+ shivang Hello, Any reviews/comments on this ?

Thanks, - Aditya G On 18/09/25 18:24, Aditya Gupta wrote: > 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 > > Note though, till GDB interface is not initialised, reading from > vmcoreinfo_data symbol is not done, so behaviour is same as previously > with no vmcoreinfo (only till GDB interface is not initialised) > > 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(a)linux.ibm.com&gt; > Tested-by: Anushree Mathur <anushree.mathur(a)linux.ibm.com&gt; > Signed-off-by: Aditya Gupta <adityag(a)linux.ibm.com&gt; > --- > Changelog > ========= > > v2: > + rename 'is_vmcoreinfo_empty' to netdump/diskdump variants in > netdump.c and diskdump.c respectively > --- > --- > defs.h | 1 + > diskdump.c | 18 ++++++++++++++++++ > kernel.c | 17 ++++++++++++----- > netdump.c | 19 +++++++++++++++++++ > 4 files changed, 50 insertions(+), 5 deletions(-) > > diff --git a/defs.h b/defs.h > index 156ac0232906..d28484ec44f9 100644 > --- a/defs.h > +++ b/defs.h > @@ -6218,6 +6218,7 @@ 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..de907551153d 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_diskdump_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 > + * the vmcoreinfo from memory, using "vmcoreinfo_data" symbol > + */ > + if (is_diskdump_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 e4213d7a663e..0e17874c503c 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); > @@ -11892,8 +11891,8 @@ 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; > @@ -11903,6 +11902,14 @@ vmcoreinfo_read_string(const char *key) > > buf = value_string = NULL; > > + if (!(pc->flags & GDB_INIT)) { > + /* > + * GDB interface hasn't been initialised yet, so can't > + * access vmcoreinfo_data > + */ > + return NULL; > + } > + > switch (get_symbol_type("vmcoreinfo_data", NULL, NULL)) > { > case TYPE_CODE_PTR: > @@ -11958,10 +11965,10 @@ 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 c7ff009e7f90..69100a92e067 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_netdump_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 > + * the vmcoreinfo from memory, using "vmcoreinfo_data" symbol > + */ > + if (is_netdump_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();