[PATCH v2] x86/boot: Don't try to search RSDP from EFI when kexec-booted

[Junichi Nomura]

On 3/25/19 5:54 PM, Boris Petkov wrote:
> I'm going to repeat that again until you get it:
> 
> If the kexec kernel should continue to use efi_systab_init() then you
> should make efi_get_rsdp_addr() exit early in the kexec-ed kernel.

Do you think this one is ok? Either works for me.

[PATCH v2] x86/boot: Don't try to search RSDP from EFI when kexec-booted

Commit 3a63f70bf4c3a ("x86/boot: Early parse RSDP and save it in
boot_params") broke kexec boot on EFI systems.  efi_get_rsdp_addr()
in the early parsing code tries to search RSDP from EFI table but
whose address is virtual.

Normally kexec(1) provides physical address of config_table via boot_params
and EFI code uses that during initialization.
For the early boot code, we just exit efi_get_rsdp_addr() early if the kernel
is booted by kexec.

Fixes: 3a63f70bf4c3a ("x86/boot: Early parse RSDP and save it in boot_params")
Signed-off-by: Jun'ichi Nomura <j-nomura@xxxxxxxxxxxxx>
Cc: Chao Fan <fanc.fnst@xxxxxxxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxx>

diff --git a/arch/x86/boot/compressed/acpi.c b/arch/x86/boot/compressed/acpi.c
--- a/arch/x86/boot/compressed/acpi.c
+++ b/arch/x86/boot/compressed/acpi.c
@@ -44,6 +44,26 @@ static acpi_physical_address get_acpi_rsdp(void)
 	return addr;
 }
 
+#ifdef CONFIG_EFI
+static bool is_kexec_booted(void)
+{
+	struct setup_data *data;
+
+	/*
+	 * kexec-tools provides EFI setup data so that kexec-ed kernel
+	 * can find proper tables.
+	 */
+	data = (struct setup_data *) boot_params->hdr.setup_data;
+	while (data) {
+		if (data->type == SETUP_EFI)
+			return true;
+		data = (struct setup_data *) data->next;
+	}
+
+	return false;
+}
+#endif
+
 /* Search EFI system tables for RSDP. */
 static acpi_physical_address efi_get_rsdp_addr(void)
 {
@@ -57,6 +77,10 @@ static acpi_physical_address efi_get_rsdp_addr(void)
 	int size, i;
 	char *sig;
 
+	/* If the system is kexec-booted, poking EFI systab may not work. */
+	if (is_kexec_booted())
+		return 0;
+
 	ei = &boot_params->efi_info;
 	sig = (char *)&ei->efi_loader_signature;