PING^2 [PATCH v2] S/390: Improve storing asan frame_pc

[Ilya Leoshkevich <iii@linux.ibm.com>]

>> Am 02.07.2019 um 17:34 schrieb Ilya Leoshkevich <iii@linux.ibm.com>:
>> 
>> Bootstrap and regtest running on x86_64-redhat-linux, s390x-redhat-linux
>> and ppc64le-redhat-linux.
>> 
>> Currently s390 emits the following sequence to store a frame_pc:
>> 
>> 	a:
>> 	.LASANPC0:
>> 
>> 		lg	%r1,.L5-.L4(%r13)
>> 		la	%r1,0(%r1,%r12)
>> 		stg	%r1,176(%r11)
>> 
>> 	.L5:
>> 		.quad	.LASANPC0@GOTOFF
>> 
>> The reason GOT indirection is used instead of larl is that gcc does not
>> know that .LASANPC0, being a code label, is aligned on a 2-byte
>> boundary, and larl can load only even addresses.
>> 
>> This patch provides such an alignment hint.  Since targets don't provide
>> their instruction alignments yet, the new macro is introduced for that
>> purpose.  It returns 1-byte alignment by default, so this change is a
>> no-op for targets other than s390.
>> 
>> As a result, we get the desired:
>> 
>> 		larl	%r1,.LASANPC0
>> 		stg	%r1,176(%r11)
>> 
>> gcc/ChangeLog:
>> 
>> 2019-06-28  Ilya Leoshkevich  <iii@linux.ibm.com>
>> 
>> 	* asan.c (asan_emit_stack_protection): Provide an alignment
>> 	hint.
>> 	* config/s390/s390.h (CODE_LABEL_BOUNDARY): Specify that s390
>> 	requires code labels to be aligned on a 2-byte boundary.
>> 	* defaults.h (CODE_LABEL_BOUNDARY): New macro.
>> 	* doc/tm.texi: Document CODE_LABEL_BOUNDARY.
>> 	* doc/tm.texi.in: Likewise.
>> 
>> gcc/testsuite/ChangeLog:
>> 
>> 2019-06-28  Ilya Leoshkevich  <iii@linux.ibm.com>
>> 
>> 	* gcc.target/s390/asan-no-gotoff.c: New test.
>> ---
>> gcc/asan.c                                     |  1 +
>> gcc/config/s390/s390.h                         |  3 +++
>> gcc/defaults.h                                 |  5 +++++
>> gcc/doc/tm.texi                                |  4 ++++
>> gcc/doc/tm.texi.in                             |  4 ++++
>> gcc/testsuite/gcc.target/s390/asan-no-gotoff.c | 15 +++++++++++++++
>> 6 files changed, 32 insertions(+)
>> create mode 100644 gcc/testsuite/gcc.target/s390/asan-no-gotoff.c
>> 
>> diff --git a/gcc/asan.c b/gcc/asan.c
>> index 605d04f87f7..2db69f476bc 100644
>> --- a/gcc/asan.c
>> +++ b/gcc/asan.c
>> @@ -1523,6 +1523,7 @@ asan_emit_stack_protection (rtx base, rtx pbase, unsigned int alignb,
>>  DECL_INITIAL (decl) = decl;
>>  TREE_ASM_WRITTEN (decl) = 1;
>>  TREE_ASM_WRITTEN (id) = 1;
>> +  SET_DECL_ALIGN (decl, CODE_LABEL_BOUNDARY);
>>  emit_move_insn (mem, expand_normal (build_fold_addr_expr (decl)));
>>  shadow_base = expand_binop (Pmode, lshr_optab, base,
>> 			      gen_int_shift_amount (Pmode, ASAN_SHADOW_SHIFT),
>> diff --git a/gcc/config/s390/s390.h b/gcc/config/s390/s390.h
>> index 969f58a2ba0..3d0266c9dff 100644
>> --- a/gcc/config/s390/s390.h
>> +++ b/gcc/config/s390/s390.h
>> @@ -334,6 +334,9 @@ extern const char *s390_host_detect_local_cpu (int argc, const char **argv);
>> /* Allocation boundary (in *bits*) for the code of a function.  */
>> #define FUNCTION_BOUNDARY 64
>> 
>> +/* Alignment required for a code label, in bits.  */
>> +#define CODE_LABEL_BOUNDARY 16
>> +
>> /* There is no point aligning anything to a rounder boundary than this.  */
>> #define BIGGEST_ALIGNMENT 64
>> 
>> diff --git a/gcc/defaults.h b/gcc/defaults.h
>> index af7ea185f1e..97c4c17537d 100644
>> --- a/gcc/defaults.h
>> +++ b/gcc/defaults.h
>> @@ -1459,4 +1459,9 @@ see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
>> #define DWARF_GNAT_ENCODINGS_DEFAULT DWARF_GNAT_ENCODINGS_GDB
>> #endif
>> 
>> +/* Alignment required for a code label, in bits.  */
>> +#ifndef CODE_LABEL_BOUNDARY
>> +#define CODE_LABEL_BOUNDARY BITS_PER_UNIT
>> +#endif
>> +
>> #endif  /* ! GCC_DEFAULTS_H */
>> diff --git a/gcc/doc/tm.texi b/gcc/doc/tm.texi
>> index 14c1ea6a323..3b50fc0c0a7 100644
>> --- a/gcc/doc/tm.texi
>> +++ b/gcc/doc/tm.texi
>> @@ -1019,6 +1019,10 @@ to a value equal to or larger than @code{STACK_BOUNDARY}.
>> Alignment required for a function entry point, in bits.
>> @end defmac
>> 
>> +@defmac CODE_LABEL_BOUNDARY
>> +Alignment required for a code label, in bits.
>> +@end defmac
>> +
>> @defmac BIGGEST_ALIGNMENT
>> Biggest alignment that any data type can require on this machine, in
>> bits.  Note that this is not the biggest alignment that is supported,
>> diff --git a/gcc/doc/tm.texi.in b/gcc/doc/tm.texi.in
>> index b4d57b86e2f..ab038b7462c 100644
>> --- a/gcc/doc/tm.texi.in
>> +++ b/gcc/doc/tm.texi.in
>> @@ -969,6 +969,10 @@ to a value equal to or larger than @code{STACK_BOUNDARY}.
>> Alignment required for a function entry point, in bits.
>> @end defmac
>> 
>> +@defmac CODE_LABEL_BOUNDARY
>> +Alignment required for a code label, in bits.
>> +@end defmac
>> +
>> @defmac BIGGEST_ALIGNMENT
>> Biggest alignment that any data type can require on this machine, in
>> bits.  Note that this is not the biggest alignment that is supported,
>> diff --git a/gcc/testsuite/gcc.target/s390/asan-no-gotoff.c b/gcc/testsuite/gcc.target/s390/asan-no-gotoff.c
>> new file mode 100644
>> index 00000000000..f555e4e96f8
>> --- /dev/null
>> +++ b/gcc/testsuite/gcc.target/s390/asan-no-gotoff.c
>> @@ -0,0 +1,15 @@
>> +/* Test that ASAN labels are referenced without unnecessary indirections.  */
>> +
>> +/* { dg-do compile } */
>> +/* { dg-options "-fPIE -O2 -fsanitize=kernel-address --param asan-stack=1" } */
>> +
>> +extern void c (int *);
>> +
>> +void a ()
>> +{
>> +  int b;
>> +  c (&b);
>> +}
>> +
>> +/* { dg-final { scan-assembler {\tlarl\t%r\d+,\.LASANPC\d+} } } */
>> +/* { dg-final { scan-assembler-not {\.LASANPC\d+@GOTOFF} } } */
>> -- 
>> 2.21.0
>> 

Gentle ping.