On Sun, 2021-04-25 at 20:50 -0500, Bill Schmidt via Gcc-patches wrote:
> Insert the hashst and hashchk instructions when -mrop-protect has been
> selected. The encrypted save slot for ROP mitigation is placed
> between the parameter save area and the alloca space (if any;
> otherwise the local variable space).
>
> Note that ROP-mitigation instructions are currently only provided for
> the ELFv2 ABI.
>
> 2021-03-25 Bill Schmidt <[email protected]>
>
> gcc/
> * config/rs6000/rs6000-internal.h (rs6000_stack): Add
> rop_check_save_offset and rop_check_size.
> * config/rs6000/rs6000-logue.c (rs6000_stack_info): Compute
> rop_check_size and rop_check_save_offset.
> (debug_stack_info): Dump rop_save_offset and rop_check_size.
> (rs6000_emit_prologue): Assert if WORLD_SAVE used with
> -mrop-protect; emit hashst[p] in prologue; emit hashchk[p] in
> epilogue.
> * config/rs6000/rs6000.md (unspec): Add UNSPEC_HASHST[P] and
> UNSPEC_HASHCHK[P].
> (hashst): New define_insn.
> (hashstp): Likewise.
> (hashchk): Likewise.
> (hashchkp): Likewise.
ok
> ---
> gcc/config/rs6000/rs6000-internal.h | 2 +
> gcc/config/rs6000/rs6000-logue.c | 86 +++++++++++++++++++++++++----
> gcc/config/rs6000/rs6000.md | 39 +++++++++++++
> 3 files changed, 116 insertions(+), 11 deletions(-)
>
> diff --git a/gcc/config/rs6000/rs6000-internal.h
> b/gcc/config/rs6000/rs6000-internal.h
> index 428a7861a98..8fc77ba6138 100644
> --- a/gcc/config/rs6000/rs6000-internal.h
> +++ b/gcc/config/rs6000/rs6000-internal.h
> @@ -39,6 +39,7 @@ typedef struct rs6000_stack {
> int gp_save_offset; /* offset to save GP regs from initial
> SP */
> int fp_save_offset; /* offset to save FP regs from initial
> SP */
> int altivec_save_offset; /* offset to save AltiVec regs from initial SP
> */
> + int rop_check_save_offset; /* offset to save ROP check from initial SP */
> int lr_save_offset; /* offset to save LR from initial SP */
> int cr_save_offset; /* offset to save CR from initial SP */
> int vrsave_save_offset; /* offset to save VRSAVE from initial SP */
> @@ -53,6 +54,7 @@ typedef struct rs6000_stack {
> int gp_size; /* size of saved GP registers */
> int fp_size; /* size of saved FP registers */
> int altivec_size; /* size of saved AltiVec registers */
> + int rop_check_size; /* size of ROP check slot */
> int cr_size; /* size to hold CR if not in fixed area
> */
> int vrsave_size; /* size to hold VRSAVE */
> int altivec_padding_size; /* size of altivec alignment padding */
ok
> diff --git a/gcc/config/rs6000/rs6000-logue.c
> b/gcc/config/rs6000/rs6000-logue.c
> index b0ac183ceff..10cf7a2de93 100644
> --- a/gcc/config/rs6000/rs6000-logue.c
> +++ b/gcc/config/rs6000/rs6000-logue.c
> @@ -595,19 +595,21 @@ rs6000_savres_strategy (rs6000_stack_t *info,
> +---------------------------------------+
> | Parameter save area (+padding*) (P) | 32
> +---------------------------------------+
> - | Alloca space (A) | 32+P
> + | Optional ROP check slot (R) | 32+P
> +---------------------------------------+
> - | Local variable space (L) | 32+P+A
> + | Alloca space (A) | 32+P+R
> +---------------------------------------+
> - | Save area for AltiVec registers (W) | 32+P+A+L
> + | Local variable space (L) | 32+P+R+A
> +---------------------------------------+
> - | AltiVec alignment padding (Y) | 32+P+A+L+W
> + | Save area for AltiVec registers (W) | 32+P+R+A+L
> +---------------------------------------+
> - | Save area for GP registers (G) | 32+P+A+L+W+Y
> + | AltiVec alignment padding (Y) | 32+P+R+A+L+W
> +---------------------------------------+
> - | Save area for FP registers (F) | 32+P+A+L+W+Y+G
> + | Save area for GP registers (G) | 32+P+R+A+L+W+Y
> +---------------------------------------+
> - old SP->| back chain to caller's caller | 32+P+A+L+W+Y+G+F
> + | Save area for FP registers (F) | 32+P+R+A+L+W+Y+G
> + +---------------------------------------+
> + old SP->| back chain to caller's caller | 32+P+R+A+L+W+Y+G+F
> +---------------------------------------+
>
> * If the alloca area is present, the parameter save area is
ok
> @@ -717,6 +719,19 @@ rs6000_stack_info (void)
> /* Does this function call anything (apart from sibling calls)? */
> info->calls_p = (!crtl->is_leaf || cfun->machine->ra_needs_full_frame);
>
> + if (TARGET_POWER10 && info->calls_p
> + && DEFAULT_ABI == ABI_ELFv2 && rs6000_rop_protect)
> + info->rop_check_size = 8;
> + else if (rs6000_rop_protect && DEFAULT_ABI != ABI_ELFv2)
> + {
> + /* We can't check this in rs6000_option_override_internal since
> + DEFAULT_ABI isn't established yet. */
> + error ("%qs requires the ELFv2 ABI", "-mrop-protect");
> + info->rop_check_size = 0;
ok
> + }
> + else
> + info->rop_check_size = 0;
> +
ok
> /* Determine if we need to save the condition code registers. */
> if (save_reg_p (CR2_REGNO)
> || save_reg_p (CR3_REGNO)
> @@ -806,8 +821,14 @@ rs6000_stack_info (void)
> gcc_assert (info->altivec_size == 0
> || info->altivec_save_offset % 16 == 0);
>
> - /* Adjust for AltiVec case. */
> - info->ehrd_offset = info->altivec_save_offset - ehrd_size;
> + if (info->rop_check_size != 0)
> + {
> + info->rop_check_save_offset
> + = info->altivec_save_offset - info->rop_check_size;
> + info->ehrd_offset = info->rop_check_save_offset - ehrd_size;
> + }
> + else
> + info->ehrd_offset = info->altivec_save_offset - ehrd_size;
ok
> }
> else
> info->ehrd_offset = info->gp_save_offset - ehrd_size;
> @@ -849,6 +870,7 @@ rs6000_stack_info (void)
> + info->gp_size
> + info->altivec_size
> + info->altivec_padding_size
> + + info->rop_check_size
> + ehrd_size
> + ehcr_size
> + info->cr_size
> @@ -987,6 +1009,10 @@ debug_stack_info (rs6000_stack_t *info)
> fprintf (stderr, "\tvrsave_save_offset = %5d\n",
> info->vrsave_save_offset);
>
> + if (info->rop_check_size)
> + fprintf (stderr, "\trop_check_save_offset = %5d\n",
> + info->rop_check_save_offset);
> +
ok
> if (info->lr_save_p)
> fprintf (stderr, "\tlr_save_offset = %5d\n", info->lr_save_offset);
>
> @@ -1026,6 +1052,9 @@ debug_stack_info (rs6000_stack_t *info)
> fprintf (stderr, "\taltivec_padding_size= %5d\n",
> info->altivec_padding_size);
>
> + if (info->rop_check_size)
> + fprintf (stderr, "\trop_check_size = %5d\n", info->rop_check_size);
> +
> if (info->cr_size)
> fprintf (stderr, "\tcr_size = %5d\n", info->cr_size);
>
> @@ -3044,7 +3073,6 @@ rs6000_emit_prologue (void)
> cfun->machine->r2_setup_needed = true;
> }
>
> -
> if (flag_stack_usage_info)
> current_function_static_stack_size = info->total_size;
>
> @@ -3105,7 +3133,8 @@ rs6000_emit_prologue (void)
> && (!crtl->calls_eh_return
> || info->ehrd_offset == -432)
> && info->vrsave_save_offset == -224
> - && info->altivec_save_offset == -416);
> + && info->altivec_save_offset == -416
> + && !rs6000_rop_protect);
>
ok
> treg = gen_rtx_REG (SImode, 11);
> emit_move_insn (treg, GEN_INT (-info->total_size));
> @@ -3252,6 +3281,24 @@ rs6000_emit_prologue (void)
> }
> }
>
> + /* The ROP hash store must occur before a stack frame is created. */
> + /* NOTE: The hashst isn't needed if we're going to do a sibcall,
> + but there's no way to know that here. Harmless except for
> + performance, of course. */
> + if (TARGET_POWER10 && rs6000_rop_protect && info->rop_check_size != 0)
> + {
> + gcc_assert (DEFAULT_ABI == ABI_ELFv2);
> + rtx stack_ptr = gen_rtx_REG (Pmode, STACK_POINTER_REGNUM);
> + rtx addr = gen_rtx_PLUS (Pmode, stack_ptr,
> + GEN_INT (info->rop_check_save_offset));
> + rtx mem = gen_rtx_MEM (Pmode, addr);
> + rtx reg0 = gen_rtx_REG (Pmode, 0);
> + if (rs6000_privileged)
> + emit_insn (gen_hashstp (mem, reg0));
> + else
> + emit_insn (gen_hashst (mem, reg0));
> + }
> +
ok
> /* If we need to save CR, put it into r12 or r11. Choose r12 except when
> r12 will be needed by out-of-line gpr save. */
> cr_save_regno = ((DEFAULT_ABI == ABI_AIX || DEFAULT_ABI == ABI_ELFv2)
> @@ -4980,6 +5027,23 @@ rs6000_emit_epilogue (enum epilogue_type epilogue_type)
> emit_insn (gen_add3_insn (sp_reg_rtx, sp_reg_rtx, sa));
> }
>
> + /* The ROP hash check must occur after the stack pointer is restored,
> + and is not performed for a sibcall. */
> + if (TARGET_POWER10 && rs6000_rop_protect && info->rop_check_size != 0
> + && epilogue_type != EPILOGUE_TYPE_SIBCALL)
> + {
> + gcc_assert (DEFAULT_ABI == ABI_ELFv2);
> + rtx stack_ptr = gen_rtx_REG (Pmode, STACK_POINTER_REGNUM);
> + rtx addr = gen_rtx_PLUS (Pmode, stack_ptr,
> + GEN_INT (info->rop_check_save_offset));
> + rtx mem = gen_rtx_MEM (Pmode, addr);
> + rtx reg0 = gen_rtx_REG (Pmode, 0);
> + if (rs6000_privileged)
> + emit_insn (gen_hashchkp (reg0, mem));
> + else
> + emit_insn (gen_hashchk (reg0, mem));
> + }
> +
ok
> if (epilogue_type != EPILOGUE_TYPE_SIBCALL && restoring_FPRs_inline)
> {
> if (cfa_restores)
> diff --git a/gcc/config/rs6000/rs6000.md b/gcc/config/rs6000/rs6000.md
> index c8cdc42533c..eec2e7532e1 100644
> --- a/gcc/config/rs6000/rs6000.md
> +++ b/gcc/config/rs6000/rs6000.md
> @@ -154,6 +154,10 @@ (define_c_enum "unspec"
> UNSPEC_CNTTZDM
> UNSPEC_PDEPD
> UNSPEC_PEXTD
> + UNSPEC_HASHST
> + UNSPEC_HASHSTP
> + UNSPEC_HASHCHK
> + UNSPEC_HASHCHKP
> ])
>
> ;;
> @@ -14948,6 +14952,41 @@ (define_insn "*cmpeqb_internal"
> "TARGET_P9_MISC && TARGET_64BIT"
> "cmpeqb %0,%1,%2"
> [(set_attr "type" "logical")])
> +
> +
> +;; ROP mitigation instructions.
> +
> +(define_insn "hashst"
> + [(set (match_operand:DI 0 "simple_offsettable_mem_operand" "=m")
> + (unspec:DI [(match_operand:DI 1 "int_reg_operand" "r")]
> + UNSPEC_HASHST))]
> + "TARGET_POWER10 && rs6000_rop_protect"
> + "hashst %1,%0"
> + [(set_attr "type" "store")])
> +
> +(define_insn "hashstp"
> + [(set (match_operand:DI 0 "simple_offsettable_mem_operand" "=m")
> + (unspec:DI [(match_operand:DI 1 "int_reg_operand" "r")]
> + UNSPEC_HASHSTP))]
> + "TARGET_POWER10 && rs6000_rop_protect && rs6000_privileged"
> + "hashstp %1,%0"
> + [(set_attr "type" "store")])
> +
> +(define_insn "hashchk"
> + [(unspec_volatile [(match_operand:DI 0 "int_reg_operand" "r")
> + (match_operand:DI 1 "simple_offsettable_mem_operand" "m")]
> + UNSPEC_HASHCHK)]
> + "TARGET_POWER10 && rs6000_rop_protect"
> + "hashchk %0,%1"
> + [(set_attr "type" "load")])
> +
> +(define_insn "hashchkp"
> + [(unspec_volatile [(match_operand:DI 0 "int_reg_operand" "r")
> + (match_operand:DI 1 "simple_offsettable_mem_operand" "m")]
> + UNSPEC_HASHCHKP)]
> + "TARGET_POWER10 && rs6000_rop_protect && rs6000_privileged"
> + "hashchkp %0,%1"
> + [(set_attr "type" "load")])
ok
lgtm,
thanks,
-Will
>
>
> (include "sync.md")
