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SubjectRe: [PATCH v4] x86/boot: Use efi_setup_data for searching RSDP on kexec-ed kernel
Date
On 4/11/19 9:58 PM, Borislav Petkov wrote:
> Something like this based on your v3. I still need to figure out a
> reliable way to check in kexec_get_rsdp_addr() whether we're a kexec-ed
> kernel but other than that, it should look something like this:

Thank you.

> +static struct efi_setup_data *get_kexec_setup_data_addr(void)
> +{
> + struct setup_data *data;
> + u64 pa_data;
> +
> + pa_data = boot_params->hdr.setup_data;
> + while (pa_data) {
> + data = (struct setup_data *) pa_data;
> + if (data->type == SETUP_EFI)
> + return (struct efi_setup_data *)(pa_data + sizeof(struct setup_data));
> +
> + pa_data = data->next;
> + }
> + return NULL;
> +}

Without #ifdef CONFIG_X86_64, I got compiler warnings on 32bit build
about casting u64 to pointer.

> +/* EFI/kexec support is 64-bit only. */
> +static acpi_physical_address kexec_get_rsdp_addr(void)
> +{

We need #ifdef CONFIG_EFI to avoid build failure about undefined
__efi_get_rsdp_addr().

> + efi_system_table_64_t *systab;
> + struct efi_setup_data *esd;
> + struct efi_info *ei;
> + char *sig;
> +
> + if (!IS_ENABLED(CONFIG_X86_64))
> + return 0;
> +
> + esd = get_kexec_setup_data_addr();
> + if (!esd)
> + return EFI_SETUP_DATA_INVALID;
>
> + if (!esd->tables) {
> + debug_putstr("Wrong kexec SETUP_EFI data.\n");
> + return 0;
> + }

I think that should be the other way around:

esd = get_kexec_setup_data_addr();
if (!esd) // the kernel is not kexec booted
return 0;

if (!esd->tables) { // kexec booted but data is invalid
debug_putstr("Wrong kexec SETUP_EFI data.\n");
return EFI_SETUP_DATA_INVALID;
}

And other error returns in kexec_get_rsdp_addr() should also be
EFI_SETUP_DATA_INVALID.

> + /* Get systab from boot params. */
> + systab = (efi_system_table_64_t *) (ei->efi_systab | ((__u64)ei->efi_systab_hi << 32));

Though there is !IS_ENABLED(CONFIG_X86_64), compiler still sees this
code and emits warning on 32bit build.

To fix 32bit build warnings, non-EFI build errors and return
values from kexec_get_rsdp_addr(), the patch becomes:

diff --git a/arch/x86/boot/compressed/acpi.c b/arch/x86/boot/compressed/acpi.c
index 0ef4ad5..715a8b0 100644
--- a/arch/x86/boot/compressed/acpi.c
+++ b/arch/x86/boot/compressed/acpi.c
@@ -8,6 +8,8 @@
#include <linux/efi.h>
#include <asm/efi.h>

+#define EFI_SETUP_DATA_INVALID -1ULL
+
/*
* Longest parameter of 'acpi=' is 'copy_dsdt', plus an extra '\0'
* for termination.
@@ -44,17 +46,114 @@ static acpi_physical_address get_acpi_rsdp(void)
return addr;
}

-/* Search EFI system tables for RSDP. */
-static acpi_physical_address efi_get_rsdp_addr(void)
+static struct efi_setup_data *get_kexec_setup_data_addr(void)
+{
+#if defined(CONFIG_EFI) && defined(CONFIG_X86_64)
+ struct setup_data *data;
+ u64 pa_data;
+
+ pa_data = boot_params->hdr.setup_data;
+ while (pa_data) {
+ data = (struct setup_data *) pa_data;
+ if (data->type == SETUP_EFI)
+ return (struct efi_setup_data *)(pa_data + sizeof(struct setup_data));
+
+ pa_data = data->next;
+ }
+#endif
+ return NULL;
+}
+
+#ifdef CONFIG_EFI
+/*
+ * Search EFI system tables for RSDP. If both ACPI_20_TABLE_GUID and
+ * ACPI_TABLE_GUID are found, take the former, which has more features.
+ */
+static acpi_physical_address
+__efi_get_rsdp_addr(unsigned long config_tables, unsigned int nr_tables,
+ bool efi_64)
+{
+ acpi_physical_address rsdp_addr = 0;
+ int i;
+
+ /* Get EFI tables from systab. */
+ for (i = 0; i < nr_tables; i++) {
+ acpi_physical_address table;
+ efi_guid_t guid;
+
+ if (efi_64) {
+ efi_config_table_64_t *tbl = (efi_config_table_64_t *) config_tables + i;
+
+ guid = tbl->guid;
+ table = tbl->table;
+
+ if (!IS_ENABLED(CONFIG_X86_64) && table >> 32) {
+ debug_putstr("Error getting RSDP address: EFI config table located above 4GB.\n");
+ return 0;
+ }
+ } else {
+ efi_config_table_32_t *tbl = (efi_config_table_32_t *) config_tables + i;
+
+ guid = tbl->guid;
+ table = tbl->table;
+ }
+
+ if (!(efi_guidcmp(guid, ACPI_TABLE_GUID)))
+ rsdp_addr = table;
+ else if (!(efi_guidcmp(guid, ACPI_20_TABLE_GUID)))
+ return table;
+ }
+
+ return rsdp_addr;
+}
+#endif
+
+/* EFI/kexec support is 64-bit only. */
+static acpi_physical_address kexec_get_rsdp_addr(void)
{
acpi_physical_address rsdp_addr = 0;
+#if defined(CONFIG_EFI) && defined(CONFIG_X86_64)
+ efi_system_table_64_t *systab;
+ struct efi_setup_data *esd;
+ struct efi_info *ei;
+ char *sig;
+
+ esd = get_kexec_setup_data_addr();
+ if (!esd)
+ return 0;

+ if (!esd->tables) {
+ debug_putstr("Wrong kexec SETUP_EFI data.\n");
+ return EFI_SETUP_DATA_INVALID;
+ }
+
+ ei = &boot_params->efi_info;
+ sig = (char *)&ei->efi_loader_signature;
+ if (strncmp(sig, EFI64_LOADER_SIGNATURE, 4)) {
+ debug_putstr("Wrong kexec EFI loader signature.\n");
+ return EFI_SETUP_DATA_INVALID;
+ }
+
+ /* Get systab from boot params. */
+ systab = (efi_system_table_64_t *) (ei->efi_systab | ((__u64)ei->efi_systab_hi << 32));
+ if (!systab)
+ error("EFI system table not found in kexec boot_params.");
+
+ rsdp_addr = __efi_get_rsdp_addr((unsigned long)esd->tables, systab->nr_tables, true);
+ if (!rsdp_addr)
+ return EFI_SETUP_DATA_INVALID;
+#endif
+
+ return rsdp_addr;
+}
+
+static acpi_physical_address efi_get_rsdp_addr(void)
+{
#ifdef CONFIG_EFI
- unsigned long systab, systab_tables, config_tables;
+ unsigned long systab, config_tables;
unsigned int nr_tables;
struct efi_info *ei;
bool efi_64;
- int size, i;
char *sig;

ei = &boot_params->efi_info;
@@ -88,49 +187,20 @@ static acpi_physical_address efi_get_rsdp_addr(void)

config_tables = stbl->tables;
nr_tables = stbl->nr_tables;
- size = sizeof(efi_config_table_64_t);
} else {
efi_system_table_32_t *stbl = (efi_system_table_32_t *)systab;

config_tables = stbl->tables;
nr_tables = stbl->nr_tables;
- size = sizeof(efi_config_table_32_t);
}

if (!config_tables)
error("EFI config tables not found.");

- /* Get EFI tables from systab. */
- for (i = 0; i < nr_tables; i++) {
- acpi_physical_address table;
- efi_guid_t guid;
-
- config_tables += size;
-
- if (efi_64) {
- efi_config_table_64_t *tbl = (efi_config_table_64_t *)config_tables;
-
- guid = tbl->guid;
- table = tbl->table;
-
- if (!IS_ENABLED(CONFIG_X86_64) && table >> 32) {
- debug_putstr("Error getting RSDP address: EFI config table located above 4GB.\n");
- return 0;
- }
- } else {
- efi_config_table_32_t *tbl = (efi_config_table_32_t *)config_tables;
-
- guid = tbl->guid;
- table = tbl->table;
- }
-
- if (!(efi_guidcmp(guid, ACPI_TABLE_GUID)))
- rsdp_addr = table;
- else if (!(efi_guidcmp(guid, ACPI_20_TABLE_GUID)))
- return table;
- }
+ return __efi_get_rsdp_addr(config_tables, nr_tables, efi_64);
+#else
+ return 0;
#endif
- return rsdp_addr;
}

static u8 compute_checksum(u8 *buffer, u32 length)
@@ -221,6 +291,12 @@ acpi_physical_address get_rsdp_addr(void)
pa = boot_params->acpi_rsdp_addr;

if (!pa)
+ pa = kexec_get_rsdp_addr();
+
+ if (pa == EFI_SETUP_DATA_INVALID)
+ return 0;
+
+ if (!pa)
pa = efi_get_rsdp_addr();

if (!pa)
diff --git a/arch/x86/boot/compressed/misc.c b/arch/x86/boot/compressed/misc.c
index c0d6c56..e98f8cf 100644
--- a/arch/x86/boot/compressed/misc.c
+++ b/arch/x86/boot/compressed/misc.c
@@ -379,6 +379,7 @@ asmlinkage __visible void *extract_kernel(void *rmode, memptr heap,
debug_putaddr(output);
debug_putaddr(output_len);
debug_putaddr(kernel_total_size);
+ debug_putaddr(boot_params->acpi_rsdp_addr);

#ifdef CONFIG_X86_64
/* Report address of 32-bit trampoline */
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