* The kdump kernel has to check whether a pfn of the crashed kernel
* was a ballooned page. vmcore is using this function to decide
* whether to access a pfn of the crashed kernel.
- * Returns 0 if the pfn is not backed by a RAM page, the caller may
+ * Returns "false" if the pfn is not backed by a RAM page, the caller may
* handle the pfn special in this case.
*/
-static int xen_oldmem_pfn_is_ram(unsigned long pfn)
+static bool xen_vmcore_pfn_is_ram(struct vmcore_cb *cb, unsigned long pfn)
{
struct xen_hvm_get_mem_type a = {
.domid = DOMID_SELF,
if (HYPERVISOR_hvm_op(HVMOP_get_mem_type, &a)) {
pr_warn_once("Unexpected HVMOP_get_mem_type failure\n");
- return -ENXIO;
+ return true;
}
return a.mem_type != HVMMEM_mmio_dm;
}
+static struct vmcore_cb xen_vmcore_cb = {
+ .pfn_is_ram = xen_vmcore_pfn_is_ram,
+};
#endif
static void xen_hvm_exit_mmap(struct mm_struct *mm)
if (is_pagetable_dying_supported())
pv_ops.mmu.exit_mmap = xen_hvm_exit_mmap;
#ifdef CONFIG_PROC_VMCORE
- WARN_ON(register_oldmem_pfn_is_ram(&xen_oldmem_pfn_is_ram));
+ register_vmcore_cb(&xen_vmcore_cb);
#endif
}
/* Device Dump Size */
static size_t vmcoredd_orig_sz;
-/*
- * Returns > 0 for RAM pages, 0 for non-RAM pages, < 0 on error
- * The called function has to take care of module refcounting.
- */
-static int (*oldmem_pfn_is_ram)(unsigned long pfn);
-
-int register_oldmem_pfn_is_ram(int (*fn)(unsigned long pfn))
+static DECLARE_RWSEM(vmcore_cb_rwsem);
+/* List of registered vmcore callbacks. */
+static LIST_HEAD(vmcore_cb_list);
+/* Whether we had a surprise unregistration of a callback. */
+static bool vmcore_cb_unstable;
+/* Whether the vmcore has been opened once. */
+static bool vmcore_opened;
+
+void register_vmcore_cb(struct vmcore_cb *cb)
{
- if (oldmem_pfn_is_ram)
- return -EBUSY;
- oldmem_pfn_is_ram = fn;
- return 0;
+ down_write(&vmcore_cb_rwsem);
+ INIT_LIST_HEAD(&cb->next);
+ list_add_tail(&cb->next, &vmcore_cb_list);
+ /*
+ * Registering a vmcore callback after the vmcore was opened is
+ * very unusual (e.g., manual driver loading).
+ */
+ if (vmcore_opened)
+ pr_warn_once("Unexpected vmcore callback registration\n");
+ up_write(&vmcore_cb_rwsem);
}
-EXPORT_SYMBOL_GPL(register_oldmem_pfn_is_ram);
+EXPORT_SYMBOL_GPL(register_vmcore_cb);
-void unregister_oldmem_pfn_is_ram(void)
+void unregister_vmcore_cb(struct vmcore_cb *cb)
{
- oldmem_pfn_is_ram = NULL;
- wmb();
+ down_write(&vmcore_cb_rwsem);
+ list_del(&cb->next);
+ /*
+ * Unregistering a vmcore callback after the vmcore was opened is
+ * very unusual (e.g., forced driver removal), but we cannot stop
+ * unregistering.
+ */
+ if (vmcore_opened) {
+ pr_warn_once("Unexpected vmcore callback unregistration\n");
+ vmcore_cb_unstable = true;
+ }
+ up_write(&vmcore_cb_rwsem);
}
-EXPORT_SYMBOL_GPL(unregister_oldmem_pfn_is_ram);
+EXPORT_SYMBOL_GPL(unregister_vmcore_cb);
static bool pfn_is_ram(unsigned long pfn)
{
- int (*fn)(unsigned long pfn);
- /* pfn is ram unless fn() checks pagetype */
+ struct vmcore_cb *cb;
bool ret = true;
- /*
- * Ask hypervisor if the pfn is really ram.
- * A ballooned page contains no data and reading from such a page
- * will cause high load in the hypervisor.
- */
- fn = oldmem_pfn_is_ram;
- if (fn)
- ret = !!fn(pfn);
+ lockdep_assert_held_read(&vmcore_cb_rwsem);
+ if (unlikely(vmcore_cb_unstable))
+ return false;
+
+ list_for_each_entry(cb, &vmcore_cb_list, next) {
+ if (unlikely(!cb->pfn_is_ram))
+ continue;
+ ret = cb->pfn_is_ram(cb, pfn);
+ if (!ret)
+ break;
+ }
return ret;
}
+static int open_vmcore(struct inode *inode, struct file *file)
+{
+ down_read(&vmcore_cb_rwsem);
+ vmcore_opened = true;
+ up_read(&vmcore_cb_rwsem);
+
+ return 0;
+}
+
/* Reads a page from the oldmem device from given offset. */
ssize_t read_from_oldmem(char *buf, size_t count,
u64 *ppos, int userbuf,
offset = (unsigned long)(*ppos % PAGE_SIZE);
pfn = (unsigned long)(*ppos / PAGE_SIZE);
+ down_read(&vmcore_cb_rwsem);
do {
if (count > (PAGE_SIZE - offset))
nr_bytes = PAGE_SIZE - offset;
tmp = copy_oldmem_page(pfn, buf, nr_bytes,
offset, userbuf);
- if (tmp < 0)
+ if (tmp < 0) {
+ up_read(&vmcore_cb_rwsem);
return tmp;
+ }
}
*ppos += nr_bytes;
count -= nr_bytes;
offset = 0;
} while (count);
+ up_read(&vmcore_cb_rwsem);
return read;
}
unsigned long from, unsigned long pfn,
unsigned long size, pgprot_t prot)
{
+ int ret;
+
/*
* Check if oldmem_pfn_is_ram was registered to avoid
* looping over all pages without a reason.
*/
- if (oldmem_pfn_is_ram)
- return remap_oldmem_pfn_checked(vma, from, pfn, size, prot);
+ down_read(&vmcore_cb_rwsem);
+ if (!list_empty(&vmcore_cb_list) || vmcore_cb_unstable)
+ ret = remap_oldmem_pfn_checked(vma, from, pfn, size, prot);
else
- return remap_oldmem_pfn_range(vma, from, pfn, size, prot);
+ ret = remap_oldmem_pfn_range(vma, from, pfn, size, prot);
+ up_read(&vmcore_cb_rwsem);
+ return ret;
}
static int mmap_vmcore(struct file *file, struct vm_area_struct *vma)
#endif
static const struct proc_ops vmcore_proc_ops = {
+ .proc_open = open_vmcore,
.proc_read = read_vmcore,
.proc_lseek = default_llseek,
.proc_mmap = mmap_vmcore,
elfcorehdr_addr = ELFCORE_ADDR_ERR;
}
-#define HAVE_OLDMEM_PFN_IS_RAM 1
-extern int register_oldmem_pfn_is_ram(int (*fn)(unsigned long pfn));
-extern void unregister_oldmem_pfn_is_ram(void);
+/**
+ * struct vmcore_cb - driver callbacks for /proc/vmcore handling
+ * @pfn_is_ram: check whether a PFN really is RAM and should be accessed when
+ * reading the vmcore. Will return "true" if it is RAM or if the
+ * callback cannot tell. If any callback returns "false", it's not
+ * RAM and the page must not be accessed; zeroes should be
+ * indicated in the vmcore instead. For example, a ballooned page
+ * contains no data and reading from such a page will cause high
+ * load in the hypervisor.
+ * @next: List head to manage registered callbacks internally; initialized by
+ * register_vmcore_cb().
+ *
+ * vmcore callbacks allow drivers managing physical memory ranges to
+ * coordinate with vmcore handling code, for example, to prevent accessing
+ * physical memory ranges that should not be accessed when reading the vmcore,
+ * although included in the vmcore header as memory ranges to dump.
+ */
+struct vmcore_cb {
+ bool (*pfn_is_ram)(struct vmcore_cb *cb, unsigned long pfn);
+ struct list_head next;
+};
+extern void register_vmcore_cb(struct vmcore_cb *cb);
+extern void unregister_vmcore_cb(struct vmcore_cb *cb);
#else /* !CONFIG_CRASH_DUMP */
static inline bool is_kdump_kernel(void) { return 0; }
projects / kernel.git / commitdiff