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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 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, Deepak Gupta X-Mailer: b4 0.14.0 X-Rspam-User: X-Stat-Signature: ko6rbb3dirdpp1js8p8rwymrnzjodcn9 X-Rspamd-Queue-Id: 843254001D X-Rspamd-Server: rspam11 X-HE-Tag: 1727798877-470152 X-HE-Meta: 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 pniLwaD0 qb833Zx6P5/7dh3VfigrunB7FvLoL4wpN8Eqfs3Gq1dEbwlO418+rqoXRqB49QAT2/l/mkgAt1HYt9EGcqj1f7RWkl5ZPHvqjY+1DAC2nIx+EiqbxBQNFZQOPN6T/THDigoXmMmItlzh7lXK5yn8QhDs99F/32Ja/SKF63kXr2jjk7wlE5iAF+2HwAJTE9PEcZZD9ytF5h9V02ych/Yxws8bcZtWd/iW2PkhRk9QGvk/874COfh+WrIsYeWJzeFtY4QYFJYQwZFUCsTe/fK5SMCNh7/xy6t8lTc110wTadISwNZSopBVXZht19Ac6I3H476vAxAjcScnhB144uL8sA13pvIztQXGNzqEhKlXMAmxutVCpq+xVJcpI8X/KwOvUUqFS80tXaHYvhhQru7OJeIr1lenYYvz7zJeSY7osjEtJ0Lcs/M1u8nuXfNeBN4lrJT4zv9ta0aaNxSM= 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: zicfiss / zicfilp introduces a new exception to priv isa `software check exception` with cause code = 18. This patch implements software check exception. Additionally it implements a cfi violation handler which checks for code in xtval. If xtval=2, it means that sw check exception happened because of an indirect branch not landing on 4 byte aligned PC or not landing on `lpad` instruction or label value embedded in `lpad` not matching label value setup in `x7`. If xtval=3, it means that sw check exception happened because of mismatch between link register (x1 or x5) and top of shadow stack (on execution of `sspopchk`). In case of cfi violation, SIGSEGV is raised with code=SEGV_CPERR. SEGV_CPERR was introduced by x86 shadow stack patches. Signed-off-by: Deepak Gupta --- arch/riscv/include/asm/asm-prototypes.h | 1 + arch/riscv/include/asm/entry-common.h | 2 ++ arch/riscv/kernel/entry.S | 3 +++ arch/riscv/kernel/traps.c | 42 +++++++++++++++++++++++++++++++++ 4 files changed, 48 insertions(+) diff --git a/arch/riscv/include/asm/asm-prototypes.h b/arch/riscv/include/asm/asm-prototypes.h index cd627ec289f1..5a27cefd7805 100644 --- a/arch/riscv/include/asm/asm-prototypes.h +++ b/arch/riscv/include/asm/asm-prototypes.h @@ -51,6 +51,7 @@ DECLARE_DO_ERROR_INFO(do_trap_ecall_u); DECLARE_DO_ERROR_INFO(do_trap_ecall_s); DECLARE_DO_ERROR_INFO(do_trap_ecall_m); DECLARE_DO_ERROR_INFO(do_trap_break); +DECLARE_DO_ERROR_INFO(do_trap_software_check); asmlinkage void handle_bad_stack(struct pt_regs *regs); asmlinkage void do_page_fault(struct pt_regs *regs); diff --git a/arch/riscv/include/asm/entry-common.h b/arch/riscv/include/asm/entry-common.h index 2293e535f865..4068c7e5452a 100644 --- a/arch/riscv/include/asm/entry-common.h +++ b/arch/riscv/include/asm/entry-common.h @@ -39,4 +39,6 @@ static inline int handle_misaligned_store(struct pt_regs *regs) } #endif +bool handle_user_cfi_violation(struct pt_regs *regs); + #endif /* _ASM_RISCV_ENTRY_COMMON_H */ diff --git a/arch/riscv/kernel/entry.S b/arch/riscv/kernel/entry.S index a1f258fd7bbc..aaef4604d841 100644 --- a/arch/riscv/kernel/entry.S +++ b/arch/riscv/kernel/entry.S @@ -471,6 +471,9 @@ SYM_DATA_START_LOCAL(excp_vect_table) RISCV_PTR do_page_fault /* load page fault */ RISCV_PTR do_trap_unknown RISCV_PTR do_page_fault /* store page fault */ + RISCV_PTR do_trap_unknown /* cause=16 */ + RISCV_PTR do_trap_unknown /* cause=17 */ + RISCV_PTR do_trap_software_check /* cause=18 is sw check exception */ SYM_DATA_END_LABEL(excp_vect_table, SYM_L_LOCAL, excp_vect_table_end) #ifndef CONFIG_MMU diff --git a/arch/riscv/kernel/traps.c b/arch/riscv/kernel/traps.c index 51ebfd23e007..225b1d198ab6 100644 --- a/arch/riscv/kernel/traps.c +++ b/arch/riscv/kernel/traps.c @@ -354,6 +354,48 @@ void do_trap_ecall_u(struct pt_regs *regs) } +#define CFI_TVAL_FCFI_CODE 2 +#define CFI_TVAL_BCFI_CODE 3 +/* handle cfi violations */ +bool handle_user_cfi_violation(struct pt_regs *regs) +{ + bool ret = false; + unsigned long tval = csr_read(CSR_TVAL); + + if (((tval == CFI_TVAL_FCFI_CODE) && cpu_supports_indirect_br_lp_instr()) || + ((tval == CFI_TVAL_BCFI_CODE) && cpu_supports_shadow_stack())) { + do_trap_error(regs, SIGSEGV, SEGV_CPERR, regs->epc, + "Oops - control flow violation"); + ret = true; + } + + return ret; +} +/* + * software check exception is defined with risc-v cfi spec. Software 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(struct pt_regs *regs) +{ + if (user_mode(regs)) { + irqentry_enter_from_user_mode(regs); + + /* not a cfi violation, then merge into flow of unknown 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) {