Few vmcores don't have vmcoreinfo elf note, such as those created using
virsh-dump.

On architectures such as PowerPC64, vmcoreinfo is mandatory to fetch the
first_vmalloc_address, for vmcores of upstream linux, since crash-utility commit:

    commit 5b24e363a898 ("get vmalloc start address from vmcoreinfo")

Try reading from the 'vmcoreinfo_data' symbol instead, if the vmcoreinfo
crash tries to read in case of diskdump/netdump is empty/missing.

The approach to read 'vmcoreinfo_data' was used for a live kernel, which can be
reused in the case of missing vmcoreinfo note also, as the
'vmcoreinfo_data' symbol is available with vmcore too

Hence rename 'vmcoreinfo_read_string' in kernel.c to
'vmcoreinfo_read_from_memory', and use it in netdump.c and diskdump.c
too.

Reported-by: Anushree Mathur <anushree.mathur@linux.ibm.com>
Tested-by: Anushree Mathur <anushree.mathur@linux.ibm.com>
Signed-off-by: Aditya Gupta <adityag@linux.ibm.com>
---
 defs.h     |  1 +
 diskdump.c | 18 ++++++++++++++++++
 kernel.c   |  9 ++++-----
 netdump.c  | 19 +++++++++++++++++++
 4 files changed, 42 insertions(+), 5 deletions(-)

diff --git a/defs.h b/defs.h
index 2231cb68b804..910264e12314 100644
--- a/defs.h
+++ b/defs.h
@@ -6166,6 +6166,7 @@ void dump_kernel_table(int);
 void dump_bt_info(struct bt_info *, char *where);
 void dump_log(int);
 void parse_kernel_version(char *);
+char *vmcoreinfo_read_from_memory(const char *);

 #define LOG_LEVEL(v) ((v) & 0x07)
 #define SHOW_LOG_LEVEL    (0x1)
diff --git a/diskdump.c b/diskdump.c
index ce3cbb7b12dd..30d0c87f84c1 100644
--- a/diskdump.c
+++ b/diskdump.c
@@ -1041,6 +1041,13 @@ pfn_to_pos(ulong pfn)
        return desc_pos;
 }

+/**
+ * Check if vmcoreinfo in vmcore is missing/empty
+ */
+static bool is_vmcoreinfo_empty(void)
+{
+       return (dd->sub_header_kdump->size_vmcoreinfo == 0);
+}

 /*
  *  Determine whether a file is a diskdump creation, and if TRUE,
@@ -1088,6 +1095,17 @@ is_diskdump(char *file)

        pc->read_vmcoreinfo = vmcoreinfo_read_string;

+       /*
+        * vmcoreinfo can be empty in case of dump collected via virsh-dump
+        *
+        * check if vmcoreinfo is not available in vmcore, and try to read
+        * thev vmcore from memory, using "vmcoreinfo_data" symbol
+        */
+       if (is_vmcoreinfo_empty()) {
+               error(WARNING, "vmcoreinfo is empty, will read from symbols\n");
+               pc->read_vmcoreinfo = vmcoreinfo_read_from_memory;
+       }
+
        if ((pc->flags2 & GET_LOG) && KDUMP_CMPRS_VALID()) {
                pc->dfd = dd->dfd;
                pc->readmem = read_diskdump;
diff --git a/kernel.c b/kernel.c
index adb19ad8725d..7d26a5c5a0a1 100644
--- a/kernel.c
+++ b/kernel.c
@@ -99,7 +99,6 @@ static ulong dump_audit_skb_queue(ulong);
 static ulong __dump_audit(char *);
 static void dump_audit(void);
 static void dump_printk_safe_seq_buf(int);
-static char *vmcoreinfo_read_string(const char *);
 static void check_vmcoreinfo(void);
 static int is_pvops_xen(void);
 static int get_linux_banner_from_vmlinux(char *, size_t);
@@ -11852,8 +11851,8 @@ dump_printk_safe_seq_buf(int msg_flags)
  * Returns a string (that has to be freed by the caller) that contains the
  * value for key or NULL if the key has not been found.
  */
-static char *
-vmcoreinfo_read_string(const char *key)
+char *
+vmcoreinfo_read_from_memory(const char *key)
 {
        char *buf, *value_string, *p1, *p2;
        size_t value_length;
@@ -11918,10 +11917,10 @@ check_vmcoreinfo(void)
                switch (get_symbol_type("vmcoreinfo_data", NULL, NULL))
                {
                case TYPE_CODE_PTR:
-                       pc->read_vmcoreinfo = vmcoreinfo_read_string;
+                       pc->read_vmcoreinfo = vmcoreinfo_read_from_memory;
                        break;
                case TYPE_CODE_ARRAY:
-                       pc->read_vmcoreinfo = vmcoreinfo_read_string;
+                       pc->read_vmcoreinfo = vmcoreinfo_read_from_memory;
                        break;
                }
        }
diff --git a/netdump.c b/netdump.c
index b4e2a5cb2037..c69c7a1e80db 100644
--- a/netdump.c
+++ b/netdump.c
@@ -111,6 +111,14 @@ map_cpus_to_prstatus(void)
        FREEBUF(nt_ptr);
 }

+/**
+ * Check if vmcoreinfo in vmcore is missing/empty
+ */
+static bool is_vmcoreinfo_empty(void)
+{
+       return (nd->size_vmcoreinfo == 0);
+}
+
 /*
  *  Determine whether a file is a netdump/diskdump/kdump creation,
  *  and if TRUE, initialize the vmcore_data structure.
@@ -464,6 +472,17 @@ is_netdump(char *file, ulong source_query)

        pc->read_vmcoreinfo = vmcoreinfo_read_string;

+       /*
+        * vmcoreinfo can be empty in case of dump collected via virsh-dump
+        *
+        * check if vmcoreinfo is not available in vmcore, and try to read
+        * thev vmcore from memory, using "vmcoreinfo_data" symbol
+        */
+       if (is_vmcoreinfo_empty()) {
+               error(WARNING, "vmcoreinfo is empty, will read from symbols\n");
+               pc->read_vmcoreinfo = vmcoreinfo_read_from_memory;
+       }
+
        if ((source_query == KDUMP_LOCAL) &&
            (pc->flags2 & GET_OSRELEASE))
                kdump_get_osrelease();
--
2.46.2