[PATCH] x86: Add -mharden-sls=[none|all|return|indirect-branch]
H.J. Lu
hjl.tools@gmail.com
Tue Nov 16 18:20:03 GMT 2021
Add -mharden-sls= to mitigate against straight line speculation (SLS)
for function return and indirect branch by adding an INT3 instruction
after function return and indirect branch.
gcc/
PR target/102952
* config/i386/i386-opts.h (harden_sls): New enum.
* config/i386/i386.c (output_indirect_thunk): Mitigate against
SLS for function return.
(ix86_output_function_return): Likewise.
(ix86_output_jmp_thunk_or_indirect): Mitigate against indirect
branch.
(ix86_output_indirect_jmp): Likewise.
(ix86_output_call_insn): Likewise.
* config/i386/i386.opt: Add -mharden-sls=.
* doc/invoke.texi: Document -mharden-sls=.
gcc/testsuite/
PR target/102952
* gcc.target/i386/harden-sls-1.c: New test.
* gcc.target/i386/harden-sls-2.c: Likewise.
* gcc.target/i386/harden-sls-3.c: Likewise.
* gcc.target/i386/harden-sls-4.c: Likewise.
---
gcc/config/i386/i386-opts.h | 7 +++++
gcc/config/i386/i386.c | 30 ++++++++++++++++----
gcc/config/i386/i386.opt | 20 +++++++++++++
gcc/doc/invoke.texi | 10 ++++++-
gcc/testsuite/gcc.target/i386/harden-sls-1.c | 14 +++++++++
gcc/testsuite/gcc.target/i386/harden-sls-2.c | 14 +++++++++
gcc/testsuite/gcc.target/i386/harden-sls-3.c | 14 +++++++++
gcc/testsuite/gcc.target/i386/harden-sls-4.c | 14 +++++++++
8 files changed, 116 insertions(+), 7 deletions(-)
create mode 100644 gcc/testsuite/gcc.target/i386/harden-sls-1.c
create mode 100644 gcc/testsuite/gcc.target/i386/harden-sls-2.c
create mode 100644 gcc/testsuite/gcc.target/i386/harden-sls-3.c
create mode 100644 gcc/testsuite/gcc.target/i386/harden-sls-4.c
diff --git a/gcc/config/i386/i386-opts.h b/gcc/config/i386/i386-opts.h
index 04e4ad608fb..171d3106d0a 100644
--- a/gcc/config/i386/i386-opts.h
+++ b/gcc/config/i386/i386-opts.h
@@ -121,4 +121,11 @@ enum instrument_return {
instrument_return_nop5
};
+enum harden_sls {
+ harden_sls_none = 0,
+ harden_sls_return = 1 << 0,
+ harden_sls_indirect_branch = 1 << 1,
+ harden_sls_all = harden_sls_return | harden_sls_indirect_branch
+};
+
#endif
diff --git a/gcc/config/i386/i386.c b/gcc/config/i386/i386.c
index cc9f9322fad..0a902d66321 100644
--- a/gcc/config/i386/i386.c
+++ b/gcc/config/i386/i386.c
@@ -5914,6 +5914,8 @@ output_indirect_thunk (unsigned int regno)
}
fputs ("\tret\n", asm_out_file);
+ if ((ix86_harden_sls & harden_sls_return))
+ fputs ("\tint3\n", asm_out_file);
}
/* Output a funtion with a call and return thunk for indirect branch.
@@ -15987,6 +15989,8 @@ ix86_output_jmp_thunk_or_indirect (const char *thunk_name, const int regno)
fprintf (asm_out_file, "\tjmp\t");
assemble_name (asm_out_file, thunk_name);
putc ('\n', asm_out_file);
+ if ((ix86_harden_sls & harden_sls_indirect_branch))
+ fputs ("\tint3\n", asm_out_file);
}
else
output_indirect_thunk (regno);
@@ -16212,10 +16216,14 @@ ix86_output_indirect_jmp (rtx call_op)
gcc_unreachable ();
ix86_output_indirect_branch (call_op, "%0", true);
- return "";
+ if ((ix86_harden_sls & harden_sls_indirect_branch))
+ return "int3";
+ else
+ return "";
}
else
- return "%!jmp\t%A0";
+ return ((ix86_harden_sls & harden_sls_indirect_branch)
+ ? "%!jmp\t%A0\n\tint3" : "%!jmp\t%A0");
}
/* Output return instrumentation for current function if needed. */
@@ -16283,10 +16291,15 @@ ix86_output_function_return (bool long_p)
return "";
}
- if (!long_p)
- return "%!ret";
+ if ((ix86_harden_sls & harden_sls_return))
+ return "%!ret\n\tint3";
+ else
+ {
+ if (!long_p)
+ return "%!ret";
- return "rep%; ret";
+ return "rep%; ret";
+ }
}
/* Output indirect function return. RET_OP is the function return
@@ -16381,7 +16394,12 @@ ix86_output_call_insn (rtx_insn *insn, rtx call_op)
if (output_indirect_p && !direct_p)
ix86_output_indirect_branch (call_op, xasm, true);
else
- output_asm_insn (xasm, &call_op);
+ {
+ output_asm_insn (xasm, &call_op);
+ if (!direct_p
+ && (ix86_harden_sls & harden_sls_indirect_branch))
+ return "int3";
+ }
return "";
}
diff --git a/gcc/config/i386/i386.opt b/gcc/config/i386/i386.opt
index b38ac13fc91..c5452c49597 100644
--- a/gcc/config/i386/i386.opt
+++ b/gcc/config/i386/i386.opt
@@ -1121,6 +1121,26 @@ mrecord-return
Target Var(ix86_flag_record_return) Init(0)
Generate a __return_loc section pointing to all return instrumentation code.
+mharden-sls=
+Target RejectNegative Joined Enum(harden_sls) Var(ix86_harden_sls) Init(harden_sls_none)
+Generate code to mitigate against straight line speculation.
+
+Enum
+Name(harden_sls) Type(enum harden_sls)
+Known choices for mitigation against straight line speculation with -mharden-sls=:
+
+EnumValue
+Enum(harden_sls) String(none) Value(harden_sls_none)
+
+EnumValue
+Enum(harden_sls) String(all) Value(harden_sls_all)
+
+EnumValue
+Enum(harden_sls) String(return) Value(harden_sls_return)
+
+EnumValue
+Enum(harden_sls) String(indirect-branch) Value(harden_sls_indirect_branch)
+
mavx512bf16
Target Mask(ISA2_AVX512BF16) Var(ix86_isa_flags2) Save
Support MMX, SSE, SSE2, SSE3, SSSE3, SSE4.1, SSE4.2, AVX, AVX2, AVX512F and
diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index 6070288856c..f3b4b467765 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -1425,7 +1425,7 @@ See RS/6000 and PowerPC Options.
-mstack-protector-guard-symbol=@var{symbol} @gol
-mgeneral-regs-only -mcall-ms2sysv-xlogues -mrelax-cmpxchg-loop @gol
-mindirect-branch=@var{choice} -mfunction-return=@var{choice} @gol
--mindirect-branch-register -mneeded}
+-mindirect-branch-register -mharden-sls=@var{choice} -mneeded}
@emph{x86 Windows Options}
@gccoptlist{-mconsole -mcygwin -mno-cygwin -mdll @gol
@@ -32382,6 +32382,14 @@ not be reachable in the large code model.
@opindex mindirect-branch-register
Force indirect call and jump via register.
+@item -mharden-sls=@var{choice}
+@opindex mharden-sls
+Generate code to mitigate against straight line speculation (SLS) with
+@var{choice}. The default is @samp{none} which disables all SLS
+hardening. @samp{return} enables SLS hardening for function return.
+@samp{indirect-branch} enables SLS hardening for indirect branch.
+@samp{all} enables all SLS hardening.
+
@end table
These @samp{-m} switches are supported in addition to the above
diff --git a/gcc/testsuite/gcc.target/i386/harden-sls-1.c b/gcc/testsuite/gcc.target/i386/harden-sls-1.c
new file mode 100644
index 00000000000..6f70dc94a23
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/harden-sls-1.c
@@ -0,0 +1,14 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -mindirect-branch=thunk-extern -mharden-sls=all" } */
+/* { dg-additional-options "-fno-pic" { target { ! *-*-darwin* } } } */
+
+extern void foo (void);
+
+void
+bar (void)
+{
+ foo ();
+}
+
+/* { dg-final { scan-assembler "jmp\[ \t\]+_?foo" } } */
+/* { dg-final { scan-assembler-not {int3} } } */
diff --git a/gcc/testsuite/gcc.target/i386/harden-sls-2.c b/gcc/testsuite/gcc.target/i386/harden-sls-2.c
new file mode 100644
index 00000000000..a7c59078d03
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/harden-sls-2.c
@@ -0,0 +1,14 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -mindirect-branch=thunk-extern -mharden-sls=all" } */
+/* { dg-additional-options "-fno-pic" { target { ! *-*-darwin* } } } */
+
+extern void (*fptr) (void);
+
+void
+foo (void)
+{
+ fptr ();
+}
+
+/* { dg-final { scan-assembler "jmp\[ \t\]+_?__x86_indirect_thunk_(r|e)ax" } } */
+/* { dg-final { scan-assembler-times "int3" 1 } } */
diff --git a/gcc/testsuite/gcc.target/i386/harden-sls-3.c b/gcc/testsuite/gcc.target/i386/harden-sls-3.c
new file mode 100644
index 00000000000..1a6056b6d7b
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/harden-sls-3.c
@@ -0,0 +1,14 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -mindirect-branch=thunk -mharden-sls=all" } */
+/* { dg-additional-options "-fno-pic" { target { ! *-*-darwin* } } } */
+
+extern void (*fptr) (void);
+
+void
+foo (void)
+{
+ fptr ();
+}
+
+/* { dg-final { scan-assembler "jmp\[ \t\]+_?__x86_indirect_thunk_(r|e)ax" } } */
+/* { dg-final { scan-assembler-times "int3" 2 } } */
diff --git a/gcc/testsuite/gcc.target/i386/harden-sls-4.c b/gcc/testsuite/gcc.target/i386/harden-sls-4.c
new file mode 100644
index 00000000000..c33147f11b5
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/harden-sls-4.c
@@ -0,0 +1,14 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -mindirect-branch=keep -mharden-sls=all" } */
+/* { dg-additional-options "-fno-pic" { target { ! *-*-darwin* } } } */
+
+extern void (*fptr) (void);
+
+void
+foo (void)
+{
+ fptr ();
+}
+
+/* { dg-final { scan-assembler "jmp\[ \t\]+\\*_?fptr" } } */
+/* { dg-final { scan-assembler-times "int3" 1 } } */
--
2.33.1
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