Hi Ilya,
This looks great, thanks! You'll an okay from a global maintainer though,
or of all affected maintainers separately.
Segher
On Tue, Jul 02, 2019 at 05:34:07PM +0200, Ilya Leoshkevich wrote:
> 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 <i...@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 <i...@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
