[8/9] Support TLS variables on FreeBSD/riscv.

  Derive the pointer to the DTV array from the tp register.

gdb/ChangeLog:

	* riscv-fbsd-tdep.c (riscv_fbsd_get_thread_local_address): New.
	(riscv_fbsd_init_abi): Install gdbarch
	"fetch_tls_load_module_address" and "get_thread_local_address"
	methods.
---
 gdb/ChangeLog         |  7 +++++++
 gdb/riscv-fbsd-tdep.c | 27 +++++++++++++++++++++++++++
 2 files changed, 34 insertions(+)
  

* John Baldwin <jhb@FreeBSD.org> [2019-01-22 10:43:01 -0800]:

> Derive the pointer to the DTV array from the tp register.
> 
> gdb/ChangeLog:
> 
> 	* riscv-fbsd-tdep.c (riscv_fbsd_get_thread_local_address): New.
> 	(riscv_fbsd_init_abi): Install gdbarch
> 	"fetch_tls_load_module_address" and "get_thread_local_address"
> 	methods.
> ---
>  gdb/ChangeLog         |  7 +++++++
>  gdb/riscv-fbsd-tdep.c | 27 +++++++++++++++++++++++++++
>  2 files changed, 34 insertions(+)

These look good to me.

Thanks,
Andrew



> 
> diff --git a/gdb/ChangeLog b/gdb/ChangeLog
> index 06c637c80a..5d228614db 100644
> --- a/gdb/ChangeLog
> +++ b/gdb/ChangeLog
> @@ -1,3 +1,10 @@
> +2019-01-22  John Baldwin  <jhb@FreeBSD.org>
> +
> +	* riscv-fbsd-tdep.c (riscv_fbsd_get_thread_local_address): New.
> +	(riscv_fbsd_init_abi): Install gdbarch
> +	"fetch_tls_load_module_address" and "get_thread_local_address"
> +	methods.
> +
>  2019-01-22  John Baldwin  <jhb@FreeBSD.org>
>  
>  	* i386-fbsd-tdep.c (i386fbsd_get_thread_local_address): New.
> diff --git a/gdb/riscv-fbsd-tdep.c b/gdb/riscv-fbsd-tdep.c
> index 97ad28f59a..3125a2285e 100644
> --- a/gdb/riscv-fbsd-tdep.c
> +++ b/gdb/riscv-fbsd-tdep.c
> @@ -174,6 +174,28 @@ static const struct tramp_frame riscv_fbsd_sigframe =
>    riscv_fbsd_sigframe_init
>  };
>  
> +/* Implement the "get_thread_local_address" gdbarch method.  */
> +
> +static CORE_ADDR
> +riscv_fbsd_get_thread_local_address (struct gdbarch *gdbarch, ptid_t ptid,
> +				     CORE_ADDR lm_addr, CORE_ADDR offset)
> +{
> +  struct regcache *regcache;
> +
> +  regcache = get_thread_arch_regcache (ptid, gdbarch);
> +
> +  target_fetch_registers (regcache, RISCV_TP_REGNUM);
> +
> +  ULONGEST tp;
> +  if (regcache->cooked_read (RISCV_TP_REGNUM, &tp) != REG_VALID)
> +    error (_("Unable to fetch %%tp"));
> +
> +  /* %tp points to the end of the TCB which contains two pointers.
> +      The first pointer in the TCB points to the DTV array.  */
> +  CORE_ADDR dtv_addr = tp - (gdbarch_ptr_bit (gdbarch) / 8) * 2;
> +  return fbsd_get_thread_local_address (gdbarch, dtv_addr, lm_addr, offset);
> +}
> +
>  /* Implement the 'init_osabi' method of struct gdb_osabi_handler.  */
>  
>  static void
> @@ -193,6 +215,11 @@ riscv_fbsd_init_abi (struct gdbarch_info info, struct gdbarch *gdbarch)
>  
>    set_gdbarch_iterate_over_regset_sections
>      (gdbarch, riscv_fbsd_iterate_over_regset_sections);
> +
> +  set_gdbarch_fetch_tls_load_module_address (gdbarch,
> +					     svr4_fetch_objfile_link_map);
> +  set_gdbarch_get_thread_local_address (gdbarch,
> +					riscv_fbsd_get_thread_local_address);
>  }
>  
>  void
> -- 
> 2.19.2
>