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Date:   Tue, 22 Mar 2022 19:16:28 -0700 (PDT)
From:   Palmer Dabbelt <palmer@...belt.com>
To:     keescook@...omium.org
CC:     Paul Walmsley <paul.walmsley@...ive.com>, keescook@...omium.org,
        aou@...s.berkeley.edu, peterz@...radead.org, jszhang@...nel.org,
        geert@...ux-m68k.org, mark.rutland@....com, chenhuang5@...wei.com,
        linux-riscv@...ts.infradead.org, wangkefeng.wang@...wei.com,
        linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org
Subject:     Re: [PATCH] riscv: Rename "sp_in_global" to "current_stack_pointer"

On Wed, 23 Feb 2022 22:04:11 PST (-0800), keescook@...omium.org wrote:
> To follow the existing per-arch conventions, rename "sp_in_global" to
> "current_stack_pointer". This will let it be used in non-arch places
> (like HARDENED_USERCOPY).
>
> Cc: Paul Walmsley <paul.walmsley@...ive.com>
> Cc: Palmer Dabbelt <palmer@...belt.com>
> Cc: Albert Ou <aou@...s.berkeley.edu>
> Cc: Peter Zijlstra <peterz@...radead.org>
> Cc: Jisheng Zhang <jszhang@...nel.org>
> Cc: Geert Uytterhoeven <geert@...ux-m68k.org>
> Cc: Mark Rutland <mark.rutland@....com>
> Cc: Chen Huang <chenhuang5@...wei.com>
> Cc: linux-riscv@...ts.infradead.org
> Signed-off-by: Kees Cook <keescook@...omium.org>
> ---
>  arch/riscv/Kconfig               | 1 +
>  arch/riscv/include/asm/current.h | 2 ++
>  arch/riscv/kernel/stacktrace.c   | 4 +---
>  3 files changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
> index 5adcbd9b5e88..b120c32697af 100644
> --- a/arch/riscv/Kconfig
> +++ b/arch/riscv/Kconfig
> @@ -16,6 +16,7 @@ config RISCV
>  	select ARCH_ENABLE_HUGEPAGE_MIGRATION if HUGETLB_PAGE && MIGRATION
>  	select ARCH_ENABLE_SPLIT_PMD_PTLOCK if PGTABLE_LEVELS > 2
>  	select ARCH_HAS_BINFMT_FLAT
> +	select ARCH_HAS_CURRENT_STACK_POINTER
>  	select ARCH_HAS_DEBUG_VM_PGTABLE
>  	select ARCH_HAS_DEBUG_VIRTUAL if MMU
>  	select ARCH_HAS_DEBUG_WX
> diff --git a/arch/riscv/include/asm/current.h b/arch/riscv/include/asm/current.h
> index 1de233d8e8de..21774d868c65 100644
> --- a/arch/riscv/include/asm/current.h
> +++ b/arch/riscv/include/asm/current.h
> @@ -33,6 +33,8 @@ static __always_inline struct task_struct *get_current(void)
>
>  #define current get_current()
>
> +register unsigned long current_stack_pointer __asm__("sp");
> +
>  #endif /* __ASSEMBLY__ */
>
>  #endif /* _ASM_RISCV_CURRENT_H */
> diff --git a/arch/riscv/kernel/stacktrace.c b/arch/riscv/kernel/stacktrace.c
> index 201ee206fb57..278380e2e956 100644
> --- a/arch/riscv/kernel/stacktrace.c
> +++ b/arch/riscv/kernel/stacktrace.c
> @@ -14,8 +14,6 @@
>
>  #include <asm/stacktrace.h>
>
> -register unsigned long sp_in_global __asm__("sp");
> -
>  #ifdef CONFIG_FRAME_POINTER
>
>  void notrace walk_stackframe(struct task_struct *task, struct pt_regs *regs,
> @@ -77,7 +75,7 @@ void notrace walk_stackframe(struct task_struct *task,
>  		sp = user_stack_pointer(regs);
>  		pc = instruction_pointer(regs);
>  	} else if (task == NULL || task == current) {
> -		sp = sp_in_global;
> +		sp = current_stack_pointer;
>  		pc = (unsigned long)walk_stackframe;
>  	} else {
>  		/* task blocked in __switch_to */

Sorry to be slow on this one.  This looks good, but another use of 
sp_in_global snuck into fixes and I don't merge fixes into for-next so 
that makes this a bit of a headache.

There's a bunch of stuff in flight, so I'm going to hold off on this 
until after my first week's merge window PR.  I intend on merging the 
following, which is at palmer/riscv-sp for now (I'll probably just 
cherry-pick that, I usually start basing stuff on Linus' merge of my PR 
and just cherry-pick in single patches).

   commit 7c4f6bb6fb352cfa6028191c2888356b9157a332
   gpg: Signature made Tue 22 Mar 2022 11:12:19 AM PDT
   gpg:                using RSA key 2B3C3747446843B24A943A7A2E1319F35FBB1889
   gpg:                issuer "palmer@...belt.com"
   gpg: Good signature from "Palmer Dabbelt <palmer@...belt.com>" [ultimate]
   gpg:                 aka "Palmer Dabbelt <palmer@...osinc.com>" [ultimate]
   Author: Kees Cook <keescook@...omium.org>
   Date:   Wed Feb 23 22:04:11 2022 -0800
   
       riscv: Rename "sp_in_global" to "current_stack_pointer"
   
       To follow the existing per-arch conventions, rename "sp_in_global" to
       "current_stack_pointer". This will let it be used in non-arch places
       (like HARDENED_USERCOPY).
   
       Signed-off-by: Kees Cook <keescook@...omium.org>
       Signed-off-by: Palmer Dabbelt <palmer@...osinc.com>
   
   diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
   index 5adcbd9b5e88..b120c32697af 100644
   --- a/arch/riscv/Kconfig
   +++ b/arch/riscv/Kconfig
   @@ -16,6 +16,7 @@ config RISCV
    	select ARCH_ENABLE_HUGEPAGE_MIGRATION if HUGETLB_PAGE && MIGRATION
    	select ARCH_ENABLE_SPLIT_PMD_PTLOCK if PGTABLE_LEVELS > 2
    	select ARCH_HAS_BINFMT_FLAT
   +	select ARCH_HAS_CURRENT_STACK_POINTER
    	select ARCH_HAS_DEBUG_VM_PGTABLE
    	select ARCH_HAS_DEBUG_VIRTUAL if MMU
    	select ARCH_HAS_DEBUG_WX
   diff --git a/arch/riscv/include/asm/current.h b/arch/riscv/include/asm/current.h
   index 1de233d8e8de..21774d868c65 100644
   --- a/arch/riscv/include/asm/current.h
   +++ b/arch/riscv/include/asm/current.h
   @@ -33,6 +33,8 @@ static __always_inline struct task_struct *get_current(void)
   
    #define current get_current()
   
   +register unsigned long current_stack_pointer __asm__("sp");
   +
    #endif /* __ASSEMBLY__ */
   
    #endif /* _ASM_RISCV_CURRENT_H */
   diff --git a/arch/riscv/kernel/stacktrace.c b/arch/riscv/kernel/stacktrace.c
   index 14d2b53ec322..08d11a53f39e 100644
   --- a/arch/riscv/kernel/stacktrace.c
   +++ b/arch/riscv/kernel/stacktrace.c
   @@ -14,8 +14,6 @@
   
    #include <asm/stacktrace.h>
   
   -register unsigned long sp_in_global __asm__("sp");
   -
    #ifdef CONFIG_FRAME_POINTER
   
    void notrace walk_stackframe(struct task_struct *task, struct pt_regs *regs,
   @@ -30,7 +28,7 @@ void notrace walk_stackframe(struct task_struct *task, struct pt_regs *regs,
    		pc = instruction_pointer(regs);
    	} else if (task == NULL || task == current) {
    		fp = (unsigned long)__builtin_frame_address(0);
   -		sp = sp_in_global;
   +		sp = current_stack_pointer;
    		pc = (unsigned long)walk_stackframe;
    	} else {
    		/* task blocked in __switch_to */
   @@ -78,7 +76,7 @@ void notrace walk_stackframe(struct task_struct *task,
    		sp = user_stack_pointer(regs);
    		pc = instruction_pointer(regs);
    	} else if (task == NULL || task == current) {
   -		sp = sp_in_global;
   +		sp = current_stack_pointer;
    		pc = (unsigned long)walk_stackframe;
    	} else {
    		/* task blocked in __switch_to */
   
Thanks!

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