From nobody Wed Dec 10 20:12:42 2025 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 923E229E11D; Thu, 13 Nov 2025 00:43:43 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1762994623; cv=none; b=I0S4BoEIS5xxPR93B6fS4/ePSzCUJmQ7N3Nk2m2kkqWo+G7M0SdvFw3Jwa90xZv03GXr2x8nPRLQgNeypXU3Nzvwh+twtr5Sj6bH7dZvP24r5o6d6BxLIisezPy12O8l1y5+0gCFNSiQCslwOOoD8r2QgOja4v8I30gGVHvhGaw= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1762994623; c=relaxed/simple; bh=vMYayqG7i34xaYjkz9IFwg9slehT42ee2ag10Gs3R/M=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=M16LlE9HXJVTVSEGRv8Xb9YwSJuMJT44K2KMKEUlsgCaGgJyNf3oJM/XiGYF8TcrVzpILdlgRWi1GqPsL61Q8L1h9YYTRlM8Sn/z3GmoCyGRbxJbdkvUndrdlXJxsy9F+t3RweJMjBMPwIAWUTjRTqfFqjw4D5Upu3QuGgPR+ww= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=U0PxUrdx; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="U0PxUrdx" Received: by smtp.kernel.org (Postfix) with ESMTPS id 19647C2BCB9; Thu, 13 Nov 2025 00:43:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1762994623; bh=vMYayqG7i34xaYjkz9IFwg9slehT42ee2ag10Gs3R/M=; h=From:Date:Subject:References:In-Reply-To:To:Cc:Reply-To:From; b=U0PxUrdx037U/egN3S2eJTn6KoURkN1kfa/foZnVQrBMeD3Euag1YM2tedey/XhF7 TKM7JRIGEJ4iJzO6WgCdbhEGj0NH557viwr5G5FR2XomDc0WmTAMYQJ1uH6ubMGm9X fr6J8N2KLl8niRiY8c13Ge+lYwlGxYg2rIkex14UJn8ruhnkHXflEJ5slFpqUPMCRA i2PyGvEQaeprZ/sALcxa/nUXgM4LQtLzngoXteJOPsOP63zCfGsOdMbnIlesbM4ZAW Ik/USVblBcyBrVqwy7jFD5pHQezgWW7pQ+XnlEnpGxmePewtx4bJguQQU35BSEeKez fLH/vEPHEv7cg== Received: from aws-us-west-2-korg-lkml-1.web.codeaurora.org (localhost.localdomain [127.0.0.1]) by smtp.lore.kernel.org (Postfix) with ESMTP id EF49CCD4F2D; Thu, 13 Nov 2025 00:43:42 +0000 (UTC) From: Deepak Gupta via B4 Relay Date: Wed, 12 Nov 2025 16:43:12 -0800 Subject: [PATCH v23 14/28] riscv: Implements arch agnostic indirect branch tracking prctls Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Message-Id: <20251112-v5_user_cfi_series-v23-14-b55691eacf4f@rivosinc.com> References: <20251112-v5_user_cfi_series-v23-0-b55691eacf4f@rivosinc.com> In-Reply-To: <20251112-v5_user_cfi_series-v23-0-b55691eacf4f@rivosinc.com> To: Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. 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=1762994618; l=5718; i=debug@rivosinc.com; s=20251023; h=from:subject:message-id; bh=yFCOzn/pyDccak0xANk/vKLfOoWrfQcAvujrS/kNvhE=; b=EtFDJebpS2KNv9z97B4rIrgMJUXPW+AdSiq3o/RzvI757+wbuWYnE+/AHC45WEAhwOxJkPmyB EbAKcn3BonDBKpWXk8YBfDoiK5UgJbXTHakpPuQADinZKtfH6iLtPd1 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 From: Deepak Gupta prctls implemented are: PR_SET_INDIR_BR_LP_STATUS, PR_GET_INDIR_BR_LP_STATUS and PR_LOCK_INDIR_BR_LP_STATUS Reviewed-by: Zong Li Signed-off-by: Deepak Gupta Tested-by: Andreas Korb --- arch/riscv/include/asm/usercfi.h | 14 +++++++ arch/riscv/kernel/entry.S | 4 ++ arch/riscv/kernel/process.c | 5 +++ arch/riscv/kernel/usercfi.c | 79 ++++++++++++++++++++++++++++++++++++= ++++ 4 files changed, 102 insertions(+) diff --git a/arch/riscv/include/asm/usercfi.h b/arch/riscv/include/asm/user= cfi.h index d71093f414df..4501d741a609 100644 --- a/arch/riscv/include/asm/usercfi.h +++ b/arch/riscv/include/asm/usercfi.h @@ -16,6 +16,8 @@ struct kernel_clone_args; struct cfi_state { unsigned long ubcfi_en : 1; /* Enable for backward cfi. */ unsigned long ubcfi_locked : 1; + unsigned long ufcfi_en : 1; /* Enable for forward cfi. Note that ELP goes= in sstatus */ + unsigned long ufcfi_locked : 1; unsigned long user_shdw_stk; /* Current user shadow stack pointer */ unsigned long shdw_stk_base; /* Base address of shadow stack */ unsigned long shdw_stk_size; /* size of shadow stack */ @@ -32,6 +34,10 @@ bool is_shstk_locked(struct task_struct *task); bool is_shstk_allocated(struct task_struct *task); void set_shstk_lock(struct task_struct *task); void set_shstk_status(struct task_struct *task, bool enable); +bool is_indir_lp_enabled(struct task_struct *task); +bool is_indir_lp_locked(struct task_struct *task); +void set_indir_lp_status(struct task_struct *task, bool enable); +void set_indir_lp_lock(struct task_struct *task); =20 #define PR_SHADOW_STACK_SUPPORTED_STATUS_MASK (PR_SHADOW_STACK_ENABLE) =20 @@ -57,6 +63,14 @@ void set_shstk_status(struct task_struct *task, bool ena= ble); =20 #define set_shstk_status(task, enable) do {} while (0) =20 +#define is_indir_lp_enabled(task) false + +#define is_indir_lp_locked(task) false + +#define set_indir_lp_status(task, enable) do {} while (0) + +#define set_indir_lp_lock(task) do {} while (0) + #endif /* CONFIG_RISCV_USER_CFI */ =20 #endif /* __ASSEMBLER__ */ diff --git a/arch/riscv/kernel/entry.S b/arch/riscv/kernel/entry.S index 8410850953d6..036a6ca7641f 100644 --- a/arch/riscv/kernel/entry.S +++ b/arch/riscv/kernel/entry.S @@ -174,6 +174,10 @@ SYM_CODE_START(handle_exception) * or vector in kernel space. */ li t0, SR_SUM | SR_FS_VS +#ifdef CONFIG_64BIT + li t1, SR_ELP + or t0, t0, t1 +#endif =20 REG_L s0, TASK_TI_USER_SP(tp) csrrc s1, CSR_STATUS, t0 diff --git a/arch/riscv/kernel/process.c b/arch/riscv/kernel/process.c index a137d3483646..49f527e3acfd 100644 --- a/arch/riscv/kernel/process.c +++ b/arch/riscv/kernel/process.c @@ -163,6 +163,11 @@ void start_thread(struct pt_regs *regs, unsigned long = pc, set_shstk_status(current, false); set_shstk_base(current, 0, 0); set_active_shstk(current, 0); + /* + * disable indirect branch tracking on exec. + * libc will enable it later via prctl. + */ + set_indir_lp_status(current, false); =20 #ifdef CONFIG_64BIT regs->status &=3D ~SR_UXL; diff --git a/arch/riscv/kernel/usercfi.c b/arch/riscv/kernel/usercfi.c index 0b77b812e4d7..a384ce9ed25c 100644 --- a/arch/riscv/kernel/usercfi.c +++ b/arch/riscv/kernel/usercfi.c @@ -72,6 +72,35 @@ void set_shstk_lock(struct task_struct *task) task->thread_info.user_cfi_state.ubcfi_locked =3D 1; } =20 +bool is_indir_lp_enabled(struct task_struct *task) +{ + return task->thread_info.user_cfi_state.ufcfi_en; +} + +bool is_indir_lp_locked(struct task_struct *task) +{ + return task->thread_info.user_cfi_state.ufcfi_locked; +} + +void set_indir_lp_status(struct task_struct *task, bool enable) +{ + if (!cpu_supports_indirect_br_lp_instr()) + return; + + task->thread_info.user_cfi_state.ufcfi_en =3D enable ? 1 : 0; + + if (enable) + task->thread.envcfg |=3D ENVCFG_LPE; + else + task->thread.envcfg &=3D ~ENVCFG_LPE; + + csr_write(CSR_ENVCFG, task->thread.envcfg); +} + +void set_indir_lp_lock(struct task_struct *task) +{ + task->thread_info.user_cfi_state.ufcfi_locked =3D 1; +} /* * If size is 0, then to be compatible with regular stack we want it to be= as big as * regular stack. Else PAGE_ALIGN it and return back @@ -370,3 +399,53 @@ int arch_lock_shadow_stack_status(struct task_struct *= task, =20 return 0; } + +int arch_get_indir_br_lp_status(struct task_struct *t, unsigned long __use= r *status) +{ + unsigned long fcfi_status =3D 0; + + if (!cpu_supports_indirect_br_lp_instr()) + return -EINVAL; + + /* indirect branch tracking is enabled on the task or not */ + fcfi_status |=3D (is_indir_lp_enabled(t) ? PR_INDIR_BR_LP_ENABLE : 0); + + return copy_to_user(status, &fcfi_status, sizeof(fcfi_status)) ? -EFAULT = : 0; +} + +int arch_set_indir_br_lp_status(struct task_struct *t, unsigned long statu= s) +{ + bool enable_indir_lp =3D false; + + if (!cpu_supports_indirect_br_lp_instr()) + return -EINVAL; + + /* indirect branch tracking is locked and further can't be modified by us= er */ + if (is_indir_lp_locked(t)) + return -EINVAL; + + /* Reject unknown flags */ + if (status & ~PR_INDIR_BR_LP_ENABLE) + return -EINVAL; + + enable_indir_lp =3D (status & PR_INDIR_BR_LP_ENABLE); + set_indir_lp_status(t, enable_indir_lp); + + return 0; +} + +int arch_lock_indir_br_lp_status(struct task_struct *task, + unsigned long arg) +{ + /* + * If indirect branch tracking is not supported or not enabled on task, + * nothing to lock here + */ + if (!cpu_supports_indirect_br_lp_instr() || + !is_indir_lp_enabled(task) || arg !=3D 0) + return -EINVAL; + + set_indir_lp_lock(task); + + return 0; +} --=20 2.43.0