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AJvYcCVMZ/AgdvRP/IOvmoO8qhGcahWfj12tcDpOH+W+enOIupcSLsTA5teOala5Tl6GdqQ3TNzu08U2hQ==@kvack.org X-Gm-Message-State: AOJu0YwKGv92YRJJaQYgiBJcxGxC8ZPBZY86xJi3eamVjm5vkVfn9GVY Lrf/qv7wjx4VjHsPHzFXp/ftrElT6xmzGcnAPCOihYwzumig+Tgein1DAmljDVaVB13gTLFH4UG vpDiNWKijVoj9k939G6HNI4xsHq7fi+YWUmoW2AejBQ== X-Gm-Gg: ASbGncsKmrrqUEiOc+Eh3+vWFx45kiSloneaq7DulTgZ2jcZGDk0r3xGzgfY7EaSSdz pZ/zf7VmS6SsQiKNFlz/fsw8TGzf7tfpwFdfKvgxyz1tRT8tTFOvXu/KO4E2lpD1x/3SRef1obl nFS+8waf/yoEpMjIEpGqTm4nvUnqr4eV1myCEgovRNwpx3HmX5kwAs6i7SU/kq0fWTVB6RbwlGh GFQcG/r X-Google-Smtp-Source: AGHT+IEsY/f+Tj3u2hxiQCd69XmHGIDqZZR/UYSpflr/g5ySMTGOn/8ny5hxzQ44lrvSZqgfPjGQAPQXva81ZPiNP2c= X-Received: by 2002:a05:690c:4884:b0:70f:9fcd:2075 with SMTP id 00721157ae682-71836c27373mr5257327b3.3.1752615239506; Tue, 15 Jul 2025 14:33:59 -0700 (PDT) MIME-Version: 1.0 References: <20250604-v5_user_cfi_series-v17-0-4565c2cf869f@rivosinc.com> <20250604-v5_user_cfi_series-v17-15-4565c2cf869f@rivosinc.com> In-Reply-To: From: Deepak Gupta Date: Tue, 15 Jul 2025 14:33:47 -0700 X-Gm-Features: Ac12FXzRTF7Dfs5zrF9r6Tx3chJ4aSIUc73QZXj0R8v3aOAPdwPOPGlfEeN5Jbw Message-ID: Subject: Re: [PATCH v17 15/27] riscv/traps: Introduce software check exception and uprobe handling To: Zong Li Cc: 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?= , Benno Lossin , Andreas Hindborg , Alice Ryhl , Trevor Gross , 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 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Stat-Signature: ydaq4h9ap9pxgk1tz8nyxzzpuojtrn53 X-Rspamd-Queue-Id: 930AE140004 X-Rspamd-Server: rspam10 X-Rspam-User: X-HE-Tag: 1752615240-636834 X-HE-Meta: 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 eYGAqOLj GlWX16CHQa1iIUzmLIsxkrKmDu+wIoshqLr0Epgywb2GjQIyS61ZOHMKcZSdBk+3UZAeYDszzKBp9YRZetDYoanFlZAdF0wCNtnIdePKxHaOCBXqP1pfMiEVSYuVjBBgYi4qD1K2ORVtbPi55KcvFTVkfIT4OCIvPcyuNpHXPYc9pSbO82ZKyRkPuHH61NAihvaqUpANvTJ8AXApKItNTYsWi8wOA50acQMyJaRjmnNRpmVu1KsXhjkyTD/GGtXarfSvl6/Bc2ZSUJ+ngRJRnBete34h36IpciPLEp/5n+cexLW7AqHzbyFdxxPvGI4bMjtxHt3x5qYZOmrgmVj4XN2JQ2L+cO6DAA9lREHlyn8kbSEWyHkMwYQch1GWqpy3+1ECHGerBz4uyQ+XTPsKCpb1tFdyf0I3jZqpFCATx96YAPj90rhIhKlmXWw== 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: Hi Zong, On Thu, Jun 19, 2025 at 7:16=E2=80=AFPM Zong Li wrote: > > On Mon, Jun 16, 2025 at 3:31=E2=80=AFPM Zong Li wrot= e: > > > > On Thu, Jun 5, 2025 at 1:17=E2=80=AFAM Deepak Gupta wrote: > > > > > > zicfiss / zicfilp introduces a new exception to priv isa `software ch= eck > > > exception` with cause code =3D 18. This patch implements software che= ck > > > exception. > > > ..... > > When a user mode CFI violation occurs, the ELP state should be 1, and > > the system traps into supervisor mode. During this trap, sstatus.SPELP > > is set to 1, and the ELP state is reset to 0. If we don=E2=80=99t clear > > sstatus.SPELP, the ELP state will become 1 again after executing the > > sret instruction. As a result, the system might trigger another > > forward CFI violation upon executing the next instruction in the user > > program, unless it happens to be a lpad instruction. > > > > The previous patch was tested on QEMU, but QEMU does not set the > > sstatus.SPELP bit to 1 when a forward CFI violation occurs. Therefore, > > I suspect that QEMU might also require some fixes. > > Hi Deepak, > The issue with QEMU was that the sw-check exception bit in medeleg > couldn't be set. This has been fixed in the latest QEMU mainline. I > have re-tested the latest QEMU version, and it works. What was this issue, can you point me to the patch in mainline? > > > > > Thanks > > > > > + > > > + if (is_fcfi || is_bcfi) { > > > + do_trap_error(regs, SIGSEGV, SEGV_CPERR, regs->epc, > > > + "Oops - control flow violation"); > > > + return true; > > > + } > > > + > > > + return false; > > > +} > > > + > > > +/* > > > + * software check exception is defined with risc-v cfi spec. Softwar= e check > > > + * exception is raised when:- > > > + * a) An indirect branch doesn't land on 4 byte aligned PC or `lpad` > > > + * instruction or `label` value programmed in `lpad` instr doesn'= t > > > + * match with value setup in `x7`. reported code in `xtval` is 2. > > > + * b) `sspopchk` instruction finds a mismatch between top of shadow = stack (ssp) > > > + * and x1/x5. reported code in `xtval` is 3. > > > + */ > > > +asmlinkage __visible __trap_section void do_trap_software_check(stru= ct pt_regs *regs) > > > +{ > > > + if (user_mode(regs)) { > > > + irqentry_enter_from_user_mode(regs); > > > + > > > + /* not a cfi violation, then merge into flow of unkno= wn trap handler */ > > > + if (!handle_user_cfi_violation(regs)) > > > + do_trap_unknown(regs); > > > + > > > + irqentry_exit_to_user_mode(regs); > > > + } else { > > > + /* sw check exception coming from kernel is a bug in = kernel */ > > > + die(regs, "Kernel BUG"); > > > + } > > > +} > > > + > > > #ifdef CONFIG_MMU > > > asmlinkage __visible noinstr void do_page_fault(struct pt_regs *regs= ) > > > { > > > > > > -- > > > 2.43.0 > > >