uint64_t *regs);
void _Unw_jmp(uint64_t pc, uint64_t *regs);

static void
copy_ctx(struct _Unwind_Context *ctx1, struct _Unwind_Context *ctx2)
{
    if (ctx1 != ctx2) {
        (void) memcpy(ctx2, ctx1, sizeof (*ctx2));
    }
}

static _Unwind_Personality_Fn
ctx_who(struct _Unwind_Context *ctx)
{
    return (ctx->pfn);
}

/* ARGSUSED */
_Unwind_Reason_Code
_Unw_very_boring_personality(int version, int actions, uint64_t exclass,
    struct _Unwind_Exception *exception_object,
    struct _Unwind_Context *ctx)
{
    _Unwind_Reason_Code res = _URC_CONTINUE_UNWIND;
    uint64_t fp;

    fp =  _Unwind_GetCFA(ctx);
    if (fp == 0 || _Unwind_GetIP(ctx) == 0) {
        return (_URC_END_OF_STACK);
    }
    return (res);
}

/*
 * The only static variables in this code - changed by debugging hook below
 */
static int using_ehf = 1;
static uintptr_t def_per_fcn = (uintptr_t)&_Unw_very_boring_personality;

void
_SUNW_Unw_set_defaults(int use, uintptr_t def_per)
{
    using_ehf = use;
    def_per_fcn = def_per;
}

static void
complete_context(struct _Unwind_Context *ctx)
{
    struct eh_frame_fields sf;
    struct eh_frame_fields *sfp = 0;

    ctx->pfn = (_Unwind_Personality_Fn)def_per_fcn;
    ctx->lsda = 0;
    ctx->func = 0;
    ctx->range = 0;
    ctx->fde = 0;
    if (using_ehf && (0 != _Unw_EhfhLookup(ctx))) {
        sfp = _Unw_Decode_FDE(&sf, ctx);
    }
    (void) _Unw_Rollback_Registers(sfp, ctx);
}

/*
 * input: FP1 (or FP2 if from _Unwind_Resume (from_landing_pad))
 *
 * FP2 = FP1[0];
 * BP3 = FP2[0];
 * PC3 = FP2[1];
 * SP3 = FP2 + 16;
 *
 * output: PC3, SP3, and BP3
 *
 * remaining callee saves registers are also captured in context
 */
static void
finish_capture(struct _Unwind_Context *ctx, int from_landing_pad)
{
    uint64_t fp1 = ctx->current_regs[FP_RBP];
    uint64_t fp2 = from_landing_pad ? fp1 : ((uint64_t *)fp1)[0];

    ctx->pc = ((uint64_t *)fp2)[1];
    ctx->current_regs[SP_RSP] = fp2 + 16;
    ctx->current_regs[FP_RBP] = ((uint64_t *)fp2)[0];
    complete_context(ctx);
}

static int
down_one(struct _Unwind_Context *old_ctx, struct _Unwind_Context *new_ctx)
{
    uint64_t old_cfa = old_ctx->cfa;
    uint64_t old_pc = old_ctx->pc;
    uint64_t new_cfa;

    if (old_cfa == 0 || old_pc == 0) {
        new_ctx->pc = 0;
        new_ctx->cfa = 0;
        new_ctx->ra = 0;
        return (1);
    }
    if (old_ctx->ra == 0) {
        new_ctx->pc = 0;
        new_ctx->cfa = 0;
        new_ctx->ra = 0;
        return (0);
    }
    /* now shift ----------------------------- */
    _Unw_Propagate_Registers(old_ctx, new_ctx);
    complete_context(new_ctx);
    new_cfa = new_ctx->cfa;
    if ((new_cfa < old_cfa) || (new_cfa & 7)) {
        new_ctx->pc = 0;
        new_ctx->cfa = 0;
        new_ctx->ra = 0;
    }
    return (0);
}

static void
jmp_ctx(struct _Unwind_Context *ctx)
{
    _Unw_jmp(ctx->pc, ctx->current_regs);
}

/*
 * Here starts the real work - the entry points from either a language
 * runtime or directly from user code.
 *
 * The two ..._Body functions are intended as private interfaces for
 * Sun code as well so should remain accessible.
 */
_Unwind_Reason_Code
_Unwind_RaiseException_Body(struct _Unwind_Exception *exception_object,
    struct _Unwind_Context *entry_ctx, int phase)
{
    struct _Unwind_Context context;
    struct _Unwind_Context *ctx = &context;
    _Unwind_Reason_Code res;

    if (phase & _UA_SEARCH_PHASE) {
        finish_capture(entry_ctx, 0);
        copy_ctx(entry_ctx, ctx);

        for (;;) {
            res = (*ctx_who(ctx))(1, phase,
                exception_object->exception_class,
                exception_object, ctx);
            if (res != _URC_CONTINUE_UNWIND)
                break;
            if (down_one(ctx, ctx))
                return (_URC_FATAL_PHASE1_ERROR);
        }
        switch (res) {
        case _URC_HANDLER_FOUND:
            exception_object->private_2 = _Unwind_GetCFA(ctx);
            break;
        default:
            return (res);
        }
    } else {
        finish_capture(entry_ctx, 1);
        if (down_one(entry_ctx, entry_ctx))
            return (_URC_FATAL_PHASE2_ERROR);
    }

    phase = _UA_CLEANUP_PHASE;
    copy_ctx(entry_ctx, ctx);

    for (;;) {
        if (exception_object->private_2 == _Unwind_GetCFA(ctx)) {
            phase |= _UA_HANDLER_FRAME;
        }
        res = (*ctx_who(ctx))(1, phase,
            exception_object->exception_class,
            exception_object, ctx);
        if ((phase & _UA_HANDLER_FRAME) && res != _URC_INSTALL_CONTEXT)
            return (_URC_FATAL_PHASE2_ERROR);
        if (res != _URC_CONTINUE_UNWIND)
            break;
        if (down_one(ctx, ctx))
            return (_URC_FATAL_PHASE2_ERROR);
    }
    switch (res) {
    case _URC_INSTALL_CONTEXT:
        exception_object->private_1 = 0;
        jmp_ctx(ctx); /* does not return */
        break;
    default:
        break;
    }
    return (res);
}

_Unwind_Reason_Code
_Unwind_RaiseException(struct _Unwind_Exception *exception_object)
{
    struct _Unwind_Context entry_context;
    struct _Unwind_Context *entry_ctx = &entry_context;

    _Unw_capture_regs(entry_ctx->current_regs);

    return (_Unwind_RaiseException_Body(exception_object, entry_ctx,
        _UA_SEARCH_PHASE));
}

_Unwind_Reason_Code
_Unwind_ForcedUnwind_Body(struct _Unwind_Exception *exception_object,
    _Unwind_Stop_Fn stop, void *stop_parameter,
    struct _Unwind_Context *ctx, int resume)
{
    _Unwind_Reason_Code res;
    int phase = _UA_CLEANUP_PHASE | _UA_FORCE_UNWIND;

    int again;
    int doper;

    finish_capture(ctx, resume);
    if (resume && down_one(ctx, ctx))
        return (_URC_FATAL_PHASE2_ERROR);

    do {
        again = 0;
        doper = 0;
        res = (*stop)(1, phase,
            exception_object->exception_class,
            exception_object, ctx, stop_parameter);
        switch (res) {
        case _URC_CONTINUE_UNWIND:
            /* keep going - don't call personality */
            again = 1;
            break;
        case _URC_NO_REASON:
            /* keep going - do call personality */
            again = 1;
            doper = 1;
            break;
        case _URC_NORMAL_STOP:  /* done */
            break;
        case _URC_INSTALL_CONTEXT:  /* resume execution */
            break;
        default:        /* failure */
            break;
        }
        if (doper) {
            res = (*ctx_who(ctx))(1, phase,
                exception_object->exception_class,
                exception_object, ctx);
        }
        switch (res) {
        case _URC_INSTALL_CONTEXT:
            exception_object->private_1 = (uint64_t)stop;
            exception_object->private_2 = (uint64_t)stop_parameter;
            jmp_ctx(ctx); /* does not return */
            break;
        case _URC_CONTINUE_UNWIND:
        case _URC_NO_REASON:
            break;
        case _URC_END_OF_STACK:
            ctx->cfa = ctx->ra = ctx->pc = 0;
            res = (*stop)(1, phase,
                exception_object->exception_class,
                exception_object, ctx, stop_parameter);
            return (_URC_END_OF_STACK);
        default:
            again = 0;
            break;
        }
        if (again) {
            if (down_one(ctx, ctx)) {
                return (_URC_FATAL_PHASE2_ERROR);
            }
        }
    } while (again);

    return (res);
}

_Unwind_Reason_Code
_Unwind_ForcedUnwind(struct _Unwind_Exception *exception_object,
    _Unwind_Stop_Fn stop, void *stop_parameter)
{
    struct _Unwind_Context context;
    struct _Unwind_Context *ctx = &context;

    _Unw_capture_regs(ctx->current_regs);

    return (_Unwind_ForcedUnwind_Body(exception_object, stop,
        stop_parameter, ctx, 0));
}

void
_Unwind_Resume(struct _Unwind_Exception *exception_object)
{

    struct _Unwind_Context context;
    struct _Unwind_Context *ctx = &context;

    _Unw_capture_regs(ctx->current_regs);

    if (exception_object->private_1)
        (void) _Unwind_ForcedUnwind_Body(exception_object,
            (_Unwind_Stop_Fn)exception_object->private_1,
            (void *)exception_object->private_2,
            ctx, 1);
    else
        (void) _Unwind_RaiseException_Body(exception_object, ctx,
            _UA_CLEANUP_PHASE);
}

/* Calls destructor function for exception object */
void
_Unwind_DeleteException(struct _Unwind_Exception *exception_object)
{
    if (exception_object->exception_cleanup != 0)
        (*(exception_object->exception_cleanup))(_URC_NO_REASON,
            exception_object);
}


/*
 * stack frame context accessors defined in ABI
 * (despite all the dire text in the ABI these are reliable Get/Set routines)
 * Note: RA is handled as GR value
 */
uint64_t
_Unwind_GetGR(struct _Unwind_Context *context, int index)
{
    uint64_t res = 0;
    if (index <= EIR_R15) {
        res = context->current_regs[index];
    } else if (index == RET_ADD) {
        res = context->ra;
    }
    return (res);
}


void
_Unwind_SetGR(struct _Unwind_Context *context, int index,
uint64_t new_value)
{
    if (index <= EIR_R15) {
        context->current_regs[index] = new_value;
    } else if (index == RET_ADD) {
        context->ra = new_value;
    }
}


uint64_t
_Unwind_GetIP(struct _Unwind_Context *context)
{
    return (context->pc);
}

void
_Unwind_SetIP(struct _Unwind_Context *context, uint64_t new_value)
{
    context->pc = new_value;
}


void *
_Unwind_GetLanguageSpecificData(struct _Unwind_Context *context)
{
    return (context->lsda);
}


uint64_t
_Unwind_GetRegionStart(struct _Unwind_Context *context)
{
    return (context->func);
}

uint64_t
_Unwind_GetCFA(struct _Unwind_Context *context)
{
    return (context->cfa);
}