On Fri, Sep 19, 2014 at 2:53 PM, Ilya Enkovich <enkovich....@gmail.com> wrote:
>> > This patch adds i386 target hooks for Pointer Bounds Checker.
> New version with fixes and better documentation for ix86_load_bounds and
> ix86_store_bounds is below.
> +/* Expand pass uses this hook to load bounds for function parameter
> + PTR passed in SLOT in case its bounds are not passed in a register.
> +
> + If SLOT is a memory, then bounds are loaded as for regular pointer
> + loaded from memory. PTR may be NULL in case SLOT is a memory.
> + In such case value of PTR (if required) may be loaded from SLOT.
> +
> + If SLOT is NULL or a register then SLOT_NO is an integer constant
> + holding number of the target dependent special slot which should be
> + used to obtain bounds.
> +
> + Return loaded bounds. */
OK, I hope I understand this target-handling of SLOT_NO. Can you
please clarify when SLOT is a register?
I propose to write this function in the following (hopefully equivalent) way:
--cut here--
{
if (!slot)
{
gcc_assert (CONST_INT_P (slot_no));
addr = plus_constant (Pmode, arg_pointer_rtx,
-(INTVAL (slot_no) + 1) * GET_MODE_SIZE (Pmode));
gcc_assert (ptr);
}
else if (REG_P (slot))
{
gcc_assert (CONST_INT_P (slot_no));
addr = plus_constant (Pmode, arg_pointer_rtx,
-(INTVAL (slot_no) + 1) * GET_MODE_SIZE (Pmode));
ptr = slot;
}
else if (MEM_P (slot))
{
addr = XEXP (slot, 0);
if (!register_operand (addr, Pmode))
addr = copy_addr_to_reg (addr);
if (!ptr)
ptr = copy_addr_to_reg (slot);
}
else
gcc_unreachable ();
if (!index_register_operand (ptr, Pmode))
ptr = copy_addr_to_reg (ptr);
...
}
--cut here--
Please add a comment in each of if/else, explaining what the code is
doing. This is non-trivial to understand.
> +
> +static rtx
> +ix86_load_bounds (rtx slot, rtx ptr, rtx slot_no)
> +{
> + rtx addr = NULL;
> + rtx reg;
> +
> + if (!ptr)
> + {
> + gcc_assert (MEM_P (slot));
> + ptr = copy_addr_to_reg (slot);
> + }
> +
> + if (!slot || REG_P (slot))
> + {
> + if (slot)
> + ptr = slot;
> +
> + gcc_assert (CONST_INT_P (slot_no));
> +
> + /* Here we have the case when more than four pointers are
> + passed in registers. In this case we are out of bound
> + registers and have to use bndldx to load bound. RA,
> + RA - 8, etc. are used for address translation in bndldx. */
> + addr = plus_constant (Pmode, arg_pointer_rtx,
> + -(INTVAL (slot_no) + 1) * GET_MODE_SIZE (Pmode));
> + }
> + else if (MEM_P (slot))
> + {
> + addr = XEXP (slot, 0);
> + if (!register_operand (addr, Pmode))
> + addr = copy_addr_to_reg (addr);
> + }
> + else
> + gcc_unreachable ();
> +
> + if (!register_operand (ptr, Pmode))
> + ptr = copy_addr_to_reg (ptr);
> +
> + reg = gen_reg_rtx (BNDmode);
> + emit_insn (BNDmode == BND64mode
> + ? gen_bnd64_ldx (reg, addr, ptr)
> + : gen_bnd32_ldx (reg, addr, ptr));
> +
> + return reg;
> +}
> +
> +/* Expand pass uses this hook to store BOUNDS for call argument PTR
> + passed in SLOT in case BOUNDS are not passed in a register.
> +
> + If SLOT is a memory, then BOUNDS are stored as for regular pointer
> + stored in memory. PTR may be NULL in case SLOT is a memory.
> + In such case value of PTR (if required) may be loaded from SLOT.
> +
> + If SLOT is NULL or a register then SLOT_NO is an integer constant
> + holding number of the target dependent special slot which should be
> + used to store BOUNDS. */
> +
> +static void
> +ix86_store_bounds (rtx ptr, rtx slot, rtx bounds, rtx slot_no)
This function can be written in exactly the same way as the above
proposed code, up to the check for ptr register_operand.
> +{
> + rtx addr;
> +
> + if (ptr)
> + {
> + if (!register_operand (ptr, Pmode))
> + ptr = copy_addr_to_reg (ptr);
> + }
> + else
> + {
> + gcc_assert (MEM_P (slot));
> + ptr = copy_addr_to_reg (slot);
> + }
> +
> + if (!slot || REG_P (slot))
> + {
> + gcc_assert (CONST_INT_P (slot_no));
> + addr = plus_constant (Pmode, stack_pointer_rtx,
> + -(INTVAL (slot_no) + 1) * GET_MODE_SIZE (Pmode));
> + }
> + else if (MEM_P (slot))
> + addr = XEXP (slot, 0);
> + else
> + gcc_unreachable ();
> +
> + if (!register_operand (addr, Pmode))
> + addr = copy_addr_to_reg (addr);
The above check is needed since addr handling in the gen_bndX_stx
expander (patch 2/n) is different that addr handling in gen_bndX_ldx.
This handling should be unified in a follow-up patch.
> + /* Avoid registers which connot be used as index. */
> + if (!index_register_operand (ptr, Pmode))
> + {
> + rtx temp = gen_reg_rtx (Pmode);
> + emit_move_insn (temp, ptr);
> + ptr = temp;
> + }
> +
> + gcc_assert (POINTER_BOUNDS_MODE_P (GET_MODE (bounds)));
> + if (!register_operand (bounds, BNDmode))
> + bounds = copy_to_mode_reg (BNDmode, bounds);
> +
> + emit_insn (BNDmode == BND64mode
> + ? gen_bnd64_stx (addr, ptr, bounds)
> + : gen_bnd32_stx (addr, ptr, bounds));
> +}
> +
> +/* Load and return bounds returned by function in SLOT. */
> +
> +static rtx
> +ix86_load_returned_bounds (rtx slot)
> +{
> + rtx res;
> +
> + gcc_assert (REG_P (slot));
> + res = gen_reg_rtx (BNDmode);
> + emit_move_insn (res, slot);
> +
> + return res;
> +}
> +
> +/* Store BOUNDS returned by function into SLOT. */
> +
> +static void
> +ix86_store_returned_bounds (rtx slot, rtx bounds)
> +{
> + gcc_assert (REG_P (slot));
> + emit_move_insn (slot, bounds);
> +}
> +
> /* Returns a function decl for a vectorized version of the builtin function
> with builtin function code FN and the result vector type TYPE, or
> NULL_TREE
> if it is not available. */
> @@ -47480,6 +47701,61 @@ ix86_atomic_assign_expand_fenv (tree *hold, tree
> *clear, tree *update)
> atomic_feraiseexcept_call);
> }
>
> +static enum machine_mode
> +ix86_mpx_bound_mode ()
> +{
> + /* Do not support pointer checker if MPX
> + is not enabled. */
> + if (!TARGET_MPX)
> + {
> + if (flag_check_pointer_bounds)
> + warning (0, "Pointer Checker requires MPX support on this target."
> + " Use -mmpx options to enable MPX.");
> + return VOIDmode;
> + }
> +
> + return BNDmode;
> +}
> +
> +static tree
> +ix86_make_bounds_constant (HOST_WIDE_INT lb, HOST_WIDE_INT ub)
> +{
> + tree low = lb ? build_minus_one_cst (pointer_sized_int_node)
> + : build_zero_cst (pointer_sized_int_node);
> + tree high = ub ? build_zero_cst (pointer_sized_int_node)
> + : build_minus_one_cst (pointer_sized_int_node);
> +
> + /* This function is supposed to be used to create zero and
> + none bounds only. */
> + gcc_assert (lb == 0 || lb == -1);
> + gcc_assert (ub == 0 || ub == -1);
> +
> + return build_complex (NULL, low, high);
> +}
> +
> +static int
> +ix86_initialize_bounds (tree var, tree lb, tree ub, tree *stmts)
> +{
> + tree size_ptr = build_pointer_type (size_type_node);
> + tree lhs, modify, var_p;
> +
> + ub = build1 (BIT_NOT_EXPR, size_type_node, ub);
> + var_p = build1 (CONVERT_EXPR, size_ptr,
> + build_fold_addr_expr (var));
> +
> + lhs = build1 (INDIRECT_REF, size_type_node, var_p);
> + modify = build2 (MODIFY_EXPR, TREE_TYPE (lhs), lhs, lb);
> + append_to_statement_list (modify, stmts);
> +
> + lhs = build1 (INDIRECT_REF, size_type_node,
> + build2 (POINTER_PLUS_EXPR, size_ptr, var_p,
> + TYPE_SIZE_UNIT (size_type_node)));
> + modify = build2 (MODIFY_EXPR, TREE_TYPE (lhs), lhs, ub);
> + append_to_statement_list (modify, stmts);
> +
> + return 2;
> +}
The above two functions are outside of my expertise. Although they
look trivial, I'd be more comfortable if a tree expert reviews them.
> +
> /* Initialize the GCC target structure. */
> #undef TARGET_RETURN_IN_MEMORY
> #define TARGET_RETURN_IN_MEMORY ix86_return_in_memory
> @@ -47897,6 +48173,33 @@ ix86_atomic_assign_expand_fenv (tree *hold, tree
> *clear, tree *update)
> #undef TARGET_CALL_FUSAGE_CONTAINS_NON_CALLEE_CLOBBERS
> #define TARGET_CALL_FUSAGE_CONTAINS_NON_CALLEE_CLOBBERS true
>
> +#undef TARGET_LOAD_BOUNDS_FOR_ARG
> +#define TARGET_LOAD_BOUNDS_FOR_ARG ix86_load_bounds
> +
> +#undef TARGET_STORE_BOUNDS_FOR_ARG
> +#define TARGET_STORE_BOUNDS_FOR_ARG ix86_store_bounds
> +
> +#undef TARGET_LOAD_RETURNED_BOUNDS
> +#define TARGET_LOAD_RETURNED_BOUNDS ix86_load_returned_bounds
> +
> +#undef TARGET_STORE_RETURNED_BOUNDS
> +#define TARGET_STORE_RETURNED_BOUNDS ix86_store_returned_bounds
> +
> +#undef TARGET_CHKP_BOUND_MODE
> +#define TARGET_CHKP_BOUND_MODE ix86_mpx_bound_mode
> +
> +#undef TARGET_BUILTIN_CHKP_FUNCTION
> +#define TARGET_BUILTIN_CHKP_FUNCTION ix86_builtin_mpx_function
> +
> +#undef TARGET_CHKP_FUNCTION_VALUE_BOUNDS
> +#define TARGET_CHKP_FUNCTION_VALUE_BOUNDS ix86_function_value_bounds
> +
> +#undef TARGET_CHKP_MAKE_BOUNDS_CONSTANT
> +#define TARGET_CHKP_MAKE_BOUNDS_CONSTANT ix86_make_bounds_constant
> +
> +#undef TARGET_CHKP_INITIALIZE_BOUNDS
> +#define TARGET_CHKP_INITIALIZE_BOUNDS ix86_initialize_bounds
> +
> struct gcc_target targetm = TARGET_INITIALIZER;
>
> #include "gt-i386.h"
Uros.
