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 <wschm...@linux.ibm.com>
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.
---
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 */
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
@@ -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;
+ }
+ else
+ info->rop_check_size = 0;
+
/* 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;
}
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);
+
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);
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));
+ }
+
/* 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));
+ }
+
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")])
(include "sync.md")
--
2.27.0
