From 2bcf018340cbf233f7145e643fc1bb367f23fd90 Mon Sep 17 00:00:00 2001 From: David Hildenbrand Date: Mon, 16 Oct 2017 22:23:58 +0200 Subject: [PATCH] s390x/tcg: low-address protection support This is a neat way to implement low address protection, whereby only the first 512 bytes of the first two pages (each 4096 bytes) of every address space are protected. Store a tec of 0 for the access exception, this is what is defined by Enhanced Suppression on Protection in case of a low address protection (Bit 61 set to 0, rest undefined). We have to make sure to to pass the access address, not the masked page address into mmu_translate*(). Drop the check from testblock. So we can properly test this via kvm-unit-tests. This will check every access going through one of the MMUs. Reviewed-by: Richard Henderson Signed-off-by: David Hildenbrand Message-Id: <20171016202358.3633-3-david@redhat.com> [CH: restored error message for access register mode] Signed-off-by: Cornelia Huck --- target/s390x/excp_helper.c | 3 +- target/s390x/mem_helper.c | 8 ---- target/s390x/mmu_helper.c | 96 +++++++++++++++++++++++++++++----------------- 3 files changed, 62 insertions(+), 45 deletions(-) diff --git a/target/s390x/excp_helper.c b/target/s390x/excp_helper.c index cff308a18d..e04b670663 100644 --- a/target/s390x/excp_helper.c +++ b/target/s390x/excp_helper.c @@ -95,7 +95,6 @@ int s390_cpu_handle_mmu_fault(CPUState *cs, vaddr orig_vaddr, DPRINTF("%s: address 0x%" VADDR_PRIx " rw %d mmu_idx %d\n", __func__, orig_vaddr, rw, mmu_idx); - orig_vaddr &= TARGET_PAGE_MASK; vaddr = orig_vaddr; if (mmu_idx < MMU_REAL_IDX) { @@ -127,7 +126,7 @@ int s390_cpu_handle_mmu_fault(CPUState *cs, vaddr orig_vaddr, qemu_log_mask(CPU_LOG_MMU, "%s: set tlb %" PRIx64 " -> %" PRIx64 " (%x)\n", __func__, (uint64_t)vaddr, (uint64_t)raddr, prot); - tlb_set_page(cs, orig_vaddr, raddr, prot, + tlb_set_page(cs, orig_vaddr & TARGET_PAGE_MASK, raddr, prot, mmu_idx, TARGET_PAGE_SIZE); return 0; diff --git a/target/s390x/mem_helper.c b/target/s390x/mem_helper.c index bbbe1c62b3..69a16867d4 100644 --- a/target/s390x/mem_helper.c +++ b/target/s390x/mem_helper.c @@ -1687,18 +1687,10 @@ void HELPER(stctl)(CPUS390XState *env, uint32_t r1, uint64_t a2, uint32_t r3) uint32_t HELPER(testblock)(CPUS390XState *env, uint64_t real_addr) { uintptr_t ra = GETPC(); - CPUState *cs = CPU(s390_env_get_cpu(env)); int i; real_addr = wrap_address(env, real_addr) & TARGET_PAGE_MASK; - /* Check low-address protection */ - if ((env->cregs[0] & CR0_LOWPROT) && real_addr < 0x2000) { - cpu_restore_state(cs, ra); - program_interrupt(env, PGM_PROTECTION, 4); - return 1; - } - for (i = 0; i < TARGET_PAGE_SIZE; i += 8) { cpu_stq_real_ra(env, real_addr + i, 0, ra); } diff --git a/target/s390x/mmu_helper.c b/target/s390x/mmu_helper.c index 9daa0fd8e2..31e3f3f415 100644 --- a/target/s390x/mmu_helper.c +++ b/target/s390x/mmu_helper.c @@ -106,6 +106,37 @@ static void trigger_page_fault(CPUS390XState *env, target_ulong vaddr, trigger_access_exception(env, type, ilen, tec); } +/* check whether the address would be proteted by Low-Address Protection */ +static bool is_low_address(uint64_t addr) +{ + return addr <= 511 || (addr >= 4096 && addr <= 4607); +} + +/* check whether Low-Address Protection is enabled for mmu_translate() */ +static bool lowprot_enabled(const CPUS390XState *env, uint64_t asc) +{ + if (!(env->cregs[0] & CR0_LOWPROT)) { + return false; + } + if (!(env->psw.mask & PSW_MASK_DAT)) { + return true; + } + + /* Check the private-space control bit */ + switch (asc) { + case PSW_ASC_PRIMARY: + return !(env->cregs[1] & _ASCE_PRIVATE_SPACE); + case PSW_ASC_SECONDARY: + return !(env->cregs[7] & _ASCE_PRIVATE_SPACE); + case PSW_ASC_HOME: + return !(env->cregs[13] & _ASCE_PRIVATE_SPACE); + default: + /* We don't support access register mode */ + error_report("unsupported addressing mode"); + exit(1); + } +} + /** * Translate real address to absolute (= physical) * address by taking care of the prefix mapping. @@ -323,6 +354,24 @@ int mmu_translate(CPUS390XState *env, target_ulong vaddr, int rw, uint64_t asc, } *flags = PAGE_READ | PAGE_WRITE | PAGE_EXEC; + if (is_low_address(vaddr & TARGET_PAGE_MASK) && lowprot_enabled(env, asc)) { + /* + * If any part of this page is currently protected, make sure the + * TLB entry will not be reused. + * + * As the protected range is always the first 512 bytes of the + * two first pages, we are able to catch all writes to these areas + * just by looking at the start address (triggering the tlb miss). + */ + *flags |= PAGE_WRITE_INV; + if (is_low_address(vaddr) && rw == MMU_DATA_STORE) { + if (exc) { + trigger_access_exception(env, PGM_PROTECTION, ILEN_AUTO, 0); + } + return -EACCES; + } + } + vaddr &= TARGET_PAGE_MASK; if (!(env->psw.mask & PSW_MASK_DAT)) { @@ -392,50 +441,17 @@ int mmu_translate(CPUS390XState *env, target_ulong vaddr, int rw, uint64_t asc, } /** - * lowprot_enabled: Check whether low-address protection is enabled - */ -static bool lowprot_enabled(const CPUS390XState *env) -{ - if (!(env->cregs[0] & CR0_LOWPROT)) { - return false; - } - if (!(env->psw.mask & PSW_MASK_DAT)) { - return true; - } - - /* Check the private-space control bit */ - switch (env->psw.mask & PSW_MASK_ASC) { - case PSW_ASC_PRIMARY: - return !(env->cregs[1] & _ASCE_PRIVATE_SPACE); - case PSW_ASC_SECONDARY: - return !(env->cregs[7] & _ASCE_PRIVATE_SPACE); - case PSW_ASC_HOME: - return !(env->cregs[13] & _ASCE_PRIVATE_SPACE); - default: - /* We don't support access register mode */ - error_report("unsupported addressing mode"); - exit(1); - } -} - -/** * translate_pages: Translate a set of consecutive logical page addresses * to absolute addresses */ static int translate_pages(S390CPU *cpu, vaddr addr, int nr_pages, target_ulong *pages, bool is_write) { - bool lowprot = is_write && lowprot_enabled(&cpu->env); uint64_t asc = cpu->env.psw.mask & PSW_MASK_ASC; CPUS390XState *env = &cpu->env; int ret, i, pflags; for (i = 0; i < nr_pages; i++) { - /* Low-address protection? */ - if (lowprot && (addr < 512 || (addr >= 4096 && addr < 4096 + 512))) { - trigger_access_exception(env, PGM_PROTECTION, ILEN_AUTO, 0); - return -EACCES; - } ret = mmu_translate(env, addr, is_write, asc, &pages[i], &pflags, true); if (ret) { return ret; @@ -509,9 +525,19 @@ int s390_cpu_virt_mem_rw(S390CPU *cpu, vaddr laddr, uint8_t ar, void *hostbuf, int mmu_translate_real(CPUS390XState *env, target_ulong raddr, int rw, target_ulong *addr, int *flags) { - /* TODO: low address protection once we flush the tlb on cr changes */ + const bool lowprot_enabled = env->cregs[0] & CR0_LOWPROT; + *flags = PAGE_READ | PAGE_WRITE; - *addr = mmu_real2abs(env, raddr); + if (is_low_address(raddr & TARGET_PAGE_MASK) && lowprot_enabled) { + /* see comment in mmu_translate() how this works */ + *flags |= PAGE_WRITE_INV; + if (is_low_address(raddr) && rw == MMU_DATA_STORE) { + trigger_access_exception(env, PGM_PROTECTION, ILEN_AUTO, 0); + return -EACCES; + } + } + + *addr = mmu_real2abs(env, raddr & TARGET_PAGE_MASK); /* TODO: storage key handling */ return 0; -- 2.11.0