-mstack-protector-guard and friends (PR78875)

Currently, on PowerPC, code compiled with -fstack-protector will load
the canary from -0x7010(13) (for -m64) or from -0x7008(2) (for -m32)
if GCC was compiled against GNU libc 2.4 or newer or some other libc
that supports -fstack-protector, and from the global variable
__stack_chk_guard otherwise.

This does not work well for Linux and other OS kernels and similar.
For such non-standard applications, this patch creates a few new
command-line options.  The relevant new use cases are:

-mstack-protector-guard=global
Use the __stack_chk_guard variable, no matter how this GCC was
configured.

-mstack-protector-guard=tls
Use the canary from TLS.  This will error out if this GCC was built
with a C library that does not support it.

-mstack-protector-guard=tls -mstack-protector-register=<reg>
-mstack-protector-offset=<offset>
Load the canary from offset <off> from base register <reg>.


	PR target/78875
	* config/rs6000/rs6000-opts.h (stack_protector_guard): New enum.
	* config/rs6000/rs6000.c (rs6000_option_override_internal): Handle
	the new options.
	* config/rs6000/rs6000.md (stack_protect_set): Handle the new more
	flexible settings.
	(stack_protect_test): Ditto.
	* config/rs6000/rs6000.opt (mstack-protector-guard=,
	mstack-protector-guard-reg=, mstack-protector-guard-offset=): New
	options.
	* doc/invoke.texi (Option Summary) [RS/6000 and PowerPC Options]:
	Add -mstack-protector-guard=, -mstack-protector-guard-reg=, and
	-mstack-protector-guard-offset=.
	(RS/6000 and PowerPC Options): Ditto.

gcc/testsuite/
	* gcc.target/powerpc/ssp-1.c: New testcase.
	* gcc.target/powerpc/ssp-2.c: New testcase.

From-SVN: r244556

gcc/ChangeLog

+2017-01-17  Segher Boessenkool  <segher@kernel.crashing.org>
+
+	PR target/78875
+	* config/rs6000/rs6000-opts.h (stack_protector_guard): New enum.
+	* config/rs6000/rs6000.c (rs6000_option_override_internal): Handle
+	the new options.
+	* config/rs6000/rs6000.md (stack_protect_set): Handle the new more
+	flexible settings.
+	(stack_protect_test): Ditto.
+	* config/rs6000/rs6000.opt (mstack-protector-guard=,
+	mstack-protector-guard-reg=, mstack-protector-guard-offset=): New
+	options.
+	* doc/invoke.texi (Option Summary) [RS/6000 and PowerPC Options]:
+	Add -mstack-protector-guard=, -mstack-protector-guard-reg=, and
+	-mstack-protector-guard-offset=.
+	(RS/6000 and PowerPC Options): Ditto.
+
 2017-01-17  Uros Bizjak  <ubizjak@gmail.com>
 
 	* config/i386/i386.h (MASK_CLASS_P): New define.

gcc/config/rs6000/rs6000-opts.h

@@ -154,6 +154,12 @@ enum rs6000_vector {
   VECTOR_OTHER			/* Some other vector unit */
 };
 
+/* Where to get the canary for the stack protector.  */
+enum stack_protector_guard {
+  SSP_TLS,			/* per-thread canary in TLS block */
+  SSP_GLOBAL			/* global canary */
+};
+
 /* No enumeration is defined to index the -mcpu= values (entries in
    processor_target_table), with the type int being used instead, but
    we need to distinguish the special "native" value.  */

gcc/config/rs6000/rs6000.c

@@ -4942,6 +4942,54 @@ rs6000_option_override_internal (bool global_init_p)
 				    atoi (rs6000_sched_insert_nops_str));
     }
 
+  /* Handle stack protector */
+  if (!global_options_set.x_rs6000_stack_protector_guard)
+#ifdef TARGET_THREAD_SSP_OFFSET
+    rs6000_stack_protector_guard = SSP_TLS;
+#else
+    rs6000_stack_protector_guard = SSP_GLOBAL;
+#endif
+
+#ifdef TARGET_THREAD_SSP_OFFSET
+  rs6000_stack_protector_guard_offset = TARGET_THREAD_SSP_OFFSET;
+  rs6000_stack_protector_guard_reg = TARGET_64BIT ? 13 : 2;
+#endif
+
+  if (global_options_set.x_rs6000_stack_protector_guard_offset_str)
+    {
+      char *endp;
+      const char *str = rs6000_stack_protector_guard_offset_str;
+
+      errno = 0;
+      long offset = strtol (str, &endp, 0);
+      if (!*str || *endp || errno)
+	error ("%qs is not a valid number "
+	       "in -mstack-protector-guard-offset=", str);
+
+      if (!IN_RANGE (offset, -0x8000, 0x7fff)
+	  || (TARGET_64BIT && (offset & 3)))
+	error ("%qs is not a valid offset "
+	       "in -mstack-protector-guard-offset=", str);
+
+      rs6000_stack_protector_guard_offset = offset;
+    }
+
+  if (global_options_set.x_rs6000_stack_protector_guard_reg_str)
+    {
+      const char *str = rs6000_stack_protector_guard_reg_str;
+      int reg = decode_reg_name (str);
+
+      if (!IN_RANGE (reg, 1, 31))
+	error ("%qs is not a valid base register "
+	       "in -mstack-protector-guard-reg=", str);
+
+      rs6000_stack_protector_guard_reg = reg;
+    }
+
+  if (rs6000_stack_protector_guard == SSP_TLS
+      && !IN_RANGE (rs6000_stack_protector_guard_reg, 1, 31))
+    error ("-mstack-protector-guard=tls needs a valid base register");
+
   if (global_init_p)
     {
 #ifdef TARGET_REGNAMES

gcc/config/rs6000/rs6000.md

@@ -11681,19 +11681,23 @@
 
 
 (define_expand "stack_protect_set"
-  [(match_operand 0 "memory_operand" "")
-   (match_operand 1 "memory_operand" "")]
+  [(match_operand 0 "memory_operand")
+   (match_operand 1 "memory_operand")]
   ""
 {
-#ifdef TARGET_THREAD_SSP_OFFSET
-  rtx tlsreg = gen_rtx_REG (Pmode, TARGET_64BIT ? 13 : 2);
-  rtx addr = gen_rtx_PLUS (Pmode, tlsreg, GEN_INT (TARGET_THREAD_SSP_OFFSET));
-  operands[1] = gen_rtx_MEM (Pmode, addr);
-#endif
+  if (rs6000_stack_protector_guard == SSP_TLS)
+    {
+      rtx reg = gen_rtx_REG (Pmode, rs6000_stack_protector_guard_reg);
+      rtx offset = GEN_INT (rs6000_stack_protector_guard_offset);
+      rtx addr = gen_rtx_PLUS (Pmode, reg, offset);
+      operands[1] = gen_rtx_MEM (Pmode, addr);
+    }
+
   if (TARGET_64BIT)
     emit_insn (gen_stack_protect_setdi (operands[0], operands[1]));
   else
     emit_insn (gen_stack_protect_setsi (operands[0], operands[1]));
+
   DONE;
 })
 
@@ -11716,21 +11720,26 @@
    (set_attr "length" "12")])
 
 (define_expand "stack_protect_test"
-  [(match_operand 0 "memory_operand" "")
-   (match_operand 1 "memory_operand" "")
-   (match_operand 2 "" "")]
+  [(match_operand 0 "memory_operand")
+   (match_operand 1 "memory_operand")
+   (match_operand 2 "")]
   ""
 {
-  rtx test, op0, op1;
-#ifdef TARGET_THREAD_SSP_OFFSET
-  rtx tlsreg = gen_rtx_REG (Pmode, TARGET_64BIT ? 13 : 2);
-  rtx addr = gen_rtx_PLUS (Pmode, tlsreg, GEN_INT (TARGET_THREAD_SSP_OFFSET));
-  operands[1] = gen_rtx_MEM (Pmode, addr);
-#endif
-  op0 = operands[0];
-  op1 = gen_rtx_UNSPEC (Pmode, gen_rtvec (1, operands[1]), UNSPEC_SP_TEST);
-  test = gen_rtx_EQ (VOIDmode, op0, op1);
-  emit_jump_insn (gen_cbranchsi4 (test, op0, op1, operands[2]));
+  rtx guard = operands[1];
+
+  if (rs6000_stack_protector_guard == SSP_TLS)
+    {
+      rtx reg = gen_rtx_REG (Pmode, rs6000_stack_protector_guard_reg);
+      rtx offset = GEN_INT (rs6000_stack_protector_guard_offset);
+      rtx addr = gen_rtx_PLUS (Pmode, reg, offset);
+      guard = gen_rtx_MEM (Pmode, addr);
+    }
+
+  operands[1] = gen_rtx_UNSPEC (Pmode, gen_rtvec (1, guard), UNSPEC_SP_TEST);
+  rtx test = gen_rtx_EQ (VOIDmode, operands[0], operands[1]);
+  rtx jump = gen_cbranchsi4 (test, operands[0], operands[1], operands[2]);
+  emit_jump_insn (jump);
+
   DONE;
 })
 

gcc/config/rs6000/rs6000.opt

@@ -672,3 +672,31 @@ Enable default conversions between __float128 & long double.
 mvsx-small-integer
 Target Report Mask(VSX_SMALL_INTEGER) Var(rs6000_isa_flags)
 Enable small integers to be in VSX registers.
+
+mstack-protector-guard=
+Target RejectNegative Joined Enum(stack_protector_guard) Var(rs6000_stack_protector_guard) Init(SSP_TLS)
+Use given stack-protector guard.
+
+Enum
+Name(stack_protector_guard) Type(enum stack_protector_guard)
+Valid arguments to -mstack-protector-guard=:
+
+EnumValue
+Enum(stack_protector_guard) String(tls) Value(SSP_TLS)
+
+EnumValue
+Enum(stack_protector_guard) String(global) Value(SSP_GLOBAL)
+
+mstack-protector-guard-reg=
+Target RejectNegative Joined Var(rs6000_stack_protector_guard_reg_str)
+Use the given base register for addressing the stack-protector guard.
+
+TargetVariable
+int rs6000_stack_protector_guard_reg = 0
+
+mstack-protector-guard-offset=
+Target RejectNegative Joined Integer Var(rs6000_stack_protector_guard_offset_str)
+Use the given offset for addressing the stack-protector guard.
+
+TargetVariable
+long rs6000_stack_protector_guard_offset = 0

gcc/doc/invoke.texi

@@ -1041,6 +1041,8 @@ See RS/6000 and PowerPC Options.
 -mupper-regs  -mno-upper-regs @gol
 -mfloat128  -mno-float128  -mfloat128-hardware  -mno-float128-hardware @gol
 -mgnu-attribute  -mno-gnu-attribute @gol
+-mstack-protector-guard=@var{guard} -mstack-protector-guard-reg=@var{reg} @gol
+-mstack-protector-guard-offset=@var{offset} @gol
 -mlra  -mno-lra}
 
 @emph{RX Options}
@@ -22202,6 +22204,23 @@ that is compatible with functions compiled with older versions of
 GCC.
 
 The @option{-mno-compat-align-parm} option is the default.
+
+@item -mstack-protector-guard=@var{guard}
+@itemx -mstack-protector-guard-reg=@var{reg}
+@itemx -mstack-protector-guard-offset=@var{offset}
+@opindex mstack-protector-guard
+@opindex mstack-protector-guard-reg
+@opindex mstack-protector-guard-offset
+Generate stack protection code using canary at @var{guard}.  Supported
+locations are @samp{global} for global canary or @samp{tls} for per-thread
+canary in the TLS block (the default with GNU libc version 2.4 or later).
+
+With the latter choice the options
+@option{-mstack-protector-guard-reg=@var{reg}} and
+@option{-mstack-protector-guard-offset=@var{offset}} furthermore specify
+which register to use as base register for reading the canary, and from what
+offset from that base register. The default for those is as specified in the
+relevant ABI.
 @end table
 
 @node RX Options

gcc/testsuite/ChangeLog

+2017-01-17  Segher Boessenkool  <segher@kernel.crashing.org>
+
+	PR target/78875
+	* gcc.target/powerpc/ssp-1.c: New testcase.
+	* gcc.target/powerpc/ssp-2.c: New testcase.
+
 2017-01-17  Wilco Dijkstra  <wdijkstr@arm.com>
 
 	* gcc.target/aarch64/eh_return.c: New test.