Re: [PATCH 2/5] x86_64: disable V86 mode on full 64-bit configuration

[Samuel Thibault]

Applied, thanks!

Luca Dariz, le sam. 29 juil. 2023 19:47:50 +0200, a ecrit:
> * i386/i386/pcb.c: simplify exception stack location and adapt thread
>   gettrs/setters
> * i386/i386/thread.h: don't include V86 fields on full 64-bit
> * x86_64/locore.S: don't include checks for V86 mode on full 64-bit
> ---
>  i386/i386/pcb.c    | 35 ++++++++++++++++++++++++++---------
>  i386/i386/thread.h |  6 ++++++
>  x86_64/locore.S    |  8 ++++++++
>  3 files changed, 40 insertions(+), 9 deletions(-)
> 
> diff --git a/i386/i386/pcb.c b/i386/i386/pcb.c
> index fb535709..d1c5fb50 100644
> --- a/i386/i386/pcb.c
> +++ b/i386/i386/pcb.c
> @@ -145,9 +145,14 @@ void switch_ktss(pcb_t pcb)
>        *      won`t save the v86 segments, so we leave room.
>        */
>  
> +#if !defined(__x86_64__) || defined(USER32)
>       pcb_stack_top = (pcb->iss.efl & EFL_VM)
>                       ? (long) (&pcb->iss + 1)
>                       : (long) (&pcb->iss.v86_segs);
> +#else
> +     pcb_stack_top = (vm_offset_t) (&pcb->iss + 1);
> +#endif
> +
>  #ifdef __x86_64__
>       assert((pcb_stack_top & 0xF) == 0);
>  #endif
> @@ -534,6 +539,7 @@ kern_return_t thread_setstatus(
>                                   | EFL_USER_SET;
>  #endif /* __x86_64__ && !USER32 */
>  
> +#if !defined(__x86_64__) || defined(USER32)
>               /*
>                * Segment registers.  Set differently in V8086 mode.
>                */
> @@ -563,8 +569,9 @@ kern_return_t thread_setstatus(
>                       thread->pcb->ims.v86s.flags =
>                           saved_state->efl & (EFL_TF | EFL_IF);
>                   }
> -             }
> -             else if (flavor == i386_THREAD_STATE) {
> +             } else
> +#endif
> +             if (flavor == i386_THREAD_STATE) {
>                   /*
>                    * 386 mode.  Set segment registers for flat
>                    * 32-bit address space.
> @@ -630,7 +637,7 @@ kern_return_t thread_setstatus(
>  #endif
>               break;
>           }
> -
> +#if !defined(__x86_64__) || defined(USER32)
>           case i386_V86_ASSIST_STATE:
>           {
>               struct i386_v86_assist_state *state;
> @@ -657,7 +664,7 @@ kern_return_t thread_setstatus(
>                       USER_REGS(thread)->efl & (EFL_TF | EFL_IF);
>               break;
>           }
> -
> +#endif
>           case i386_DEBUG_STATE:
>           {
>               struct i386_debug_state *state;
> @@ -710,13 +717,20 @@ kern_return_t thread_getstatus(
>  {
>       switch (flavor)  {
>           case THREAD_STATE_FLAVOR_LIST:
> -             if (*count < 4)
> +#if !defined(__x86_64__) || defined(USER32)
> +             unsigned int ncount = 4;
> +#else
> +             unsigned int ncount = 3;
> +#endif
> +             if (*count < ncount)
>                   return (KERN_INVALID_ARGUMENT);
>               tstate[0] = i386_THREAD_STATE;
>               tstate[1] = i386_FLOAT_STATE;
>               tstate[2] = i386_ISA_PORT_MAP_STATE;
> +#if !defined(__x86_64__) || defined(USER32)
>               tstate[3] = i386_V86_ASSIST_STATE;
> -             *count = 4;
> +#endif
> +             *count = ncount;
>               break;
>  
>           case i386_THREAD_STATE:
> @@ -770,6 +784,7 @@ kern_return_t thread_getstatus(
>  
>               state->cs = saved_state->cs;
>               state->ss = saved_state->ss;
> +#if !defined(__x86_64__) || defined(USER32)
>               if (saved_state->efl & EFL_VM) {
>                   /*
>                    * V8086 mode.
> @@ -789,7 +804,9 @@ kern_return_t thread_getstatus(
>                           saved_state->efl &= ~EFL_IF;
>                   }
>               }
> -             else {
> +             else
> +#endif
> +             {
>                   /*
>                    * 386 mode.
>                    */
> @@ -835,7 +852,7 @@ kern_return_t thread_getstatus(
>               *count = i386_ISA_PORT_MAP_STATE_COUNT;
>               break;
>           }
> -
> +#if !defined(__x86_64__) || defined(USER32)
>           case i386_V86_ASSIST_STATE:
>           {
>               struct i386_v86_assist_state *state;
> @@ -850,7 +867,7 @@ kern_return_t thread_getstatus(
>               *count = i386_V86_ASSIST_STATE_COUNT;
>               break;
>           }
> -
> +#endif
>           case i386_DEBUG_STATE:
>           {
>               struct i386_debug_state *state;
> diff --git a/i386/i386/thread.h b/i386/i386/thread.h
> index b5fc5ffb..2378154f 100644
> --- a/i386/i386/thread.h
> +++ b/i386/i386/thread.h
> @@ -85,12 +85,14 @@ struct i386_saved_state {
>       unsigned long   efl;
>       unsigned long   uesp;
>       unsigned long   ss;
> +#if !defined(__x86_64__) || defined(USER32)
>       struct v86_segs {
>           unsigned long v86_es;       /* virtual 8086 segment registers */
>           unsigned long v86_ds;
>           unsigned long v86_fs;
>           unsigned long v86_gs;
>       } v86_segs;
> +#endif
>  };
>  
>  /*
> @@ -144,6 +146,7 @@ struct i386_fpsave_state {
>       };
>  };
>  
> +#if !defined(__x86_64__) || defined(USER32)
>  /*
>   *   v86_assist_state:
>   *
> @@ -157,6 +160,7 @@ struct v86_assist_state {
>       unsigned short          flags;  /* 8086 flag bits */
>  };
>  #define      V86_IF_PENDING          0x8000  /* unused bit */
> +#endif
>  
>  /*
>   *   i386_interrupt_state:
> @@ -197,7 +201,9 @@ struct i386_interrupt_state {
>  struct i386_machine_state {
>       struct user_ldt *       ldt;
>       struct i386_fpsave_state *ifps;
> +#if !defined(__x86_64__) || defined(USER32)
>       struct v86_assist_state v86s;
> +#endif
>       struct real_descriptor user_gdt[USER_GDT_SLOTS];
>       struct i386_debug_state ids;
>  };
> diff --git a/x86_64/locore.S b/x86_64/locore.S
> index ac7138b7..413d43c4 100644
> --- a/x86_64/locore.S
> +++ b/x86_64/locore.S
> @@ -383,8 +383,10 @@ ENTRY(t_segnp)
>                                       /* indicate fault type */
>  
>  trap_check_kernel_exit:
> +#ifdef USER32
>       testq   $(EFL_VM),32(%rsp)      /* is trap from V86 mode? */
>       jnz     EXT(alltraps)           /* isn`t kernel trap if so */
> +#endif
>       /* Note: handling KERNEL_RING value by hand */
>       testq   $2,24(%rsp)             /* is trap from kernel mode? */
>       jnz     EXT(alltraps)           /* if so:  */
> @@ -477,8 +479,10 @@ push_segregs:
>   */
>  ENTRY(t_debug)
>       INT_FIX
> +#ifdef USER32
>       testq   $(EFL_VM),16(%rsp)      /* is trap from V86 mode? */
>       jnz     0f                      /* isn`t kernel trap if so */
> +#endif
>       /* Note: handling KERNEL_RING value by hand */
>       testq   $2,8(%rsp)              /* is trap from kernel mode? */
>       jnz     0f                      /* if so: */
> @@ -544,8 +548,10 @@ trap_push_segs:
>  #endif
>  trap_set_segs:
>       cld                             /* clear direction flag */
> +#ifdef USER32
>       testl   $(EFL_VM),R_EFLAGS(%rsp) /* in V86 mode? */
>       jnz     trap_from_user          /* user mode trap if so */
> +#endif
>       /* Note: handling KERNEL_RING value by hand */
>       testb   $2,R_CS(%rsp)           /* user mode trap? */
>       jz      trap_from_kernel        /* kernel trap if not */
> @@ -799,8 +805,10 @@ LEXT(return_to_iret)                     /* ( label for 
> kdb_kintr and hardclock) */
>  
>       popq    %rsp                    /* switch back to old stack */
>  
> +#ifdef USER32
>       testl   $(EFL_VM),I_EFL(%rsp)   /* if in V86 */
>       jnz     0f                      /* or */
> +#endif
>       /* Note: handling KERNEL_RING value by hand */
>       testb   $2,I_CS(%rsp)           /* user mode, */
>       jz      1f                      /* check for ASTs */
> -- 
> 2.39.2
> 
> 

-- 
Samuel
---
Pour une évaluation indépendante, transparente et rigoureuse !
Je soutiens la Commission d'Évaluation de l'Inria.