From nobody Fri Dec 19 19:04:25 2025 Received: from mail-pf1-f170.google.com (mail-pf1-f170.google.com [209.85.210.170]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 20A0C34C127 for ; Thu, 4 Dec 2025 20:04:29 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.210.170 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1764878675; cv=none; b=C8kWvnQVLPAudpFeOpzJctX5H99X1eMXFf7fygfOSfzNJc6osJw+fMeezki7YQ9Yb97/dI0Oifyi+lWxd6p79b/MaCtOK8uVoHsv0g8r6sOGOraBR1tKuS9VIrA+Lp7F5KWNQ9V4AwjIbSjdi8w91mB+Z+q+0NgaxEO/hOqenMw= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1764878675; c=relaxed/simple; bh=BmRDk5kl415SSdS7KRLKb7mvXOYSjIyVafSykDVbYjI=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=POHdt2imSSQqA93ZwqQ7pyuf7NBKWKmITLhHDQrKnvcuQ5WQ5G0hVggSn0wtIFYMBZ/yvRuVdSiFE4JQ0baDH8PP1Ao309cPbJo+znY+RjvyVmwMQs6+wvrpP9NmhLBFUfTe58eNy6X0o29MWENlenPR2S+OQU/L1qOq2g49wjo= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=rivosinc.com; spf=pass smtp.mailfrom=rivosinc.com; dkim=pass (2048-bit key) header.d=rivosinc.com header.i=@rivosinc.com header.b=Ve8Ct3Kk; arc=none smtp.client-ip=209.85.210.170 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=rivosinc.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=rivosinc.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=rivosinc.com header.i=@rivosinc.com header.b="Ve8Ct3Kk" Received: by mail-pf1-f170.google.com with SMTP id d2e1a72fcca58-7ba92341f83so1632043b3a.0 for ; Thu, 04 Dec 2025 12:04:28 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=rivosinc.com; s=google; t=1764878667; x=1765483467; darn=vger.kernel.org; h=cc:to:in-reply-to:references:message-id:content-transfer-encoding :mime-version:subject:date:from:from:to:cc:subject:date:message-id :reply-to; bh=mHOUzGluaxo3JyDkvm0DelDdzPjfzrCQtbG2RJzIJW4=; b=Ve8Ct3Kktsbdn4Vw5ESHYKY4QG03VlfO12djnG6JWJENUpExuj1T1tL4imCA1TzW0w 5KPgu3QMKcoM8r+bsRScs6JxnZBw4kYs5VTEvyQ7BAbj4IXzJ2pf7bngxFl2hPuXOAO8 fGroc7Ttx/L99lmE8LP91dp/5DxeybeA9Br2FUHH06j1+cZUf0Q6jIcex2vSbuiM0oYp oDXhtQSHNssuf4Oh6x5ofXetxVQ+qa0GObPsLZaEM3SChiBWdFtInTEe57D8qsOf1UGf 9bxh10IVWl/4P7qOQCsGfne9YejAJJ80dbbfTA3fgHxrWX+eUoOfIGMt22jXI0I91qd4 mDQQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1764878667; x=1765483467; h=cc:to:in-reply-to:references:message-id:content-transfer-encoding :mime-version:subject:date:from:x-gm-gg:x-gm-message-state:from:to :cc:subject:date:message-id:reply-to; bh=mHOUzGluaxo3JyDkvm0DelDdzPjfzrCQtbG2RJzIJW4=; b=fRXTID/XrOlB/crktnZlL6aunRuTUKRqKGMQiu+MJKAYiGQCZoJ3Q3tcSZU3PfdBth HVWNp/kOTQ9AvAlTu6kvyVy5P3R2xq2kfZQvGw2PiSGaaE3EY96GDwty+pbewpFzpoik RlxVFRZb0WwuGUZ6AkztVQqEywJyR2k8cQ5nAGQrLDcL/9hpgxUYKbyWBgqIHmBGzeCL AcKVE0VajWSFUUvkCFMw0nTaYsWj2fdxmFHYHduNaRGK9SvnHUe025Ah3ryEdklP35YP IInl5ieAmpu1v+xYB3HN1sXTfvUBc813GiPNmXfAex/wBN6VSGMPz38y4OqDiuyPVihw 547g== X-Gm-Message-State: AOJu0YzGN5nsKCvKMWIuwxJAGzVvsvucPixU6IXH1YmOuXoPL4NmludC 3NFBisRj629cJRsSpOob0VEqloH+yo3P1YVf1x2YwOjYpPO+8U0aujNMrOIWtBWhXcg= X-Gm-Gg: ASbGncv42sfr7DyXHVKrnm5iHtmgWuZDoJoTQ69+IhZYUNDUnYB8cmhcC0K+b/yt+lj WwVeI8/5MZ8JTL/eyUaKqMi1FP9KtNrofzntigapAUXBCkngwQTEpAb2U3MFlkWGkSaPIZV0iR0 79Mi1zBFrWdZ3Djd5v/UoSUUTQngQFHiJ0d9jYi6WR8q8we2Zca59oGhhdzXDJNgO2ev9LAnn0o LGiYyKfIaLQpsz24XygY7phVcpkhFUqf9zl8QZKsiag9Gvc3uufHma5+8+FIusmKXXybS2lVJZC e1SjHnmIw1YGEkq60Zawxm2ek6HOWQcrKKtLNMwdINiKgCtWpDB3D57umpTu0EbahF1L/pjx39l vA4SOEctYNidkXo+PcTe2KPz+RxdvGegJfUW5aESE/HE97DyscQD3kgQGC8dZwx7Z1ZZIgnD+DJ VpE/Oytfd5/WpQtF8X1/3f X-Google-Smtp-Source: AGHT+IGNLu7L4dxKZ303vItIG098+8ymQjbL/ZwPmdXmE6qFCt2YmM8p56pKX3RYmGLCYMsXVf+DBw== X-Received: by 2002:a05:7022:ba8:b0:11b:9386:7ed2 with SMTP id a92af1059eb24-11df64bf864mr2937483c88.47.1764878666983; Thu, 04 Dec 2025 12:04:26 -0800 (PST) Received: from debug.ba.rivosinc.com ([64.71.180.162]) by smtp.gmail.com with ESMTPSA id a92af1059eb24-11df76e2eefsm10417454c88.6.2025.12.04.12.04.25 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 04 Dec 2025 12:04:26 -0800 (PST) From: Deepak Gupta Date: Thu, 04 Dec 2025 12:04:03 -0800 Subject: [PATCH v24 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: <20251204-v5_user_cfi_series-v24-14-ada7a3ba14dc@rivosinc.com> References: <20251204-v5_user_cfi_series-v24-0-ada7a3ba14dc@rivosinc.com> In-Reply-To: <20251204-v5_user_cfi_series-v24-0-ada7a3ba14dc@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 , Andreas Korb , Valentin Haudiquet , Deepak Gupta X-Mailer: b4 0.13.0 X-Developer-Signature: v=1; a=ed25519-sha256; t=1764878635; l=5844; i=debug@rivosinc.com; s=20251023; h=from:subject:message-id; bh=BmRDk5kl415SSdS7KRLKb7mvXOYSjIyVafSykDVbYjI=; b=ilUG3cMsBqOV9RL2lZohsBPPP9XlcpJJeeL071SF1KM9njw4zjsKLGFqFN8kbYi6Kq1D0bP1e Sn0Ds7Eft1EB9QkVtB7A5V/s0PWZ9m5nOI6qVGGwNU7MEGXlo4mjhr2 X-Developer-Key: i=debug@rivosinc.com; a=ed25519; pk=O37GQv1thBhZToXyQKdecPDhtWVbEDRQ0RIndijvpjk= 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 Tested-by: Andreas Korb Tested-by: Valentin Haudiquet Signed-off-by: Deepak Gupta --- 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 2.45.0