On Wed, Nov 17, 2021 at 2:46 PM H.J. Lu <hjl.to...@gmail.com> wrote:
>
> On Wed, Nov 17, 2021 at 1:05 AM Uros Bizjak <ubiz...@gmail.com> wrote:
> >
> > On Tue, Nov 16, 2021 at 7:20 PM H.J. Lu via Gcc-patches
> > <gcc-patches@gcc.gnu.org> wrote:
> > >
> > > 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");
> > > }
> >
> > Just change existing returns to fputs and end function with:
> >
> > return (ix86_harden_sls & harden_sls_indirect_branch) ? "int3" : "";
>
> But fputs doesn't support %A0.
Sorry for the thinko, output_asm_insn instead of fputs will do the trick.
Uros.
>
> > > /* 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";
> > > + }
> > > }
> >
> > Also here.
>
> But fputs doesn't know "%!".
>
> >
> > >
> > > /* 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
> > >
>
>
>
> --
> H.J.
