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>

6 files changed, 183 insertions, 0 deletions

diff --git a/drivers/xen/Kconfig b/drivers/xen/Kconfig
index 7cd226da15fe..936760455dd5 100644
--- a/drivers/xen/Kconfig
+++ b/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
diff --git a/drivers/xen/xenfs/Makefile b/drivers/xen/xenfs/Makefile
index b019865fcc56..1a83010ddffa 100644
--- a/drivers/xen/xenfs/Makefile
+++ b/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
diff --git a/drivers/xen/xenfs/super.c b/drivers/xen/xenfs/super.c
index 06092e0fe8ce..8559a71f36b1 100644
--- a/drivers/xen/xenfs/super.c
+++ b/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
                 {""},
         };
 
diff --git a/drivers/xen/xenfs/xenfs.h b/drivers/xen/xenfs/xenfs.h
index 6b80c7779c02..2c5934ea9b1e 100644
--- a/drivers/xen/xenfs/xenfs.h
+++ b/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 */
diff --git a/drivers/xen/xenfs/xensyms.c b/drivers/xen/xenfs/xensyms.c
new file mode 100644
index 000000000000..f8b12856753f
--- /dev/null
+++ b/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
+};
diff --git a/include/xen/interface/platform.h b/include/xen/interface/platform.h
index 5cc49ea8d840..8e035871360e 100644
--- a/include/xen/interface/platform.h
+++ b/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;
 };