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riscv: alternatives: move length validation inside the subsection

Changbin Du posted 1 patch 3 years, 10 months ago 
arch/riscv/include/asm/alternative-macros.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
riscv: alternatives: move length validation inside the subsection
Posted by Changbin Du 3 years, 10 months ago 
Apply the same fix from commit 966a0acce2fc ("arm64/alternatives: move
length validation inside the subsection") to riscv.  Due to the one-pass
design of LLVM's integrated assembler, it can not compute the length of
instructions if the .org directive is outside of the subsection that these
instructions are in.

Here is the build error reported by llvm:

In file included from ./arch/riscv/include/asm/pgtable.h:108:
./arch/riscv/include/asm/tlbflush.h:23:2: error: expected assembly-time absolute expression
        ALT_FLUSH_TLB_PAGE(__asm__ __volatile__ ("sfence.vma %0" : : "r" (addr) : "memory"));
        ^
./arch/riscv/include/asm/errata_list.h:41:5: note: expanded from macro 'ALT_FLUSH_TLB_PAGE'
asm(ALTERNATIVE("sfence.vma %0", "sfence.vma", SIFIVE_VENDOR_ID,        \
    ^
./arch/riscv/include/asm/alternative-macros.h:187:2: note: expanded from macro 'ALTERNATIVE'
        _ALTERNATIVE_CFG(old_content, new_content, vendor_id, errata_id, CONFIG_k)
        ^
./arch/riscv/include/asm/alternative-macros.h:113:2: note: expanded from macro '_ALTERNATIVE_CFG'
        __ALTERNATIVE_CFG(old_c, new_c, vendor_id, errata_id, IS_ENABLED(CONFIG_k))
        ^
./arch/riscv/include/asm/alternative-macros.h:110:2: note: expanded from macro '__ALTERNATIVE_CFG'
        ALT_NEW_CONTENT(vendor_id, errata_id, enable, new_c)
        ^
./arch/riscv/include/asm/alternative-macros.h:98:3: note: expanded from macro 'ALT_NEW_CONTENT'
        ".org   . - (887b - 886b) + (889b - 888b)\n"                    \
         ^
<inline asm>:25:6: note: instantiated into assembly here
.org    . - (887b - 886b) + (889b - 888b)
        ^

Signed-off-by: Changbin Du <changbin.du@gmail.com>
---
 arch/riscv/include/asm/alternative-macros.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/riscv/include/asm/alternative-macros.h b/arch/riscv/include/asm/alternative-macros.h
index e13b1f6bb400..c7d7f1945768 100644
--- a/arch/riscv/include/asm/alternative-macros.h
+++ b/arch/riscv/include/asm/alternative-macros.h
@@ -94,9 +94,9 @@
 	new_c "\n"							\
 	".option pop\n"							\
 	"889 :\n"							\
-	".previous\n"							\
 	".org	. - (887b - 886b) + (889b - 888b)\n"			\
 	".org	. - (889b - 888b) + (887b - 886b)\n"			\
+	".previous\n"							\
 	".endif\n"
 
 #define __ALTERNATIVE_CFG(old_c, new_c, vendor_id, errata_id, enable)	\
-- 
2.26.2
Re: riscv: alternatives: move length validation inside the subsection
Posted by Nathan Chancellor 3 years, 10 months ago 
On Thu, Jun 02, 2022 at 07:27:34PM +0800, Changbin Du wrote:
> Apply the same fix from commit 966a0acce2fc ("arm64/alternatives: move
> length validation inside the subsection") to riscv.  Due to the one-pass
> design of LLVM's integrated assembler, it can not compute the length of
> instructions if the .org directive is outside of the subsection that these
> instructions are in.
> 
> Here is the build error reported by llvm:
> 
> In file included from ./arch/riscv/include/asm/pgtable.h:108:
> ./arch/riscv/include/asm/tlbflush.h:23:2: error: expected assembly-time absolute expression
>         ALT_FLUSH_TLB_PAGE(__asm__ __volatile__ ("sfence.vma %0" : : "r" (addr) : "memory"));
>         ^
> ./arch/riscv/include/asm/errata_list.h:41:5: note: expanded from macro 'ALT_FLUSH_TLB_PAGE'
> asm(ALTERNATIVE("sfence.vma %0", "sfence.vma", SIFIVE_VENDOR_ID,        \
>     ^
> ./arch/riscv/include/asm/alternative-macros.h:187:2: note: expanded from macro 'ALTERNATIVE'
>         _ALTERNATIVE_CFG(old_content, new_content, vendor_id, errata_id, CONFIG_k)
>         ^
> ./arch/riscv/include/asm/alternative-macros.h:113:2: note: expanded from macro '_ALTERNATIVE_CFG'
>         __ALTERNATIVE_CFG(old_c, new_c, vendor_id, errata_id, IS_ENABLED(CONFIG_k))
>         ^
> ./arch/riscv/include/asm/alternative-macros.h:110:2: note: expanded from macro '__ALTERNATIVE_CFG'
>         ALT_NEW_CONTENT(vendor_id, errata_id, enable, new_c)
>         ^
> ./arch/riscv/include/asm/alternative-macros.h:98:3: note: expanded from macro 'ALT_NEW_CONTENT'
>         ".org   . - (887b - 886b) + (889b - 888b)\n"                    \
>          ^
> <inline asm>:25:6: note: instantiated into assembly here
> .org    . - (887b - 886b) + (889b - 888b)
>         ^
> 
> Signed-off-by: Changbin Du <changbin.du@gmail.com>

Thanks for the patch! I already sent an equivalent change two weeks ago
as https://lore.kernel.org/20220516214520.3252074-1-nathan@kernel.org/,
which I think is slightly better because it handles the __ASSEMBLY__
version of the macro as well.

Cheers,
Nathan

> ---
>  arch/riscv/include/asm/alternative-macros.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/riscv/include/asm/alternative-macros.h b/arch/riscv/include/asm/alternative-macros.h
> index e13b1f6bb400..c7d7f1945768 100644
> --- a/arch/riscv/include/asm/alternative-macros.h
> +++ b/arch/riscv/include/asm/alternative-macros.h
> @@ -94,9 +94,9 @@
>  	new_c "\n"							\
>  	".option pop\n"							\
>  	"889 :\n"							\
> -	".previous\n"							\
>  	".org	. - (887b - 886b) + (889b - 888b)\n"			\
>  	".org	. - (889b - 888b) + (887b - 886b)\n"			\
> +	".previous\n"							\
>  	".endif\n"
>  
>  #define __ALTERNATIVE_CFG(old_c, new_c, vendor_id, errata_id, enable)	\
> -- 
> 2.26.2
>
Re: riscv: alternatives: move length validation inside the subsection
Posted by Changbin Du 3 years, 10 months ago 
On Thu, Jun 02, 2022 at 07:43:01AM -0700, Nathan Chancellor wrote:
> On Thu, Jun 02, 2022 at 07:27:34PM +0800, Changbin Du wrote:
> > Apply the same fix from commit 966a0acce2fc ("arm64/alternatives: move
> > length validation inside the subsection") to riscv.  Due to the one-pass
> > design of LLVM's integrated assembler, it can not compute the length of
> > instructions if the .org directive is outside of the subsection that these
> > instructions are in.
> > 
> > Here is the build error reported by llvm:
> > 
> > In file included from ./arch/riscv/include/asm/pgtable.h:108:
> > ./arch/riscv/include/asm/tlbflush.h:23:2: error: expected assembly-time absolute expression
> >         ALT_FLUSH_TLB_PAGE(__asm__ __volatile__ ("sfence.vma %0" : : "r" (addr) : "memory"));
> >         ^
> > ./arch/riscv/include/asm/errata_list.h:41:5: note: expanded from macro 'ALT_FLUSH_TLB_PAGE'
> > asm(ALTERNATIVE("sfence.vma %0", "sfence.vma", SIFIVE_VENDOR_ID,        \
> >     ^
> > ./arch/riscv/include/asm/alternative-macros.h:187:2: note: expanded from macro 'ALTERNATIVE'
> >         _ALTERNATIVE_CFG(old_content, new_content, vendor_id, errata_id, CONFIG_k)
> >         ^
> > ./arch/riscv/include/asm/alternative-macros.h:113:2: note: expanded from macro '_ALTERNATIVE_CFG'
> >         __ALTERNATIVE_CFG(old_c, new_c, vendor_id, errata_id, IS_ENABLED(CONFIG_k))
> >         ^
> > ./arch/riscv/include/asm/alternative-macros.h:110:2: note: expanded from macro '__ALTERNATIVE_CFG'
> >         ALT_NEW_CONTENT(vendor_id, errata_id, enable, new_c)
> >         ^
> > ./arch/riscv/include/asm/alternative-macros.h:98:3: note: expanded from macro 'ALT_NEW_CONTENT'
> >         ".org   . - (887b - 886b) + (889b - 888b)\n"                    \
> >          ^
> > <inline asm>:25:6: note: instantiated into assembly here
> > .org    . - (887b - 886b) + (889b - 888b)
> >         ^
> > 
> > Signed-off-by: Changbin Du <changbin.du@gmail.com>
> 
> Thanks for the patch! I already sent an equivalent change two weeks ago
> as https://lore.kernel.org/20220516214520.3252074-1-nathan@kernel.org/,
> which I think is slightly better because it handles the __ASSEMBLY__
> version of the macro as well.
> 
Agreed. Thank you, and please ignore this one.

> Cheers,
> Nathan
>

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