From: David Vrabel <david.vrabel@xxxxxxxxxx> Add the code needed to handle and load kexec images into Xen memory or into the crash region. This is needed for the new KEXEC_CMD_load and KEXEC_CMD_unload hypercall sub-ops. Much of this code is derived from the Linux kernel. Signed-off-by: David Vrabel <david.vrabel at citrix.com> Reviewed-by: Andrew Cooper <andrew.cooper3 at citrix.com> --- xen/common/Makefile | 1 + xen/common/kimage.c | 821 ++++++++++++++++++++++++++++++++++++++++++++++ xen/include/xen/kimage.h | 62 ++++ 3 files changed, 884 insertions(+), 0 deletions(-) create mode 100644 xen/common/kimage.c create mode 100644 xen/include/xen/kimage.h diff --git a/xen/common/Makefile b/xen/common/Makefile index 686f7a1..3683ae3 100644 --- a/xen/common/Makefile +++ b/xen/common/Makefile @@ -13,6 +13,7 @@ obj-y += irq.o obj-y += kernel.o obj-y += keyhandler.o obj-$(HAS_KEXEC) += kexec.o +obj-$(HAS_KEXEC) += kimage.o obj-y += lib.o obj-y += memory.o obj-y += multicall.o diff --git a/xen/common/kimage.c b/xen/common/kimage.c new file mode 100644 index 0000000..02ee37e --- /dev/null +++ b/xen/common/kimage.c @@ -0,0 +1,821 @@ +/* + * Kexec Image + * + * Copyright (C) 2013 Citrix Systems R&D Ltd. + * + * Derived from kernel/kexec.c from Linux: + * + * Copyright (C) 2002-2004 Eric Biederman <ebiederm at xmission.com> + * + * This source code is licensed under the GNU General Public License, + * Version 2. See the file COPYING for more details. + */ + +#include <xen/config.h> +#include <xen/types.h> +#include <xen/init.h> +#include <xen/kernel.h> +#include <xen/errno.h> +#include <xen/spinlock.h> +#include <xen/guest_access.h> +#include <xen/mm.h> +#include <xen/kexec.h> +#include <xen/kimage.h> + +#include <asm/page.h> + +/* + * When kexec transitions to the new kernel there is a one-to-one + * mapping between physical and virtual addresses. On processors + * where you can disable the MMU this is trivial, and easy. For + * others it is still a simple predictable page table to setup. + * + * The code for the transition from the current kernel to the the new + * kernel is placed in the page-size control_code_buffer. This memory + * must be identity mapped in the transition from virtual to physical + * addresses. + * + * The assembly stub in the control code buffer is passed a linked list + * of descriptor pages detailing the source pages of the new kernel, + * and the destination addresses of those source pages. As this data + * structure is not used in the context of the current OS, it must + * be self-contained. + * + * The code has been made to work with highmem pages and will use a + * destination page in its final resting place (if it happens + * to allocate it). The end product of this is that most of the + * physical address space, and most of RAM can be used. + * + * Future directions include: + * - allocating a page table with the control code buffer identity + * mapped, to simplify machine_kexec and make kexec_on_panic more + * reliable. + */ + +/* + * KIMAGE_NO_DEST is an impossible destination address..., for + * allocating pages whose destination address we do not care about. + */ +#define KIMAGE_NO_DEST (-1UL) + +/* + * Offset of the last entry in an indirection page. + */ +#define KIMAGE_LAST_ENTRY (PAGE_SIZE/sizeof(kimage_entry_t) - 1) + + +static int kimage_is_destination_range(struct kexec_image *image, + paddr_t start, paddr_t end); +static struct page_info *kimage_alloc_page(struct kexec_image *image, + paddr_t dest); + +static struct page_info *kimage_alloc_zeroed_page(unsigned memflags) +{ + struct page_info *page; + + page = alloc_domheap_page(NULL, memflags); + if ( !page ) + return NULL; + + clear_domain_page(page_to_mfn(page)); + + return page; +} + +static int do_kimage_alloc(struct kexec_image **rimage, paddr_t entry, + unsigned long nr_segments, + xen_kexec_segment_t *segments, uint8_t type) +{ + struct kexec_image *image; + unsigned long i; + int result; + + /* Allocate a controlling structure */ + result = -ENOMEM; + image = xzalloc(typeof(*image)); + if ( !image ) + goto out; + + image->entry_maddr = entry; + image->type = type; + image->nr_segments = nr_segments; + image->segments = segments; + + image->next_crash_page = kexec_crash_area.start; + + INIT_PAGE_LIST_HEAD(&image->control_pages); + INIT_PAGE_LIST_HEAD(&image->dest_pages); + INIT_PAGE_LIST_HEAD(&image->unusable_pages); + + /* + * Verify we have good destination addresses. The caller is + * responsible for making certain we don't attempt to load the new + * image into invalid or reserved areas of RAM. This just + * verifies it is an address we can use. + * + * Since the kernel does everything in page size chunks ensure the + * destination addresses are page aligned. Too many special cases + * crop of when we don't do this. The most insidious is getting + * overlapping destination addresses simply because addresses are + * changed to page size granularity. + */ + result = -EADDRNOTAVAIL; + for ( i = 0; i < nr_segments; i++ ) + { + paddr_t mstart, mend; + + mstart = image->segments[i].dest_maddr; + mend = mstart + image->segments[i].dest_size; + if ( (mstart & ~PAGE_MASK) || (mend & ~PAGE_MASK) ) + goto out; + } + + /* + * Verify our destination addresses do not overlap. If we allowed + * overlapping destination addresses through very weird things can + * happen with no easy explanation as one segment stops on + * another. + */ + result = -EINVAL; + for ( i = 0; i < nr_segments; i++ ) + { + paddr_t mstart, mend; + unsigned long j; + + mstart = image->segments[i].dest_maddr; + mend = mstart + image->segments[i].dest_size; + for (j = 0; j < i; j++ ) + { + paddr_t pstart, pend; + pstart = image->segments[j].dest_maddr; + pend = pstart + image->segments[j].dest_size; + /* Do the segments overlap? */ + if ( (mend > pstart) && (mstart < pend) ) + goto out; + } + } + + /* + * Ensure our buffer sizes are strictly less than our memory + * sizes. This should always be the case, and it is easier to + * check up front than to be surprised later on. + */ + result = -EINVAL; + for ( i = 0; i < nr_segments; i++ ) + { + if ( image->segments[i].buf_size > image->segments[i].dest_size ) + goto out; + } + + /* + * Page for the relocation code must still be accessible after the + * processor has switched to 32-bit mode. + */ + result = -ENOMEM; + image->control_code_page = kimage_alloc_control_page(image, MEMF_bits(32)); + if ( !image->control_code_page ) + goto out; + + /* Add an empty indirection page. */ + image->entry_page = kimage_alloc_control_page(image, 0); + if ( !image->entry_page ) + goto out; + + image->head = page_to_maddr(image->entry_page); + + result = 0; +out: + if ( result == 0 ) + *rimage = image; + else if ( image ) + { + image->segments = NULL; /* caller frees segments after an error */ + kimage_free(image); + } + + return result; + +} + +static int kimage_normal_alloc(struct kexec_image **rimage, paddr_t entry, + unsigned long nr_segments, + xen_kexec_segment_t *segments) +{ + return do_kimage_alloc(rimage, entry, nr_segments, segments, + KEXEC_TYPE_DEFAULT); +} + +static int kimage_crash_alloc(struct kexec_image **rimage, paddr_t entry, + unsigned long nr_segments, + xen_kexec_segment_t *segments) +{ + unsigned long i; + int result; + + /* Verify we have a valid entry point */ + if ( (entry < kexec_crash_area.start) + || (entry > kexec_crash_area.start + kexec_crash_area.size)) + return -EADDRNOTAVAIL; + + /* + * Verify we have good destination addresses. Normally + * the caller is responsible for making certain we don't + * attempt to load the new image into invalid or reserved + * areas of RAM. But crash kernels are preloaded into a + * reserved area of ram. We must ensure the addresses + * are in the reserved area otherwise preloading the + * kernel could corrupt things. + */ + for ( i = 0; i < nr_segments; i++ ) + { + paddr_t mstart, mend; + + if ( guest_handle_is_null(segments[i].buf.h) ) + continue; + + mstart = segments[i].dest_maddr; + mend = mstart + segments[i].dest_size; + /* Ensure we are within the crash kernel limits. */ + if ( (mstart < kexec_crash_area.start ) + || (mend > kexec_crash_area.start + kexec_crash_area.size)) + return -EADDRNOTAVAIL; + } + + /* Allocate and initialize a controlling structure. */ + return do_kimage_alloc(rimage, entry, nr_segments, segments, + KEXEC_TYPE_CRASH); +} + +static int kimage_is_destination_range(struct kexec_image *image, + paddr_t start, + paddr_t end) +{ + unsigned long i; + + for ( i = 0; i < image->nr_segments; i++ ) + { + paddr_t mstart, mend; + + mstart = image->segments[i].dest_maddr; + mend = mstart + image->segments[i].dest_size; + if ( (end > mstart) && (start < mend) ) + return 1; + } + + return 0; +} + +static void kimage_free_page_list(struct page_list_head *list) +{ + struct page_info *page, *next; + + page_list_for_each_safe(page, next, list) + { + page_list_del(page, list); + free_domheap_page(page); + } +} + +static struct page_info *kimage_alloc_normal_control_page( + struct kexec_image *image, unsigned memflags) +{ + /* + * Control pages are special, they are the intermediaries that are + * needed while we copy the rest of the pages to their final + * resting place. As such they must not conflict with either the + * destination addresses or memory the kernel is already using. + * + * The only case where we really need more than one of these are + * for architectures where we cannot disable the MMU and must + * instead generate an identity mapped page table for all of the + * memory. + * + * At worst this runs in O(N) of the image size. + */ + struct page_list_head extra_pages; + struct page_info *page = NULL; + + INIT_PAGE_LIST_HEAD(&extra_pages); + + /* + * Loop while I can allocate a page and the page allocated is a + * destination page. + */ + do { + unsigned long mfn, emfn; + paddr_t addr, eaddr; + + page = kimage_alloc_zeroed_page(memflags); + if ( !page ) + break; + mfn = page_to_mfn(page); + emfn = mfn + 1; + addr = page_to_maddr(page); + eaddr = addr + PAGE_SIZE; + if ( kimage_is_destination_range(image, addr, eaddr) ) + { + page_list_add(page, &extra_pages); + page = NULL; + } + } while ( !page ); + + if ( page ) + { + /* Remember the allocated page... */ + page_list_add(page, &image->control_pages); + + /* + * Because the page is already in it's destination location we + * will never allocate another page at that address. + * Therefore kimage_alloc_page will not return it (again) and + * we don't need to give it an entry in image->segments[]. + */ + } + /* + * Deal with the destination pages I have inadvertently allocated. + * + * Ideally I would convert multi-page allocations into single page + * allocations, and add everything to image->dest_pages. + * + * For now it is simpler to just free the pages. + */ + kimage_free_page_list(&extra_pages); + + return page; +} + +static struct page_info *kimage_alloc_crash_control_page(struct kexec_image *image) +{ + /* + * Control pages are special, they are the intermediaries that are + * needed while we copy the rest of the pages to their final + * resting place. As such they must not conflict with either the + * destination addresses or memory the kernel is already using. + * + * Control pages are also the only pags we must allocate when + * loading a crash kernel. All of the other pages are specified + * by the segments and we just memcpy into them directly. + * + * The only case where we really need more than one of these are + * for architectures where we cannot disable the MMU and must + * instead generate an identity mapped page table for all of the + * memory. + * + * Given the low demand this implements a very simple allocator + * that finds the first hole of the appropriate size in the + * reserved memory region, and allocates all of the memory up to + * and including the hole. + */ + paddr_t hole_start, hole_end; + struct page_info *page = NULL; + + hole_start = PAGE_ALIGN(image->next_crash_page); + hole_end = hole_start + PAGE_SIZE; + while ( hole_end <= kexec_crash_area.start + kexec_crash_area.size ) + { + unsigned long i; + + /* See if I overlap any of the segments. */ + for ( i = 0; i < image->nr_segments; i++ ) + { + paddr_t mstart, mend; + + mstart = image->segments[i].dest_maddr; + mend = mstart + image->segments[i].dest_size; + if ( (hole_end > mstart) && (hole_start < mend) ) + { + /* Advance the hole to the end of the segment. */ + hole_start = PAGE_ALIGN(mend); + hole_end = hole_start + PAGE_SIZE; + break; + } + } + /* If I don't overlap any segments I have found my hole! */ + if ( i == image->nr_segments ) + { + page = maddr_to_page(hole_start); + break; + } + } + if ( page ) + { + image->next_crash_page = hole_end; + clear_domain_page(page_to_mfn(page)); + } + + return page; +} + + +struct page_info *kimage_alloc_control_page(struct kexec_image *image, + unsigned memflags) +{ + struct page_info *pages = NULL; + + switch ( image->type ) + { + case KEXEC_TYPE_DEFAULT: + pages = kimage_alloc_normal_control_page(image, memflags); + break; + case KEXEC_TYPE_CRASH: + pages = kimage_alloc_crash_control_page(image); + break; + } + return pages; +} + +static int kimage_add_entry(struct kexec_image *image, kimage_entry_t entry) +{ + kimage_entry_t *entries; + + if ( image->next_entry == KIMAGE_LAST_ENTRY ) + { + struct page_info *page; + + page = kimage_alloc_page(image, KIMAGE_NO_DEST); + if ( !page ) + return -ENOMEM; + + entries = __map_domain_page(image->entry_page); + entries[image->next_entry] = page_to_maddr(page) | IND_INDIRECTION; + unmap_domain_page(entries); + + image->entry_page = page; + image->next_entry = 0; + } + + entries = __map_domain_page(image->entry_page); + entries[image->next_entry] = entry; + image->next_entry++; + unmap_domain_page(entries); + + return 0; +} + +static int kimage_set_destination(struct kexec_image *image, + paddr_t destination) +{ + return kimage_add_entry(image, (destination & PAGE_MASK) | IND_DESTINATION); +} + + +static int kimage_add_page(struct kexec_image *image, paddr_t maddr) +{ + return kimage_add_entry(image, (maddr & PAGE_MASK) | IND_SOURCE); +} + + +static void kimage_free_extra_pages(struct kexec_image *image) +{ + kimage_free_page_list(&image->dest_pages); + kimage_free_page_list(&image->unusable_pages); +} + +static void kimage_terminate(struct kexec_image *image) +{ + kimage_entry_t *entries; + + entries = __map_domain_page(image->entry_page); + entries[image->next_entry] = IND_DONE; + unmap_domain_page(entries); +} + +/* + * Iterate over all the entries in the indirection pages. + * + * Call unmap_domain_page(ptr) after the loop exits. + */ +#define for_each_kimage_entry(image, ptr, entry) \ + for ( ptr = map_domain_page(image->head >> PAGE_SHIFT); \ + (entry = *ptr) && !(entry & IND_DONE); \ + ptr = (entry & IND_INDIRECTION) ? \ + (unmap_domain_page(ptr), map_domain_page(entry >> PAGE_SHIFT)) \ + : ptr + 1 ) + +static void kimage_free_entry(kimage_entry_t entry) +{ + struct page_info *page; + + page = mfn_to_page(entry >> PAGE_SHIFT); + free_domheap_page(page); +} + +static void kimage_free_all_entries(struct kexec_image *image) +{ + kimage_entry_t *ptr, entry; + kimage_entry_t ind = 0; + + if ( !image->head ) + return; + + for_each_kimage_entry(image, ptr, entry) + { + if ( entry & IND_INDIRECTION ) + { + /* Free the previous indirection page */ + if ( ind & IND_INDIRECTION ) + kimage_free_entry(ind); + /* Save this indirection page until we are done with it. */ + ind = entry; + } + else if ( entry & IND_SOURCE ) + kimage_free_entry(entry); + } + unmap_domain_page(ptr); + + /* Free the final indirection page. */ + if ( ind & IND_INDIRECTION ) + kimage_free_entry(ind); +} + +void kimage_free(struct kexec_image *image) +{ + if ( !image ) + return; + + kimage_free_extra_pages(image); + kimage_free_all_entries(image); + kimage_free_page_list(&image->control_pages); + xfree(image->segments); + xfree(image); +} + +static kimage_entry_t *kimage_dst_used(struct kexec_image *image, + paddr_t maddr) +{ + kimage_entry_t *ptr, entry; + unsigned long destination = 0; + + for_each_kimage_entry(image, ptr, entry) + { + if ( entry & IND_DESTINATION ) + destination = entry & PAGE_MASK; + else if ( entry & IND_SOURCE ) + { + if ( maddr == destination ) + return ptr; + destination += PAGE_SIZE; + } + } + unmap_domain_page(ptr); + + return NULL; +} + +static struct page_info *kimage_alloc_page(struct kexec_image *image, + paddr_t destination) +{ + /* + * Here we implement safeguards to ensure that a source page is + * not copied to its destination page before the data on the + * destination page is no longer useful. + * + * To do this we maintain the invariant that a source page is + * either its own destination page, or it is not a destination + * page at all. + * + * That is slightly stronger than required, but the proof that no + * problems will not occur is trivial, and the implementation is + * simply to verify. + * + * When allocating all pages normally this algorithm will run in + * O(N) time, but in the worst case it will run in O(N^2) time. + * If the runtime is a problem the data structures can be fixed. + */ + struct page_info *page; + paddr_t addr; + + /* + * Walk through the list of destination pages, and see if I have a + * match. + */ + page_list_for_each(page, &image->dest_pages) + { + addr = page_to_maddr(page); + if ( addr == destination ) + { + page_list_del(page, &image->dest_pages); + return page; + } + } + page = NULL; + for (;;) + { + kimage_entry_t *old; + + /* Allocate a page, if we run out of memory give up. */ + page = kimage_alloc_zeroed_page(0); + if ( !page ) + return NULL; + addr = page_to_maddr(page); + + /* If it is the destination page we want use it. */ + if ( addr == destination ) + break; + + /* If the page is not a destination page use it. */ + if ( !kimage_is_destination_range(image, addr, + addr + PAGE_SIZE) ) + break; + + /* + * I know that the page is someones destination page. See if + * there is already a source page for this destination page. + * And if so swap the source pages. + */ + old = kimage_dst_used(image, addr); + if ( old ) + { + /* If so move it. */ + unsigned long old_mfn = *old >> PAGE_SHIFT; + unsigned long mfn = addr >> PAGE_SHIFT; + + copy_domain_page(mfn, old_mfn); + clear_domain_page(old_mfn); + *old = (addr & ~PAGE_MASK) | IND_SOURCE; + unmap_domain_page(old); + + page = mfn_to_page(old_mfn); + break; + } + else + { + /* + * Place the page on the destination list; I will use it + * later. + */ + page_list_add(page, &image->dest_pages); + } + } + return page; +} + +static int kimage_load_normal_segment(struct kexec_image *image, + xen_kexec_segment_t *segment) +{ + unsigned long to_copy; + unsigned long src_offset; + paddr_t dest, end; + int ret; + + to_copy = segment->buf_size; + src_offset = 0; + dest = segment->dest_maddr; + + ret = kimage_set_destination(image, dest); + if ( ret < 0 ) + return ret; + + while ( to_copy ) + { + unsigned long dest_mfn; + struct page_info *page; + void *dest_va; + size_t size; + + dest_mfn = dest >> PAGE_SHIFT; + + size = min_t(unsigned long, PAGE_SIZE, to_copy); + + page = kimage_alloc_page(image, dest); + if ( !page ) + return -ENOMEM; + ret = kimage_add_page(image, page_to_maddr(page)); + if ( ret < 0 ) + return ret; + + dest_va = __map_domain_page(page); + ret = copy_from_guest_offset(dest_va, segment->buf.h, src_offset, size); + unmap_domain_page(dest_va); + if ( ret ) + return -EFAULT; + + to_copy -= size; + src_offset += size; + dest += PAGE_SIZE; + } + + /* Remainder of the destination should be zeroed. */ + end = segment->dest_maddr + segment->dest_size; + for ( ; dest < end; dest += PAGE_SIZE ) + kimage_add_entry(image, IND_ZERO); + + return 0; +} + +static int kimage_load_crash_segment(struct kexec_image *image, + xen_kexec_segment_t *segment) +{ + /* + * For crash dumps kernels we simply copy the data from user space + * to it's destination. + */ + paddr_t dest; + unsigned long sbytes, dbytes; + int ret = 0; + unsigned long src_offset = 0; + + sbytes = segment->buf_size; + dbytes = segment->dest_size; + dest = segment->dest_maddr; + + while ( dbytes ) + { + unsigned long dest_mfn; + void *dest_va; + size_t schunk, dchunk; + + dest_mfn = dest >> PAGE_SHIFT; + + dchunk = PAGE_SIZE; + schunk = min(dchunk, sbytes); + + dest_va = map_domain_page(dest_mfn); + if ( !dest_va ) + return -EINVAL; + + ret = copy_from_guest_offset(dest_va, segment->buf.h, src_offset, schunk); + memset(dest_va + schunk, 0, dchunk - schunk); + + unmap_domain_page(dest_va); + if ( ret ) + return -EFAULT; + + dbytes -= dchunk; + sbytes -= schunk; + dest += dchunk; + src_offset += schunk; + } + + return 0; +} + +static int kimage_load_segment(struct kexec_image *image, xen_kexec_segment_t *segment) +{ + int result = -ENOMEM; + + if ( !guest_handle_is_null(segment->buf.h) ) + { + switch ( image->type ) + { + case KEXEC_TYPE_DEFAULT: + result = kimage_load_normal_segment(image, segment); + break; + case KEXEC_TYPE_CRASH: + result = kimage_load_crash_segment(image, segment); + break; + } + } + + return result; +} + +int kimage_alloc(struct kexec_image **rimage, uint8_t type, uint16_t arch, + uint64_t entry_maddr, + uint32_t nr_segments, xen_kexec_segment_t *segment) +{ + int result; + + switch( type ) + { + case KEXEC_TYPE_DEFAULT: + result = kimage_normal_alloc(rimage, entry_maddr, nr_segments, segment); + break; + case KEXEC_TYPE_CRASH: + result = kimage_crash_alloc(rimage, entry_maddr, nr_segments, segment); + break; + default: + result = -EINVAL; + break; + } + if ( result < 0 ) + return result; + + (*rimage)->arch = arch; + + return result; +} + +int kimage_load_segments(struct kexec_image *image) +{ + int s; + int result; + + for ( s = 0; s < image->nr_segments; s++ ) { + result = kimage_load_segment(image, &image->segments[s]); + if ( result < 0 ) + return result; + } + kimage_terminate(image); + return 0; +} + +/* + * Local variables: + * mode: C + * c-file-style: "BSD" + * c-basic-offset: 4 + * tab-width: 4 + * indent-tabs-mode: nil + * End: + */ diff --git a/xen/include/xen/kimage.h b/xen/include/xen/kimage.h new file mode 100644 index 0000000..0ebd37a --- /dev/null +++ b/xen/include/xen/kimage.h @@ -0,0 +1,62 @@ +#ifndef __XEN_KIMAGE_H__ +#define __XEN_KIMAGE_H__ + +#define IND_DESTINATION 0x1 +#define IND_INDIRECTION 0x2 +#define IND_DONE 0x4 +#define IND_SOURCE 0x8 +#define IND_ZERO 0x10 + +#ifndef __ASSEMBLY__ + +#include <xen/list.h> +#include <xen/mm.h> +#include <public/kexec.h> + +#define KEXEC_SEGMENT_MAX 16 + +typedef paddr_t kimage_entry_t; + +struct kexec_image { + uint8_t type; + uint16_t arch; + uint64_t entry_maddr; + uint32_t nr_segments; + xen_kexec_segment_t *segments; + + kimage_entry_t head; + struct page_info *entry_page; + unsigned next_entry; + + struct page_info *control_code_page; + struct page_info *aux_page; + + struct page_list_head control_pages; + struct page_list_head dest_pages; + struct page_list_head unusable_pages; + + /* Address of next control page to allocate for crash kernels. */ + paddr_t next_crash_page; +}; + +int kimage_alloc(struct kexec_image **rimage, uint8_t type, uint16_t arch, + uint64_t entry_maddr, + uint32_t nr_segments, xen_kexec_segment_t *segment); +void kimage_free(struct kexec_image *image); +int kimage_load_segments(struct kexec_image *image); +struct page_info *kimage_alloc_control_page(struct kexec_image *image, + unsigned memflags); + +#endif /* __ASSEMBLY__ */ + +#endif /* __XEN_KIMAGE_H__ */ + +/* + * Local variables: + * mode: C + * c-file-style: "BSD" + * c-basic-offset: 4 + * tab-width: 4 + * indent-tabs-mode: nil + * End: + */ -- 1.7.2.5