Commit 6ee3cf6a authored by Ard Biesheuvel's avatar Ard Biesheuvel Committed by Catalin Marinas
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arm64: lds: move special code sections out of kernel exec segment 



There are a few code sections that are emitted into the kernel's
executable .text segment simply because they contain code, but are
actually never executed via this mapping, so they can happily live in a
region that gets mapped without executable permissions, reducing the
risk of being gadgetized.

Note that the kexec and hibernate region contents are always copied into
a fresh page, and so there is no need to align them as long as the
overall size of each is below 4 KiB.

Signed-off-by: default avatarArd Biesheuvel <ardb@kernel.org>
Acked-by: default avatarMark Rutland <mark.rutland@arm.com>
Link: https://lore.kernel.org/r/20220429131347.3621090-2-ardb@kernel.org


Signed-off-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
parent bc5dfb4f

arch/arm64/kernel/vmlinux.lds.S

+12 −9
Original line number Diff line number Diff line
@@ -93,7 +93,6 @@ jiffies = jiffies_64; 


#ifdef CONFIG_HIBERNATION

#define HIBERNATE_TEXT					\

	. = ALIGN(SZ_4K);				\

	__hibernate_exit_text_start = .;		\

	*(.hibernate_exit.text)				\

	__hibernate_exit_text_end = .;
@@ -103,7 +102,6 @@ jiffies = jiffies_64; 


#ifdef CONFIG_KEXEC_CORE

#define KEXEC_TEXT					\

	. = ALIGN(SZ_4K);				\

	__relocate_new_kernel_start = .;		\

	*(.kexec_relocate.text)				\

	__relocate_new_kernel_end = .;
@@ -170,9 +168,6 @@ SECTIONS 
			KPROBES_TEXT

			HYPERVISOR_TEXT

			IDMAP_TEXT

			HIBERNATE_TEXT

			KEXEC_TEXT

			TRAMP_TEXT

			*(.gnu.warning)

		. = ALIGN(16);

		*(.got)			/* Global offset table		*/
@@ -194,6 +189,14 @@ SECTIONS 


	HYPERVISOR_DATA_SECTIONS



	/* code sections that are never executed via the kernel mapping */

	.rodata.text : {

		TRAMP_TEXT

		HIBERNATE_TEXT

		KEXEC_TEXT

		. = ALIGN(PAGE_SIZE);

	}



	idmap_pg_dir = .;

	. += IDMAP_DIR_SIZE;

	idmap_pg_end = .;
@@ -337,8 +340,8 @@ ASSERT(__hyp_idmap_text_end - __hyp_idmap_text_start <= PAGE_SIZE, 
ASSERT(__idmap_text_end - (__idmap_text_start & ~(SZ_4K - 1)) <= SZ_4K,

	"ID map text too big or misaligned")

#ifdef CONFIG_HIBERNATION

ASSERT(__hibernate_exit_text_end - (__hibernate_exit_text_start & ~(SZ_4K - 1))

	<= SZ_4K, "Hibernate exit text too big or misaligned")

ASSERT(__hibernate_exit_text_end - __hibernate_exit_text_start <= SZ_4K,

       "Hibernate exit text is bigger than 4 KiB")

#endif

#ifdef CONFIG_UNMAP_KERNEL_AT_EL0

ASSERT((__entry_tramp_text_end - __entry_tramp_text_start) <= 3*PAGE_SIZE,
@@ -362,7 +365,7 @@ ASSERT(swapper_pg_dir - tramp_pg_dir == TRAMP_SWAPPER_OFFSET, 


#ifdef CONFIG_KEXEC_CORE

/* kexec relocation code should fit into one KEXEC_CONTROL_PAGE_SIZE */

ASSERT(__relocate_new_kernel_end - (__relocate_new_kernel_start & ~(SZ_4K - 1))

	<= SZ_4K, "kexec relocation code is too big or misaligned")

ASSERT(__relocate_new_kernel_end - __relocate_new_kernel_start <= SZ_4K,

       "kexec relocation code is bigger than 4 KiB")

ASSERT(KEXEC_CONTROL_PAGE_SIZE >= SZ_4K, "KEXEC_CONTROL_PAGE_SIZE is broken")

#endif