[PARISC] only make executable areas executable

Currently parisc has the whole kernel marked as RWX, meaning any
kernel page at all is eligible to be executed.  This can cause a
theoretical problem on systems with combined I/D TLB because the act
of referencing a page causes a TLB insertion with an executable bit.
This TLB entry may be used by the CPU as the basis for speculating the
page into the I-Cache.  If this speculated page is subsequently used
for a user process, there is the possibility we will get a stale
I-cache line picked up as the binary executes.

As a point of good practise, only mark actual kernel text pages as
executable.  The same has to be done for init_text pages, but they're
converted to data pages (and the I-Cache flushed) when the init memory
is released.

Signed-off-by: James Bottomley <James.Bottomley@suse.de>

1 files changed, 143 insertions, 117 deletions

diff --git a/arch/parisc/mm/init.c b/arch/parisc/mm/init.c
index b7ed8d7a9b33..7e6b4656f3d7 100644
--- a/arch/parisc/mm/init.c
+++ b/arch/parisc/mm/init.c
@@ -369,24 +369,158 @@ static void __init setup_bootmem(void)
         request_resource(&sysram_resources[0], &pdcdata_resource);
 }
 
+static void __init map_pages(unsigned long start_vaddr,
+                             unsigned long start_paddr, unsigned long size,
+                             pgprot_t pgprot, int force)
+{
+        pgd_t *pg_dir;
+        pmd_t *pmd;
+        pte_t *pg_table;
+        unsigned long end_paddr;
+        unsigned long start_pmd;
+        unsigned long start_pte;
+        unsigned long tmp1;
+        unsigned long tmp2;
+        unsigned long address;
+        unsigned long vaddr;
+        unsigned long ro_start;
+        unsigned long ro_end;
+        unsigned long fv_addr;
+        unsigned long gw_addr;
+        extern const unsigned long fault_vector_20;
+        extern void * const linux_gateway_page;
+
+        ro_start = __pa((unsigned long)_text);
+        ro_end   = __pa((unsigned long)&data_start);
+        fv_addr  = __pa((unsigned long)&fault_vector_20) & PAGE_MASK;
+        gw_addr  = __pa((unsigned long)&linux_gateway_page) & PAGE_MASK;
+
+        end_paddr = start_paddr + size;
+
+        pg_dir = pgd_offset_k(start_vaddr);
+
+#if PTRS_PER_PMD == 1
+        start_pmd = 0;
+#else
+        start_pmd = ((start_vaddr >> PMD_SHIFT) & (PTRS_PER_PMD - 1));
+#endif
+        start_pte = ((start_vaddr >> PAGE_SHIFT) & (PTRS_PER_PTE - 1));
+
+        address = start_paddr;
+        vaddr = start_vaddr;
+        while (address < end_paddr) {
+#if PTRS_PER_PMD == 1
+                pmd = (pmd_t *)__pa(pg_dir);
+#else
+                pmd = (pmd_t *)pgd_address(*pg_dir);
+
+                /*
+                 * pmd is physical at this point
+                 */
+
+                if (!pmd) {
+                        pmd = (pmd_t *) alloc_bootmem_low_pages_node(NODE_DATA(0), PAGE_SIZE << PMD_ORDER);
+                        pmd = (pmd_t *) __pa(pmd);
+                }
+
+                pgd_populate(NULL, pg_dir, __va(pmd));
+#endif
+                pg_dir++;
+
+                /* now change pmd to kernel virtual addresses */
+
+                pmd = (pmd_t *)__va(pmd) + start_pmd;
+                for (tmp1 = start_pmd; tmp1 < PTRS_PER_PMD; tmp1++, pmd++) {
+
+                        /*
+                         * pg_table is physical at this point
+                         */
+
+                        pg_table = (pte_t *)pmd_address(*pmd);
+                        if (!pg_table) {
+                                pg_table = (pte_t *)
+                                        alloc_bootmem_low_pages_node(NODE_DATA(0), PAGE_SIZE);
+                                pg_table = (pte_t *) __pa(pg_table);
+                        }
+
+                        pmd_populate_kernel(NULL, pmd, __va(pg_table));
+
+                        /* now change pg_table to kernel virtual addresses */
+
+                        pg_table = (pte_t *) __va(pg_table) + start_pte;
+                        for (tmp2 = start_pte; tmp2 < PTRS_PER_PTE; tmp2++, pg_table++) {
+                                pte_t pte;
+
+                                /*
+                                 * Map the fault vector writable so we can
+                                 * write the HPMC checksum.
+                                 */
+                                if (force)
+                                        pte =  __mk_pte(address, pgprot);
+                                else if (core_kernel_text(vaddr) &&
+                                         address != fv_addr)
+                                        pte = __mk_pte(address, PAGE_KERNEL_EXEC);
+                                else
+#if defined(CONFIG_PARISC_PAGE_SIZE_4KB)
+                                if (address >= ro_start && address < ro_end
+                                                        && address != fv_addr
+                                                        && address != gw_addr)
+                                        pte = __mk_pte(address, PAGE_KERNEL_RO);
+                                else
+#endif
+                                        pte = __mk_pte(address, pgprot);
+
+                                if (address >= end_paddr) {
+                                        if (force)
+                                                break;
+                                        else
+                                                pte_val(pte) = 0;
+                                }
+
+                                set_pte(pg_table, pte);
+
+                                address += PAGE_SIZE;
+                                vaddr += PAGE_SIZE;
+                        }
+                        start_pte = 0;
+
+                        if (address >= end_paddr)
+                            break;
+                }
+                start_pmd = 0;
+        }
+}
+
 void free_initmem(void)
 {
         unsigned long addr;
         unsigned long init_begin = (unsigned long)__init_begin;
         unsigned long init_end = (unsigned long)__init_end;
 
-#ifdef CONFIG_DEBUG_KERNEL
+        /* The init text pages are marked R-X.  We have to
+         * flush the icache and mark them RW-
+         *
+         * This is tricky, because map_pages is in the init section.
+         * Do a dummy remap of the data section first (the data
+         * section is already PAGE_KERNEL) to pull in the TLB entries
+         * for map_kernel */
+        map_pages(init_begin, __pa(init_begin), init_end - init_begin,
+                  PAGE_KERNEL_RWX, 1);
+        /* now remap at PAGE_KERNEL since the TLB is pre-primed to execute
+         * map_pages */
+        map_pages(init_begin, __pa(init_begin), init_end - init_begin,
+                  PAGE_KERNEL, 1);
+
+        /* force the kernel to see the new TLB entries */
+        __flush_tlb_range(0, init_begin, init_end);
         /* Attempt to catch anyone trying to execute code here
          * by filling the page with BRK insns.
          */
         memset((void *)init_begin, 0x00, init_end - init_begin);
+        /* finally dump all the instructions which were cached, since the
+         * pages are no-longer executable */
         flush_icache_range(init_begin, init_end);
-#endif
         
-        /* align __init_begin and __init_end to page size,
-           ignoring linker script where we might have tried to save RAM */
-        init_begin = PAGE_ALIGN(init_begin);
-        init_end = PAGE_ALIGN(init_end);
         for (addr = init_begin; addr < init_end; addr += PAGE_SIZE) {
                 ClearPageReserved(virt_to_page(addr));
                 init_page_count(virt_to_page(addr));
@@ -616,114 +750,6 @@ void show_mem(unsigned int filter)
 #endif
 }
 
-
-static void __init map_pages(unsigned long start_vaddr, unsigned long start_paddr, unsigned long size, pgprot_t pgprot)
-{
-        pgd_t *pg_dir;
-        pmd_t *pmd;
-        pte_t *pg_table;
-        unsigned long end_paddr;
-        unsigned long start_pmd;
-        unsigned long start_pte;
-        unsigned long tmp1;
-        unsigned long tmp2;
-        unsigned long address;
-        unsigned long ro_start;
-        unsigned long ro_end;
-        unsigned long fv_addr;
-        unsigned long gw_addr;
-        extern const unsigned long fault_vector_20;
-        extern void * const linux_gateway_page;
-
-        ro_start = __pa((unsigned long)_text);
-        ro_end   = __pa((unsigned long)&data_start);
-        fv_addr  = __pa((unsigned long)&fault_vector_20) & PAGE_MASK;
-        gw_addr  = __pa((unsigned long)&linux_gateway_page) & PAGE_MASK;
-
-        end_paddr = start_paddr + size;
-
-        pg_dir = pgd_offset_k(start_vaddr);
-
-#if PTRS_PER_PMD == 1
-        start_pmd = 0;
-#else
-        start_pmd = ((start_vaddr >> PMD_SHIFT) & (PTRS_PER_PMD - 1));
-#endif
-        start_pte = ((start_vaddr >> PAGE_SHIFT) & (PTRS_PER_PTE - 1));
-
-        address = start_paddr;
-        while (address < end_paddr) {
-#if PTRS_PER_PMD == 1
-                pmd = (pmd_t *)__pa(pg_dir);
-#else
-                pmd = (pmd_t *)pgd_address(*pg_dir);
-
-                /*
-                 * pmd is physical at this point
-                 */
-
-                if (!pmd) {
-                        pmd = (pmd_t *) alloc_bootmem_low_pages_node(NODE_DATA(0),PAGE_SIZE << PMD_ORDER);
-                        pmd = (pmd_t *) __pa(pmd);
-                }
-
-                pgd_populate(NULL, pg_dir, __va(pmd));
-#endif
-                pg_dir++;
-
-                /* now change pmd to kernel virtual addresses */
-
-                pmd = (pmd_t *)__va(pmd) + start_pmd;
-                for (tmp1 = start_pmd; tmp1 < PTRS_PER_PMD; tmp1++,pmd++) {
-
-                        /*
-                         * pg_table is physical at this point
-                         */
-
-                        pg_table = (pte_t *)pmd_address(*pmd);
-                        if (!pg_table) {
-                                pg_table = (pte_t *)
-                                        alloc_bootmem_low_pages_node(NODE_DATA(0),PAGE_SIZE);
-                                pg_table = (pte_t *) __pa(pg_table);
-                        }
-
-                        pmd_populate_kernel(NULL, pmd, __va(pg_table));
-
-                        /* now change pg_table to kernel virtual addresses */
-
-                        pg_table = (pte_t *) __va(pg_table) + start_pte;
-                        for (tmp2 = start_pte; tmp2 < PTRS_PER_PTE; tmp2++,pg_table++) {
-                                pte_t pte;
-
-                                /*
-                                 * Map the fault vector writable so we can
-                                 * write the HPMC checksum.
-                                 */
-#if defined(CONFIG_PARISC_PAGE_SIZE_4KB)
-                                if (address >= ro_start && address < ro_end
-                                                        && address != fv_addr
-                                                        && address != gw_addr)
-                                    pte = __mk_pte(address, PAGE_KERNEL_RO);
-                                else
-#endif
-                                    pte = __mk_pte(address, pgprot);
-
-                                if (address >= end_paddr)
-                                        pte_val(pte) = 0;
-
-                                set_pte(pg_table, pte);
-
-                                address += PAGE_SIZE;
-                        }
-                        start_pte = 0;
-
-                        if (address >= end_paddr)
-                            break;
-                }
-                start_pmd = 0;
-        }
-}
-
 /*
  * pagetable_init() sets up the page tables
  *
@@ -748,14 +774,14 @@ static void __init pagetable_init(void)
                 size = pmem_ranges[range].pages << PAGE_SHIFT;
 
                 map_pages((unsigned long)__va(start_paddr), start_paddr,
-                        size, PAGE_KERNEL);
+                          size, PAGE_KERNEL, 0);
         }
 
 #ifdef CONFIG_BLK_DEV_INITRD
         if (initrd_end && initrd_end > mem_limit) {
                 printk(KERN_INFO "initrd: mapping %08lx-%08lx\n", initrd_start, initrd_end);
                 map_pages(initrd_start, __pa(initrd_start),
-                        initrd_end - initrd_start, PAGE_KERNEL);
+                          initrd_end - initrd_start, PAGE_KERNEL, 0);
         }
 #endif
 
@@ -780,7 +806,7 @@ static void __init gateway_init(void)
          */
 
         map_pages(linux_gateway_page_addr, __pa(&linux_gateway_page),
-                PAGE_SIZE, PAGE_GATEWAY);
+                  PAGE_SIZE, PAGE_GATEWAY, 1);
 }
 
 #ifdef CONFIG_HPUX