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 <[email protected]> wrote:
> >
> > On Mon, Feb 10, 2020 at 12:01 PM Uros Bizjak <[email protected]> wrote:
> > >
> > > On Mon, Feb 10, 2020 at 8:53 PM H.J. Lu <[email protected]> wrote:
> > > >
> > > > On Mon, Feb 10, 2020 at 11:40 AM Uros Bizjak <[email protected]> wrote:
> > > > >
> > > > > On Mon, Feb 10, 2020 at 8:22 PM H.J. Lu <[email protected]> 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
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"
--
2.24.1
