i386: Also skip ENDBR32 at the target function entry
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Message ID 20200213120601.GA160128@gmail.com
State New
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  • i386: Also skip ENDBR32 at the target function entry
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Commit Message

H.J. Lu Feb. 13, 2020, 12:06 p.m. UTC
On Thu, Feb 13, 2020 at 09:29:32AM +0100, Uros Bizjak wrote:
> On Wed, Feb 12, 2020 at 1:21 PM H.J. Lu <hjl.tools@gmail.com> wrote:
> >
> > On Mon, Feb 10, 2020 at 12:01 PM Uros Bizjak <ubizjak@gmail.com> wrote:
> > >
> > > On Mon, Feb 10, 2020 at 8:53 PM H.J. Lu <hjl.tools@gmail.com> wrote:
> > > >
> > > > On Mon, Feb 10, 2020 at 11:40 AM Uros Bizjak <ubizjak@gmail.com> wrote:
> > > > >
> > > > > On Mon, Feb 10, 2020 at 8:22 PM H.J. Lu <hjl.tools@gmail.com> wrote:
> > > > > >
> > > > > > Since nested function isn't only called directly, there is ENDBR32 at
> > > > > > function entry and we need to skip it for direct jump in trampoline.
> > > > >
> > > > > Hm, I'm afraid I don't understand this comment. Can you perhaps rephrase it?
> > > > >
> > > >
> > > > ix86_trampoline_init has
> > > >
> > > >      /* Compute offset from the end of the jmp to the target function.
> > > >          In the case in which the trampoline stores the static chain on
> > > >          the stack, we need to skip the first insn which pushes the
> > > >          (call-saved) register static chain; this push is 1 byte.  */
> > > >       offset += 5;
> > > >       disp = expand_binop (SImode, sub_optab, fnaddr,
> > > >                            plus_constant (Pmode, XEXP (m_tramp, 0),
> > > >                                           offset - (MEM_P (chain) ? 1 : 0)),
> > > >                            NULL_RTX, 1, OPTAB_DIRECT);
> > > >       emit_move_insn (mem, disp);
> > > >
> > > > Without CET, we got
> > > >
> > > > 0000011 <bar.1878>:
> > > >   11: 56                    push   %esi
> > > >   12: 55                    push   %ebp   <<<<<< trampoline jumps here.
> > > >   13: 89 e5                mov    %esp,%ebp
> > > >   15: 83 ec 08              sub    $0x8,%esp
> > > >
> > > > With CET, if bar isn't only called directly, we got
> > > >
> > > > 00000015 <bar.1878>:
> > > >   15: f3 0f 1e fb          endbr32
> > > >   19: 56                    push   %esi
> > > >   1a: 55                    push   %ebp   <<<<<<<< trampoline jumps here.
> > > >   1b: 89 e5                mov    %esp,%ebp
> > > >   1d: 83 ec 08              sub    $0x8,%esp
> > > >
> > > > We need to add 4 bytes for trampoline to skip endbr32.
> > > >
> > > > Here is the updated patch to check if nested function isn't only
> > > > called directly,
> > >
> > > Please figure out the final patch. I don't want to waste my time
> > > reviewing different version every half hour. Ping me in a couple of
> > > days.
> >
> > This is the final version:
> >
> > https://gcc.gnu.org/ml/gcc-patches/2020-02/msg00586.html
> >
> > You can try the testcase in the patch on any machine with CET binutils
> > since ENDBR32 is nop on none-CET machines.  Without this patch,
> > the test will fail.
> 
> Please rephrase the comment. I don't understand what it tries to say.
> 

Here is the patch with updated comments.  OK for master and 8/9 branches?

Thanks.

H.J.
---
Since pass_insert_endbranch inserts ENDBR32 at entry of the target
function if it may be called indirectly, we also need to skip the
4-byte ENDBR32 for direct jump in trampoline if it is the case.

Tested on Linux/x86-64 CET machine with and without -m32.

gcc/

	PR target/93656
	* config/i386/i386.c (ix86_trampoline_init): Skip ENDBR32 at
	the target function entry.

gcc/testsuite/

	PR target/93656
	* gcc.target/i386/pr93656.c: New test.
---
 gcc/config/i386/i386.c                  | 9 ++++++++-
 gcc/testsuite/gcc.target/i386/pr93656.c | 4 ++++
 2 files changed, 12 insertions(+), 1 deletion(-)
 create mode 100644 gcc/testsuite/gcc.target/i386/pr93656.c

Comments

Uros Bizjak Feb. 13, 2020, 12:28 p.m. UTC | #1
On Thu, Feb 13, 2020 at 1:06 PM H.J. Lu <hjl.tools@gmail.com> wrote:
>
> On Thu, Feb 13, 2020 at 09:29:32AM +0100, Uros Bizjak wrote:
> > On Wed, Feb 12, 2020 at 1:21 PM H.J. Lu <hjl.tools@gmail.com> wrote:
> > >
> > > On Mon, Feb 10, 2020 at 12:01 PM Uros Bizjak <ubizjak@gmail.com> wrote:
> > > >
> > > > On Mon, Feb 10, 2020 at 8:53 PM H.J. Lu <hjl.tools@gmail.com> wrote:
> > > > >
> > > > > On Mon, Feb 10, 2020 at 11:40 AM Uros Bizjak <ubizjak@gmail.com> wrote:
> > > > > >
> > > > > > On Mon, Feb 10, 2020 at 8:22 PM H.J. Lu <hjl.tools@gmail.com> wrote:
> > > > > > >
> > > > > > > Since nested function isn't only called directly, there is ENDBR32 at
> > > > > > > function entry and we need to skip it for direct jump in trampoline.
> > > > > >
> > > > > > Hm, I'm afraid I don't understand this comment. Can you perhaps rephrase it?
> > > > > >
> > > > >
> > > > > ix86_trampoline_init has
> > > > >
> > > > >      /* Compute offset from the end of the jmp to the target function.
> > > > >          In the case in which the trampoline stores the static chain on
> > > > >          the stack, we need to skip the first insn which pushes the
> > > > >          (call-saved) register static chain; this push is 1 byte.  */
> > > > >       offset += 5;
> > > > >       disp = expand_binop (SImode, sub_optab, fnaddr,
> > > > >                            plus_constant (Pmode, XEXP (m_tramp, 0),
> > > > >                                           offset - (MEM_P (chain) ? 1 : 0)),
> > > > >                            NULL_RTX, 1, OPTAB_DIRECT);
> > > > >       emit_move_insn (mem, disp);
> > > > >
> > > > > Without CET, we got
> > > > >
> > > > > 0000011 <bar.1878>:
> > > > >   11: 56                    push   %esi
> > > > >   12: 55                    push   %ebp   <<<<<< trampoline jumps here.
> > > > >   13: 89 e5                mov    %esp,%ebp
> > > > >   15: 83 ec 08              sub    $0x8,%esp
> > > > >
> > > > > With CET, if bar isn't only called directly, we got
> > > > >
> > > > > 00000015 <bar.1878>:
> > > > >   15: f3 0f 1e fb          endbr32
> > > > >   19: 56                    push   %esi
> > > > >   1a: 55                    push   %ebp   <<<<<<<< trampoline jumps here.
> > > > >   1b: 89 e5                mov    %esp,%ebp
> > > > >   1d: 83 ec 08              sub    $0x8,%esp
> > > > >
> > > > > We need to add 4 bytes for trampoline to skip endbr32.
> > > > >
> > > > > Here is the updated patch to check if nested function isn't only
> > > > > called directly,
> > > >
> > > > Please figure out the final patch. I don't want to waste my time
> > > > reviewing different version every half hour. Ping me in a couple of
> > > > days.
> > >
> > > This is the final version:
> > >
> > > https://gcc.gnu.org/ml/gcc-patches/2020-02/msg00586.html
> > >
> > > You can try the testcase in the patch on any machine with CET binutils
> > > since ENDBR32 is nop on none-CET machines.  Without this patch,
> > > the test will fail.
> >
> > Please rephrase the comment. I don't understand what it tries to say.
> >
>
> Here is the patch with updated comments.  OK for master and 8/9 branches?
>
> Thanks.
>
> H.J.
> ---
> Since pass_insert_endbranch inserts ENDBR32 at entry of the target
> function if it may be called indirectly, we also need to skip the
> 4-byte ENDBR32 for direct jump in trampoline if it is the case.

"
Skip ENDBR32 at the entry if called indirectly.
"
pass_insert_endbranch inserts ENDBR at the entry of the target
function.  We need to skip
>
> Tested on Linux/x86-64 CET machine with and without -m32.
>
> gcc/
>
>         PR target/93656
>         * config/i386/i386.c (ix86_trampoline_init): Skip ENDBR32 at
>         the target function entry.
>
> gcc/testsuite/
>
>         PR target/93656
>         * gcc.target/i386/pr93656.c: New test.
> ---
>  gcc/config/i386/i386.c                  | 9 ++++++++-
>  gcc/testsuite/gcc.target/i386/pr93656.c | 4 ++++
>  2 files changed, 12 insertions(+), 1 deletion(-)
>  create mode 100644 gcc/testsuite/gcc.target/i386/pr93656.c
>
> diff --git a/gcc/config/i386/i386.c b/gcc/config/i386/i386.c
> index 44bc0e0176a..52640b74cc8 100644
> --- a/gcc/config/i386/i386.c
> +++ b/gcc/config/i386/i386.c
> @@ -16839,9 +16839,16 @@ ix86_trampoline_init (rtx m_tramp, tree fndecl, rtx chain_value)
>          the stack, we need to skip the first insn which pushes the
>          (call-saved) register static chain; this push is 1 byte.  */
>        offset += 5;
> +      int skip = MEM_P (chain) ? 1 : 0;

offset += 5 - MEM_P (chain) ? 1: 0;

> +      /* Since pass_insert_endbranch inserts ENDBR32 at entry of the
> +        target function if it may be called indirectly, we also need
> +        to skip the 4-byte ENDBR32 if it is the case.  */

/* Skip ENDBR32 at the entry of the target function when called indirectly.  */

> +      if (need_endbr
> +         && !cgraph_node::get (fndecl)->only_called_directly_p ())
> +       skip += 4;

offset += 4;

>        disp = expand_binop (SImode, sub_optab, fnaddr,
>                            plus_constant (Pmode, XEXP (m_tramp, 0),
> -                                         offset - (MEM_P (chain) ? 1 : 0)),
> +                                         offset - skip),

plus_constant (Pmode, XEXP (m_tramp, 0), offset),

Uros.

>                            NULL_RTX, 1, OPTAB_DIRECT);
>        emit_move_insn (mem, disp);
>      }
> diff --git a/gcc/testsuite/gcc.target/i386/pr93656.c b/gcc/testsuite/gcc.target/i386/pr93656.c
> new file mode 100644
> index 00000000000..f0ac8c8edaa
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/i386/pr93656.c
> @@ -0,0 +1,4 @@
> +/* { dg-do run { target { ia32 && cet } } } */
> +/* { dg-options "-O2 -fcf-protection" } */
> +
> +#include "pr67770.c"
> --
> 2.24.1
>
H.J. Lu Feb. 13, 2020, 12:42 p.m. UTC | #2
On Thu, Feb 13, 2020 at 01:28:43PM +0100, Uros Bizjak wrote:
> On Thu, Feb 13, 2020 at 1:06 PM H.J. Lu <hjl.tools@gmail.com> wrote:
> >
> > On Thu, Feb 13, 2020 at 09:29:32AM +0100, Uros Bizjak wrote:
> > > On Wed, Feb 12, 2020 at 1:21 PM H.J. Lu <hjl.tools@gmail.com> wrote:
> > > >
> > > > On Mon, Feb 10, 2020 at 12:01 PM Uros Bizjak <ubizjak@gmail.com> wrote:
> > > > >
> > > > > On Mon, Feb 10, 2020 at 8:53 PM H.J. Lu <hjl.tools@gmail.com> wrote:
> > > > > >
> > > > > > On Mon, Feb 10, 2020 at 11:40 AM Uros Bizjak <ubizjak@gmail.com> wrote:
> > > > > > >
> > > > > > > On Mon, Feb 10, 2020 at 8:22 PM H.J. Lu <hjl.tools@gmail.com> wrote:
> > > > > > > >
> > > > > > > > Since nested function isn't only called directly, there is ENDBR32 at
> > > > > > > > function entry and we need to skip it for direct jump in trampoline.
> > > > > > >
> > > > > > > Hm, I'm afraid I don't understand this comment. Can you perhaps rephrase it?
> > > > > > >
> > > > > >
> > > > > > ix86_trampoline_init has
> > > > > >
> > > > > >      /* Compute offset from the end of the jmp to the target function.
> > > > > >          In the case in which the trampoline stores the static chain on
> > > > > >          the stack, we need to skip the first insn which pushes the
> > > > > >          (call-saved) register static chain; this push is 1 byte.  */
> > > > > >       offset += 5;
> > > > > >       disp = expand_binop (SImode, sub_optab, fnaddr,
> > > > > >                            plus_constant (Pmode, XEXP (m_tramp, 0),
> > > > > >                                           offset - (MEM_P (chain) ? 1 : 0)),
> > > > > >                            NULL_RTX, 1, OPTAB_DIRECT);
> > > > > >       emit_move_insn (mem, disp);
> > > > > >
> > > > > > Without CET, we got
> > > > > >
> > > > > > 0000011 <bar.1878>:
> > > > > >   11: 56                    push   %esi
> > > > > >   12: 55                    push   %ebp   <<<<<< trampoline jumps here.
> > > > > >   13: 89 e5                mov    %esp,%ebp
> > > > > >   15: 83 ec 08              sub    $0x8,%esp
> > > > > >
> > > > > > With CET, if bar isn't only called directly, we got
> > > > > >
> > > > > > 00000015 <bar.1878>:
> > > > > >   15: f3 0f 1e fb          endbr32
> > > > > >   19: 56                    push   %esi
> > > > > >   1a: 55                    push   %ebp   <<<<<<<< trampoline jumps here.
> > > > > >   1b: 89 e5                mov    %esp,%ebp
> > > > > >   1d: 83 ec 08              sub    $0x8,%esp
> > > > > >
> > > > > > We need to add 4 bytes for trampoline to skip endbr32.
> > > > > >
> > > > > > Here is the updated patch to check if nested function isn't only
> > > > > > called directly,
> > > > >
> > > > > Please figure out the final patch. I don't want to waste my time
> > > > > reviewing different version every half hour. Ping me in a couple of
> > > > > days.
> > > >
> > > > This is the final version:
> > > >
> > > > https://gcc.gnu.org/ml/gcc-patches/2020-02/msg00586.html
> > > >
> > > > You can try the testcase in the patch on any machine with CET binutils
> > > > since ENDBR32 is nop on none-CET machines.  Without this patch,
> > > > the test will fail.
> > >
> > > Please rephrase the comment. I don't understand what it tries to say.
> > >
> >
> > Here is the patch with updated comments.  OK for master and 8/9 branches?
> >
> > Thanks.
> >
> > H.J.
> > ---
> > Since pass_insert_endbranch inserts ENDBR32 at entry of the target
> > function if it may be called indirectly, we also need to skip the
> > 4-byte ENDBR32 for direct jump in trampoline if it is the case.
> 
> "
> Skip ENDBR32 at the entry if called indirectly.
> "
> pass_insert_endbranch inserts ENDBR at the entry of the target
> function.  We need to skip
> >
> > Tested on Linux/x86-64 CET machine with and without -m32.
> >
> > gcc/
> >
> >         PR target/93656
> >         * config/i386/i386.c (ix86_trampoline_init): Skip ENDBR32 at
> >         the target function entry.
> >
> > gcc/testsuite/
> >
> >         PR target/93656
> >         * gcc.target/i386/pr93656.c: New test.
> > ---
> >  gcc/config/i386/i386.c                  | 9 ++++++++-
> >  gcc/testsuite/gcc.target/i386/pr93656.c | 4 ++++
> >  2 files changed, 12 insertions(+), 1 deletion(-)
> >  create mode 100644 gcc/testsuite/gcc.target/i386/pr93656.c
> >
> > diff --git a/gcc/config/i386/i386.c b/gcc/config/i386/i386.c
> > index 44bc0e0176a..52640b74cc8 100644
> > --- a/gcc/config/i386/i386.c
> > +++ b/gcc/config/i386/i386.c
> > @@ -16839,9 +16839,16 @@ ix86_trampoline_init (rtx m_tramp, tree fndecl, rtx chain_value)
> >          the stack, we need to skip the first insn which pushes the
> >          (call-saved) register static chain; this push is 1 byte.  */
> >        offset += 5;
> > +      int skip = MEM_P (chain) ? 1 : 0;
> 
> offset += 5 - MEM_P (chain) ? 1: 0;

This is done on purpose sinc there is

  gcc_assert (offset <= TRAMPOLINE_SIZE);

after it.  We shouldn't update offset.

> 
> > +      /* Since pass_insert_endbranch inserts ENDBR32 at entry of the
> > +        target function if it may be called indirectly, we also need
> > +        to skip the 4-byte ENDBR32 if it is the case.  */
> 
> /* Skip ENDBR32 at the entry of the target function when called indirectly.  */

Fixed.

> 
> > +      if (need_endbr
> > +         && !cgraph_node::get (fndecl)->only_called_directly_p ())
> > +       skip += 4;
> 
> offset += 4;
> 
> >        disp = expand_binop (SImode, sub_optab, fnaddr,
> >                            plus_constant (Pmode, XEXP (m_tramp, 0),
> > -                                         offset - (MEM_P (chain) ? 1 : 0)),
> > +                                         offset - skip),
> 
> plus_constant (Pmode, XEXP (m_tramp, 0), offset),
> 
> Uros.
> 

Here is the updated patch.  OK for master and 8/9 branches?

Thanks.


H.J.
--
Skip ENDBR32 at the entry of the target function when called indirectly.

Tested on Linux/x86-64 CET machine with and without -m32.

gcc/

	PR target/93656
	* config/i386/i386.c (ix86_trampoline_init): Skip ENDBR32 at
	the target function entry.

gcc/testsuite/

	PR target/93656
	* gcc.target/i386/pr93656.c: New test.
---
 gcc/config/i386/i386.c                  | 8 +++++++-
 gcc/testsuite/gcc.target/i386/pr93656.c | 4 ++++
 2 files changed, 11 insertions(+), 1 deletion(-)
 create mode 100644 gcc/testsuite/gcc.target/i386/pr93656.c

diff --git a/gcc/config/i386/i386.c b/gcc/config/i386/i386.c
index 44bc0e0176a..3f3dcd53eb2 100644
--- a/gcc/config/i386/i386.c
+++ b/gcc/config/i386/i386.c
@@ -16839,9 +16839,15 @@ ix86_trampoline_init (rtx m_tramp, tree fndecl, rtx chain_value)
 	 the stack, we need to skip the first insn which pushes the
 	 (call-saved) register static chain; this push is 1 byte.  */
       offset += 5;
+      int skip = MEM_P (chain) ? 1 : 0;
+      /* Skip ENDBR32 at the entry of the target function when called
+	 indirectly.  */
+      if (need_endbr
+	  && !cgraph_node::get (fndecl)->only_called_directly_p ())
+	skip += 4;
       disp = expand_binop (SImode, sub_optab, fnaddr,
 			   plus_constant (Pmode, XEXP (m_tramp, 0),
-					  offset - (MEM_P (chain) ? 1 : 0)),
+					  offset - skip),
 			   NULL_RTX, 1, OPTAB_DIRECT);
       emit_move_insn (mem, disp);
     }
diff --git a/gcc/testsuite/gcc.target/i386/pr93656.c b/gcc/testsuite/gcc.target/i386/pr93656.c
new file mode 100644
index 00000000000..f0ac8c8edaa
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/pr93656.c
@@ -0,0 +1,4 @@
+/* { dg-do run { target { ia32 && cet } } } */
+/* { dg-options "-O2 -fcf-protection" } */
+
+#include "pr67770.c"
Uros Bizjak Feb. 13, 2020, 1:09 p.m. UTC | #3
On Thu, Feb 13, 2020 at 1:42 PM H.J. Lu <hjl.tools@gmail.com> wrote:
>
> On Thu, Feb 13, 2020 at 01:28:43PM +0100, Uros Bizjak wrote:
> > On Thu, Feb 13, 2020 at 1:06 PM H.J. Lu <hjl.tools@gmail.com> wrote:
> > >
> > > On Thu, Feb 13, 2020 at 09:29:32AM +0100, Uros Bizjak wrote:
> > > > On Wed, Feb 12, 2020 at 1:21 PM H.J. Lu <hjl.tools@gmail.com> wrote:
> > > > >
> > > > > On Mon, Feb 10, 2020 at 12:01 PM Uros Bizjak <ubizjak@gmail.com> wrote:
> > > > > >
> > > > > > On Mon, Feb 10, 2020 at 8:53 PM H.J. Lu <hjl.tools@gmail.com> wrote:
> > > > > > >
> > > > > > > On Mon, Feb 10, 2020 at 11:40 AM Uros Bizjak <ubizjak@gmail.com> wrote:
> > > > > > > >
> > > > > > > > On Mon, Feb 10, 2020 at 8:22 PM H.J. Lu <hjl.tools@gmail.com> wrote:
> > > > > > > > >
> > > > > > > > > Since nested function isn't only called directly, there is ENDBR32 at
> > > > > > > > > function entry and we need to skip it for direct jump in trampoline.
> > > > > > > >
> > > > > > > > Hm, I'm afraid I don't understand this comment. Can you perhaps rephrase it?
> > > > > > > >
> > > > > > >
> > > > > > > ix86_trampoline_init has
> > > > > > >
> > > > > > >      /* Compute offset from the end of the jmp to the target function.
> > > > > > >          In the case in which the trampoline stores the static chain on
> > > > > > >          the stack, we need to skip the first insn which pushes the
> > > > > > >          (call-saved) register static chain; this push is 1 byte.  */
> > > > > > >       offset += 5;
> > > > > > >       disp = expand_binop (SImode, sub_optab, fnaddr,
> > > > > > >                            plus_constant (Pmode, XEXP (m_tramp, 0),
> > > > > > >                                           offset - (MEM_P (chain) ? 1 : 0)),
> > > > > > >                            NULL_RTX, 1, OPTAB_DIRECT);
> > > > > > >       emit_move_insn (mem, disp);
> > > > > > >
> > > > > > > Without CET, we got
> > > > > > >
> > > > > > > 0000011 <bar.1878>:
> > > > > > >   11: 56                    push   %esi
> > > > > > >   12: 55                    push   %ebp   <<<<<< trampoline jumps here.
> > > > > > >   13: 89 e5                mov    %esp,%ebp
> > > > > > >   15: 83 ec 08              sub    $0x8,%esp
> > > > > > >
> > > > > > > With CET, if bar isn't only called directly, we got
> > > > > > >
> > > > > > > 00000015 <bar.1878>:
> > > > > > >   15: f3 0f 1e fb          endbr32
> > > > > > >   19: 56                    push   %esi
> > > > > > >   1a: 55                    push   %ebp   <<<<<<<< trampoline jumps here.
> > > > > > >   1b: 89 e5                mov    %esp,%ebp
> > > > > > >   1d: 83 ec 08              sub    $0x8,%esp
> > > > > > >
> > > > > > > We need to add 4 bytes for trampoline to skip endbr32.
> > > > > > >
> > > > > > > Here is the updated patch to check if nested function isn't only
> > > > > > > called directly,
> > > > > >
> > > > > > Please figure out the final patch. I don't want to waste my time
> > > > > > reviewing different version every half hour. Ping me in a couple of
> > > > > > days.
> > > > >
> > > > > This is the final version:
> > > > >
> > > > > https://gcc.gnu.org/ml/gcc-patches/2020-02/msg00586.html
> > > > >
> > > > > You can try the testcase in the patch on any machine with CET binutils
> > > > > since ENDBR32 is nop on none-CET machines.  Without this patch,
> > > > > the test will fail.
> > > >
> > > > Please rephrase the comment. I don't understand what it tries to say.
> > > >
> > >
> > > Here is the patch with updated comments.  OK for master and 8/9 branches?
> > >
> > > Thanks.
> > >
> > > H.J.
> > > ---
> > > Since pass_insert_endbranch inserts ENDBR32 at entry of the target
> > > function if it may be called indirectly, we also need to skip the
> > > 4-byte ENDBR32 for direct jump in trampoline if it is the case.
> >
> > "
> > Skip ENDBR32 at the entry if called indirectly.
> > "
> > pass_insert_endbranch inserts ENDBR at the entry of the target
> > function.  We need to skip
> > >
> > > Tested on Linux/x86-64 CET machine with and without -m32.
> > >
> > > gcc/
> > >
> > >         PR target/93656
> > >         * config/i386/i386.c (ix86_trampoline_init): Skip ENDBR32 at
> > >         the target function entry.
> > >
> > > gcc/testsuite/
> > >
> > >         PR target/93656
> > >         * gcc.target/i386/pr93656.c: New test.
> > > ---
> > >  gcc/config/i386/i386.c                  | 9 ++++++++-
> > >  gcc/testsuite/gcc.target/i386/pr93656.c | 4 ++++
> > >  2 files changed, 12 insertions(+), 1 deletion(-)
> > >  create mode 100644 gcc/testsuite/gcc.target/i386/pr93656.c
> > >
> > > diff --git a/gcc/config/i386/i386.c b/gcc/config/i386/i386.c
> > > index 44bc0e0176a..52640b74cc8 100644
> > > --- a/gcc/config/i386/i386.c
> > > +++ b/gcc/config/i386/i386.c
> > > @@ -16839,9 +16839,16 @@ ix86_trampoline_init (rtx m_tramp, tree fndecl, rtx chain_value)
> > >          the stack, we need to skip the first insn which pushes the
> > >          (call-saved) register static chain; this push is 1 byte.  */
> > >        offset += 5;
> > > +      int skip = MEM_P (chain) ? 1 : 0;
> >
> > offset += 5 - MEM_P (chain) ? 1: 0;
>
> This is done on purpose sinc there is
>
>   gcc_assert (offset <= TRAMPOLINE_SIZE);
>
> after it.  We shouldn't update offset.
>
> >
> > > +      /* Since pass_insert_endbranch inserts ENDBR32 at entry of the
> > > +        target function if it may be called indirectly, we also need
> > > +        to skip the 4-byte ENDBR32 if it is the case.  */
> >
> > /* Skip ENDBR32 at the entry of the target function when called indirectly.  */
>
> Fixed.
>
> >
> > > +      if (need_endbr
> > > +         && !cgraph_node::get (fndecl)->only_called_directly_p ())
> > > +       skip += 4;
> >
> > offset += 4;
> >
> > >        disp = expand_binop (SImode, sub_optab, fnaddr,
> > >                            plus_constant (Pmode, XEXP (m_tramp, 0),
> > > -                                         offset - (MEM_P (chain) ? 1 : 0)),
> > > +                                         offset - skip),
> >
> > plus_constant (Pmode, XEXP (m_tramp, 0), offset),
> >
> > Uros.
> >
>
> Here is the updated patch.  OK for master and 8/9 branches?
>
> Thanks.
>
>
> H.J.
> --
> Skip ENDBR32 at the entry of the target function when called indirectly.

Hm, this was sent too early, I was trying to say:

"Skip ENDBR32 at the entry of target function when initializing trampoline."

>
> Tested on Linux/x86-64 CET machine with and without -m32.
>
> gcc/
>
>         PR target/93656
>         * config/i386/i386.c (ix86_trampoline_init): Skip ENDBR32 at
>         the target function entry.
>
> gcc/testsuite/
>
>         PR target/93656
>         * gcc.target/i386/pr93656.c: New test.

LGTM for mainline, please wait a week before backporting.

Uros.

> ---
>  gcc/config/i386/i386.c                  | 8 +++++++-
>  gcc/testsuite/gcc.target/i386/pr93656.c | 4 ++++
>  2 files changed, 11 insertions(+), 1 deletion(-)
>  create mode 100644 gcc/testsuite/gcc.target/i386/pr93656.c
>
> diff --git a/gcc/config/i386/i386.c b/gcc/config/i386/i386.c
> index 44bc0e0176a..3f3dcd53eb2 100644
> --- a/gcc/config/i386/i386.c
> +++ b/gcc/config/i386/i386.c
> @@ -16839,9 +16839,15 @@ ix86_trampoline_init (rtx m_tramp, tree fndecl, rtx chain_value)
>          the stack, we need to skip the first insn which pushes the
>          (call-saved) register static chain; this push is 1 byte.  */
>        offset += 5;
> +      int skip = MEM_P (chain) ? 1 : 0;
> +      /* Skip ENDBR32 at the entry of the target function when called
> +        indirectly.  */

Just say "Skip ENDBR32 at the entry of the target function."

The condition below is clear, the purpose is not.

> +      if (need_endbr
> +         && !cgraph_node::get (fndecl)->only_called_directly_p ())
> +       skip += 4;
>        disp = expand_binop (SImode, sub_optab, fnaddr,
>                            plus_constant (Pmode, XEXP (m_tramp, 0),
> -                                         offset - (MEM_P (chain) ? 1 : 0)),
> +                                         offset - skip),
>                            NULL_RTX, 1, OPTAB_DIRECT);
>        emit_move_insn (mem, disp);
>      }
> diff --git a/gcc/testsuite/gcc.target/i386/pr93656.c b/gcc/testsuite/gcc.target/i386/pr93656.c
> new file mode 100644
> index 00000000000..f0ac8c8edaa
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/i386/pr93656.c
> @@ -0,0 +1,4 @@
> +/* { dg-do run { target { ia32 && cet } } } */
> +/* { dg-options "-O2 -fcf-protection" } */
> +
> +#include "pr67770.c"
> --
> 2.24.1
>
H.J. Lu Feb. 13, 2020, 1:20 p.m. UTC | #4
On Thu, Feb 13, 2020 at 5:10 AM Uros Bizjak <ubizjak@gmail.com> wrote:
>
> On Thu, Feb 13, 2020 at 1:42 PM H.J. Lu <hjl.tools@gmail.com> wrote:
> >
> > On Thu, Feb 13, 2020 at 01:28:43PM +0100, Uros Bizjak wrote:
> > > On Thu, Feb 13, 2020 at 1:06 PM H.J. Lu <hjl.tools@gmail.com> wrote:
> > > >
> > > > On Thu, Feb 13, 2020 at 09:29:32AM +0100, Uros Bizjak wrote:
> > > > > On Wed, Feb 12, 2020 at 1:21 PM H.J. Lu <hjl.tools@gmail.com> wrote:
> > > > > >
> > > > > > On Mon, Feb 10, 2020 at 12:01 PM Uros Bizjak <ubizjak@gmail.com> wrote:
> > > > > > >
> > > > > > > On Mon, Feb 10, 2020 at 8:53 PM H.J. Lu <hjl.tools@gmail.com> wrote:
> > > > > > > >
> > > > > > > > On Mon, Feb 10, 2020 at 11:40 AM Uros Bizjak <ubizjak@gmail.com> wrote:
> > > > > > > > >
> > > > > > > > > On Mon, Feb 10, 2020 at 8:22 PM H.J. Lu <hjl.tools@gmail.com> wrote:
> > > > > > > > > >
> > > > > > > > > > Since nested function isn't only called directly, there is ENDBR32 at
> > > > > > > > > > function entry and we need to skip it for direct jump in trampoline.
> > > > > > > > >
> > > > > > > > > Hm, I'm afraid I don't understand this comment. Can you perhaps rephrase it?
> > > > > > > > >
> > > > > > > >
> > > > > > > > ix86_trampoline_init has
> > > > > > > >
> > > > > > > >      /* Compute offset from the end of the jmp to the target function.
> > > > > > > >          In the case in which the trampoline stores the static chain on
> > > > > > > >          the stack, we need to skip the first insn which pushes the
> > > > > > > >          (call-saved) register static chain; this push is 1 byte.  */
> > > > > > > >       offset += 5;
> > > > > > > >       disp = expand_binop (SImode, sub_optab, fnaddr,
> > > > > > > >                            plus_constant (Pmode, XEXP (m_tramp, 0),
> > > > > > > >                                           offset - (MEM_P (chain) ? 1 : 0)),
> > > > > > > >                            NULL_RTX, 1, OPTAB_DIRECT);
> > > > > > > >       emit_move_insn (mem, disp);
> > > > > > > >
> > > > > > > > Without CET, we got
> > > > > > > >
> > > > > > > > 0000011 <bar.1878>:
> > > > > > > >   11: 56                    push   %esi
> > > > > > > >   12: 55                    push   %ebp   <<<<<< trampoline jumps here.
> > > > > > > >   13: 89 e5                mov    %esp,%ebp
> > > > > > > >   15: 83 ec 08              sub    $0x8,%esp
> > > > > > > >
> > > > > > > > With CET, if bar isn't only called directly, we got
> > > > > > > >
> > > > > > > > 00000015 <bar.1878>:
> > > > > > > >   15: f3 0f 1e fb          endbr32
> > > > > > > >   19: 56                    push   %esi
> > > > > > > >   1a: 55                    push   %ebp   <<<<<<<< trampoline jumps here.
> > > > > > > >   1b: 89 e5                mov    %esp,%ebp
> > > > > > > >   1d: 83 ec 08              sub    $0x8,%esp
> > > > > > > >
> > > > > > > > We need to add 4 bytes for trampoline to skip endbr32.
> > > > > > > >
> > > > > > > > Here is the updated patch to check if nested function isn't only
> > > > > > > > called directly,
> > > > > > >
> > > > > > > Please figure out the final patch. I don't want to waste my time
> > > > > > > reviewing different version every half hour. Ping me in a couple of
> > > > > > > days.
> > > > > >
> > > > > > This is the final version:
> > > > > >
> > > > > > https://gcc.gnu.org/ml/gcc-patches/2020-02/msg00586.html
> > > > > >
> > > > > > You can try the testcase in the patch on any machine with CET binutils
> > > > > > since ENDBR32 is nop on none-CET machines.  Without this patch,
> > > > > > the test will fail.
> > > > >
> > > > > Please rephrase the comment. I don't understand what it tries to say.
> > > > >
> > > >
> > > > Here is the patch with updated comments.  OK for master and 8/9 branches?
> > > >
> > > > Thanks.
> > > >
> > > > H.J.
> > > > ---
> > > > Since pass_insert_endbranch inserts ENDBR32 at entry of the target
> > > > function if it may be called indirectly, we also need to skip the
> > > > 4-byte ENDBR32 for direct jump in trampoline if it is the case.
> > >
> > > "
> > > Skip ENDBR32 at the entry if called indirectly.
> > > "
> > > pass_insert_endbranch inserts ENDBR at the entry of the target
> > > function.  We need to skip
> > > >
> > > > Tested on Linux/x86-64 CET machine with and without -m32.
> > > >
> > > > gcc/
> > > >
> > > >         PR target/93656
> > > >         * config/i386/i386.c (ix86_trampoline_init): Skip ENDBR32 at
> > > >         the target function entry.
> > > >
> > > > gcc/testsuite/
> > > >
> > > >         PR target/93656
> > > >         * gcc.target/i386/pr93656.c: New test.
> > > > ---
> > > >  gcc/config/i386/i386.c                  | 9 ++++++++-
> > > >  gcc/testsuite/gcc.target/i386/pr93656.c | 4 ++++
> > > >  2 files changed, 12 insertions(+), 1 deletion(-)
> > > >  create mode 100644 gcc/testsuite/gcc.target/i386/pr93656.c
> > > >
> > > > diff --git a/gcc/config/i386/i386.c b/gcc/config/i386/i386.c
> > > > index 44bc0e0176a..52640b74cc8 100644
> > > > --- a/gcc/config/i386/i386.c
> > > > +++ b/gcc/config/i386/i386.c
> > > > @@ -16839,9 +16839,16 @@ ix86_trampoline_init (rtx m_tramp, tree fndecl, rtx chain_value)
> > > >          the stack, we need to skip the first insn which pushes the
> > > >          (call-saved) register static chain; this push is 1 byte.  */
> > > >        offset += 5;
> > > > +      int skip = MEM_P (chain) ? 1 : 0;
> > >
> > > offset += 5 - MEM_P (chain) ? 1: 0;
> >
> > This is done on purpose sinc there is
> >
> >   gcc_assert (offset <= TRAMPOLINE_SIZE);
> >
> > after it.  We shouldn't update offset.
> >
> > >
> > > > +      /* Since pass_insert_endbranch inserts ENDBR32 at entry of the
> > > > +        target function if it may be called indirectly, we also need
> > > > +        to skip the 4-byte ENDBR32 if it is the case.  */
> > >
> > > /* Skip ENDBR32 at the entry of the target function when called indirectly.  */
> >
> > Fixed.
> >
> > >
> > > > +      if (need_endbr
> > > > +         && !cgraph_node::get (fndecl)->only_called_directly_p ())
> > > > +       skip += 4;
> > >
> > > offset += 4;
> > >
> > > >        disp = expand_binop (SImode, sub_optab, fnaddr,
> > > >                            plus_constant (Pmode, XEXP (m_tramp, 0),
> > > > -                                         offset - (MEM_P (chain) ? 1 : 0)),
> > > > +                                         offset - skip),
> > >
> > > plus_constant (Pmode, XEXP (m_tramp, 0), offset),
> > >
> > > Uros.
> > >
> >
> > Here is the updated patch.  OK for master and 8/9 branches?
> >
> > Thanks.
> >
> >
> > H.J.
> > --
> > Skip ENDBR32 at the entry of the target function when called indirectly.
>
> Hm, this was sent too early, I was trying to say:
>
> "Skip ENDBR32 at the entry of target function when initializing trampoline."
>
> >
> > Tested on Linux/x86-64 CET machine with and without -m32.
> >
> > gcc/
> >
> >         PR target/93656
> >         * config/i386/i386.c (ix86_trampoline_init): Skip ENDBR32 at
> >         the target function entry.
> >
> > gcc/testsuite/
> >
> >         PR target/93656
> >         * gcc.target/i386/pr93656.c: New test.
>
> LGTM for mainline, please wait a week before backporting.
>
> Uros.
>
> > ---
> >  gcc/config/i386/i386.c                  | 8 +++++++-
> >  gcc/testsuite/gcc.target/i386/pr93656.c | 4 ++++
> >  2 files changed, 11 insertions(+), 1 deletion(-)
> >  create mode 100644 gcc/testsuite/gcc.target/i386/pr93656.c
> >
> > diff --git a/gcc/config/i386/i386.c b/gcc/config/i386/i386.c
> > index 44bc0e0176a..3f3dcd53eb2 100644
> > --- a/gcc/config/i386/i386.c
> > +++ b/gcc/config/i386/i386.c
> > @@ -16839,9 +16839,15 @@ ix86_trampoline_init (rtx m_tramp, tree fndecl, rtx chain_value)
> >          the stack, we need to skip the first insn which pushes the
> >          (call-saved) register static chain; this push is 1 byte.  */
> >        offset += 5;
> > +      int skip = MEM_P (chain) ? 1 : 0;
> > +      /* Skip ENDBR32 at the entry of the target function when called
> > +        indirectly.  */
>
> Just say "Skip ENDBR32 at the entry of the target function."
>
> The condition below is clear, the purpose is not.
>

This is the patch I am checking in.  I will backport it next week.

Thanks.

Patch
diff mbox series

diff --git a/gcc/config/i386/i386.c b/gcc/config/i386/i386.c
index 44bc0e0176a..52640b74cc8 100644
--- a/gcc/config/i386/i386.c
+++ b/gcc/config/i386/i386.c
@@ -16839,9 +16839,16 @@  ix86_trampoline_init (rtx m_tramp, tree fndecl, rtx chain_value)
 	 the stack, we need to skip the first insn which pushes the
 	 (call-saved) register static chain; this push is 1 byte.  */
       offset += 5;
+      int skip = MEM_P (chain) ? 1 : 0;
+      /* Since pass_insert_endbranch inserts ENDBR32 at entry of the
+	 target function if it may be called indirectly, we also need
+	 to skip the 4-byte ENDBR32 if it is the case.  */
+      if (need_endbr
+	  && !cgraph_node::get (fndecl)->only_called_directly_p ())
+	skip += 4;
       disp = expand_binop (SImode, sub_optab, fnaddr,
 			   plus_constant (Pmode, XEXP (m_tramp, 0),
-					  offset - (MEM_P (chain) ? 1 : 0)),
+					  offset - skip),
 			   NULL_RTX, 1, OPTAB_DIRECT);
       emit_move_insn (mem, disp);
     }
diff --git a/gcc/testsuite/gcc.target/i386/pr93656.c b/gcc/testsuite/gcc.target/i386/pr93656.c
new file mode 100644
index 00000000000..f0ac8c8edaa
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/pr93656.c
@@ -0,0 +1,4 @@ 
+/* { dg-do run { target { ia32 && cet } } } */
+/* { dg-options "-O2 -fcf-protection" } */
+
+#include "pr67770.c"