xen: xensyms support

Export Xen symbols to dom0 via /proc/xen/xensyms (similar to
/proc/kallsyms).

Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Reviewed-by: David Vrabel <david.vrabel@citrix.com>
Signed-off-by: David Vrabel <david.vrabel@citrix.com>

drivers/xen/Kconfig

@@ -280,4 +280,12 @@ config XEN_ACPI
 	def_bool y
 	depends on X86 && ACPI
 
+config XEN_SYMS
+       bool "Xen symbols"
+       depends on X86 && XEN_DOM0 && XENFS
+       default y if KALLSYMS
+       help
+          Exports hypervisor symbols (along with their types and addresses) via
+          /proc/xen/xensyms file, similar to /proc/kallsyms
+
 endmenu

drivers/xen/xenfs/Makefile

@@ -2,3 +2,4 @@ obj-$(CONFIG_XENFS) += xenfs.o
 
 xenfs-y			  = super.o
 xenfs-$(CONFIG_XEN_DOM0) += xenstored.o
+xenfs-$(CONFIG_XEN_SYMS) += xensyms.o

drivers/xen/xenfs/super.c

@@ -57,6 +57,9 @@ static int xenfs_fill_super(struct super_block *sb, void *data, int silent)
 		{ "privcmd", &xen_privcmd_fops, S_IRUSR|S_IWUSR },
 		{ "xsd_kva", &xsd_kva_file_ops, S_IRUSR|S_IWUSR},
 		{ "xsd_port", &xsd_port_file_ops, S_IRUSR|S_IWUSR},
+#ifdef CONFIG_XEN_SYMS
+		{ "xensyms", &xensyms_ops, S_IRUSR},
+#endif
 		{""},
 	};
 

drivers/xen/xenfs/xenfs.h

@@ -3,5 +3,6 @@
 
 extern const struct file_operations xsd_kva_file_ops;
 extern const struct file_operations xsd_port_file_ops;
+extern const struct file_operations xensyms_ops;
 
 #endif	/* _XENFS_XENBUS_H */

drivers/xen/xenfs/xensyms.c

@@ -0,0 +1,152 @@
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/seq_file.h>
+#include <linux/fs.h>
+#include <linux/mm.h>
+#include <linux/proc_fs.h>
+#include <linux/slab.h>
+#include <xen/interface/platform.h>
+#include <asm/xen/hypercall.h>
+#include <xen/xen-ops.h>
+#include "xenfs.h"
+
+
+#define XEN_KSYM_NAME_LEN 127 /* Hypervisor may have different name length */
+
+struct xensyms {
+	struct xen_platform_op op;
+	char *name;
+	uint32_t namelen;
+};
+
+/* Grab next output page from the hypervisor */
+static int xensyms_next_sym(struct xensyms *xs)
+{
+	int ret;
+	struct xenpf_symdata *symdata = &xs->op.u.symdata;
+	uint64_t symnum;
+
+	memset(xs->name, 0, xs->namelen);
+	symdata->namelen = xs->namelen;
+
+	symnum = symdata->symnum;
+
+	ret = HYPERVISOR_dom0_op(&xs->op);
+	if (ret < 0)
+		return ret;
+
+	/*
+	 * If hypervisor's symbol didn't fit into the buffer then allocate
+	 * a larger buffer and try again.
+	 */
+	if (unlikely(symdata->namelen > xs->namelen)) {
+		kfree(xs->name);
+
+		xs->namelen = symdata->namelen;
+		xs->name = kzalloc(xs->namelen, GFP_KERNEL);
+		if (!xs->name)
+			return -ENOMEM;
+
+		set_xen_guest_handle(symdata->name, xs->name);
+		symdata->symnum--; /* Rewind */
+
+		ret = HYPERVISOR_dom0_op(&xs->op);
+		if (ret < 0)
+			return ret;
+	}
+
+	if (symdata->symnum == symnum)
+		/* End of symbols */
+		return 1;
+
+	return 0;
+}
+
+static void *xensyms_start(struct seq_file *m, loff_t *pos)
+{
+	struct xensyms *xs = (struct xensyms *)m->private;
+
+	xs->op.u.symdata.symnum = *pos;
+
+	if (xensyms_next_sym(xs))
+		return NULL;
+
+	return m->private;
+}
+
+static void *xensyms_next(struct seq_file *m, void *p, loff_t *pos)
+{
+	struct xensyms *xs = (struct xensyms *)m->private;
+
+	xs->op.u.symdata.symnum = ++(*pos);
+
+	if (xensyms_next_sym(xs))
+		return NULL;
+
+	return p;
+}
+
+static int xensyms_show(struct seq_file *m, void *p)
+{
+	struct xensyms *xs = (struct xensyms *)m->private;
+	struct xenpf_symdata *symdata = &xs->op.u.symdata;
+
+	seq_printf(m, "%016llx %c %s\n", symdata->address,
+		   symdata->type, xs->name);
+
+	return 0;
+}
+
+static void xensyms_stop(struct seq_file *m, void *p)
+{
+}
+
+static const struct seq_operations xensyms_seq_ops = {
+	.start = xensyms_start,
+	.next = xensyms_next,
+	.show = xensyms_show,
+	.stop = xensyms_stop,
+};
+
+static int xensyms_open(struct inode *inode, struct file *file)
+{
+	struct seq_file *m;
+	struct xensyms *xs;
+	int ret;
+
+	ret = seq_open_private(file, &xensyms_seq_ops,
+			       sizeof(struct xensyms));
+	if (ret)
+		return ret;
+
+	m = file->private_data;
+	xs = (struct xensyms *)m->private;
+
+	xs->namelen = XEN_KSYM_NAME_LEN + 1;
+	xs->name = kzalloc(xs->namelen, GFP_KERNEL);
+	if (!xs->name) {
+		seq_release_private(inode, file);
+		return -ENOMEM;
+	}
+	set_xen_guest_handle(xs->op.u.symdata.name, xs->name);
+	xs->op.cmd = XENPF_get_symbol;
+	xs->op.u.symdata.namelen = xs->namelen;
+
+	return 0;
+}
+
+static int xensyms_release(struct inode *inode, struct file *file)
+{
+	struct seq_file *m = file->private_data;
+	struct xensyms *xs = (struct xensyms *)m->private;
+
+	kfree(xs->name);
+	return seq_release_private(inode, file);
+}
+
+const struct file_operations xensyms_ops = {
+	.open = xensyms_open,
+	.read = seq_read,
+	.llseek = seq_lseek,
+	.release = xensyms_release
+};

include/xen/interface/platform.h

@@ -474,6 +474,23 @@ struct xenpf_core_parking {
 };
 DEFINE_GUEST_HANDLE_STRUCT(xenpf_core_parking);
 
+#define XENPF_get_symbol      63
+struct xenpf_symdata {
+	/* IN/OUT variables */
+	uint32_t	namelen; /* size of 'name' buffer */
+
+	/* IN/OUT variables */
+	uint32_t	symnum; /* IN:  Symbol to read                       */
+				/* OUT: Next available symbol. If same as IN */
+				/* then  we reached the end                  */
+
+	/* OUT variables */
+	GUEST_HANDLE(char) name;
+	uint64_t	address;
+	char            type;
+};
+DEFINE_GUEST_HANDLE_STRUCT(xenpf_symdata);
+
 struct xen_platform_op {
 	uint32_t cmd;
 	uint32_t interface_version; /* XENPF_INTERFACE_VERSION */
@@ -495,6 +512,7 @@ struct xen_platform_op {
 		struct xenpf_cpu_hotadd        cpu_add;
 		struct xenpf_mem_hotadd        mem_add;
 		struct xenpf_core_parking      core_parking;
+		struct xenpf_symdata           symdata;
 		uint8_t                        pad[128];
 	} u;
 };