The following commit has been merged into the x86/boot branch of tip:
Commit-ID: 4d8e5a682be4136758a8beadd5aecc7f76276504
Gitweb: https://git.kernel.org/tip/4d8e5a682be4136758a8beadd5aecc7f76276504
Author: Ingo Molnar <mingo@kernel.org>
AuthorDate: Thu, 15 May 2025 14:05:21 +02:00
Committer: Ingo Molnar <mingo@kernel.org>
CommitterDate: Sun, 14 Dec 2025 09:19:37 +01:00
x86/boot/e820: Print gaps in the E820 table
Gaps in the E820 table are not obvious at a glance and can
easily be overlooked.
Print out gaps in the E820 table:
Before:
BIOS-provided physical RAM map:
BIOS-e820: [mem 0x0000000000000000-0x000000000009fbff] usable
BIOS-e820: [mem 0x000000000009fc00-0x000000000009ffff] reserved
BIOS-e820: [mem 0x00000000000f0000-0x00000000000fffff] reserved
BIOS-e820: [mem 0x0000000000100000-0x000000007ffdbfff] usable
BIOS-e820: [mem 0x000000007ffdc000-0x000000007fffffff] reserved
BIOS-e820: [mem 0x00000000b0000000-0x00000000bfffffff] reserved
BIOS-e820: [mem 0x00000000fed1c000-0x00000000fed1ffff] reserved
BIOS-e820: [mem 0x00000000feffc000-0x00000000feffffff] reserved
BIOS-e820: [mem 0x00000000fffc0000-0x00000000ffffffff] reserved
BIOS-e820: [mem 0x000000fd00000000-0x000000ffffffffff] reserved
After:
BIOS-provided physical RAM map:
BIOS-e820: [mem 0x0000000000000000-0x000000000009fbff] usable
BIOS-e820: [mem 0x000000000009fc00-0x000000000009ffff] reserved
BIOS-e820: [gap 0x00000000000a0000-0x00000000000effff]
BIOS-e820: [mem 0x00000000000f0000-0x00000000000fffff] reserved
BIOS-e820: [mem 0x0000000000100000-0x000000007ffdbfff] usable
BIOS-e820: [mem 0x000000007ffdc000-0x000000007fffffff] reserved
BIOS-e820: [gap 0x0000000080000000-0x00000000afffffff]
BIOS-e820: [mem 0x00000000b0000000-0x00000000bfffffff] reserved
BIOS-e820: [gap 0x00000000c0000000-0x00000000fed1bfff]
BIOS-e820: [mem 0x00000000fed1c000-0x00000000fed1ffff] reserved
BIOS-e820: [gap 0x00000000fed20000-0x00000000feffbfff]
BIOS-e820: [mem 0x00000000feffc000-0x00000000feffffff] reserved
BIOS-e820: [gap 0x00000000ff000000-0x00000000fffbffff]
BIOS-e820: [mem 0x00000000fffc0000-0x00000000ffffffff] reserved
BIOS-e820: [gap 0x0000000100000000-0x000000fcffffffff]
BIOS-e820: [mem 0x000000fd00000000-0x000000ffffffffff] reserved
Also warn about badly ordered E820 table entries:
BUG: out of order E820 entry!
( this is printed before the entry is printed, so there's no need to
print any additional data with the warning. )
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: H . Peter Anvin <hpa@zytor.com>
Cc: Andy Shevchenko <andy@kernel.org>
Cc: Arnd Bergmann <arnd@kernel.org>
Cc: David Woodhouse <dwmw@amazon.co.uk>
Cc: Juergen Gross <jgross@suse.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Paul Menzel <pmenzel@molgen.mpg.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://patch.msgid.link/20250515120549.2820541-6-mingo@kernel.org
---
arch/x86/kernel/e820.c | 22 ++++++++++++++++++----
1 file changed, 18 insertions(+), 4 deletions(-)
diff --git a/arch/x86/kernel/e820.c b/arch/x86/kernel/e820.c
index 09c712a..460645d 100644
--- a/arch/x86/kernel/e820.c
+++ b/arch/x86/kernel/e820.c
@@ -202,18 +202,32 @@ static void __init e820_print_type(enum e820_type type)
static void __init e820__print_table(const char *who)
{
+ u64 range_end_prev = 0;
int i;
for (i = 0; i < e820_table->nr_entries; i++) {
struct e820_entry *entry = e820_table->entries + i;
+ u64 range_start, range_end;
- pr_info("%s: [mem %#018Lx-%#018Lx] ",
- who,
- entry->addr,
- entry->addr + entry->size-1);
+ range_start = entry->addr;
+ range_end = entry->addr + entry->size;
+ /* Out of order E820 maps should not happen: */
+ if (range_start < range_end_prev)
+ pr_info(FW_BUG "out of order E820 entry!\n");
+
+ if (range_start > range_end_prev) {
+ pr_info("%s: [gap %#018Lx-%#018Lx]\n",
+ who,
+ range_end_prev,
+ range_start-1);
+ }
+
+ pr_info("%s: [mem %#018Lx-%#018Lx] ", who, range_start, range_end-1);
e820_print_type(entry->type);
pr_cont("\n");
+
+ range_end_prev = range_end;
}
}