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Date:   Sat, 23 Mar 2019 09:37:59 +0100
From:   LEROY Christophe <christophe.leroy@....fr>
To:     Masahiro Yamada <yamada.masahiro@...ionext.com>
Cc:     linux-arm-kernel@...ts.infradead.org,
        linuxppc-dev@...ts.ozlabs.org, linux-mtd@...ts.infradead.org,
        Ingo Molnar <mingo@...hat.com>,
        Paul Burton <paul.burton@...s.com>,
        linux-kernel@...r.kernel.org, linux-mips@...r.kernel.org,
        x86@...nel.org, Arnd Bergmann <arnd@...db.de>,
        Dave Hansen <dave@...1.net>, linux-s390@...r.kernel.org,
        linux-arch <linux-arch@...r.kernel.org>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH] compiler: allow all arches to enable
 CONFIG_OPTIMIZE_INLINING

Masahiro Yamada <yamada.masahiro@...ionext.com> a écrit :

> 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@...ionext.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(-)

The arch fixups can be done regardless of the Kconfig change as far as  
they are done before.

I guess it would then be easier to manage and review with a series of  
small patches addressing each arch independently

Christophe

>
> 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


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