From d7dd2ff11b7fcd425aca5a875983c862d19a67ae Mon Sep 17 00:00:00 2001 From: James Bottomley Date: Thu, 14 Apr 2011 18:25:21 -0500 Subject: [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 --- arch/parisc/kernel/entry.S | 3 +++ arch/parisc/kernel/head.S | 5 +++-- arch/parisc/kernel/module.c | 10 +++++++++- arch/parisc/kernel/vmlinux.lds.S | 1 + 4 files changed, 16 insertions(+), 3 deletions(-) (limited to 'arch/parisc/kernel') diff --git a/arch/parisc/kernel/entry.S b/arch/parisc/kernel/entry.S index ead8d2a1034c..6f0594439143 100644 --- a/arch/parisc/kernel/entry.S +++ b/arch/parisc/kernel/entry.S @@ -692,6 +692,9 @@ ENTRY(fault_vector_11) END(fault_vector_11) #endif + /* Fault vector is separately protected and *must* be on its own page */ + .align PAGE_SIZE +ENTRY(end_fault_vector) .import handle_interruption,code .import do_cpu_irq_mask,code diff --git a/arch/parisc/kernel/head.S b/arch/parisc/kernel/head.S index 145c5e4caaa0..37aabd772fbb 100644 --- a/arch/parisc/kernel/head.S +++ b/arch/parisc/kernel/head.S @@ -106,8 +106,9 @@ $bss_loop: #endif - /* Now initialize the PTEs themselves */ - ldo 0+_PAGE_KERNEL(%r0),%r3 /* Hardwired 0 phys addr start */ + /* Now initialize the PTEs themselves. We use RWX for + * everything ... it will get remapped correctly later */ + ldo 0+_PAGE_KERNEL_RWX(%r0),%r3 /* Hardwired 0 phys addr start */ ldi (1<<(KERNEL_INITIAL_ORDER-PAGE_SHIFT)),%r11 /* PFN count */ load32 PA(pg0),%r1 diff --git a/arch/parisc/kernel/module.c b/arch/parisc/kernel/module.c index 6e81bb596e5b..cedbbb8b18d9 100644 --- a/arch/parisc/kernel/module.c +++ b/arch/parisc/kernel/module.c @@ -61,8 +61,10 @@ #include #include #include +#include #include +#include #include #if 0 @@ -214,7 +216,13 @@ void *module_alloc(unsigned long size) { if (size == 0) return NULL; - return vmalloc(size); + /* using RWX means less protection for modules, but it's + * easier than trying to map the text, data, init_text and + * init_data correctly */ + return __vmalloc_node_range(size, 1, VMALLOC_START, VMALLOC_END, + GFP_KERNEL | __GFP_HIGHMEM, + PAGE_KERNEL_RWX, -1, + __builtin_return_address(0)); } #ifndef CONFIG_64BIT diff --git a/arch/parisc/kernel/vmlinux.lds.S b/arch/parisc/kernel/vmlinux.lds.S index 8f1e4efd143e..bf6a43a322ec 100644 --- a/arch/parisc/kernel/vmlinux.lds.S +++ b/arch/parisc/kernel/vmlinux.lds.S @@ -134,6 +134,7 @@ SECTIONS . = ALIGN(16384); __init_begin = .; INIT_TEXT_SECTION(16384) + . = ALIGN(PAGE_SIZE); INIT_DATA_SECTION(16) /* we have to discard exit text and such at runtime, not link time */ .exit.text : -- cgit v1.2.3 From b7d45818444a31948cfc7849136013a0ea54b2fb Mon Sep 17 00:00:00 2001 From: James Bottomley Date: Fri, 15 Apr 2011 12:37:22 -0500 Subject: [PARISC] prevent speculative re-read on cache flush According to Appendix F, the TLB is the primary arbiter of speculation. Thus, if a page has a TLB entry, it may be speculatively read into the cache. On linux, this can cause us incoherencies because if we're about to do a disk read, we call get_user_pages() to do the flush/invalidate in user space, but we still potentially have the user TLB entries, and the cache could speculate the lines back into userspace (thus causing stale data to be used). This is fixed by purging the TLB entries before we flush through the tmpalias space. Now, the only way the line could be re-speculated is if the user actually tries to touch it (which is not allowed). Signed-off-by: James Bottomley --- arch/parisc/kernel/cache.c | 13 ++++++++++++- 1 file changed, 12 insertions(+), 1 deletion(-) (limited to 'arch/parisc/kernel') diff --git a/arch/parisc/kernel/cache.c b/arch/parisc/kernel/cache.c index 3f11331c2775..83335f3da5fc 100644 --- a/arch/parisc/kernel/cache.c +++ b/arch/parisc/kernel/cache.c @@ -304,10 +304,20 @@ void flush_dcache_page(struct page *page) offset = (pgoff - mpnt->vm_pgoff) << PAGE_SHIFT; addr = mpnt->vm_start + offset; + /* The TLB is the engine of coherence on parisc: The + * CPU is entitled to speculate any page with a TLB + * mapping, so here we kill the mapping then flush the + * page along a special flush only alias mapping. + * This guarantees that the page is no-longer in the + * cache for any process and nor may it be + * speculatively read in (until the user or kernel + * specifically accesses it, of course) */ + + flush_tlb_page(mpnt, addr); if (old_addr == 0 || (old_addr & (SHMLBA - 1)) != (addr & (SHMLBA - 1))) { __flush_cache_page(mpnt, addr, page_to_phys(page)); if (old_addr) - printk(KERN_ERR "INEQUIVALENT ALIASES 0x%lx and 0x%lx in file %s\n", old_addr, addr, mpnt->vm_file ? mpnt->vm_file->f_path.dentry->d_name.name : "(null)"); + printk(KERN_ERR "INEQUIVALENT ALIASES 0x%lx and 0x%lx in file %s\n", old_addr, addr, mpnt->vm_file ? (char *)mpnt->vm_file->f_path.dentry->d_name.name : "(null)"); old_addr = addr; } } @@ -499,6 +509,7 @@ flush_cache_page(struct vm_area_struct *vma, unsigned long vmaddr, unsigned long { BUG_ON(!vma->vm_mm->context); + flush_tlb_page(vma, vmaddr); __flush_cache_page(vma, vmaddr, page_to_phys(pfn_to_page(pfn))); } -- cgit v1.2.3