[PATCH] x86/kexec: Warn when E820 table is truncated in boot_params

[Adriano Vero]

setup_e820_entries() silently truncated the E820 memory map to
E820_MAX_ENTRIES_ZEROPAGE (128) entries when the kexec table exceeded
that limit, with no indication to the user that entries were dropped.

Add a pr_warn() when truncation occurs so that operators are aware
that memory regions beyond the 128-entry limit are not passed to the
kexec kernel via boot_params.

The underlying limitation (boot_params.e820_table is fixed at 128
entries by the x86 boot protocol) remains; this change only makes
the truncation visible.

Signed-off-by: Adriano Vero <litaliano00.contact@xxxxxxxxx>
---
 arch/x86/kernel/kexec-bzimage64.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/kexec-bzimage64.c b/arch/x86/kernel/kexec-bzimage64.c
index 5630c7dca..27a7a9e82 100644
--- a/arch/x86/kernel/kexec-bzimage64.c
+++ b/arch/x86/kernel/kexec-bzimage64.c
@@ -109,9 +109,11 @@ static int setup_e820_entries(struct boot_params *params)
 
 	nr_e820_entries = e820_table_kexec->nr_entries;
 
-	/* TODO: Pass entries more than E820_MAX_ENTRIES_ZEROPAGE in bootparams setup data */
-	if (nr_e820_entries > E820_MAX_ENTRIES_ZEROPAGE)
+	if (nr_e820_entries > E820_MAX_ENTRIES_ZEROPAGE) {
+		pr_warn("E820 table has %u entries, truncating to %u supported by boot_params\n",
+			nr_e820_entries, E820_MAX_ENTRIES_ZEROPAGE);
 		nr_e820_entries = E820_MAX_ENTRIES_ZEROPAGE;
+	}
 
 	params->e820_entries = nr_e820_entries;
 	memcpy(&params->e820_table, &e820_table_kexec->entries, nr_e820_entries*sizeof(struct e820_entry));
-- 
2.53.0