From 3b31afe1a56cfb7b92f563b53686b378bdbead54 Mon Sep 17 00:00:00 2001 From: Andi Kleen Date: Thu, 29 Nov 2018 23:11:47 +0000 Subject: [PATCH] Support instrumenting returns of instrumented functions 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/: 2018-11-29 Andi Kleen * 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/: 2018-11-29 Andi Kleen * gcc.target/i386/returninst1.c: New test. * gcc.target/i386/returninst2.c: New test. * gcc.target/i386/returninst3.c: New test. From-SVN: r266652 --- gcc/ChangeLog | 9 ++++++ 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/ChangeLog | 6 ++++ gcc/testsuite/gcc.target/i386/returninst1.c | 14 ++++++++ gcc/testsuite/gcc.target/i386/returninst2.c | 21 ++++++++++++ gcc/testsuite/gcc.target/i386/returninst3.c | 9 ++++++ 9 files changed, 136 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/ChangeLog b/gcc/ChangeLog index d2e8b1f2d3e..9f19bc685ed 100644 --- a/gcc/ChangeLog +++ b/gcc/ChangeLog @@ -1,3 +1,12 @@ +2018-11-29 Andi Kleen + + * 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. + 2018-11-29 Eric Botcazou PR target/87807 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 209b74aa4dc..98928d99265 100644 --- a/gcc/config/i386/i386.c +++ b/gcc/config/i386/i386.c @@ -28385,12 +28385,47 @@ 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]; @@ -28503,6 +28538,7 @@ 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 1705815a2ec..bacfabe378e 100644 --- a/gcc/config/i386/i386.opt +++ b/gcc/config/i386/i386.opt @@ -1067,3 +1067,24 @@ 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 6a694a695a1..d457980dbf7 100644 --- a/gcc/doc/invoke.texi +++ b/gcc/doc/invoke.texi @@ -1316,6 +1316,7 @@ 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 @@ -29077,6 +29078,19 @@ 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/ChangeLog b/gcc/testsuite/ChangeLog index d996dce7265..ebe2813c93f 100644 --- a/gcc/testsuite/ChangeLog +++ b/gcc/testsuite/ChangeLog @@ -1,3 +1,9 @@ +2018-11-29 Andi Kleen + + * gcc.target/i386/returninst1.c: New test. + * gcc.target/i386/returninst2.c: New test. + * gcc.target/i386/returninst3.c: New test. + 2018-11-29 Eric Botcazou * gcc.target/sparc/20181129-1.c: New test. 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; +} -- 2.30.2