Re: [RFC v17 10/14] i386: split tcg btp_helper into softmmu and user parts

[Claudio Fontana <cfontana@suse.de>]

On 2/10/21 5:28 PM, Alex Bennée wrote:
> 
> Claudio Fontana <cfontana@suse.de> writes:
> 
> s/btp/bpt/ in subject line...
> 
>> Signed-off-by: Claudio Fontana <cfontana@suse.de>
>> ---
>>  target/i386/tcg/helper-tcg.h                 |   3 +
>>  target/i386/tcg/bpt_helper.c                 | 275 -----------------
>>  target/i386/tcg/softmmu/bpt_helper_softmmu.c | 293 +++++++++++++++++++
>>  target/i386/tcg/user/bpt_helper_user.c       |  33 +++
> 
> So I'm not sure about totally mirroring the file names in softmmu/user
> subdirs. I can see it makes sense in some cases where there are genuine
> functional differences between the two. However for everything that
> exists only for one mode we might as well throw the stubs into one file.
> Maybe target/tcg/user/stubs.c in this case?


Hi Alex, I think you are right, repeating the _softmmu , _user seems too much.

On similar things in the past Paolo mentioned that he favours simpler naming.

In this case I could do for example:

target/i386/tcg/seg_helper.c          - seg helper common parts
target/i386/tcg/softmmu/seg_helper.c  - seg helper softmmu-only code
target/i386/tcg/user/seg_helper.c     - seg helper user-only code

For the parts that are just stubs really (like here bpt for user), I would like to see if I can remove them completely if possible..

Overall though, I am wondering whether this kind of change (extended more to the rest of the target/ code) is an interesting approach,
or does it make harder to work with the *_helper code, as people have to chase down more files?


Thank you!

Claudio



> 
>>  target/i386/tcg/softmmu/meson.build          |   1 +
>>  target/i386/tcg/user/meson.build             |   1 +
>>  6 files changed, 331 insertions(+), 275 deletions(-)
>>  create mode 100644 target/i386/tcg/softmmu/bpt_helper_softmmu.c
>>  create mode 100644 target/i386/tcg/user/bpt_helper_user.c
>>
>> diff --git a/target/i386/tcg/helper-tcg.h b/target/i386/tcg/helper-tcg.h
>> index c133c63555..b420b3356d 100644
>> --- a/target/i386/tcg/helper-tcg.h
>> +++ b/target/i386/tcg/helper-tcg.h
>> @@ -92,4 +92,7 @@ void do_interrupt_x86_hardirq(CPUX86State *env, int intno, int is_hw);
>>  /* smm_helper.c */
>>  void do_smm_enter(X86CPU *cpu);
>>  
>> +/* bpt_helper.c */
>> +bool check_hw_breakpoints(CPUX86State *env, bool force_dr6_update);
>> +
>>  #endif /* I386_HELPER_TCG_H */
>> diff --git a/target/i386/tcg/bpt_helper.c b/target/i386/tcg/bpt_helper.c
>> index 979230ac12..2433991f07 100644
>> --- a/target/i386/tcg/bpt_helper.c
>> +++ b/target/i386/tcg/bpt_helper.c
>> @@ -23,219 +23,6 @@
>>  #include "exec/helper-proto.h"
>>  #include "helper-tcg.h"
>>  
>> -
>> -#ifndef CONFIG_USER_ONLY
>> -static inline bool hw_local_breakpoint_enabled(unsigned long dr7, int index)
>> -{
>> -    return (dr7 >> (index * 2)) & 1;
>> -}
>> -
>> -static inline bool hw_global_breakpoint_enabled(unsigned long dr7, int index)
>> -{
>> -    return (dr7 >> (index * 2)) & 2;
>> -
>> -}
>> -static inline bool hw_breakpoint_enabled(unsigned long dr7, int index)
>> -{
>> -    return hw_global_breakpoint_enabled(dr7, index) ||
>> -           hw_local_breakpoint_enabled(dr7, index);
>> -}
>> -
>> -static inline int hw_breakpoint_type(unsigned long dr7, int index)
>> -{
>> -    return (dr7 >> (DR7_TYPE_SHIFT + (index * 4))) & 3;
>> -}
>> -
>> -static inline int hw_breakpoint_len(unsigned long dr7, int index)
>> -{
>> -    int len = ((dr7 >> (DR7_LEN_SHIFT + (index * 4))) & 3);
>> -    return (len == 2) ? 8 : len + 1;
>> -}
>> -
>> -static int hw_breakpoint_insert(CPUX86State *env, int index)
>> -{
>> -    CPUState *cs = env_cpu(env);
>> -    target_ulong dr7 = env->dr[7];
>> -    target_ulong drN = env->dr[index];
>> -    int err = 0;
>> -
>> -    switch (hw_breakpoint_type(dr7, index)) {
>> -    case DR7_TYPE_BP_INST:
>> -        if (hw_breakpoint_enabled(dr7, index)) {
>> -            err = cpu_breakpoint_insert(cs, drN, BP_CPU,
>> -                                        &env->cpu_breakpoint[index]);
>> -        }
>> -        break;
>> -
>> -    case DR7_TYPE_IO_RW:
>> -        /* Notice when we should enable calls to bpt_io.  */
>> -        return hw_breakpoint_enabled(env->dr[7], index)
>> -               ? HF_IOBPT_MASK : 0;
>> -
>> -    case DR7_TYPE_DATA_WR:
>> -        if (hw_breakpoint_enabled(dr7, index)) {
>> -            err = cpu_watchpoint_insert(cs, drN,
>> -                                        hw_breakpoint_len(dr7, index),
>> -                                        BP_CPU | BP_MEM_WRITE,
>> -                                        &env->cpu_watchpoint[index]);
>> -        }
>> -        break;
>> -
>> -    case DR7_TYPE_DATA_RW:
>> -        if (hw_breakpoint_enabled(dr7, index)) {
>> -            err = cpu_watchpoint_insert(cs, drN,
>> -                                        hw_breakpoint_len(dr7, index),
>> -                                        BP_CPU | BP_MEM_ACCESS,
>> -                                        &env->cpu_watchpoint[index]);
>> -        }
>> -        break;
>> -    }
>> -    if (err) {
>> -        env->cpu_breakpoint[index] = NULL;
>> -    }
>> -    return 0;
>> -}
>> -
>> -static void hw_breakpoint_remove(CPUX86State *env, int index)
>> -{
>> -    CPUState *cs = env_cpu(env);
>> -
>> -    switch (hw_breakpoint_type(env->dr[7], index)) {
>> -    case DR7_TYPE_BP_INST:
>> -        if (env->cpu_breakpoint[index]) {
>> -            cpu_breakpoint_remove_by_ref(cs, env->cpu_breakpoint[index]);
>> -            env->cpu_breakpoint[index] = NULL;
>> -        }
>> -        break;
>> -
>> -    case DR7_TYPE_DATA_WR:
>> -    case DR7_TYPE_DATA_RW:
>> -        if (env->cpu_breakpoint[index]) {
>> -            cpu_watchpoint_remove_by_ref(cs, env->cpu_watchpoint[index]);
>> -            env->cpu_breakpoint[index] = NULL;
>> -        }
>> -        break;
>> -
>> -    case DR7_TYPE_IO_RW:
>> -        /* HF_IOBPT_MASK cleared elsewhere.  */
>> -        break;
>> -    }
>> -}
>> -
>> -void cpu_x86_update_dr7(CPUX86State *env, uint32_t new_dr7)
>> -{
>> -    target_ulong old_dr7 = env->dr[7];
>> -    int iobpt = 0;
>> -    int i;
>> -
>> -    new_dr7 |= DR7_FIXED_1;
>> -
>> -    /* If nothing is changing except the global/local enable bits,
>> -       then we can make the change more efficient.  */
>> -    if (((old_dr7 ^ new_dr7) & ~0xff) == 0) {
>> -        /* Fold the global and local enable bits together into the
>> -           global fields, then xor to show which registers have
>> -           changed collective enable state.  */
>> -        int mod = ((old_dr7 | old_dr7 * 2) ^ (new_dr7 | new_dr7 * 2)) & 0xff;
>> -
>> -        for (i = 0; i < DR7_MAX_BP; i++) {
>> -            if ((mod & (2 << i * 2)) && !hw_breakpoint_enabled(new_dr7, i)) {
>> -                hw_breakpoint_remove(env, i);
>> -            }
>> -        }
>> -        env->dr[7] = new_dr7;
>> -        for (i = 0; i < DR7_MAX_BP; i++) {
>> -            if (mod & (2 << i * 2) && hw_breakpoint_enabled(new_dr7, i)) {
>> -                iobpt |= hw_breakpoint_insert(env, i);
>> -            } else if (hw_breakpoint_type(new_dr7, i) == DR7_TYPE_IO_RW
>> -                       && hw_breakpoint_enabled(new_dr7, i)) {
>> -                iobpt |= HF_IOBPT_MASK;
>> -            }
>> -        }
>> -    } else {
>> -        for (i = 0; i < DR7_MAX_BP; i++) {
>> -            hw_breakpoint_remove(env, i);
>> -        }
>> -        env->dr[7] = new_dr7;
>> -        for (i = 0; i < DR7_MAX_BP; i++) {
>> -            iobpt |= hw_breakpoint_insert(env, i);
>> -        }
>> -    }
>> -
>> -    env->hflags = (env->hflags & ~HF_IOBPT_MASK) | iobpt;
>> -}
>> -
>> -static bool check_hw_breakpoints(CPUX86State *env, bool force_dr6_update)
>> -{
>> -    target_ulong dr6;
>> -    int reg;
>> -    bool hit_enabled = false;
>> -
>> -    dr6 = env->dr[6] & ~0xf;
>> -    for (reg = 0; reg < DR7_MAX_BP; reg++) {
>> -        bool bp_match = false;
>> -        bool wp_match = false;
>> -
>> -        switch (hw_breakpoint_type(env->dr[7], reg)) {
>> -        case DR7_TYPE_BP_INST:
>> -            if (env->dr[reg] == env->eip) {
>> -                bp_match = true;
>> -            }
>> -            break;
>> -        case DR7_TYPE_DATA_WR:
>> -        case DR7_TYPE_DATA_RW:
>> -            if (env->cpu_watchpoint[reg] &&
>> -                env->cpu_watchpoint[reg]->flags & BP_WATCHPOINT_HIT) {
>> -                wp_match = true;
>> -            }
>> -            break;
>> -        case DR7_TYPE_IO_RW:
>> -            break;
>> -        }
>> -        if (bp_match || wp_match) {
>> -            dr6 |= 1 << reg;
>> -            if (hw_breakpoint_enabled(env->dr[7], reg)) {
>> -                hit_enabled = true;
>> -            }
>> -        }
>> -    }
>> -
>> -    if (hit_enabled || force_dr6_update) {
>> -        env->dr[6] = dr6;
>> -    }
>> -
>> -    return hit_enabled;
>> -}
>> -
>> -void breakpoint_handler(CPUState *cs)
>> -{
>> -    X86CPU *cpu = X86_CPU(cs);
>> -    CPUX86State *env = &cpu->env;
>> -    CPUBreakpoint *bp;
>> -
>> -    if (cs->watchpoint_hit) {
>> -        if (cs->watchpoint_hit->flags & BP_CPU) {
>> -            cs->watchpoint_hit = NULL;
>> -            if (check_hw_breakpoints(env, false)) {
>> -                raise_exception(env, EXCP01_DB);
>> -            } else {
>> -                cpu_loop_exit_noexc(cs);
>> -            }
>> -        }
>> -    } else {
>> -        QTAILQ_FOREACH(bp, &cs->breakpoints, entry) {
>> -            if (bp->pc == env->eip) {
>> -                if (bp->flags & BP_CPU) {
>> -                    check_hw_breakpoints(env, true);
>> -                    raise_exception(env, EXCP01_DB);
>> -                }
>> -                break;
>> -            }
>> -        }
>> -    }
>> -}
>> -#endif
>> -
>>  void helper_single_step(CPUX86State *env)
>>  {
>>  #ifndef CONFIG_USER_ONLY
>> @@ -252,41 +39,6 @@ void helper_rechecking_single_step(CPUX86State *env)
>>      }
>>  }
>>  
>> -void helper_set_dr(CPUX86State *env, int reg, target_ulong t0)
>> -{
>> -#ifndef CONFIG_USER_ONLY
>> -    switch (reg) {
>> -    case 0: case 1: case 2: case 3:
>> -        if (hw_breakpoint_enabled(env->dr[7], reg)
>> -            && hw_breakpoint_type(env->dr[7], reg) != DR7_TYPE_IO_RW) {
>> -            hw_breakpoint_remove(env, reg);
>> -            env->dr[reg] = t0;
>> -            hw_breakpoint_insert(env, reg);
>> -        } else {
>> -            env->dr[reg] = t0;
>> -        }
>> -        return;
>> -    case 4:
>> -        if (env->cr[4] & CR4_DE_MASK) {
>> -            break;
>> -        }
>> -        /* fallthru */
>> -    case 6:
>> -        env->dr[6] = t0 | DR6_FIXED_1;
>> -        return;
>> -    case 5:
>> -        if (env->cr[4] & CR4_DE_MASK) {
>> -            break;
>> -        }
>> -        /* fallthru */
>> -    case 7:
>> -        cpu_x86_update_dr7(env, t0);
>> -        return;
>> -    }
>> -    raise_exception_err_ra(env, EXCP06_ILLOP, 0, GETPC());
>> -#endif
>> -}
>> -
>>  target_ulong helper_get_dr(CPUX86State *env, int reg)
>>  {
>>      switch (reg) {
>> @@ -307,30 +59,3 @@ target_ulong helper_get_dr(CPUX86State *env, int reg)
>>      }
>>      raise_exception_err_ra(env, EXCP06_ILLOP, 0, GETPC());
>>  }
>> -
>> -/* Check if Port I/O is trapped by a breakpoint.  */
>> -void helper_bpt_io(CPUX86State *env, uint32_t port,
>> -                   uint32_t size, target_ulong next_eip)
>> -{
>> -#ifndef CONFIG_USER_ONLY
>> -    target_ulong dr7 = env->dr[7];
>> -    int i, hit = 0;
>> -
>> -    for (i = 0; i < DR7_MAX_BP; ++i) {
>> -        if (hw_breakpoint_type(dr7, i) == DR7_TYPE_IO_RW
>> -            && hw_breakpoint_enabled(dr7, i)) {
>> -            int bpt_len = hw_breakpoint_len(dr7, i);
>> -            if (port + size - 1 >= env->dr[i]
>> -                && port <= env->dr[i] + bpt_len - 1) {
>> -                hit |= 1 << i;
>> -            }
>> -        }
>> -    }
>> -
>> -    if (hit) {
>> -        env->dr[6] = (env->dr[6] & ~0xf) | hit;
>> -        env->eip = next_eip;
>> -        raise_exception(env, EXCP01_DB);
>> -    }
>> -#endif
>> -}
>> diff --git a/target/i386/tcg/softmmu/bpt_helper_softmmu.c b/target/i386/tcg/softmmu/bpt_helper_softmmu.c
>> new file mode 100644
>> index 0000000000..1f3dd09cad
>> --- /dev/null
>> +++ b/target/i386/tcg/softmmu/bpt_helper_softmmu.c
>> @@ -0,0 +1,293 @@
>> +/*
>> + *  i386 breakpoint helpers - softmmu-only code
>> + *
>> + *  Copyright (c) 2003 Fabrice Bellard
>> + *
>> + * This library is free software; you can redistribute it and/or
>> + * modify it under the terms of the GNU Lesser General Public
>> + * License as published by the Free Software Foundation; either
>> + * version 2.1 of the License, or (at your option) any later version.
>> + *
>> + * This library is distributed in the hope that it will be useful,
>> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
>> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
>> + * Lesser General Public License for more details.
>> + *
>> + * You should have received a copy of the GNU Lesser General Public
>> + * License along with this library; if not, see <http://www.gnu.org/licenses/>.
>> + */
>> +
>> +#include "qemu/osdep.h"
>> +#include "cpu.h"
>> +#include "exec/exec-all.h"
>> +#include "exec/helper-proto.h"
>> +#include "tcg/helper-tcg.h"
>> +
>> +
>> +static inline bool hw_local_breakpoint_enabled(unsigned long dr7, int index)
>> +{
>> +    return (dr7 >> (index * 2)) & 1;
>> +}
>> +
>> +static inline bool hw_global_breakpoint_enabled(unsigned long dr7, int index)
>> +{
>> +    return (dr7 >> (index * 2)) & 2;
>> +
>> +}
>> +static inline bool hw_breakpoint_enabled(unsigned long dr7, int index)
>> +{
>> +    return hw_global_breakpoint_enabled(dr7, index) ||
>> +           hw_local_breakpoint_enabled(dr7, index);
>> +}
>> +
>> +static inline int hw_breakpoint_type(unsigned long dr7, int index)
>> +{
>> +    return (dr7 >> (DR7_TYPE_SHIFT + (index * 4))) & 3;
>> +}
>> +
>> +static inline int hw_breakpoint_len(unsigned long dr7, int index)
>> +{
>> +    int len = ((dr7 >> (DR7_LEN_SHIFT + (index * 4))) & 3);
>> +    return (len == 2) ? 8 : len + 1;
>> +}
>> +
>> +static int hw_breakpoint_insert(CPUX86State *env, int index)
>> +{
>> +    CPUState *cs = env_cpu(env);
>> +    target_ulong dr7 = env->dr[7];
>> +    target_ulong drN = env->dr[index];
>> +    int err = 0;
>> +
>> +    switch (hw_breakpoint_type(dr7, index)) {
>> +    case DR7_TYPE_BP_INST:
>> +        if (hw_breakpoint_enabled(dr7, index)) {
>> +            err = cpu_breakpoint_insert(cs, drN, BP_CPU,
>> +                                        &env->cpu_breakpoint[index]);
>> +        }
>> +        break;
>> +
>> +    case DR7_TYPE_IO_RW:
>> +        /* Notice when we should enable calls to bpt_io.  */
>> +        return hw_breakpoint_enabled(env->dr[7], index)
>> +               ? HF_IOBPT_MASK : 0;
>> +
>> +    case DR7_TYPE_DATA_WR:
>> +        if (hw_breakpoint_enabled(dr7, index)) {
>> +            err = cpu_watchpoint_insert(cs, drN,
>> +                                        hw_breakpoint_len(dr7, index),
>> +                                        BP_CPU | BP_MEM_WRITE,
>> +                                        &env->cpu_watchpoint[index]);
>> +        }
>> +        break;
>> +
>> +    case DR7_TYPE_DATA_RW:
>> +        if (hw_breakpoint_enabled(dr7, index)) {
>> +            err = cpu_watchpoint_insert(cs, drN,
>> +                                        hw_breakpoint_len(dr7, index),
>> +                                        BP_CPU | BP_MEM_ACCESS,
>> +                                        &env->cpu_watchpoint[index]);
>> +        }
>> +        break;
>> +    }
>> +    if (err) {
>> +        env->cpu_breakpoint[index] = NULL;
>> +    }
>> +    return 0;
>> +}
>> +
>> +static void hw_breakpoint_remove(CPUX86State *env, int index)
>> +{
>> +    CPUState *cs = env_cpu(env);
>> +
>> +    switch (hw_breakpoint_type(env->dr[7], index)) {
>> +    case DR7_TYPE_BP_INST:
>> +        if (env->cpu_breakpoint[index]) {
>> +            cpu_breakpoint_remove_by_ref(cs, env->cpu_breakpoint[index]);
>> +            env->cpu_breakpoint[index] = NULL;
>> +        }
>> +        break;
>> +
>> +    case DR7_TYPE_DATA_WR:
>> +    case DR7_TYPE_DATA_RW:
>> +        if (env->cpu_breakpoint[index]) {
>> +            cpu_watchpoint_remove_by_ref(cs, env->cpu_watchpoint[index]);
>> +            env->cpu_breakpoint[index] = NULL;
>> +        }
>> +        break;
>> +
>> +    case DR7_TYPE_IO_RW:
>> +        /* HF_IOBPT_MASK cleared elsewhere.  */
>> +        break;
>> +    }
>> +}
>> +
>> +void cpu_x86_update_dr7(CPUX86State *env, uint32_t new_dr7)
>> +{
>> +    target_ulong old_dr7 = env->dr[7];
>> +    int iobpt = 0;
>> +    int i;
>> +
>> +    new_dr7 |= DR7_FIXED_1;
>> +
>> +    /* If nothing is changing except the global/local enable bits,
>> +       then we can make the change more efficient.  */
>> +    if (((old_dr7 ^ new_dr7) & ~0xff) == 0) {
>> +        /* Fold the global and local enable bits together into the
>> +           global fields, then xor to show which registers have
>> +           changed collective enable state.  */
>> +        int mod = ((old_dr7 | old_dr7 * 2) ^ (new_dr7 | new_dr7 * 2)) & 0xff;
>> +
>> +        for (i = 0; i < DR7_MAX_BP; i++) {
>> +            if ((mod & (2 << i * 2)) && !hw_breakpoint_enabled(new_dr7, i)) {
>> +                hw_breakpoint_remove(env, i);
>> +            }
>> +        }
>> +        env->dr[7] = new_dr7;
>> +        for (i = 0; i < DR7_MAX_BP; i++) {
>> +            if (mod & (2 << i * 2) && hw_breakpoint_enabled(new_dr7, i)) {
>> +                iobpt |= hw_breakpoint_insert(env, i);
>> +            } else if (hw_breakpoint_type(new_dr7, i) == DR7_TYPE_IO_RW
>> +                       && hw_breakpoint_enabled(new_dr7, i)) {
>> +                iobpt |= HF_IOBPT_MASK;
>> +            }
>> +        }
>> +    } else {
>> +        for (i = 0; i < DR7_MAX_BP; i++) {
>> +            hw_breakpoint_remove(env, i);
>> +        }
>> +        env->dr[7] = new_dr7;
>> +        for (i = 0; i < DR7_MAX_BP; i++) {
>> +            iobpt |= hw_breakpoint_insert(env, i);
>> +        }
>> +    }
>> +
>> +    env->hflags = (env->hflags & ~HF_IOBPT_MASK) | iobpt;
>> +}
>> +
>> +bool check_hw_breakpoints(CPUX86State *env, bool force_dr6_update)
>> +{
>> +    target_ulong dr6;
>> +    int reg;
>> +    bool hit_enabled = false;
>> +
>> +    dr6 = env->dr[6] & ~0xf;
>> +    for (reg = 0; reg < DR7_MAX_BP; reg++) {
>> +        bool bp_match = false;
>> +        bool wp_match = false;
>> +
>> +        switch (hw_breakpoint_type(env->dr[7], reg)) {
>> +        case DR7_TYPE_BP_INST:
>> +            if (env->dr[reg] == env->eip) {
>> +                bp_match = true;
>> +            }
>> +            break;
>> +        case DR7_TYPE_DATA_WR:
>> +        case DR7_TYPE_DATA_RW:
>> +            if (env->cpu_watchpoint[reg] &&
>> +                env->cpu_watchpoint[reg]->flags & BP_WATCHPOINT_HIT) {
>> +                wp_match = true;
>> +            }
>> +            break;
>> +        case DR7_TYPE_IO_RW:
>> +            break;
>> +        }
>> +        if (bp_match || wp_match) {
>> +            dr6 |= 1 << reg;
>> +            if (hw_breakpoint_enabled(env->dr[7], reg)) {
>> +                hit_enabled = true;
>> +            }
>> +        }
>> +    }
>> +
>> +    if (hit_enabled || force_dr6_update) {
>> +        env->dr[6] = dr6;
>> +    }
>> +
>> +    return hit_enabled;
>> +}
>> +
>> +void breakpoint_handler(CPUState *cs)
>> +{
>> +    X86CPU *cpu = X86_CPU(cs);
>> +    CPUX86State *env = &cpu->env;
>> +    CPUBreakpoint *bp;
>> +
>> +    if (cs->watchpoint_hit) {
>> +        if (cs->watchpoint_hit->flags & BP_CPU) {
>> +            cs->watchpoint_hit = NULL;
>> +            if (check_hw_breakpoints(env, false)) {
>> +                raise_exception(env, EXCP01_DB);
>> +            } else {
>> +                cpu_loop_exit_noexc(cs);
>> +            }
>> +        }
>> +    } else {
>> +        QTAILQ_FOREACH(bp, &cs->breakpoints, entry) {
>> +            if (bp->pc == env->eip) {
>> +                if (bp->flags & BP_CPU) {
>> +                    check_hw_breakpoints(env, true);
>> +                    raise_exception(env, EXCP01_DB);
>> +                }
>> +                break;
>> +            }
>> +        }
>> +    }
>> +}
>> +
>> +void helper_set_dr(CPUX86State *env, int reg, target_ulong t0)
>> +{
>> +    switch (reg) {
>> +    case 0: case 1: case 2: case 3:
>> +        if (hw_breakpoint_enabled(env->dr[7], reg)
>> +            && hw_breakpoint_type(env->dr[7], reg) != DR7_TYPE_IO_RW) {
>> +            hw_breakpoint_remove(env, reg);
>> +            env->dr[reg] = t0;
>> +            hw_breakpoint_insert(env, reg);
>> +        } else {
>> +            env->dr[reg] = t0;
>> +        }
>> +        return;
>> +    case 4:
>> +        if (env->cr[4] & CR4_DE_MASK) {
>> +            break;
>> +        }
>> +        /* fallthru */
>> +    case 6:
>> +        env->dr[6] = t0 | DR6_FIXED_1;
>> +        return;
>> +    case 5:
>> +        if (env->cr[4] & CR4_DE_MASK) {
>> +            break;
>> +        }
>> +        /* fallthru */
>> +    case 7:
>> +        cpu_x86_update_dr7(env, t0);
>> +        return;
>> +    }
>> +    raise_exception_err_ra(env, EXCP06_ILLOP, 0, GETPC());
>> +}
>> +
>> +/* Check if Port I/O is trapped by a breakpoint.  */
>> +void helper_bpt_io(CPUX86State *env, uint32_t port,
>> +                   uint32_t size, target_ulong next_eip)
>> +{
>> +    target_ulong dr7 = env->dr[7];
>> +    int i, hit = 0;
>> +
>> +    for (i = 0; i < DR7_MAX_BP; ++i) {
>> +        if (hw_breakpoint_type(dr7, i) == DR7_TYPE_IO_RW
>> +            && hw_breakpoint_enabled(dr7, i)) {
>> +            int bpt_len = hw_breakpoint_len(dr7, i);
>> +            if (port + size - 1 >= env->dr[i]
>> +                && port <= env->dr[i] + bpt_len - 1) {
>> +                hit |= 1 << i;
>> +            }
>> +        }
>> +    }
>> +
>> +    if (hit) {
>> +        env->dr[6] = (env->dr[6] & ~0xf) | hit;
>> +        env->eip = next_eip;
>> +        raise_exception(env, EXCP01_DB);
>> +    }
>> +}
>> diff --git a/target/i386/tcg/user/bpt_helper_user.c b/target/i386/tcg/user/bpt_helper_user.c
>> new file mode 100644
>> index 0000000000..2a31ddb0bf
>> --- /dev/null
>> +++ b/target/i386/tcg/user/bpt_helper_user.c
>> @@ -0,0 +1,33 @@
>> +/*
>> + *  i386 breakpoint helpers - user-mode code
>> + *
>> + *  Copyright (c) 2003 Fabrice Bellard
>> + *
>> + * This library is free software; you can redistribute it and/or
>> + * modify it under the terms of the GNU Lesser General Public
>> + * License as published by the Free Software Foundation; either
>> + * version 2.1 of the License, or (at your option) any later version.
>> + *
>> + * This library is distributed in the hope that it will be useful,
>> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
>> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
>> + * Lesser General Public License for more details.
>> + *
>> + * You should have received a copy of the GNU Lesser General Public
>> + * License along with this library; if not, see <http://www.gnu.org/licenses/>.
>> + */
>> +
>> +#include "qemu/osdep.h"
>> +#include "cpu.h"
>> +#include "exec/exec-all.h"
>> +#include "exec/helper-proto.h"
>> +#include "tcg/helper-tcg.h"
>> +
>> +void helper_set_dr(CPUX86State *env, int reg, target_ulong t0)
>> +{
>> +}
>> +
>> +void helper_bpt_io(CPUX86State *env, uint32_t port,
>> +                   uint32_t size, target_ulong next_eip)
>> +{
>> +}
>> diff --git a/target/i386/tcg/softmmu/meson.build b/target/i386/tcg/softmmu/meson.build
>> index e1ab2e4b43..d004ecea62 100644
>> --- a/target/i386/tcg/softmmu/meson.build
>> +++ b/target/i386/tcg/softmmu/meson.build
>> @@ -2,4 +2,5 @@ i386_softmmu_ss.add(when: ['CONFIG_TCG', 'CONFIG_SOFTMMU'], if_true: files(
>>    'tcg-cpu-softmmu.c',
>>    'smm_helper.c',
>>    'excp_helper_softmmu.c',
>> +  'bpt_helper_softmmu.c',
>>  ))
>> diff --git a/target/i386/tcg/user/meson.build b/target/i386/tcg/user/meson.build
>> index e1eddd19bb..317f101b28 100644
>> --- a/target/i386/tcg/user/meson.build
>> +++ b/target/i386/tcg/user/meson.build
>> @@ -2,4 +2,5 @@ i386_user_ss.add(when: ['CONFIG_TCG', 'CONFIG_USER_ONLY'], if_true: files(
>>    'tcg-cpu-user.c',
>>    'smm_helper_user.c',
>>    'excp_helper_user.c',
>> +  'bpt_helper_user.c',
>>  ))
> 
>