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Date: Wed, 30 Mar 2022 21:59:37 -0700
From: Kees Cook <keescook@...omium.org>
To: Palmer Dabbelt <palmer@...belt.com>
Cc: Paul Walmsley <paul.walmsley@...ive.com>, 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, Mar 30, 2022 at 04:12:18PM -0700, Palmer Dabbelt wrote:
> On Tue, 22 Mar 2022 19:16:28 PDT (-0700), Palmer Dabbelt wrote:
> > 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!
>
> Thanks, this is on for-next. I put HARDENED_USERCOPY=y test in for SLAB
> and SLUB, not sure if there's anything else that's interesting to test
> (we're missing some bits needed for STACKLEAK).
Excellent; thank you!
--
Kees Cook
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