Andi Kleen <a...@linux.intel.com> writes:
Ping^3!
> Andi Kleen <a...@linux.intel.com> writes:
>
> Ping!^2
>
>> Andi Kleen <a...@firstfloor.org> writes:
>>
>> Ping!
>>
>>> From: Andi Kleen <a...@linux.intel.com>
>>>
>>> When instrumenting programs using __fentry__ it is often useful
>>> to instrument the function return too. Traditionally this
>>> has been done by patching the return address on the stack
>>> frame on entry. However this is fairly complicated (trace
>>> function has to emulate a stack) and also slow because
>>> it causes a branch misprediction on every return.
>>>
>>> Add an option to generate call or nop instrumentation for
>>> every return instead, including patch sections.
>>>
>>> This will increase the program size slightly, but can be a
>>> lot faster and simpler.
>>>
>>> This version only instruments true returns, not sibling
>>> calls or tail recursion. This matches the semantics of the
>>> original stack.
>>>
>>> gcc/:
>>>
>>> 2018-11-04 Andi Kleen <a...@linux.intel.com>
>>>
>>> * config/i386/i386-opts.h (enum instrument_return): Add.
>>> * config/i386/i386.c (output_return_instrumentation): Add.
>>> (ix86_output_function_return): Call output_return_instrumentation.
>>> (ix86_output_call_insn): Call output_return_instrumentation.
>>> * config/i386/i386.opt: Add -minstrument-return=.
>>> * doc/invoke.texi (-minstrument-return): Document.
>>>
>>> gcc/testsuite/:
>>>
>>> 2018-11-04 Andi Kleen <a...@linux.intel.com>
>>>
>>> * gcc.target/i386/returninst1.c: New test.
>>> * gcc.target/i386/returninst2.c: New test.
>>> * gcc.target/i386/returninst3.c: New test.
>>> ---
>>> gcc/config/i386/i386-opts.h | 6 ++++
>>> gcc/config/i386/i386.c | 36 +++++++++++++++++++++
>>> gcc/config/i386/i386.opt | 21 ++++++++++++
>>> gcc/doc/invoke.texi | 14 ++++++++
>>> gcc/testsuite/gcc.target/i386/returninst1.c | 14 ++++++++
>>> gcc/testsuite/gcc.target/i386/returninst2.c | 21 ++++++++++++
>>> gcc/testsuite/gcc.target/i386/returninst3.c | 9 ++++++
>>> 7 files changed, 121 insertions(+)
>>> create mode 100644 gcc/testsuite/gcc.target/i386/returninst1.c
>>> create mode 100644 gcc/testsuite/gcc.target/i386/returninst2.c
>>> create mode 100644 gcc/testsuite/gcc.target/i386/returninst3.c
>>>
>>> diff --git a/gcc/config/i386/i386-opts.h b/gcc/config/i386/i386-opts.h
>>> index 46366cbfa72..35e9413100e 100644
>>> --- a/gcc/config/i386/i386-opts.h
>>> +++ b/gcc/config/i386/i386-opts.h
>>> @@ -119,4 +119,10 @@ enum indirect_branch {
>>> indirect_branch_thunk_extern
>>> };
>>>
>>> +enum instrument_return {
>>> + instrument_return_none = 0,
>>> + instrument_return_call,
>>> + instrument_return_nop5
>>> +};
>>> +
>>> #endif
>>> diff --git a/gcc/config/i386/i386.c b/gcc/config/i386/i386.c
>>> index f9ef0b4445b..f7cd94a8139 100644
>>> --- a/gcc/config/i386/i386.c
>>> +++ b/gcc/config/i386/i386.c
>>> @@ -28336,12 +28336,47 @@ ix86_output_indirect_jmp (rtx call_op)
>>> return "%!jmp\t%A0";
>>> }
>>>
>>> +/* Output return instrumentation for current function if needed. */
>>> +
>>> +static void
>>> +output_return_instrumentation (void)
>>> +{
>>> + if (ix86_instrument_return != instrument_return_none
>>> + && flag_fentry
>>> + && !DECL_NO_INSTRUMENT_FUNCTION_ENTRY_EXIT (cfun->decl))
>>> + {
>>> + if (ix86_flag_record_return)
>>> + fprintf (asm_out_file, "1:\n");
>>> + switch (ix86_instrument_return)
>>> + {
>>> + case instrument_return_call:
>>> + fprintf (asm_out_file, "\tcall\t__return__\n");
>>> + break;
>>> + case instrument_return_nop5:
>>> + /* 5 byte nop: nopl 0(%[re]ax,%[re]ax,1) */
>>> + fprintf (asm_out_file, ASM_BYTE "0x0f, 0x1f, 0x44, 0x00, 0x00\n");
>>> + break;
>>> + case instrument_return_none:
>>> + break;
>>> + }
>>> +
>>> + if (ix86_flag_record_return)
>>> + {
>>> + fprintf (asm_out_file, "\t.section __return_loc, \"a\",@progbits\n");
>>> + fprintf (asm_out_file, "\t.%s 1b\n", TARGET_64BIT ? "quad" : "long");
>>> + fprintf (asm_out_file, "\t.previous\n");
>>> + }
>>> + }
>>> +}
>>> +
>>> /* Output function return. CALL_OP is the jump target. Add a REP
>>> prefix to RET if LONG_P is true and function return is kept. */
>>>
>>> const char *
>>> ix86_output_function_return (bool long_p)
>>> {
>>> + output_return_instrumentation ();
>>> +
>>> if (cfun->machine->function_return_type != indirect_branch_keep)
>>> {
>>> char thunk_name[32];
>>> @@ -28454,6 +28489,7 @@ ix86_output_call_insn (rtx_insn *insn, rtx call_op)
>>>
>>> if (SIBLING_CALL_P (insn))
>>> {
>>> + output_return_instrumentation ();
>>> if (direct_p)
>>> {
>>> if (ix86_nopic_noplt_attribute_p (call_op))
>>> diff --git a/gcc/config/i386/i386.opt b/gcc/config/i386/i386.opt
>>> index e7fbf9b6f99..5925b75244f 100644
>>> --- a/gcc/config/i386/i386.opt
>>> +++ b/gcc/config/i386/i386.opt
>>> @@ -1063,3 +1063,24 @@ Support WAITPKG built-in functions and code
>>> generation.
>>> mcldemote
>>> Target Report Mask(ISA_CLDEMOTE) Var(ix86_isa_flags2) Save
>>> Support CLDEMOTE built-in functions and code generation.
>>> +
>>> +minstrument-return=
>>> +Target Report RejectNegative Joined Enum(instrument_return)
>>> Var(ix86_instrument_return) Init(instrument_return_none)
>>> +Instrument function exit in instrumented functions with __fentry__.
>>> +
>>> +Enum
>>> +Name(instrument_return) Type(enum instrument_return)
>>> +Known choices for return instrumentation with -minstrument-return=
>>> +
>>> +EnumValue
>>> +Enum(instrument_return) String(none) Value(instrument_return_none)
>>> +
>>> +EnumValue
>>> +Enum(instrument_return) String(call) Value(instrument_return_call)
>>> +
>>> +EnumValue
>>> +Enum(instrument_return) String(nop5) Value(instrument_return_nop5)
>>> +
>>> +mrecord-return
>>> +Target Report Var(ix86_flag_record_return) Init(0)
>>> +Generate a __return_loc section pointing to all return instrumentation
>>> code.
>>> diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
>>> index 1743c64582e..939be3e251b 100644
>>> --- a/gcc/doc/invoke.texi
>>> +++ b/gcc/doc/invoke.texi
>>> @@ -1301,6 +1301,7 @@ See RS/6000 and PowerPC Options.
>>> -mcmodel=@var{code-model} -mabi=@var{name} -maddress-mode=@var{mode} @gol
>>> -m32 -m64 -mx32 -m16 -miamcu -mlarge-data-threshold=@var{num} @gol
>>> -msse2avx -mfentry -mrecord-mcount -mnop-mcount -m8bit-idiv @gol
>>> +-minstrument-return=@var{type} @gol
>>> -mavx256-split-unaligned-load -mavx256-split-unaligned-store @gol
>>> -malign-data=@var{type} -mstack-protector-guard=@var{guard} @gol
>>> -mstack-protector-guard-reg=@var{reg} @gol
>>> @@ -28442,6 +28443,19 @@ the profiling functions as NOPs. This is useful
>>> when they
>>> should be patched in later dynamically. This is likely only
>>> useful together with @option{-mrecord-mcount}.
>>>
>>> +@item -minstrument-return=@var{type}
>>> +@opindex minstrument-return
>>> +Instrument function exit in -pg -mfentry instrumented functions with
>>> +call to specified function. This only instruments true returns ending
>>> +with ret, but not sibling calls ending with jump. Valid types
>>> +are @var{none} to not instrument, @var{call} to generate a call to
>>> __return__,
>>> +or @var{nop5} to generate a 5 byte nop.
>>> +
>>> +@item -mrecord-return
>>> +@itemx -mno-record-return
>>> +@opindex mrecord-return
>>> +Generate a __return_loc section pointing to all return instrumentation
>>> code.
>>> +
>>> @item -mskip-rax-setup
>>> @itemx -mno-skip-rax-setup
>>> @opindex mskip-rax-setup
>>> diff --git a/gcc/testsuite/gcc.target/i386/returninst1.c
>>> b/gcc/testsuite/gcc.target/i386/returninst1.c
>>> new file mode 100644
>>> index 00000000000..f970e75a774
>>> --- /dev/null
>>> +++ b/gcc/testsuite/gcc.target/i386/returninst1.c
>>> @@ -0,0 +1,14 @@
>>> +/* { dg-do compile } */
>>> +/* { dg-options "-pg -mfentry -minstrument-return=call -mrecord-return" }
>>> */
>>> +/* { dg-final { scan-assembler "call.*__return__" } } */
>>> +/* { dg-final { scan-assembler "section.*return_loc" } } */
>>> +
>>> +int func(int a)
>>> +{
>>> + return a+1;
>>> +}
>>> +
>>> +int func2(int a)
>>> +{
>>> + return a+1;
>>> +}
>>> diff --git a/gcc/testsuite/gcc.target/i386/returninst2.c
>>> b/gcc/testsuite/gcc.target/i386/returninst2.c
>>> new file mode 100644
>>> index 00000000000..716b38556dd
>>> --- /dev/null
>>> +++ b/gcc/testsuite/gcc.target/i386/returninst2.c
>>> @@ -0,0 +1,21 @@
>>> +/* { dg-do compile } */
>>> +/* { dg-options "-pg -mfentry -minstrument-return=nop5 -mrecord-return" }
>>> */
>>> +/* { dg-final { scan-assembler-times "0x0f, 0x1f, 0x44, 0x00, 0x00" 3 } }
>>> */
>>> +/* { dg-final { scan-assembler "section.*return_loc" } } */
>>> +
>>> +int func(int a)
>>> +{
>>> + return a+1;
>>> +}
>>> +
>>> +int func2(int a)
>>> +{
>>> + return a+1;
>>> +}
>>> +
>>> +extern void func4(int);
>>> +
>>> +int func3(int a)
>>> +{
>>> + func4(a + 1);
>>> +}
>>> diff --git a/gcc/testsuite/gcc.target/i386/returninst3.c
>>> b/gcc/testsuite/gcc.target/i386/returninst3.c
>>> new file mode 100644
>>> index 00000000000..5bbc60e8bd4
>>> --- /dev/null
>>> +++ b/gcc/testsuite/gcc.target/i386/returninst3.c
>>> @@ -0,0 +1,9 @@
>>> +/* { dg-do compile } */
>>> +/* { dg-options "-pg -mfentry -minstrument-return=call" } */
>>> +/* { dg-final { scan-assembler-not "call.*__return__" } } */
>>> +
>>> +__attribute__((no_instrument_function))
>>> +int func(int a)
>>> +{
>>> + return a+1;
>>> +}
