On Fri, Oct 31, 2025 at 5:34 PM Aditya Gupta <[email protected]> wrote:
>
> + shivang
>
>
> Hello,
>
> Any reviews/comments on this ?
Oh, sorry, I forgot this patch :(
I will merge it.
>
>
> 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 <[email protected]>
> > Tested-by: Anushree Mathur <[email protected]>
> > Signed-off-by: Aditya Gupta <[email protected]>
> > ---
> > 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();
>
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