Re: [Qemu-devel] [PATCH] target-i386:slightly refactor dr7 related function

[li guang <lig.fnst@cn.fujitsu.com>]

在 2012-12-03一的 10:43 +0100，Jan Kiszka写道：
> On 2012-12-03 04:07, liguang wrote:
> > 1. define names of breakpoints in dr7
> > 2. slightly refactor bits field of breakpoint
> >    related functions.
> 
> Two topics, (at least) two patches, please. The code is hairy - not your
> fault, you actually try to improve it. But splitting up makes review
> easier. Thanks in advance.

OK, I'll split this patch.

> 
> > 
> > Signed-off-by: liguang <lig.fnst@cn.fujitsu.com>
> > ---
> >  target-i386/cpu.h         |    6 ++++
> >  target-i386/helper.c      |   59 ++++++++++++++++++++++++++++----------------
> >  target-i386/machine.c     |    2 +-
> >  target-i386/misc_helper.c |    4 +-
> >  target-i386/seg_helper.c  |    4 +-
> >  5 files changed, 48 insertions(+), 27 deletions(-)
> > 
> > diff --git a/target-i386/cpu.h b/target-i386/cpu.h
> > index 90ef1ff..2da6ea0 100644
> > --- a/target-i386/cpu.h
> > +++ b/target-i386/cpu.h
> > @@ -231,6 +231,12 @@
> >  #define DR7_TYPE_SHIFT  16
> >  #define DR7_LEN_SHIFT   18
> >  #define DR7_FIXED_1     0x00000400
> > +#define DR7_L0_3        0x55
> 
> DR7_LOCAL_BP_MASK or so.
> 
> > +#define DR7_MAX_BP      4
> > +#define DR7_BP_INST     0x0
> > +#define DR7_DATA_WR     0x1
> > +#define DR7_IO_RW       0x2
> > +#define DR7_DATA_RW     0x3
> >  
> >  #define PG_PRESENT_BIT	0
> >  #define PG_RW_BIT	1
> > diff --git a/target-i386/helper.c b/target-i386/helper.c
> > index bf206cf..54d6712 100644
> > --- a/target-i386/helper.c
> > +++ b/target-i386/helper.c
> > @@ -966,27 +966,26 @@ hwaddr cpu_get_phys_page_debug(CPUX86State *env, target_ulong addr)
> >  
> >  void hw_breakpoint_insert(CPUX86State *env, int index)
> >  {
> > -    int type, err = 0;
> > +    int type = 0, err = 0;
> >  
> >      switch (hw_breakpoint_type(env->dr[7], index)) {
> > -    case 0:
> > +    case DR7_BP_INST:
> >          if (hw_breakpoint_enabled(env->dr[7], index))
> >              err = cpu_breakpoint_insert(env, env->dr[index], BP_CPU,
> >                                          &env->cpu_breakpoint[index]);
> >          break;
> > -    case 1:
> > +    case DR7_DATA_WR:
> >          type = BP_CPU | BP_MEM_WRITE;
> > -        goto insert_wp;
> > -    case 2:
> > -         /* No support for I/O watchpoints yet */
> > -        break;
> > -    case 3:
> > -        type = BP_CPU | BP_MEM_ACCESS;
> > -    insert_wp:
> > +    case DR7_DATA_RW:
> > +        if (!type)
> > +            type = BP_CPU | BP_MEM_ACCESS;
> 
> Coding style.
> 
> But, to be honest, I find the goto approach cleaner. Alternatively, test
> for "type" (or "wp_type") != 0 outside the switch, moving the
> cpu_watchpoint_insert there.

okay.

> 
> >          err = cpu_watchpoint_insert(env, env->dr[index],
> >                                      hw_breakpoint_len(env->dr[7], index),
> >                                      type, &env->cpu_watchpoint[index]);
> >          break;
> > +    case DR7_IO_RW:
> > +         /* No support for I/O watchpoints yet */
> > +        break;
> >      }
> >      if (err)
> >          env->cpu_breakpoint[index] = NULL;
> > @@ -997,15 +996,15 @@ void hw_breakpoint_remove(CPUX86State *env, int index)
> >      if (!env->cpu_breakpoint[index])
> >          return;
> >      switch (hw_breakpoint_type(env->dr[7], index)) {
> > -    case 0:
> > +    case DR7_BP_INST:
> >          if (hw_breakpoint_enabled(env->dr[7], index))
> >              cpu_breakpoint_remove_by_ref(env, env->cpu_breakpoint[index]);
> >          break;
> > -    case 1:
> > -    case 3:
> > +    case DR7_DATA_WR:
> > +    case DR7_DATA_RW:
> >          cpu_watchpoint_remove_by_ref(env, env->cpu_watchpoint[index]);
> >          break;
> > -    case 2:
> > +    case DR7_IO_RW:
> >          /* No support for I/O watchpoints yet */
> >          break;
> >      }
> > @@ -1014,22 +1013,38 @@ void hw_breakpoint_remove(CPUX86State *env, int index)
> >  int check_hw_breakpoints(CPUX86State *env, int force_dr6_update)
> >  {
> >      target_ulong dr6;
> > -    int reg, type;
> > +    int index, type = 0;
> >      int hit_enabled = 0;
> >  
> >      dr6 = env->dr[6] & ~0xf;
> > -    for (reg = 0; reg < 4; reg++) {
> > -        type = hw_breakpoint_type(env->dr[7], reg);
> > -        if ((type == 0 && env->dr[reg] == env->eip) ||
> > -            ((type & 1) && env->cpu_watchpoint[reg] &&
> > -             (env->cpu_watchpoint[reg]->flags & BP_WATCHPOINT_HIT))) {
> > -            dr6 |= 1 << reg;
> > -            if (hw_breakpoint_enabled(env->dr[7], reg))
> > +    for (index = 0; index < DR7_MAX_BP; index++) {
> > +        switch (hw_breakpoint_type(env->dr[7], index)) {
> > +        case DR7_BP_INST:
> > +            if (env->dr[index] != env->eip)
> > +                break;
> > +            type = 1;
> 
> "type" is not very telling as it is used here. Either continue to assign
> it to hw_breakpoint_type and clear it on DR7_IO_RW, or rename it to a
> boolean like "bp_match".

bp_match is a nicer name, thanks!

> 
> > +            break;
> > +        case DR7_DATA_WR:
> > +        case DR7_DATA_RW:
> > +            if (!env->cpu_watchpoint[index])
> > +                break;
> > +            if (!(env->cpu_watchpoint[index]->flags & BP_WATCHPOINT_HIT))
> > +                break;
> 
> Let's fold these two into one.
> 
> In general: coding style.
> 
> > +            type = 1;
> > +            break;
> > +        case DR7_IO_RW:
> > +            break;
> > +        }
> > +        if (type) {
> > +            dr6 |= 1 << index;
> > +            if (hw_breakpoint_enabled(env->dr[7], index))
> >                  hit_enabled = 1;
> > +            type = 0;
> 
> If you go for "wp_match", just set to false under DR7_IO_RW.
> 
> >          }
> >      }
> >      if (hit_enabled || force_dr6_update)
> >          env->dr[6] = dr6;
> > +
> >      return hit_enabled;
> >  }
> >  
> > diff --git a/target-i386/machine.c b/target-i386/machine.c
> > index 4771508..a4b1a1e 100644
> > --- a/target-i386/machine.c
> > +++ b/target-i386/machine.c
> > @@ -265,7 +265,7 @@ static int cpu_post_load(void *opaque, int version_id)
> >  
> >      cpu_breakpoint_remove_all(env, BP_CPU);
> >      cpu_watchpoint_remove_all(env, BP_CPU);
> > -    for (i = 0; i < 4; i++)
> > +    for (i = 0; i < DR7_MAX_BP; i++)
> 
> If touching the line, please fix the coding style as well.
> 
> >          hw_breakpoint_insert(env, i);
> >  
> >      tlb_flush(env, 1);
> > diff --git a/target-i386/misc_helper.c b/target-i386/misc_helper.c
> > index a020379..5ee0863 100644
> > --- a/target-i386/misc_helper.c
> > +++ b/target-i386/misc_helper.c
> > @@ -197,11 +197,11 @@ void helper_movl_drN_T0(CPUX86State *env, int reg, target_ulong t0)
> >          env->dr[reg] = t0;
> >          hw_breakpoint_insert(env, reg);
> >      } else if (reg == 7) {
> > -        for (i = 0; i < 4; i++) {
> > +        for (i = 0; i < DR7_MAX_BP; i++) {
> >              hw_breakpoint_remove(env, i);
> >          }
> >          env->dr[7] = t0;
> > -        for (i = 0; i < 4; i++) {
> > +        for (i = 0; i < DR7_MAX_BP; i++) {
> >              hw_breakpoint_insert(env, i);
> >          }
> >      } else {
> > diff --git a/target-i386/seg_helper.c b/target-i386/seg_helper.c
> > index ff93374..317187b 100644
> > --- a/target-i386/seg_helper.c
> > +++ b/target-i386/seg_helper.c
> > @@ -465,8 +465,8 @@ static void switch_tss(CPUX86State *env, int tss_selector,
> >  
> >  #ifndef CONFIG_USER_ONLY
> >      /* reset local breakpoints */
> > -    if (env->dr[7] & 0x55) {
> > -        for (i = 0; i < 4; i++) {
> > +    if (env->dr[7] & DR7_L0_3) {
> > +        for (i = 0; i < DR7_MAX_BP; i++) {
> >              if (hw_breakpoint_enabled(env->dr[7], i) == 0x1) {
> 
> There is a magic value remaining here. You probably want defines for the
> local vs. global enable bits as well.

okay.

Thanks!

> 
> >                  hw_breakpoint_remove(env, i);
> >              }
> > 
> 
> Jan
> 

-- 
regards!
li guang