[PATCH] [PING] Asan changes for RISC-V.

[Jim Wilson]

On Wed, Oct 28, 2020 at 4:59 PM Jim Wilson <jimw@sifive.com> wrote:

> We have only riscv64 asan support, there is no riscv32 support as yet.  So
> I
> need to be able to conditionally enable asan support for the riscv
> target.  I
> implemented this by returning zero from the asan_shadow_offset function.
> This
> requires a change to toplev.c and docs in target.def.
>
> The asan support works on a 5.5 kernel, but does not work on a 4.15 kernel.
> The problem is that the asan high memory region is a small wedge below
> 0x4000000000.  The new kernel puts shared libraries at 0x3fffffffff and
> going
> down which works.  But the old kernel puts shared libraries at 0x2000000000
> and going up which does not work, as it isn't in any recognized memory
> region.  This might be fixable with more asan work, but we don't really
> need
> support for old kernel versions.
>
> The asan port is curious in that it uses 1<<29 for the shadow offset, but
> all
> other 64-bit targets use a number larger than 1<<32.  But what we have is
> working OK for now.
>
> I did a make check RUNTESTFLAGS="asan.exp" on Fedora rawhide image running
> on
> qemu and the results look reasonable.
>
>                 === gcc Summary ===
>
> # of expected passes            1905
> # of unexpected failures        11
> # of unsupported tests          224
>
>                 === g++ Summary ===
>
> # of expected passes            2002
> # of unexpected failures        6
> # of unresolved testcases       1
> # of unsupported tests          175
>
> OK?
>
> Jim
>
> 2020-10-28  Jim Wilson  <jimw@sifive.com>
>
>         gcc/
>         * config/riscv/riscv.c (riscv_asan_shadow_offset): New.
>         (TARGET_ASAN_SHADOW_OFFSET): New.
>         * doc/tm.texi: Regenerated.
>         * target.def (asan_shadow_offset); Mention that it can return zero.
>         * toplev.c (process_options): Check for and handle zero return from
>         targetm.asan_shadow_offset call.
>
> Co-Authored-By: cooper.joshua <cooper.joshua@linux.alibaba.com>
> ---
>  gcc/config/riscv/riscv.c | 16 ++++++++++++++++
>  gcc/doc/tm.texi          |  3 ++-
>  gcc/target.def           |  3 ++-
>  gcc/toplev.c             |  3 ++-
>  4 files changed, 22 insertions(+), 3 deletions(-)
>
> diff --git a/gcc/config/riscv/riscv.c b/gcc/config/riscv/riscv.c
> index 989a9f15250..6909e200de1 100644
> --- a/gcc/config/riscv/riscv.c
> +++ b/gcc/config/riscv/riscv.c
> @@ -5299,6 +5299,19 @@ riscv_gpr_save_operation_p (rtx op)
>    return true;
>  }
>
> +/* Implement TARGET_ASAN_SHADOW_OFFSET.  */
> +
> +static unsigned HOST_WIDE_INT
> +riscv_asan_shadow_offset (void)
> +{
> +  /* We only have libsanitizer support for RV64 at present.
> +
> +     This number must match kRiscv*_ShadowOffset* in the file
> +     libsanitizer/asan/asan_mapping.h which is currently 1<<29 for rv64,
> +     even though 1<<36 makes more sense.  */
> +  return TARGET_64BIT ? (HOST_WIDE_INT_1 << 29) : 0;
> +}
> +
>  /* Initialize the GCC target structure.  */
>  #undef TARGET_ASM_ALIGNED_HI_OP
>  #define TARGET_ASM_ALIGNED_HI_OP "\t.half\t"
> @@ -5482,6 +5495,9 @@ riscv_gpr_save_operation_p (rtx op)
>  #undef TARGET_NEW_ADDRESS_PROFITABLE_P
>  #define TARGET_NEW_ADDRESS_PROFITABLE_P riscv_new_address_profitable_p
>
> +#undef TARGET_ASAN_SHADOW_OFFSET
> +#define TARGET_ASAN_SHADOW_OFFSET riscv_asan_shadow_offset
> +
>  struct gcc_target targetm = TARGET_INITIALIZER;
>
>  #include "gt-riscv.h"
> diff --git a/gcc/doc/tm.texi b/gcc/doc/tm.texi
> index 24c37f655c8..39c596b647a 100644
> --- a/gcc/doc/tm.texi
> +++ b/gcc/doc/tm.texi
> @@ -12078,7 +12078,8 @@ is zero, which disables this optimization.
>  @deftypefn {Target Hook} {unsigned HOST_WIDE_INT}
> TARGET_ASAN_SHADOW_OFFSET (void)
>  Return the offset bitwise ored into shifted address to get corresponding
>  Address Sanitizer shadow memory address.  NULL if Address Sanitizer is not
> -supported by the target.
> +supported by the target.  May return 0 if Address Sanitizer is not
> supported
> +by a subtarget.
>  @end deftypefn
>
>  @deftypefn {Target Hook} {unsigned HOST_WIDE_INT} TARGET_MEMMODEL_CHECK
> (unsigned HOST_WIDE_INT @var{val})
> diff --git a/gcc/target.def b/gcc/target.def
> index ed2da154e30..268b56b6ebd 100644
> --- a/gcc/target.def
> +++ b/gcc/target.def
> @@ -4452,7 +4452,8 @@ DEFHOOK
>  (asan_shadow_offset,
>   "Return the offset bitwise ored into shifted address to get
> corresponding\n\
>  Address Sanitizer shadow memory address.  NULL if Address Sanitizer is
> not\n\
> -supported by the target.",
> +supported by the target.  May return 0 if Address Sanitizer is not
> supported\n\
> +by a subtarget.",
>   unsigned HOST_WIDE_INT, (void),
>   NULL)
>
> diff --git a/gcc/toplev.c b/gcc/toplev.c
> index 20e231f4d2a..cf89598252c 100644
> --- a/gcc/toplev.c
> +++ b/gcc/toplev.c
> @@ -1834,7 +1834,8 @@ process_options (void)
>      }
>
>    if ((flag_sanitize & SANITIZE_USER_ADDRESS)
> -      && targetm.asan_shadow_offset == NULL)
> +      && ((targetm.asan_shadow_offset == NULL)
> +         || (targetm.asan_shadow_offset () == 0)))
>      {
>        warning_at (UNKNOWN_LOCATION, 0,
>                   "%<-fsanitize=address%> not supported for this target");
> --
> 2.17.1
>
>