[PATCH] compiler: allow all arches to enable CONFIG_OPTIMIZE_INLINING

Masahiro Yamada
2019-03-20T06:22:04Z

Commit 60a3cdd06394 ("x86: add optimized inlining") introduced
CONFIG_OPTIMIZE_INLINING, but it has been available only for x86.

The idea is obviously arch-agnostic although we need some code fixups.
This commit moves the config entry from arch/x86/Kconfig.debug to
lib/Kconfig.debug so that all architectures (except MIPS for now) can
benefit from it.

At this moment, I added "depends on !MIPS" because fixing 0day bot reports
for MIPS was complex to me.

I tested this patch on my arm/arm64 boards.

This can make a huge difference in kernel image size especially when
CONFIG_OPTIMIZE_FOR_SIZE is enabled.

For example, I got 3.5% smaller arm64 kernel image for v5.1-rc1.

dec file
18983424 arch/arm64/boot/Image.before
18321920 arch/arm64/boot/Image.after

This also slightly improves the "Kernel hacking" Kconfig menu.
Commit e61aca5158a8 ("Merge branch 'kconfig-diet' from Dave Hansen')
mentioned this config option would be a good fit in the "compiler option"
menu. I did so.

I fixed up some files to avoid build warnings/errors.

[1] arch/arm64/include/asm/cpufeature.h

In file included from ././include/linux/compiler_types.h:68,
from <command-line>:
./arch/arm64/include/asm/jump_label.h: In function 'cpus_have_const_cap':
./include/linux/compiler-gcc.h:120:38: warning: asm operand 0 probably doesn't match constraints
#define asm_volatile_goto(x...) do { asm goto(x); asm (""); } while (0)
^~~
./arch/arm64/include/asm/jump_label.h:32:2: note: in expansion of macro 'asm_volatile_goto'
asm_volatile_goto(
^~~~~~~~~~~~~~~~~
./include/linux/compiler-gcc.h:120:38: error: impossible constraint in 'asm'
#define asm_volatile_goto(x...) do { asm goto(x); asm (""); } while (0)
^~~
./arch/arm64/include/asm/jump_label.h:32:2: note: in expansion of macro 'asm_volatile_goto'
asm_volatile_goto(
^~~~~~~~~~~~~~~~~

[2] arch/mips/kernel/cpu-bugs64.c

arch/mips/kernel/cpu-bugs64.c: In function 'mult_sh_align_mod.constprop':
arch/mips/kernel/cpu-bugs64.c:33:2: error: asm operand 1 probably doesn't match constraints [-Werror]
asm volatile(
^~~
arch/mips/kernel/cpu-bugs64.c:33:2: error: asm operand 1 probably doesn't match constraints [-Werror]
asm volatile(
^~~
arch/mips/kernel/cpu-bugs64.c:33:2: error: impossible constraint in 'asm'
asm volatile(
^~~
arch/mips/kernel/cpu-bugs64.c:33:2: error: impossible constraint in 'asm'
asm volatile(
^~~

[3] arch/powerpc/mm/tlb-radix.c

arch/powerpc/mm/tlb-radix.c: In function '__radix__flush_tlb_range_psize':
arch/powerpc/mm/tlb-radix.c:104:2: error: asm operand 3 probably doesn't match constraints [-Werror]
asm volatile(PPC_TLBIEL(%0, %4, %3, %2, %1)
^~~
arch/powerpc/mm/tlb-radix.c:104:2: error: impossible constraint in 'asm'
CC arch/powerpc/perf/hv-gpci.o

[4] arch/s390/include/asm/cpacf.h

In file included from arch/s390/crypto/des_s390.c:19:
./arch/s390/include/asm/cpacf.h: In function 'cpacf_query':
./arch/s390/include/asm/cpacf.h:170:2: warning: asm operand 3 probably doesn't match constraints
asm volatile(
^~~
./arch/s390/include/asm/cpacf.h:170:2: error: impossible constraint in 'asm'

[5] arch/powerpc/kernel/prom_init.c

WARNING: vmlinux.o(.text.unlikely+0x20): Section mismatch in reference from the function .prom_getprop() to the function .init.text:.call_prom()
The function .prom_getprop() references
the function __init .call_prom().
This is often because .prom_getprop lacks a __init
annotation or the annotation of .call_prom is wrong.

WARNING: vmlinux.o(.text.unlikely+0x3c): Section mismatch in reference from the function .prom_getproplen() to the function .init.text:.call_prom()
The function .prom_getproplen() references
the function __init .call_prom().
This is often because .prom_getproplen lacks a __init
annotation or the annotation of .call_prom is wrong.

[6] drivers/mtd/nand/raw/vf610_nfc.c

drivers/mtd/nand/raw/vf610_nfc.c: In function ‘vf610_nfc_cmd’:
drivers/mtd/nand/raw/vf610_nfc.c:455:3: warning: ‘offset’ may be used uninitialized in this function [-Wmaybe-uninitialized]
vf610_nfc_rd_from_sram(instr->ctx.data.buf.in + offset,
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
nfc->regs + NFC_MAIN_AREA(0) + offset,
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
trfr_sz, !nfc->data_access);
~~~~~~~~~~~~~~~~~~~~~~~~~~~

[7] arch/arm/kernel/smp.c

arch/arm/kernel/smp.c: In function ‘raise_nmi’:
arch/arm/kernel/smp.c:522:2: warning: array subscript is above array bounds [-Warray-bounds]
trace_ipi_raise_rcuidle(target, ipi_types[ipinr]);
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

The fixup is not included in this. The patch is available in ML:

http://lists.infradead.org/pipermail/linux-arm-kernel/2016-February/409393.html

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
---

arch/arm64/include/asm/cpufeature.h | 4 ++--
arch/mips/kernel/cpu-bugs64.c | 4 ++--
arch/powerpc/kernel/prom_init.c | 6 +++---
arch/powerpc/mm/tlb-radix.c | 2 +-
arch/s390/include/asm/cpacf.h | 2 +-
arch/x86/Kconfig | 3 ---
arch/x86/Kconfig.debug | 14 --------------
drivers/mtd/nand/raw/vf610_nfc.c | 2 +-
include/linux/compiler_types.h | 3 +--
lib/Kconfig.debug | 15 +++++++++++++++
10 files changed, 26 insertions(+), 29 deletions(-)

diff --git a/arch/arm64/include/asm/cpufeature.h b/arch/arm64/include/asm/cpufeature.h
index e505e1f..77d1aa5 100644
--- a/arch/arm64/include/asm/cpufeature.h
+++ b/arch/arm64/include/asm/cpufeature.h
@@ -406,7 +406,7 @@ static inline bool cpu_have_feature(unsigned int num)
}

/* System capability check for constant caps */
-static inline bool __cpus_have_const_cap(int num)
+static __always_inline bool __cpus_have_const_cap(int num)
{
if (num >= ARM64_NCAPS)
return false;
@@ -420,7 +420,7 @@ static inline bool cpus_have_cap(unsigned int num)
return test_bit(num, cpu_hwcaps);
}

-static inline bool cpus_have_const_cap(int num)
+static __always_inline bool cpus_have_const_cap(int num)
{
if (static_branch_likely(&arm64_const_caps_ready))
return __cpus_have_const_cap(num);
diff --git a/arch/mips/kernel/cpu-bugs64.c b/arch/mips/kernel/cpu-bugs64.c
index bada74a..c04b97a 100644
--- a/arch/mips/kernel/cpu-bugs64.c
+++ b/arch/mips/kernel/cpu-bugs64.c
@@ -42,8 +42,8 @@ static inline void align_mod(const int align, const int mod)
: "n"(align), "n"(mod));
}

-static inline void mult_sh_align_mod(long *v1, long *v2, long *w,
- const int align, const int mod)
+static __always_inline void mult_sh_align_mod(long *v1, long *v2, long *w,
+ const int align, const int mod)
{
unsigned long flags;
int m1, m2;
diff --git a/arch/powerpc/kernel/prom_init.c b/arch/powerpc/kernel/prom_init.c
index f33ff41..241fe6b 100644
--- a/arch/powerpc/kernel/prom_init.c
+++ b/arch/powerpc/kernel/prom_init.c
@@ -501,14 +501,14 @@ static int __init prom_next_node(phandle *nodep)
}
}

-static inline int prom_getprop(phandle node, const char *pname,
- void *value, size_t valuelen)
+static inline int __init prom_getprop(phandle node, const char *pname,
+ void *value, size_t valuelen)
{
return call_prom("getprop", 4, 1, node, ADDR(pname),
(u32)(unsigned long) value, (u32) valuelen);
}

-static inline int prom_getproplen(phandle node, const char *pname)
+static inline int __init prom_getproplen(phandle node, const char *pname)
{
return call_prom("getproplen", 2, 1, node, ADDR(pname));
}
diff --git a/arch/powerpc/mm/tlb-radix.c b/arch/powerpc/mm/tlb-radix.c
index 6a23b9e..a2b2848 100644
--- a/arch/powerpc/mm/tlb-radix.c
+++ b/arch/powerpc/mm/tlb-radix.c
@@ -928,7 +928,7 @@ void radix__tlb_flush(struct mmu_gather *tlb)
tlb->need_flush_all = 0;
}

-static inline void __radix__flush_tlb_range_psize(struct mm_struct *mm,
+static __always_inline void __radix__flush_tlb_range_psize(struct mm_struct *mm,
unsigned long start, unsigned long end,
int psize, bool also_pwc)
{
diff --git a/arch/s390/include/asm/cpacf.h b/arch/s390/include/asm/cpacf.h
index 3cc52e3..f316de4 100644
--- a/arch/s390/include/asm/cpacf.h
+++ b/arch/s390/include/asm/cpacf.h
@@ -202,7 +202,7 @@ static inline int __cpacf_check_opcode(unsigned int opcode)
}
}

-static inline int cpacf_query(unsigned int opcode, cpacf_mask_t *mask)
+static __always_inline int cpacf_query(unsigned int opcode, cpacf_mask_t *mask)
{
if (__cpacf_check_opcode(opcode)) {
__cpacf_query(opcode, mask);
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index c1f9b3c..1a3e2b5 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -310,9 +310,6 @@ config ZONE_DMA32
config AUDIT_ARCH
def_bool y if X86_64

-config ARCH_SUPPORTS_OPTIMIZED_INLINING
- def_bool y
-
config ARCH_SUPPORTS_DEBUG_PAGEALLOC
def_bool y

diff --git a/arch/x86/Kconfig.debug b/arch/x86/Kconfig.debug
index 15d0fbe..f730680 100644
--- a/arch/x86/Kconfig.debug
+++ b/arch/x86/Kconfig.debug
@@ -266,20 +266,6 @@ config CPA_DEBUG
---help---
Do change_page_attr() self-tests every 30 seconds.

-config OPTIMIZE_INLINING
- bool "Allow gcc to uninline functions marked 'inline'"
- ---help---
- This option determines if the kernel forces gcc to inline the functions
- developers have marked 'inline'. Doing so takes away freedom from gcc to
- do what it thinks is best, which is desirable for the gcc 3.x series of
- compilers. The gcc 4.x series have a rewritten inlining algorithm and
- enabling this option will generate a smaller kernel there. Hopefully
- this algorithm is so good that allowing gcc 4.x and above to make the
- decision will become the default in the future. Until then this option
- is there to test gcc for this.
-
- If unsure, say N.
-
config DEBUG_ENTRY
bool "Debug low-level entry code"
depends on DEBUG_KERNEL
diff --git a/drivers/mtd/nand/raw/vf610_nfc.c b/drivers/mtd/nand/raw/vf610_nfc.c
index a662ca1..19792d7 100644
--- a/drivers/mtd/nand/raw/vf610_nfc.c
+++ b/drivers/mtd/nand/raw/vf610_nfc.c
@@ -364,7 +364,7 @@ static int vf610_nfc_cmd(struct nand_chip *chip,
{
const struct nand_op_instr *instr;
struct vf610_nfc *nfc = chip_to_nfc(chip);
- int op_id = -1, trfr_sz = 0, offset;
+ int op_id = -1, trfr_sz = 0, offset = 0;
u32 col = 0, row = 0, cmd1 = 0, cmd2 = 0, code = 0;
bool force8bit = false;

diff --git a/include/linux/compiler_types.h b/include/linux/compiler_types.h
index ba814f1..19e58b9 100644
--- a/include/linux/compiler_types.h
+++ b/include/linux/compiler_types.h
@@ -140,8 +140,7 @@ struct ftrace_likely_data {
* Do not use __always_inline here, since currently it expands to inline again
* (which would break users of __always_inline).
*/
-#if !defined(CONFIG_ARCH_SUPPORTS_OPTIMIZED_INLINING) || \
- !defined(CONFIG_OPTIMIZE_INLINING)
+#if !defined(CONFIG_OPTIMIZE_INLINING)
#define inline inline __attribute__((__always_inline__)) __gnu_inline \
__maybe_unused notrace
#else
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 0d9e817..20f3dfc 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -310,6 +310,21 @@ config HEADERS_CHECK
exported to $(INSTALL_HDR_PATH) (usually 'usr/include' in
your build tree), to make sure they're suitable.

+config OPTIMIZE_INLINING
+ bool "Allow compiler to uninline functions marked 'inline'"
+ depends on !MIPS # TODO: look into MIPS code
+ help
+ This option determines if the kernel forces gcc to inline the functions
+ developers have marked 'inline'. Doing so takes away freedom from gcc to
+ do what it thinks is best, which is desirable for the gcc 3.x series of
+ compilers. The gcc 4.x series have a rewritten inlining algorithm and
+ enabling this option will generate a smaller kernel there. Hopefully
+ this algorithm is so good that allowing gcc 4.x and above to make the
+ decision will become the default in the future. Until then this option
+ is there to test gcc for this.
+
+ If unsure, say N.
+
config DEBUG_SECTION_MISMATCH
bool "Enable full Section mismatch analysis"
help
--
2.7.4