kernel: vmcoreinfo: allocate vmcoreinfo_data based on VMCOREINFO_BYTES

Patch series "vmcoreinfo: support VMCOREINFO_BYTES larger than PAGE_SIZE".

VMCOREINFO_BYTES is defined as a configurable size, but multiple
code paths implicitly assume it always fits into a single page.

This series removes that assumption by allocating and mapping
vmcoreinfo based on its actual size.

Patch 1 updates vmcoreinfo allocation to use get_order(VMCOREINFO_BYTES).
Patch 2 updates crash kernel handling to correctly allocate and map
multiple pages when copying vmcoreinfo.

This makes vmcoreinfo size consistent across the kernel and avoids
future breakage if VMCOREINFO_BYTES grows.

(No functional change when VMCOREINFO_BYTES == PAGE_SIZE.)

This patch (of 2):

VMCOREINFO_BYTES defines the size of vmcoreinfo data, but the current
implementation assumes a single page allocation.

Allocate vmcoreinfo_data using get_order(VMCOREINFO_BYTES) so that
vmcoreinfo can safely grow beyond PAGE_SIZE.

This avoids hidden assumptions and keeps vmcoreinfo size consistent across
the kernel.

Link: https://lkml.kernel.org/r/20251216132801.807260-1-pnina.feder@mobileye.com
Link: https://lkml.kernel.org/r/20251216132801.807260-2-pnina.feder@mobileye.com
Signed-off-by: Pnina Feder <pnina.feder@mobileye.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Baoquan He <bhe@redhat.com>
Cc: Dave Young <dyoung@redhat.com>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/kernel/vmcore_info.c b/kernel/vmcore_info.c
index fe9bf8db1922e6a269e3d4034b238266751dcbcb..22b3205dd4dc5bbcfecbc9329c4f1b3e561b0c78 100644 (file)
--- a/kernel/vmcore_info.c
+++ b/kernel/vmcore_info.c
@@ -137,7 +137,9 @@ EXPORT_SYMBOL_GPL(hwerr_log_error_type);
 
 static int __init crash_save_vmcoreinfo_init(void)
 {
-       vmcoreinfo_data = (unsigned char *)get_zeroed_page(GFP_KERNEL);
+       int order;
+       order = get_order(VMCOREINFO_BYTES);
+       vmcoreinfo_data = (unsigned char *)__get_free_pages(GFP_KERNEL | __GFP_ZERO, order);
        if (!vmcoreinfo_data) {
                pr_warn("Memory allocation for vmcoreinfo_data failed\n");
                return -ENOMEM;
@@ -146,7 +148,7 @@ static int __init crash_save_vmcoreinfo_init(void)
        vmcoreinfo_note = alloc_pages_exact(VMCOREINFO_NOTE_SIZE,
                                                GFP_KERNEL | __GFP_ZERO);
        if (!vmcoreinfo_note) {
-               free_page((unsigned long)vmcoreinfo_data);
+               free_pages((unsigned long)vmcoreinfo_data, order);
                vmcoreinfo_data = NULL;
                pr_warn("Memory allocation for vmcoreinfo_note failed\n");
                return -ENOMEM;