[v3,09/12] livepatch: Add support for modules .modinfo section metadata

Commit Message

Wieczorkiewicz, Pawel Sept. 16, 2019, 10:59 a.m. UTC

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

The hotpatch 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
hotpatch ELF file optionally as an extra step of a higher level
hotpatch build system.

The metadata section pointer and the section length is stored in the
hotpatch payload structure and is used to display the content upon
hotpatch 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]>
---
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(-)

Comments

Ross Lagerwall Sept. 19, 2019, 4:22 p.m. UTC | #1

On 9/16/19 11:59 AM, Pawel Wieczorkiewicz wrote:
> Having detailed hotpatch metadata helps to properly identify module's
> origin and version. It also allows to keep track of the history of
> hotpatch loads in the system (at least within dmesg buffer size
> limits).
> 
> The hotpatch 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
> hotpatch ELF file optionally as an extra step of a higher level
> hotpatch build system.
> 
> The metadata section pointer and the section length is stored in the
> hotpatch payload structure and is used to display the content upon
> hotpatch 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]>

Patch

diff --git a/xen/common/livepatch.c b/xen/common/livepatch.c
index 302acd3015..18935f608c 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;
 }
 
@@ -2009,6 +2041,8 @@  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 a7857d3a2e..3f088e74b2 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