[v4,09/12] livepatch: Add support for modules .modinfo section metadata

Commit Message

Wieczorkiewicz, Pawel Sept. 28, 2019, 3:13 p.m. UTC

Having detailed livepatch metadata helps to properly identify module's
origin and version. It also allows to keep track of the history of
livepatch loads in the system (at least within dmesg buffer size
limits).

The livepatch metadata are embedded in a form of .modinfo section.
Each such section contains data of the following format:
key=value\0key=value\0...key=value\0

The .modinfo section may be generated and appended to the resulting
livepatch ELF file optionally as an extra step of a higher level
livepatch build system.

The metadata section pointer and the section length is stored in the
livepatch payload structure and is used to display the content upon
livepatch apply operation.

Signed-off-by: Pawel Wieczorkiewicz <[e-mail]>
Reviewed-by: Andra-Irina Paraschiv <[e-mail]>
Reviewed-by: Bjoern Doebel <[e-mail]>
Reviewed-by: Leonard Foerster <[e-mail]>
Reviewed-by: Martin Pohlack <[e-mail]>
Reviewed-by: Norbert Manthey <[e-mail]>
Signed-off-by: Konrad Rzeszutek Wilk <[e-mail]>
Reviewed-by: Ross Lagerwall <[e-mail]>
---
Changed since v2:
  * Added .modinfo tests (Konrad)

 xen/common/livepatch.c              | 34 ++++++++++++++++++++++++++++++++++
 xen/include/xen/livepatch_payload.h |  6 ++++++
 xen/test/livepatch/Makefile         | 10 +++++++++-
 3 files changed, 49 insertions(+), 1 deletion(-)

Patch

diff --git a/xen/common/livepatch.c b/xen/common/livepatch.c
index a1d551eba3..46685f3aa8 100644
--- a/xen/common/livepatch.c
+++ b/xen/common/livepatch.c
@@ -853,6 +853,23 @@  static int prepare_payload(struct payload *payload,
 #endif
     }
 
+    sec = livepatch_elf_sec_by_name(elf, ".modinfo");
+    if ( sec )
+    {
+        if ( !section_ok(elf, sec, sizeof(*payload->metadata.data)) )
+            return -EINVAL;
+
+        payload->metadata.data = sec->load_addr;
+        payload->metadata.len = sec->sec->sh_size;
+
+        /* The metadata is required to consists of null terminated strings. */
+        if ( payload->metadata.data[payload->metadata.len - 1] != '\0' )
+        {
+            printk(XENLOG_ERR LIVEPATCH "%s: Incorrect metadata format detected\n", payload->name);
+            return -EINVAL;
+        }
+    }
+
     return 0;
 }
 
@@ -1201,6 +1218,19 @@  static int livepatch_list(struct xen_sysctl_livepatch_list *list)
  * for XEN_SYSCTL_LIVEPATCH_ACTION operation (see livepatch_action).
  */
 
+static inline void livepatch_display_metadata(const struct livepatch_metadata *metadata)
+{
+    const char *str;
+
+    if ( metadata && metadata->data && metadata->len > 0 )
+    {
+        printk(XENLOG_INFO LIVEPATCH "module metadata:\n");
+        for ( str = metadata->data; str < (metadata->data + metadata->len); str += (strlen(str) + 1) )
+            printk(XENLOG_INFO LIVEPATCH "  %s\n", str);
+    }
+
+}
+
 static int apply_payload(struct payload *data)
 {
     unsigned int i;
@@ -1233,6 +1263,8 @@  static int apply_payload(struct payload *data)
 
     arch_livepatch_revive();
 
+    livepatch_display_metadata(&data->metadata);
+
     return 0;
 }
 
@@ -2008,6 +2040,8 @@  static void livepatch_printall(unsigned char key)
                data->name, state2str(data->state), data->state, data->text_addr,
                data->rw_addr, data->ro_addr, data->pages);
 
+        livepatch_display_metadata(&data->metadata);
+
         for ( i = 0; i < data->nfuncs; i++ )
         {
             struct livepatch_func *f = &(data->funcs[i]);
diff --git a/xen/include/xen/livepatch_payload.h b/xen/include/xen/livepatch_payload.h
index ff16af0dd6..9f5f064205 100644
--- a/xen/include/xen/livepatch_payload.h
+++ b/xen/include/xen/livepatch_payload.h
@@ -33,6 +33,11 @@  struct livepatch_hooks {
     } apply, revert;
 };
 
+struct livepatch_metadata {
+    const char *data; /* Ptr to .modinfo section with ASCII data. */
+    uint32_t len;     /* Length of the metadata section. */
+};
+
 struct payload {
     uint32_t state;                      /* One of the LIVEPATCH_STATE_*. */
     int32_t rc;                          /* 0 or -XEN_EXX. */
@@ -63,6 +68,7 @@  struct payload {
     unsigned int n_load_funcs;           /* Nr of the funcs to load and execute. */
     unsigned int n_unload_funcs;         /* Nr of funcs to call durung unload. */
     char name[XEN_LIVEPATCH_NAME_SIZE];  /* Name of it. */
+    struct livepatch_metadata metadata;  /* Module meta data record */
 };
 
 /*
diff --git a/xen/test/livepatch/Makefile b/xen/test/livepatch/Makefile
index cebd3eb49c..ebb343c314 100644
--- a/xen/test/livepatch/Makefile
+++ b/xen/test/livepatch/Makefile
@@ -79,9 +79,17 @@  config.h: xen_hello_world_func.o
 xen_hello_world.o: config.h
 
 .PHONY: $(LIVEPATCH)
-$(LIVEPATCH): xen_hello_world_func.o xen_hello_world.o note.o xen_note.o
+$(LIVEPATCH): xen_hello_world_func.o xen_hello_world.o note.o xen_note.o modinfo.o
 	$(LD) $(LDFLAGS) $(build_id_linker) -r -o $(LIVEPATCH) $^
 
+.PHONY: modinfo.o
+modinfo.o:
+	(set -e; \
+	 printf "LIVEPATCH_RULEZ\0") > $@.bin
+	$(OBJCOPY) $(OBJCOPY_MAGIC) \
+		   --rename-section=.data=.modinfo,alloc,load,readonly,data,contents -S $@.bin $@
+	#rm -f $@.bin
+
 #
 # This target is only accessible if CONFIG_LIVEPATCH is defined, which
 # depends on $(build_id_linker) being available. Hence we do not