[PATCH] Revert "powerpc: Switch to relative jump labels"

[Greg Kurz]

On Fri, 28 May 2021 04:29:43 +0300
Roman Bolshakov <r.bolshakov at yadro.com> wrote:

> This reverts commit b0b3b2c78ec075cec4721986a95abbbac8c3da4f.
> 
> Otherwise, direct kernel boot with initramfs no longer works in QEMU.
> It's broken in some bizarre way because a valid initramfs is not
> recognized anymore:
> 
>   Found initrd at 0xc000000001f70000:0xc000000003d61d64
>   rootfs image is not initramfs (XZ-compressed data is corrupt); looks like an initrd
> 
> The issue is observed on v5.13-rc3 if the kernel is built with
> defconfig, GCC 7.5.0 and GNU ld 2.32.0.
> 
> Cc: Christophe Leroy <christophe.leroy at csgroup.eu>
> Reported-by: Anastasia Kovaleva <a.kovaleva at yadro.com>
> Signed-off-by: Roman Bolshakov <r.bolshakov at yadro.com>
> ---

I'm observing the very same issue and reverting the offending commit
fixes it indeed. Until someone has investigated the root cause, this
looks like a reasonable bug fix to me.

Reviewed-by: Greg Kurz <groug at kaod.org>

and

Tested-by: Greg Kurz <groug at kaod.org>

>  arch/powerpc/Kconfig                  |  1 -
>  arch/powerpc/include/asm/jump_label.h | 21 +++++++++++++++------
>  arch/powerpc/kernel/jump_label.c      |  4 ++--
>  3 files changed, 17 insertions(+), 9 deletions(-)
> 
> diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
> index 088dd2afcfe4..59e0d55ee01d 100644
> --- a/arch/powerpc/Kconfig
> +++ b/arch/powerpc/Kconfig
> @@ -189,7 +189,6 @@ config PPC
>  	select HAVE_ARCH_HUGE_VMALLOC		if HAVE_ARCH_HUGE_VMAP
>  	select HAVE_ARCH_HUGE_VMAP		if PPC_BOOK3S_64 && PPC_RADIX_MMU
>  	select HAVE_ARCH_JUMP_LABEL
> -	select HAVE_ARCH_JUMP_LABEL_RELATIVE
>  	select HAVE_ARCH_KASAN			if PPC32 && PPC_PAGE_SHIFT <= 14
>  	select HAVE_ARCH_KASAN_VMALLOC		if PPC32 && PPC_PAGE_SHIFT <= 14
>  	select HAVE_ARCH_KFENCE			if PPC32
> diff --git a/arch/powerpc/include/asm/jump_label.h b/arch/powerpc/include/asm/jump_label.h
> index 2d5c6bec2b4f..09297ec9fa52 100644
> --- a/arch/powerpc/include/asm/jump_label.h
> +++ b/arch/powerpc/include/asm/jump_label.h
> @@ -20,8 +20,7 @@ static __always_inline bool arch_static_branch(struct static_key *key, bool bran
>  	asm_volatile_goto("1:\n\t"
>  		 "nop # arch_static_branch\n\t"
>  		 ".pushsection __jump_table,  \"aw\"\n\t"
> -		 ".long 1b - ., %l[l_yes] - .\n\t"
> -		 JUMP_ENTRY_TYPE "%c0 - .\n\t"
> +		 JUMP_ENTRY_TYPE "1b, %l[l_yes], %c0\n\t"
>  		 ".popsection \n\t"
>  		 : :  "i" (&((char *)key)[branch]) : : l_yes);
>  
> @@ -35,8 +34,7 @@ static __always_inline bool arch_static_branch_jump(struct static_key *key, bool
>  	asm_volatile_goto("1:\n\t"
>  		 "b %l[l_yes] # arch_static_branch_jump\n\t"
>  		 ".pushsection __jump_table,  \"aw\"\n\t"
> -		 ".long 1b - ., %l[l_yes] - .\n\t"
> -		 JUMP_ENTRY_TYPE "%c0 - .\n\t"
> +		 JUMP_ENTRY_TYPE "1b, %l[l_yes], %c0\n\t"
>  		 ".popsection \n\t"
>  		 : :  "i" (&((char *)key)[branch]) : : l_yes);
>  
> @@ -45,12 +43,23 @@ static __always_inline bool arch_static_branch_jump(struct static_key *key, bool
>  	return true;
>  }
>  
> +#ifdef CONFIG_PPC64
> +typedef u64 jump_label_t;
> +#else
> +typedef u32 jump_label_t;
> +#endif
> +
> +struct jump_entry {
> +	jump_label_t code;
> +	jump_label_t target;
> +	jump_label_t key;
> +};
> +
>  #else
>  #define ARCH_STATIC_BRANCH(LABEL, KEY)		\
>  1098:	nop;					\
>  	.pushsection __jump_table, "aw";	\
> -	.long 1098b - ., LABEL - .;		\
> -	FTR_ENTRY_LONG KEY;			\
> +	FTR_ENTRY_LONG 1098b, LABEL, KEY;	\
>  	.popsection
>  #endif
>  
> diff --git a/arch/powerpc/kernel/jump_label.c b/arch/powerpc/kernel/jump_label.c
> index ce87dc5ea23c..144858027fa3 100644
> --- a/arch/powerpc/kernel/jump_label.c
> +++ b/arch/powerpc/kernel/jump_label.c
> @@ -11,10 +11,10 @@
>  void arch_jump_label_transform(struct jump_entry *entry,
>  			       enum jump_label_type type)
>  {
> -	struct ppc_inst *addr = (struct ppc_inst *)jump_entry_code(entry);
> +	struct ppc_inst *addr = (struct ppc_inst *)(unsigned long)entry->code;
>  
>  	if (type == JUMP_LABEL_JMP)
> -		patch_branch(addr, jump_entry_target(entry), 0);
> +		patch_branch(addr, entry->target, 0);
>  	else
>  		patch_instruction(addr, ppc_inst(PPC_INST_NOP));
>  }