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Message-ID: <c911eead-30c4-497d-8a56-1450792b24bd@ghiti.fr> Date: Thu, 15 May 2025 09:10:08 +0200 From: Alexandre Ghiti <alex@...ti.fr> To: Deepak Gupta <debug@...osinc.com>, Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>, Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org, "H. Peter Anvin" <hpa@...or.com>, Andrew Morton <akpm@...ux-foundation.org>, "Liam R. Howlett" <Liam.Howlett@...cle.com>, Vlastimil Babka <vbabka@...e.cz>, Lorenzo Stoakes <lorenzo.stoakes@...cle.com>, Paul Walmsley <paul.walmsley@...ive.com>, Palmer Dabbelt <palmer@...belt.com>, Albert Ou <aou@...s.berkeley.edu>, Conor Dooley <conor@...nel.org>, Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>, Arnd Bergmann <arnd@...db.de>, Christian Brauner <brauner@...nel.org>, Peter Zijlstra <peterz@...radead.org>, Oleg Nesterov <oleg@...hat.com>, Eric Biederman <ebiederm@...ssion.com>, Kees Cook <kees@...nel.org>, Jonathan Corbet <corbet@....net>, Shuah Khan <shuah@...nel.org>, Jann Horn <jannh@...gle.com>, Conor Dooley <conor+dt@...nel.org>, Miguel Ojeda <ojeda@...nel.org>, Alex Gaynor <alex.gaynor@...il.com>, Boqun Feng <boqun.feng@...il.com>, Gary Guo <gary@...yguo.net>, Björn Roy Baron <bjorn3_gh@...tonmail.com>, Benno Lossin <benno.lossin@...ton.me>, Andreas Hindborg <a.hindborg@...nel.org>, Alice Ryhl <aliceryhl@...gle.com>, Trevor Gross <tmgross@...ch.edu> Cc: linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org, linux-mm@...ck.org, linux-riscv@...ts.infradead.org, devicetree@...r.kernel.org, linux-arch@...r.kernel.org, linux-doc@...r.kernel.org, linux-kselftest@...r.kernel.org, alistair.francis@....com, richard.henderson@...aro.org, jim.shu@...ive.com, andybnac@...il.com, kito.cheng@...ive.com, charlie@...osinc.com, atishp@...osinc.com, evan@...osinc.com, cleger@...osinc.com, alexghiti@...osinc.com, samitolvanen@...gle.com, broonie@...nel.org, rick.p.edgecombe@...el.com, rust-for-linux@...r.kernel.org, Zong Li <zong.li@...ive.com> Subject: Re: [PATCH v15 22/27] riscv: enable kernel access to shadow stack memory via FWFT sbi call Hi Deepak, On 03/05/2025 01:30, Deepak Gupta wrote: > Kernel will have to perform shadow stack operations on user shadow stack. > Like during signal delivery and sigreturn, shadow stack token must be > created and validated respectively. Thus shadow stack access for kernel > must be enabled. > > In future when kernel shadow stacks are enabled for linux kernel, it must > be enabled as early as possible for better coverage and prevent imbalance > between regular stack and shadow stack. After `relocate_enable_mmu` has > been done, this is as early as possible it can enabled. > > Reviewed-by: Zong Li <zong.li@...ive.com> > Signed-off-by: Deepak Gupta <debug@...osinc.com> > --- > arch/riscv/kernel/asm-offsets.c | 4 ++++ > arch/riscv/kernel/head.S | 27 +++++++++++++++++++++++++++ > 2 files changed, 31 insertions(+) > > diff --git a/arch/riscv/kernel/asm-offsets.c b/arch/riscv/kernel/asm-offsets.c > index f33945432f8f..7ab41f01aa17 100644 > --- a/arch/riscv/kernel/asm-offsets.c > +++ b/arch/riscv/kernel/asm-offsets.c > @@ -514,4 +514,8 @@ void asm_offsets(void) > DEFINE(FREGS_A6, offsetof(struct __arch_ftrace_regs, a6)); > DEFINE(FREGS_A7, offsetof(struct __arch_ftrace_regs, a7)); > #endif > + DEFINE(SBI_EXT_FWFT, SBI_EXT_FWFT); > + DEFINE(SBI_EXT_FWFT_SET, SBI_EXT_FWFT_SET); > + DEFINE(SBI_FWFT_SHADOW_STACK, SBI_FWFT_SHADOW_STACK); > + DEFINE(SBI_FWFT_SET_FLAG_LOCK, SBI_FWFT_SET_FLAG_LOCK); kernel test robot reported errors when !RV64 and !SBI, the following diff fixes it: diff --git a/arch/riscv/kernel/asm-offsets.c b/arch/riscv/kernel/asm-offsets.c index 7fc085d27ca79..3aa5f56a84e9a 100644 --- a/arch/riscv/kernel/asm-offsets.c +++ b/arch/riscv/kernel/asm-offsets.c @@ -532,8 +532,10 @@ void asm_offsets(void) DEFINE(FREGS_A6, offsetof(struct __arch_ftrace_regs, a6)); DEFINE(FREGS_A7, offsetof(struct __arch_ftrace_regs, a7)); #endif +#ifdef CONFIG_RISCV_SBI DEFINE(SBI_EXT_FWFT, SBI_EXT_FWFT); DEFINE(SBI_EXT_FWFT_SET, SBI_EXT_FWFT_SET); DEFINE(SBI_FWFT_SHADOW_STACK, SBI_FWFT_SHADOW_STACK); DEFINE(SBI_FWFT_SET_FLAG_LOCK, SBI_FWFT_SET_FLAG_LOCK); +#endif } No need to resend the whole series, I'll squash it. Thanks, Alex > } > diff --git a/arch/riscv/kernel/head.S b/arch/riscv/kernel/head.S > index 356d5397b2a2..7eae9a172351 100644 > --- a/arch/riscv/kernel/head.S > +++ b/arch/riscv/kernel/head.S > @@ -15,6 +15,7 @@ > #include <asm/image.h> > #include <asm/scs.h> > #include <asm/xip_fixup.h> > +#include <asm/usercfi.h> > #include "efi-header.S" > > __HEAD > @@ -164,6 +165,19 @@ secondary_start_sbi: > call relocate_enable_mmu > #endif > call .Lsetup_trap_vector > +#if defined(CONFIG_RISCV_SBI) && defined(CONFIG_RISCV_USER_CFI) > + li a7, SBI_EXT_FWFT > + li a6, SBI_EXT_FWFT_SET > + li a0, SBI_FWFT_SHADOW_STACK > + li a1, 1 /* enable supervisor to access shadow stack access */ > + li a2, SBI_FWFT_SET_FLAG_LOCK > + ecall > + beqz a0, 1f > + la a1, riscv_nousercfi > + li a0, CMDLINE_DISABLE_RISCV_USERCFI_BCFI > + REG_S a0, (a1) > +1: > +#endif > scs_load_current > call smp_callin > #endif /* CONFIG_SMP */ > @@ -320,6 +334,19 @@ SYM_CODE_START(_start_kernel) > la tp, init_task > la sp, init_thread_union + THREAD_SIZE > addi sp, sp, -PT_SIZE_ON_STACK > +#if defined(CONFIG_RISCV_SBI) && defined(CONFIG_RISCV_USER_CFI) > + li a7, SBI_EXT_FWFT > + li a6, SBI_EXT_FWFT_SET > + li a0, SBI_FWFT_SHADOW_STACK > + li a1, 1 /* enable supervisor to access shadow stack access */ > + li a2, SBI_FWFT_SET_FLAG_LOCK > + ecall > + beqz a0, 1f > + la a1, riscv_nousercfi > + li a0, CMDLINE_DISABLE_RISCV_USERCFI_BCFI > + REG_S a0, (a1) > +1: > +#endif > scs_load_current > > #ifdef CONFIG_KASAN >
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