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X-Received-From: 2607:f8b0:400e:c05::243 Subject: [Qemu-devel] [PULL 10/24] RISC-V: Improve page table walker spec compliance X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: patches@groups.riscv.org, Michael Clark , Palmer Dabbelt , Sagar Karandikar , Bastian Koppelmann Errors-To: qemu-devel-bounces+patchwork-qemu-devel=patchwork.kernel.org@nongnu.org Sender: "Qemu-devel" X-Virus-Scanned: ClamAV using ClamSMTP - Inline PTE_TABLE check for better readability - Improve readibility of User page U mode and SUM test - Disallow non U mode from fetching from User pages - Add reserved PTE flag check: W or W|X - Add misaligned PPN check - Set READ flag for PTE X flag if mstatus.mxr is in effect - Change access checks from ternary operator to if statements - Improves page walker comments - No measurable performance impact on dd test Cc: Sagar Karandikar Cc: Bastian Koppelmann Signed-off-by: Michael Clark Signed-off-by: Palmer Dabbelt --- target/riscv/cpu_bits.h | 2 -- target/riscv/helper.c | 59 ++++++++++++++++++++++++++++++++++--------------- 2 files changed, 41 insertions(+), 20 deletions(-) diff --git a/target/riscv/cpu_bits.h b/target/riscv/cpu_bits.h index 64aa097..12b4757 100644 --- a/target/riscv/cpu_bits.h +++ b/target/riscv/cpu_bits.h @@ -407,5 +407,3 @@ #define PTE_SOFT 0x300 /* Reserved for Software */ #define PTE_PPN_SHIFT 10 - -#define PTE_TABLE(PTE) (((PTE) & (PTE_V | PTE_R | PTE_W | PTE_X)) == PTE_V) diff --git a/target/riscv/helper.c b/target/riscv/helper.c index 02cbcea..9010620 100644 --- a/target/riscv/helper.c +++ b/target/riscv/helper.c @@ -185,16 +185,36 @@ restart: #endif target_ulong ppn = pte >> PTE_PPN_SHIFT; - if (PTE_TABLE(pte)) { /* next level of page table */ + if (!(pte & PTE_V)) { + /* Invalid PTE */ + return TRANSLATE_FAIL; + } else if (!(pte & (PTE_R | PTE_W | PTE_X))) { + /* Inner PTE, continue walking */ base = ppn << PGSHIFT; - } else if ((pte & PTE_U) ? (mode == PRV_S) && !sum : !(mode == PRV_S)) { - break; - } else if (!(pte & PTE_V) || (!(pte & PTE_R) && (pte & PTE_W))) { - break; - } else if (access_type == MMU_INST_FETCH ? !(pte & PTE_X) : - access_type == MMU_DATA_LOAD ? !(pte & PTE_R) && - !(mxr && (pte & PTE_X)) : !((pte & PTE_R) && (pte & PTE_W))) { - break; + } else if ((pte & (PTE_R | PTE_W | PTE_X)) == PTE_W) { + /* Reserved leaf PTE flags: PTE_W */ + return TRANSLATE_FAIL; + } else if ((pte & (PTE_R | PTE_W | PTE_X)) == (PTE_W | PTE_X)) { + /* Reserved leaf PTE flags: PTE_W + PTE_X */ + return TRANSLATE_FAIL; + } else if ((pte & PTE_U) && ((mode != PRV_U) && + (!sum || access_type == MMU_INST_FETCH))) { + /* User PTE flags when not U mode and mstatus.SUM is not set, + or the access type is an instruction fetch */ + return TRANSLATE_FAIL; + } else if (ppn & ((1ULL << ptshift) - 1)) { + /* Misasligned PPN */ + return TRANSLATE_FAIL; + } else if (access_type == MMU_DATA_LOAD && !((pte & PTE_R) || + ((pte & PTE_X) && mxr))) { + /* Read access check failed */ + return TRANSLATE_FAIL; + } else if (access_type == MMU_DATA_STORE && !(pte & PTE_W)) { + /* Write access check failed */ + return TRANSLATE_FAIL; + } else if (access_type == MMU_INST_FETCH && !(pte & PTE_X)) { + /* Fetch access check failed */ + return TRANSLATE_FAIL; } else { /* if necessary, set accessed and dirty bits. */ target_ulong updated_pte = pte | PTE_A | @@ -202,11 +222,14 @@ restart: /* Page table updates need to be atomic with MTTCG enabled */ if (updated_pte != pte) { - /* if accessed or dirty bits need updating, and the PTE is - * in RAM, then we do so atomically with a compare and swap. - * if the PTE is in IO space, then it can't be updated. - * if the PTE changed, then we must re-walk the page table - as the PTE is no longer valid */ + /* + * - if accessed or dirty bits need updating, and the PTE is + * in RAM, then we do so atomically with a compare and swap. + * - if the PTE is in IO space or ROM, then it can't be updated + * and we return TRANSLATE_FAIL. + * - if the PTE changed by the time we went to update it, then + * it is no longer valid and we must re-walk the page table. + */ MemoryRegion *mr; hwaddr l = sizeof(target_ulong), addr1; mr = address_space_translate(cs->as, pte_addr, @@ -239,15 +262,15 @@ restart: target_ulong vpn = addr >> PGSHIFT; *physical = (ppn | (vpn & ((1L << ptshift) - 1))) << PGSHIFT; - if ((pte & PTE_R)) { + /* set permissions on the TLB entry */ + if ((pte & PTE_R) || (mode != PRV_U && (pte & PTE_X) && mxr)) { *prot |= PAGE_READ; } if ((pte & PTE_X)) { *prot |= PAGE_EXEC; } - /* only add write permission on stores or if the page - is already dirty, so that we don't miss further - page table walks to update the dirty bit */ + /* add write permission on stores or if the page is already dirty, + so that we TLB miss on later writes to update the dirty bit */ if ((pte & PTE_W) && (access_type == MMU_DATA_STORE || (pte & PTE_D))) { *prot |= PAGE_WRITE;