[Crash-utility] [PATCH v2] Reapply "vmcoreinfo: read vmcoreinfo using 'vmcoreinfo_data' when unavailable in elf note"

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&gt; Cc: Tao Liu <ltao(a)redhat.com&gt; Cc: Misbah Anjum N <misanjum(a)linux.ibm.com&gt; Signed-off-by: Shivang Upadhyay <shivangu(a)linux.ibm.com&gt; --- 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