[PATCH v6 17/76] x86/boot/compressed/64: Don't pre-map memory in KASLR code

Joerg Roedel
2020-08-24T08:56:20Z

With the page-fault handler in place the identity mapping can be built
on-demand. So remove the code which manually creates the mappings and
unexport/remove the functions used for it.

Signed-off-by: Joerg Roedel <jroedel@suse.de>
Reviewed-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20200724160336.5435-17-joro@8bytes.org
---
arch/x86/boot/compressed/ident_map_64.c | 6 ++----
arch/x86/boot/compressed/kaslr.c | 24 +-----------------------
arch/x86/boot/compressed/misc.h | 10 ----------
3 files changed, 3 insertions(+), 37 deletions(-)

diff --git a/arch/x86/boot/compressed/ident_map_64.c b/arch/x86/boot/compressed/ident_map_64.c
index ecf9353b064d..c63257bf8373 100644
--- a/arch/x86/boot/compressed/ident_map_64.c
+++ b/arch/x86/boot/compressed/ident_map_64.c
@@ -87,11 +87,9 @@ phys_addr_t physical_mask = (1ULL << __PHYSICAL_MASK_SHIFT) - 1;
static struct x86_mapping_info mapping_info;

/*
- * Adds the specified range to what will become the new identity mappings.
- * Once all ranges have been added, the new mapping is activated by calling
- * finalize_identity_maps() below.
+ * Adds the specified range to the identity mappings.
*/
-void add_identity_map(unsigned long start, unsigned long size)
+static void add_identity_map(unsigned long start, unsigned long size)
{
unsigned long end = start + size;

diff --git a/arch/x86/boot/compressed/kaslr.c b/arch/x86/boot/compressed/kaslr.c
index 9016f2268aa7..371b19a6357d 100644
--- a/arch/x86/boot/compressed/kaslr.c
+++ b/arch/x86/boot/compressed/kaslr.c
@@ -397,8 +397,6 @@ static void mem_avoid_init(unsigned long input, unsigned long input_size,
*/
mem_avoid[MEM_AVOID_ZO_RANGE].start = input;
mem_avoid[MEM_AVOID_ZO_RANGE].size = (output + init_size) - input;
- add_identity_map(mem_avoid[MEM_AVOID_ZO_RANGE].start,
- mem_avoid[MEM_AVOID_ZO_RANGE].size);

/* Avoid initrd. */
initrd_start = (u64)boot_params->ext_ramdisk_image << 32;
@@ -416,15 +414,11 @@ static void mem_avoid_init(unsigned long input, unsigned long input_size,
cmd_line_size = strnlen((char *)cmd_line, COMMAND_LINE_SIZE-1) + 1;
mem_avoid[MEM_AVOID_CMDLINE].start = cmd_line;
mem_avoid[MEM_AVOID_CMDLINE].size = cmd_line_size;
- add_identity_map(mem_avoid[MEM_AVOID_CMDLINE].start,
- mem_avoid[MEM_AVOID_CMDLINE].size);
}

/* Avoid boot parameters. */
mem_avoid[MEM_AVOID_BOOTPARAMS].start = (unsigned long)boot_params;
mem_avoid[MEM_AVOID_BOOTPARAMS].size = sizeof(*boot_params);
- add_identity_map(mem_avoid[MEM_AVOID_BOOTPARAMS].start,
- mem_avoid[MEM_AVOID_BOOTPARAMS].size);

/* We don't need to set a mapping for setup_data. */

@@ -433,11 +427,6 @@ static void mem_avoid_init(unsigned long input, unsigned long input_size,

/* Enumerate the immovable memory regions */
num_immovable_mem = count_immovable_mem_regions();
-
-#ifdef CONFIG_X86_VERBOSE_BOOTUP
- /* Make sure video RAM can be used. */
- add_identity_map(0, PMD_SIZE);
-#endif
}

/*
@@ -884,19 +873,8 @@ void choose_random_location(unsigned long input,
warn("Physical KASLR disabled: no suitable memory region!");
} else {
/* Update the new physical address location. */
- if (*output != random_addr) {
- add_identity_map(random_addr, output_size);
+ if (*output != random_addr)
*output = random_addr;
- }
-
- /*
- * This loads the identity mapping page table.
- * This should only be done if a new physical address
- * is found for the kernel, otherwise we should keep
- * the old page table to make it be like the "nokaslr"
- * case.
- */
- finalize_identity_maps();
}

diff --git a/arch/x86/boot/compressed/misc.h b/arch/x86/boot/compressed/misc.h
index f0e199174c5f..9840c82a39f1 100644
--- a/arch/x86/boot/compressed/misc.h
+++ b/arch/x86/boot/compressed/misc.h
@@ -98,17 +98,7 @@ static inline void choose_random_location(unsigned long input,
#endif

#ifdef CONFIG_X86_64
-void initialize_identity_maps(void);
-void add_identity_map(unsigned long start, unsigned long size);
-void finalize_identity_maps(void);
extern unsigned char _pgtable[];
-#else
-static inline void initialize_identity_maps(void)
-{ }
-static inline void add_identity_map(unsigned long start, unsigned long size)
-{ }
-static inline void finalize_identity_maps(void)
-{ }
#endif

#ifdef CONFIG_EARLY_PRINTK