s390: always use the packed stack layout

-mpacked-stack option has been supported by both minimum
gcc and clang versions for a while. With commit e2bc3e91d91e
("scripts/min-tool-version.sh: Raise minimum clang version to 13.0.0
for s390") minimum clang version now also supports a combination
of flags -mpacked-stack -mbackchain -pg -mfentry and fulfills
all requirements to always enable the packed stack layout.

Reviewed-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>

diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig
index be9f39f..a492376 100644 (file)
--- a/arch/s390/Kconfig
+++ b/arch/s390/Kconfig
@@ -155,7 +155,7 @@ config S390
        select HAVE_DYNAMIC_FTRACE_WITH_ARGS
        select HAVE_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
        select HAVE_DYNAMIC_FTRACE_WITH_REGS
-       select HAVE_EBPF_JIT if PACK_STACK && HAVE_MARCH_Z196_FEATURES
+       select HAVE_EBPF_JIT if HAVE_MARCH_Z196_FEATURES
        select HAVE_EFFICIENT_UNALIGNED_ACCESS
        select HAVE_FAST_GUP
        select HAVE_FENTRY
@@ -656,20 +656,6 @@ config MAX_PHYSMEM_BITS
          Increasing the number of bits also increases the kernel image size.
          By default 46 bits (64TB) are supported.
 
-config PACK_STACK
-       def_bool y
-       prompt "Pack kernel stack"
-       help
-         This option enables the compiler option -mkernel-backchain if it
-         is available. If the option is available the compiler supports
-         the new stack layout which dramatically reduces the minimum stack
-         frame size. With an old compiler a non-leaf function needs a
-         minimum of 96 bytes on 31 bit and 160 bytes on 64 bit. With
-         -mkernel-backchain the minimum size drops to 16 byte on 31 bit
-         and 24 byte on 64 bit.
-
-         Say Y if you are unsure.
-
 config CHECK_STACK
        def_bool y
        depends on !VMAP_STACK

diff --git a/arch/s390/Makefile b/arch/s390/Makefile
index 609e369..2edf25b 100644 (file)
--- a/arch/s390/Makefile
+++ b/arch/s390/Makefile
@@ -21,7 +21,7 @@ endif
 aflags_dwarf   := -Wa,-gdwarf-2
 KBUILD_AFLAGS_DECOMPRESSOR := $(CLANG_FLAGS) -m64 -D__ASSEMBLY__
 KBUILD_AFLAGS_DECOMPRESSOR += $(if $(CONFIG_DEBUG_INFO),$(aflags_dwarf))
-KBUILD_CFLAGS_DECOMPRESSOR := $(CLANG_FLAGS) -m64 -O2
+KBUILD_CFLAGS_DECOMPRESSOR := $(CLANG_FLAGS) -m64 -O2 -mpacked-stack
 KBUILD_CFLAGS_DECOMPRESSOR += -DDISABLE_BRANCH_PROFILING -D__NO_FORTIFY
 KBUILD_CFLAGS_DECOMPRESSOR += -fno-delete-null-pointer-checks -msoft-float -mbackchain
 KBUILD_CFLAGS_DECOMPRESSOR += -fno-asynchronous-unwind-tables
@@ -68,11 +68,6 @@ cflags-y += -Wa,-I$(srctree)/arch/$(ARCH)/include
 #
 cflags-$(CONFIG_FRAME_POINTER) += -fno-optimize-sibling-calls
 
-ifneq ($(call cc-option,-mpacked-stack -mbackchain -msoft-float),)
-cflags-$(CONFIG_PACK_STACK)  += -mpacked-stack -D__PACK_STACK
-aflags-$(CONFIG_PACK_STACK)  += -D__PACK_STACK
-endif
-
 KBUILD_AFLAGS_DECOMPRESSOR += $(aflags-y)
 KBUILD_CFLAGS_DECOMPRESSOR += $(cflags-y)
 
@@ -111,7 +106,7 @@ endif
 # Test CFI features of binutils
 cfi := $(call as-instr,.cfi_startproc\n.cfi_val_offset 15$(comma)-160\n.cfi_endproc,-DCONFIG_AS_CFI_VAL_OFFSET=1)
 
-KBUILD_CFLAGS  += -mbackchain -msoft-float $(cflags-y)
+KBUILD_CFLAGS  += -mpacked-stack -mbackchain -msoft-float $(cflags-y)
 KBUILD_CFLAGS  += -pipe -Wno-sign-compare
 KBUILD_CFLAGS  += -fno-asynchronous-unwind-tables $(cfi)
 KBUILD_AFLAGS  += $(aflags-y) $(cfi)

diff --git a/arch/s390/include/asm/stacktrace.h b/arch/s390/include/asm/stacktrace.h
index dd00d98..275f425 100644 (file)
--- a/arch/s390/include/asm/stacktrace.h
+++ b/arch/s390/include/asm/stacktrace.h
@@ -36,22 +36,14 @@ static inline bool on_stack(struct stack_info *info,
 
 /*
  * Stack layout of a C stack frame.
+ * Kernel uses the packed stack layout (-mpacked-stack).
  */
-#ifndef __PACK_STACK
-struct stack_frame {
-       unsigned long back_chain;
-       unsigned long empty1[5];
-       unsigned long gprs[10];
-       unsigned int  empty2[8];
-};
-#else
 struct stack_frame {
        unsigned long empty1[5];
        unsigned int  empty2[8];
        unsigned long gprs[10];
        unsigned long back_chain;
 };
-#endif
 
 /*
  * Unlike current_stack_pointer() which simply returns current value of %r15

diff --git a/arch/s390/kernel/mcount.S b/arch/s390/kernel/mcount.S
index 9d90b8b..b882052 100644 (file)
--- a/arch/s390/kernel/mcount.S
+++ b/arch/s390/kernel/mcount.S
@@ -26,12 +26,8 @@ ENDPROC(ftrace_stub)
 #define STACK_PTREGS_PSW       (STACK_PTREGS + __PT_PSW)
 #define STACK_PTREGS_ORIG_GPR2 (STACK_PTREGS + __PT_ORIG_GPR2)
 #define STACK_PTREGS_FLAGS     (STACK_PTREGS + __PT_FLAGS)
-#ifdef __PACK_STACK
-/* allocate just enough for r14, r15 and backchain */
+/* packed stack: allocate just enough for r14, r15 and backchain */
 #define TRACED_FUNC_FRAME_SIZE 24
-#else
-#define TRACED_FUNC_FRAME_SIZE STACK_FRAME_OVERHEAD
-#endif
 
        .macro  ftrace_regs_entry, allregs=0
        stg     %r14,(__SF_GPRS+8*8)(%r15)      # save traced function caller

diff --git a/arch/s390/net/bpf_jit_comp.c b/arch/s390/net/bpf_jit_comp.c
index 9ff2bd8..df5d4da 100644 (file)
--- a/arch/s390/net/bpf_jit_comp.c
+++ b/arch/s390/net/bpf_jit_comp.c
@@ -7,7 +7,6 @@
  *  - HAVE_MARCH_Z196_FEATURES: laal, laalg
  *  - HAVE_MARCH_Z10_FEATURES: msfi, cgrj, clgrj
  *  - HAVE_MARCH_Z9_109_FEATURES: alfi, llilf, clfi, oilf, nilf
- *  - PACK_STACK
  *  - 64BIT
  *
  * Copyright IBM Corp. 2012,2015