[ARM/FDPIC 13/21] [ARM] FDPIC: Support unwinding across thumb2 signal trampoline

[Kyrill Tkachov]

Hi Christophe,

Similar comments to patch 11/21

On 25/05/18 09:03, Christophe Lyon wrote:
> 2018-XX-XX  Christophe Lyon <christophe.lyon@st.com>
>         Mickaël Guêné <mickael.guene@st.com>
>
>         libgcc/
>         * unwind-arm-common.inc (FDPIC_T2_LDR_R12_WITH_FUNCDESC)
>         (FDPIC_T2_LDR_R9_WITH_GOT, FDPIC_T2_LDR_PC_WITH_RESTORER): New.
>         (__gnu_personality_sigframe_fdpic): Support Thumb address.
>         (get_eit_entry): Support Thumb code.
>
> Change-Id: I2bb8994e733e48a89c6f4e0682921186c086f8bc
>
> diff --git a/libgcc/unwind-arm-common.inc b/libgcc/unwind-arm-common.inc
> index 80d1e88..7de4033 100644
> --- a/libgcc/unwind-arm-common.inc
> +++ b/libgcc/unwind-arm-common.inc
> @@ -38,6 +38,9 @@
>  #define FDPIC_LDR_R12_WITH_FUNCDESC     0xe59fc004
>  #define FDPIC_LDR_R9_WITH_GOT           0xe59c9004
>  #define FDPIC_LDR_PC_WITH_RESTORER      0xe59cf000
> +#define FDPIC_T2_LDR_R12_WITH_FUNCDESC  0xc008f8df
> +#define FDPIC_T2_LDR_R9_WITH_GOT       0x9004f8dc
> +#define FDPIC_T2_LDR_PC_WITH_RESTORER   0xf000f8dc
>  #define FDPIC_FUNCDESC_OFFSET           12
>  /* Signal frame offsets.  */
>  #define ARM_NEW_RT_SIGFRAME_UCONTEXT    0x80
> @@ -228,7 +231,7 @@ __gnu_personality_sigframe_fdpic (_Unwind_State state,
>      _Unwind_VRS_Get (context, _UVRSC_CORE, R_SP, _UVRSD_UINT32, &sp);
>      _Unwind_VRS_Get (context, _UVRSC_CORE, R_PC, _UVRSD_UINT32, &pc);
>
> -    funcdesc = *(unsigned int *)(pc + FDPIC_FUNCDESC_OFFSET);
> +    funcdesc = *(unsigned int *)((pc & ~1) + FDPIC_FUNCDESC_OFFSET);
>      handler = *(unsigned int *)(funcdesc);
>      first_handler_instruction = *(unsigned int *)(handler & ~1);
>
> @@ -277,10 +280,13 @@ get_eit_entry (_Unwind_Control_Block *ucbp, _uw return_address)
>            /* If we are unwinding a signal handler then perhaps we have
>               reached a trampoline.  Try to detect jump to restorer
>               sequence.  */
> -         _uw *pc = (_uw *)((return_address+2) & ~3);
> -         if (pc[0] == FDPIC_LDR_R12_WITH_FUNCDESC
> -             && pc[1] == FDPIC_LDR_R9_WITH_GOT
> -             && pc[2] == FDPIC_LDR_PC_WITH_RESTORER)
> +         _uw *pc = (_uw *)((return_address+2) & ~1);
> +         if ((pc[0] == FDPIC_LDR_R12_WITH_FUNCDESC
> +              && pc[1] == FDPIC_LDR_R9_WITH_GOT
> +              && pc[2] == FDPIC_LDR_PC_WITH_RESTORER)
> +             || (pc[0] == FDPIC_T2_LDR_R12_WITH_FUNCDESC
> +                 && pc[1] == FDPIC_T2_LDR_R9_WITH_GOT
> +                 && pc[2] == FDPIC_T2_LDR_PC_WITH_RESTORER))
>              {

This largely overwrites and extends code added in patch 11/21. Can't we just merge the two
patches into a final sane one?

Thanks,
Kyrill

>                struct funcdesc_t *funcdesc = (struct funcdesc_t *)
>                  &__gnu_personality_sigframe_fdpic;
> @@ -309,13 +315,16 @@ get_eit_entry (_Unwind_Control_Block *ucbp, _uw return_address)
>        /* If we are unwinding a signal handler then perhaps we have
>           reached a trampoline.  Try to detect jump to restorer
>           sequence.  */
> -      _uw *pc = (_uw *)((return_address+2) & ~3);
> -      if (pc[0] == FDPIC_LDR_R12_WITH_FUNCDESC
> -         && pc[1] == FDPIC_LDR_R9_WITH_GOT
> -         && pc[2] == FDPIC_LDR_PC_WITH_RESTORER)
> +      _uw *pc = (_uw *)((return_address+2) & ~1);
> +      if ((pc[0] == FDPIC_LDR_R12_WITH_FUNCDESC
> +          && pc[1] == FDPIC_LDR_R9_WITH_GOT
> +          && pc[2] == FDPIC_LDR_PC_WITH_RESTORER)
> +         || (pc[0] == FDPIC_T2_LDR_R12_WITH_FUNCDESC
> +             && pc[1] == FDPIC_T2_LDR_R9_WITH_GOT
> +             && pc[2] == FDPIC_T2_LDR_PC_WITH_RESTORER))
>          {
> -         struct funcdesc_t *funcdesc = (struct funcdesc_t *)
> -           &__gnu_personality_sigframe_fdpic;
> +         struct funcdesc_t *funcdesc
> +           = (struct funcdesc_t *) &__gnu_personality_sigframe_fdpic;
>
>            UCB_PR_ADDR (ucbp) = funcdesc->ptr;
>            UCB_PR_GOT (ucbp) = funcdesc->got;
> @@ -335,13 +344,16 @@ get_eit_entry (_Unwind_Control_Block *ucbp, _uw return_address)
>        /* If we are unwinding a signal handler then perhaps we have
>           reached a trampoline.  Try to detect jump to restorer
>           sequence.  */
> -      _uw *pc = (_uw *)((return_address+2) & ~3);
> -      if (pc[0] == FDPIC_LDR_R12_WITH_FUNCDESC
> -         && pc[1] == FDPIC_LDR_R9_WITH_GOT
> -         && pc[2] == FDPIC_LDR_PC_WITH_RESTORER)
> +      _uw *pc = (_uw *)((return_address+2) & ~1);
> +      if ((pc[0] == FDPIC_LDR_R12_WITH_FUNCDESC
> +          && pc[1] == FDPIC_LDR_R9_WITH_GOT
> +          && pc[2] == FDPIC_LDR_PC_WITH_RESTORER)
> +         || (pc[0] == FDPIC_T2_LDR_R12_WITH_FUNCDESC
> +             && pc[1] == FDPIC_T2_LDR_R9_WITH_GOT
> +             && pc[2] == FDPIC_T2_LDR_PC_WITH_RESTORER))
>          {
> -         struct funcdesc_t *funcdesc = (struct funcdesc_t *)
> -           &__gnu_personality_sigframe_fdpic;
> +         struct funcdesc_t *funcdesc
> +           = (struct funcdesc_t *) &__gnu_personality_sigframe_fdpic;
>
>            UCB_PR_ADDR (ucbp) = funcdesc->ptr;
>            UCB_PR_GOT (ucbp) = funcdesc->got;
> -- 
> 2.6.3
>