On Wed, Nov 17, 2021 at 1:10 AM Uros Bizjak <ubiz...@gmail.com> wrote:
>
> On Tue, Nov 16, 2021 at 7:51 PM H.J. Lu via Gcc-patches
> <gcc-patches@gcc.gnu.org> wrote:
> >
> > Add -mindirect-branch-cs-prefix to add CS prefix to call and jmp to thunk
> > via r8-r15 registers when converting indirect call and jump to increase
> > the instruction length to 6, allowing the non-thunk form to be inlined.
> >
> > gcc/
> >
> > PR target/102952
> > * config/i386/i386.c (ix86_output_jmp_thunk_or_indirect): Emit
> > CS prefix for -mindirect-branch-cs-prefix.
> > (ix86_output_indirect_branch_via_reg): Likewise.
> > * config/i386/i386.opt: Add -mindirect-branch-cs-prefix.
> > * doc/invoke.texi: Document -mindirect-branch-cs-prefix.
> >
> > gcc/testsuite/
> >
> > PR target/102952
> > * gcc.target/i386/indirect-thunk-cs-prefix-1.c: New test.
> > * gcc.target/i386/indirect-thunk-cs-prefix-2.c: Likewise.
> > ---
> > gcc/config/i386/i386.c | 6 ++++++
> > gcc/config/i386/i386.opt | 4 ++++
> > gcc/doc/invoke.texi | 8 +++++++-
> > .../gcc.target/i386/indirect-thunk-cs-prefix-1.c | 14 ++++++++++++++
> > .../gcc.target/i386/indirect-thunk-cs-prefix-2.c | 15 +++++++++++++++
> > 5 files changed, 46 insertions(+), 1 deletion(-)
> > create mode 100644
> > gcc/testsuite/gcc.target/i386/indirect-thunk-cs-prefix-1.c
> > create mode 100644
> > gcc/testsuite/gcc.target/i386/indirect-thunk-cs-prefix-2.c
> >
> > diff --git a/gcc/config/i386/i386.c b/gcc/config/i386/i386.c
> > index 7e9b7bc347f..0a902d66321 100644
> > --- a/gcc/config/i386/i386.c
> > +++ b/gcc/config/i386/i386.c
> > @@ -15983,6 +15983,9 @@ ix86_output_jmp_thunk_or_indirect (const char
> > *thunk_name, const int regno)
> > {
> > if (thunk_name != NULL)
> > {
> > + if (regno >= FIRST_REX_INT_REG
>
> REX_INT_REGNO_P
Fixed in the v2 patch.
> > + && ix86_indirect_branch_cs_prefix)
> > + fprintf (asm_out_file, "\tcs\n");
> > fprintf (asm_out_file, "\tjmp\t");
> > assemble_name (asm_out_file, thunk_name);
> > putc ('\n', asm_out_file);
> > @@ -16036,6 +16039,9 @@ ix86_output_indirect_branch_via_reg (rtx call_op,
> > bool sibcall_p)
> > {
> > if (thunk_name != NULL)
> > {
> > + if (regno >= FIRST_REX_INT_REG
>
> REX_INT_REGNO_P
Fixed in the v2 patch.
> > + && ix86_indirect_branch_cs_prefix)
> > + fprintf (asm_out_file, "\tcs\n");
> > fprintf (asm_out_file, "\tcall\t");
> > assemble_name (asm_out_file, thunk_name);
> > putc ('\n', asm_out_file);
> > diff --git a/gcc/config/i386/i386.opt b/gcc/config/i386/i386.opt
> > index 8d499a5a4df..c5452c49597 100644
> > --- a/gcc/config/i386/i386.opt
> > +++ b/gcc/config/i386/i386.opt
> > @@ -1076,6 +1076,10 @@ Enum(indirect_branch) String(thunk-inline)
> > Value(indirect_branch_thunk_inline)
> > EnumValue
> > Enum(indirect_branch) String(thunk-extern)
> > Value(indirect_branch_thunk_extern)
> >
> > +mindirect-branch-cs-prefix
> > +Target Var(ix86_indirect_branch_cs_prefix) Init(0)
> > +Add CS prefix to call and jmp to thunk when converting indirect call and
> > jump.
>
> This is not what the function really does. It adds cs to REX prefixed regs.
Fixed in the v2 patch.
Thanks.
> > +
> > mindirect-branch-register
> > Target Var(ix86_indirect_branch_register) Init(0)
> > Force indirect call and jump via register.
> > diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
> > index f3b4b467765..c992a7152f5 100644
> > --- a/gcc/doc/invoke.texi
> > +++ b/gcc/doc/invoke.texi
> > @@ -1425,7 +1425,8 @@ 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 -mharden-sls=@var{choice} -mneeded}
> > +-mindirect-branch-register -mharden-sls=@var{choice} @gol
> > +-mindirect-branch-cs-prefix -mneeded}
> >
> > @emph{x86 Windows Options}
> > @gccoptlist{-mconsole -mcygwin -mno-cygwin -mdll @gol
> > @@ -32390,6 +32391,11 @@ hardening. @samp{return} enables SLS hardening
> > for function return.
> > @samp{indirect-branch} enables SLS hardening for indirect branch.
> > @samp{all} enables all SLS hardening.
> >
> > +@item -mindirect-branch-cs-prefix
> > +@opindex mindirect-branch-cs-prefix
> > +Add CS prefix to call and jmp to thunk via r8-r15 registers when
> > +converting indirect call and jump.
> > +
> > @end table
> >
> > These @samp{-m} switches are supported in addition to the above
> > diff --git a/gcc/testsuite/gcc.target/i386/indirect-thunk-cs-prefix-1.c
> > b/gcc/testsuite/gcc.target/i386/indirect-thunk-cs-prefix-1.c
> > new file mode 100644
> > index 00000000000..db2f3416823
> > --- /dev/null
> > +++ b/gcc/testsuite/gcc.target/i386/indirect-thunk-cs-prefix-1.c
> > @@ -0,0 +1,14 @@
> > +/* { dg-do compile { target { ! ia32 } } } */
> > +/* { dg-options "-O2 -ffixed-rax -ffixed-rbx -ffixed-rcx -ffixed-rdx
> > -ffixed-rdi -ffixed-rsi -mindirect-branch-cs-prefix
> > -mindirect-branch=thunk-extern" } */
> > +/* { dg-additional-options "-fno-pic" { target { ! *-*-darwin* } } } */
> > +
> > +extern void (*fptr) (void);
> > +
> > +void
> > +foo (void)
> > +{
> > + fptr ();
> > +}
> > +
> > +/* { dg-final { scan-assembler-times "jmp\[
> > \t\]+_?__x86_indirect_thunk_r\[0-9\]+" 1 } } */
> > +/* { dg-final { scan-assembler-times "\tcs" 1 } } */
> > diff --git a/gcc/testsuite/gcc.target/i386/indirect-thunk-cs-prefix-2.c
> > b/gcc/testsuite/gcc.target/i386/indirect-thunk-cs-prefix-2.c
> > new file mode 100644
> > index 00000000000..adfc39a49d4
> > --- /dev/null
> > +++ b/gcc/testsuite/gcc.target/i386/indirect-thunk-cs-prefix-2.c
> > @@ -0,0 +1,15 @@
> > +/* { dg-do compile { target { ! ia32 } } } */
> > +/* { dg-options "-O2 -ffixed-rax -ffixed-rbx -ffixed-rcx -ffixed-rdx
> > -ffixed-rdi -ffixed-rsi -mindirect-branch-cs-prefix
> > -mindirect-branch=thunk-extern" } */
> > +/* { dg-additional-options "-fno-pic" { target { ! *-*-darwin* } } } */
> > +
> > +extern void (*bar) (void);
> > +
> > +int
> > +foo (void)
> > +{
> > + bar ();
> > + return 0;
> > +}
> > +
> > +/* { dg-final { scan-assembler-times "call\[
> > \t\]+_?__x86_indirect_thunk_r\[0-9\]+" 1 } } */
> > +/* { dg-final { scan-assembler-times "\tcs" 1 } } */
> > --
> > 2.33.1
> >
--
H.J.
