12:32 a.m.
Hi Tao,
Thanks for the review.
On 2/25/26 11:09 AM, Tao Liu wrote:
> Hi Shivang,
>
> Thanks for the fix, no any regressions found so far, so ack.
>
> Thanks,
> Tao Liu
>
> On Tue, Feb 24, 2026 at 9:25 PM Shivang Upadhyay <shivangu(a)linux.ibm.com>
wrote:
>> Commit 7636c13 ("vmcoreinfo: read vmcoreinfo using
'vmcoreinfo_data'
>> when unavailable in elf note") moved the vmcoreinfo reading to always
>> read from memory instead of relying on diskdump/netdump's local
>> handlers. This was later reverted to fix regression in X86_64 kslar
>> images.
>>
>> Reintroduce the `vmcoreinfo_read_from_memory` as fallback to
>> diskdump/netdump vmcores.
>>
>> Sometimes, vmcoreinfo_data is found within the primary format handler,
>> but the symbol is not availbale. Pairing this case with vmcoreinfo missing
>> from memory we can hit the following warning.
>>
>> $ ~/crash-dev/crash.aft vmcore vmlinux.gz
>> ...
>> GNU gdb (GDB) 16.2
>> Copyright (C) 2024 Free Software Foundation, Inc.
>> ...
>> Type "apropos word" to search for commands related to
"word"...
>>
>> crash.aft: cannot read vmcoreinfo_data <<--------------
>> KERNEL: vmlinux.gz
>> DUMPFILE: vmcore [PARTIAL DUMP]
>> ...
>> crash.aft>
>>
>> To fix this, We will only fallback to `vmcoreinfo_read_from_memory`,
>> when the vmcoreinfo_data is not found within the format handler.
>>
>> This reverts commit 72e2776caf1ca41dffcc8aba11c55c636565725b.
>>
>> Cc: Aditya Gupta <adityag(a)linux.ibm.com>
>> Cc: Tao Liu <ltao(a)redhat.com>
>> Cc: Misbah Anjum N <misanjum(a)linux.ibm.com>
>> Signed-off-by: Shivang Upadhyay <shivangu(a)linux.ibm.com>
>> ---
>> defs.h | 1 +
>> diskdump.c | 5 +++++
>> kernel.c | 17 ++++++++++++-----
>> netdump.c | 5 +++--
>> 4 files changed, 21 insertions(+), 7 deletions(-)
>>
>> diff --git a/defs.h b/defs.h
>> index cfdfa08..a6f4372 100644
>> --- a/defs.h
>> +++ b/defs.h
>> @@ -6236,6 +6236,7 @@ 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 0ff8782..fc26915 100644
>> --- a/diskdump.c
>> +++ b/diskdump.c
>> @@ -2389,6 +2389,7 @@ vmcoreinfo_read_string(const char *key)
>> off_t offset;
>> char keybuf[BUFSIZE];
>> const off_t failed = (off_t)-1;
>> + bool info_found = false;
>>
>> if (dd->header->header_version < 3)
>> return NULL;
>> @@ -2421,6 +2422,7 @@ vmcoreinfo_read_string(const char *key)
>> }
>>
>> buf[size_vmcoreinfo] = '\n';
>> + info_found = true;
>>
>> if ((p1 = strstr(buf, keybuf))) {
>> p2 = p1 + strlen(keybuf);
>> @@ -2434,6 +2436,9 @@ err:
>> if (buf)
>> free(buf);
>>
>> + if (!info_found && value_string == NULL)
>> + return vmcoreinfo_read_from_memory(key);
>> +
>> return value_string;
>> }
>>
>> diff --git a/kernel.c b/kernel.c
>> index ccc4b3d..8781d6a 100644
>> --- a/kernel.c
>> +++ b/kernel.c
>> @@ -100,7 +100,6 @@ 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);
>> @@ -12031,8 +12030,8 @@ 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;
>> @@ -12042,6 +12041,14 @@ 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:
>> @@ -12097,10 +12104,10 @@ 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 ba1c6c4..452ef72 100644
>> --- a/netdump.c
>> +++ b/netdump.c
>> @@ -1977,8 +1977,9 @@ vmcoreinfo_read_string(const char *key)
>> size_vmcoreinfo = 0;
>> }
>>
>> - if (!vmcoreinfo)
>> - return NULL;
>> + if (!vmcoreinfo) {
>> + return vmcoreinfo_read_from_memory(key);
>> + }
>>
>> /* the '+ 1' is the equal sign */
>> for (i = 0; i < (int)(size_vmcoreinfo - key_length + 1); i++) {
>> --
>> 2.52.0
>>