vmcoreinfo: make hwerr_data visible for debugging

If the kernel is compiled with LTO, hwerr_data symbol might be lost, and
vmcoreinfo doesn't have it dumped.  This is currently seen in some
production kernels with LTO enabled.

Remove the static qualifier from hwerr_data so that the information is
still preserved when the kernel is built with LTO.  Making hwerr_data a
global symbol ensures its debug info survives the LTO link process and
appears in kallsyms.  Also document it, so it doesn't get removed in
the future as suggested by akpm.

Link: https://lkml.kernel.org/r/[email protected]
Fixes: 3fa805c ("vmcoreinfo: track and log recoverable hardware errors")
Signed-off-by: Breno Leitao <[email protected]>
Acked-by: Baoquan He <[email protected]>
Cc: Dave Young <[email protected]>
Cc: "Luck, Tony" <[email protected]>
Cc: Omar Sandoval <[email protected]>
Cc: Shuai Xue <[email protected]>
Cc: Vivek Goyal <[email protected]>
Cc: Zhiquan Li <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

Author: leitao

kernel/vmcore_info.c

@@ -36,7 +36,11 @@ struct hwerr_info {
 	time64_t timestamp;
 };
 
-static struct hwerr_info hwerr_data[HWERR_RECOV_MAX];
+/*
+ * The hwerr_data[] array is declared with global scope so that it remains
+ * accessible to vmcoreinfo even when Link Time Optimization (LTO) is enabled.
+ */
+struct hwerr_info hwerr_data[HWERR_RECOV_MAX];
 
 Elf_Word *append_elf_note(Elf_Word *buf, char *name, unsigned int type,
 			  void *data, size_t data_len)