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Peter Anvin" , Andrew Morton , "Liam R. Howlett" , Vlastimil Babka , Lorenzo Stoakes , Paul Walmsley , Palmer Dabbelt , Albert Ou , Conor Dooley , Rob Herring , Krzysztof Kozlowski , Arnd Bergmann , Christian Brauner , Peter Zijlstra , Oleg Nesterov , Eric Biederman , Kees Cook , Jonathan Corbet , Shuah Khan , Jann Horn , Conor Dooley , Miguel Ojeda , Alex Gaynor , Boqun Feng , Gary Guo , =?utf-8?q?Bj=C3=B6rn_Roy_Baron?= , Andreas Hindborg , Alice Ryhl , Trevor Gross , Benno Lossin Cc: linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-riscv@lists.infradead.org, devicetree@vger.kernel.org, linux-arch@vger.kernel.org, linux-doc@vger.kernel.org, linux-kselftest@vger.kernel.org, alistair.francis@wdc.com, richard.henderson@linaro.org, jim.shu@sifive.com, andybnac@gmail.com, kito.cheng@sifive.com, charlie@rivosinc.com, atishp@rivosinc.com, evan@rivosinc.com, cleger@rivosinc.com, alexghiti@rivosinc.com, samitolvanen@google.com, broonie@kernel.org, rick.p.edgecombe@intel.com, rust-for-linux@vger.kernel.org, Zong Li , Deepak Gupta X-Mailer: b4 0.13.0 X-Developer-Signature: v=1; a=ed25519-sha256; t=1761238267; l=2857; i=debug@rivosinc.com; s=20251023; h=from:subject:message-id; bh=6jhZAX7qSjG5giCOVCgCSSpmySXxQ3X5SeSFJU/GKzQ=; b=ZCaVgmPZIW7VK3LK8GgkkQBvDVa+uyflBrrczukk04MC55+npWLHhbPfAbtwExQcSkFtFpdbS +BKAHlfx6IJBt1jeqE2Z4QqW8yNdtteCLrx4EJUxKVKoSV6HcH1Va+f X-Developer-Key: i=debug@rivosinc.com; a=ed25519; pk=O37GQv1thBhZToXyQKdecPDhtWVbEDRQ0RIndijvpjk= X-Endpoint-Received: by B4 Relay for debug@rivosinc.com/20251023 with auth_id=553 X-Original-From: Deepak Gupta Reply-To: debug@rivosinc.com X-Stat-Signature: xdcon7nk6ssbrthbmyrmizab7tjru6tb X-Rspamd-Queue-Id: 3DEDC40013 X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1761238284-485068 X-HE-Meta: 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 bhwRJIIi 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: From: Deepak Gupta 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 Signed-off-by: Deepak Gupta --- arch/riscv/kernel/asm-offsets.c | 6 ++++++ arch/riscv/kernel/head.S | 27 +++++++++++++++++++++++++++ 2 files changed, 33 insertions(+) diff --git a/arch/riscv/kernel/asm-offsets.c b/arch/riscv/kernel/asm-offsets.c index 8a2b2656cb2f..af827448a609 100644 --- a/arch/riscv/kernel/asm-offsets.c +++ b/arch/riscv/kernel/asm-offsets.c @@ -533,4 +533,10 @@ 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 } diff --git a/arch/riscv/kernel/head.S b/arch/riscv/kernel/head.S index bdf3352acf4c..9c99c5ad6fe8 100644 --- a/arch/riscv/kernel/head.S +++ b/arch/riscv/kernel/head.S @@ -15,6 +15,7 @@ #include #include #include +#include #include "efi-header.S" __HEAD @@ -170,6 +171,19 @@ 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 */ @@ -330,6 +344,19 @@ 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 -- 2.43.0