[x86 setup] Handle case of improperly terminated E820 chain (2efa33f8) · Commits · 戴 / test

At least one system (a Geode system with a Digital Logic BIOS) has been found which suddenly stops reporting the SMAP signature when reading the E820 memory chain. We can't know what, exactly, broke in the BIOS, so if we detect this situation, declare the E820 data unusable and fall back to E801. Also, revert to original behavior of always probing all memory methods; that way all the memory information is available to the kernel. Signed-off-by:

H. Peter Anvin <hpa@zytor.com> Cc: Jordan Crouse <jordan.crouse@amd.com> Cc: Joerg Pommnitz <pommnitz@yahoo.com>

arch/i386/boot/memory.c

+23 −7

Original line number	Diff line number	Diff line
		@@ -20,6 +20,7 @@

		static int detect_memory_e820(void)
		{
		int count = 0;
		u32 next = 0;
		u32 size, id;
		u8 err;
		@@ -33,14 +34,24 @@ static int detect_memory_e820(void)
		"=m" (*desc)
		: "D" (desc), "a" (0xe820));

		if (err \|\| id != SMAP)
		/* Some BIOSes stop returning SMAP in the middle of
		the search loop. We don't know exactly how the BIOS
		screwed up the map at that point, we might have a
		partial map, the full map, or complete garbage, so
		just return failure. */
		if (id != SMAP) {
		count = 0;
		break;
		}

		if (err)
		break;

		boot_params.e820_entries++;
		count++;
		desc++;
		} while (next && boot_params.e820_entries < E820MAX);
		} while (next && count < E820MAX);

		return boot_params.e820_entries;
		return boot_params.e820_entries = count;
		}

		static int detect_memory_e801(void)
		@@ -89,11 +100,16 @@ static int detect_memory_88(void)

		int detect_memory(void)
		{
		int err = -1;

		if (detect_memory_e820() > 0)
		return 0;
		err = 0;

		if (!detect_memory_e801())
		return 0;
		err = 0;

		if (!detect_memory_88())
		err = 0;

		return detect_memory_88();
		return err;
		}

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