[PATCH 7/8] x86/boot: Map memory explicitly

Evgeniy Baskov
2022-08-01T16:39:36Z

Implicit mappings hide possible memory errors, e.g. allocations for
ACPI tables were not included in boot page table size.

Replace all implicit mappings from page fault handler with
explicit mappings.

Signed-off-by: Evgeniy Baskov <baskov@ispras.ru>

diff --git a/arch/x86/boot/compressed/acpi.c b/arch/x86/boot/compressed/acpi.c
index 9caf89063e77..633ac56262ee 100644
--- a/arch/x86/boot/compressed/acpi.c
+++ b/arch/x86/boot/compressed/acpi.c
@@ -93,6 +93,8 @@ static u8 *scan_mem_for_rsdp(u8 *start, u32 length)

end = start + length;

+ kernel_add_identity_map((unsigned long)start, (unsigned long)end, 0);
+
/* Search from given start address for the requested length */
for (address = start; address < end; address += ACPI_RSDP_SCAN_STEP) {
/*
@@ -128,6 +130,9 @@ static acpi_physical_address bios_get_rsdp_addr(void)
unsigned long address;
u8 *rsdp;

+ kernel_add_identity_map((unsigned long)ACPI_EBDA_PTR_LOCATION,
+ (unsigned long)ACPI_EBDA_PTR_LOCATION + 2, 0);
+
/* Get the location of the Extended BIOS Data Area (EBDA) */
address = *(u16 *)ACPI_EBDA_PTR_LOCATION;
address <<= 4;
@@ -215,6 +220,9 @@ static unsigned long get_acpi_srat_table(void)
if (!rsdp)
return 0;

+ kernel_add_identity_map((unsigned long)rsdp,
+ (unsigned long)(rsdp + 1), 0);
+
/* Get ACPI root table from RSDP.*/
if (!(cmdline_find_option("acpi", arg, sizeof(arg)) == 4 &&
!strncmp(arg, "rsdt", 4)) &&
@@ -235,6 +243,9 @@ static unsigned long get_acpi_srat_table(void)
if (len < sizeof(struct acpi_table_header) + size)
return 0;

+ kernel_add_identity_map((unsigned long)header,
+ (unsigned long)header + len, 0);
+
num_entries = (len - sizeof(struct acpi_table_header)) / size;
entry = (u8 *)(root_table + sizeof(struct acpi_table_header));

@@ -247,8 +258,16 @@ static unsigned long get_acpi_srat_table(void)
if (acpi_table) {
header = (struct acpi_table_header *)acpi_table;

- if (ACPI_COMPARE_NAMESEG(header->signature, ACPI_SIG_SRAT))
+ kernel_add_identity_map(acpi_table,
+ acpi_table + sizeof(*header),
+ 0);
+
+ if (ACPI_COMPARE_NAMESEG(header->signature, ACPI_SIG_SRAT)) {
+ kernel_add_identity_map(acpi_table,
+ acpi_table + header->length,
+ 0);
return acpi_table;
+ }
}
entry += size;
}
diff --git a/arch/x86/boot/compressed/efi.c b/arch/x86/boot/compressed/efi.c
index 6edd034b0b30..ce70103fbbc0 100644
--- a/arch/x86/boot/compressed/efi.c
+++ b/arch/x86/boot/compressed/efi.c
@@ -57,10 +57,14 @@ enum efi_type efi_get_type(struct boot_params *bp)
*/
unsigned long efi_get_system_table(struct boot_params *bp)
{
- unsigned long sys_tbl_pa;
+ static unsigned long sys_tbl_pa __section(".data");
struct efi_info *ei;
+ unsigned long sys_tbl_size;
enum efi_type et;

+ if (sys_tbl_pa)
+ return sys_tbl_pa;
+
/* Get systab from boot params. */
ei = &bp->efi_info;
#ifdef CONFIG_X86_64
@@ -73,6 +77,13 @@ unsigned long efi_get_system_table(struct boot_params *bp)
return 0;
}

+ if (efi_get_type(bp) == EFI_TYPE_64)
+ sys_tbl_size = sizeof(efi_system_table_64_t);
+ else
+ sys_tbl_size = sizeof(efi_system_table_32_t);
+
+ kernel_add_identity_map(sys_tbl_pa, sys_tbl_pa + sys_tbl_size, 0);
+
return sys_tbl_pa;
}

@@ -92,6 +103,10 @@ static struct efi_setup_data *get_kexec_setup_data(struct boot_params *bp,

pa_data = bp->hdr.setup_data;
while (pa_data) {
+ unsigned long pa_data_end = pa_data + sizeof(struct setup_data)
+ + sizeof(struct efi_setup_data);
+ kernel_add_identity_map(pa_data, pa_data_end, 0);
+
data = (struct setup_data *)pa_data;
if (data->type == SETUP_EFI) {
esd = (struct efi_setup_data *)(pa_data + sizeof(struct setup_data));
@@ -160,6 +175,8 @@ int efi_get_conf_table(struct boot_params *bp, unsigned long *cfg_tbl_pa,
return -EINVAL;
}

+ kernel_add_identity_map(*cfg_tbl_pa, *cfg_tbl_pa + *cfg_tbl_len, 0);
+
return 0;
}

diff --git a/arch/x86/boot/compressed/kaslr.c b/arch/x86/boot/compressed/kaslr.c
index 4a3f223973f4..073c7cfbd785 100644
--- a/arch/x86/boot/compressed/kaslr.c
+++ b/arch/x86/boot/compressed/kaslr.c
@@ -687,6 +687,8 @@ process_efi_entries(unsigned long minimum, unsigned long image_size)
u32 nr_desc;
int i;

+ kernel_add_identity_map((unsigned long)e, (unsigned long)(e + 1), 0);
+
signature = (char *)&e->efi_loader_signature;
if (strncmp(signature, EFI32_LOADER_SIGNATURE, 4) &&
strncmp(signature, EFI64_LOADER_SIGNATURE, 4))
@@ -703,6 +705,8 @@ process_efi_entries(unsigned long minimum, unsigned long image_size)
pmap = (e->efi_memmap | ((__u64)e->efi_memmap_hi << 32));
#endif

+ kernel_add_identity_map(pmap, pmap + e->efi_memmap_size, 0);
+
nr_desc = e->efi_memmap_size / e->efi_memdesc_size;
for (i = 0; i < nr_desc; i++) {
md = efi_early_memdesc_ptr(pmap, e->efi_memdesc_size, i);
--
2.35.1