From 6fdb633b0b4f6c7b5bd7be4026e0c6b4a39f6633 Mon Sep 17 00:00:00 2001 From: Will Deacon Date: Tue, 14 Nov 2017 14:07:40 +0000 Subject: [PATCH] FROMLIST: arm64: entry: Add exception trampoline page for exceptions from EL0 To allow unmapping of the kernel whilst running at EL0, we need to point the exception vectors at an entry trampoline that can map/unmap the kernel on entry/exit respectively. This patch adds the trampoline page, although it is not yet plugged into the vector table and is therefore unused. Reviewed-by: Mark Rutland Tested-by: Laura Abbott Tested-by: Shanker Donthineni Signed-off-by: Will Deacon (cherry picked from git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git commit c7b9adaf85f818d747eeff5145eb4095ccd587fb) Change-Id: Idd27ab26f1ec1db2ff756fc33ebb782201806f7c [ghackmann@google.com: adjust context] Signed-off-by: Greg Hackmann Signed-off-by: Greg Kroah-Hartman --- arch/arm64/kernel/entry.S | 85 +++++++++++++++++++++++++++++++++ arch/arm64/kernel/vmlinux.lds.S | 17 +++++++ 2 files changed, 102 insertions(+) diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S index 9f3c86da7005..08dc4b01d4da 100644 --- a/arch/arm64/kernel/entry.S +++ b/arch/arm64/kernel/entry.S @@ -29,6 +29,7 @@ #include #include #include +#include #include #include #include @@ -914,6 +915,90 @@ __ni_sys_trace: bl do_ni_syscall b __sys_trace_return +#ifdef CONFIG_UNMAP_KERNEL_AT_EL0 +/* + * Exception vectors trampoline. + */ + .pushsection ".entry.tramp.text", "ax" + + .macro tramp_map_kernel, tmp + mrs \tmp, ttbr1_el1 + sub \tmp, \tmp, #(SWAPPER_DIR_SIZE + RESERVED_TTBR0_SIZE) + bic \tmp, \tmp, #USER_ASID_FLAG + msr ttbr1_el1, \tmp + .endm + + .macro tramp_unmap_kernel, tmp + mrs \tmp, ttbr1_el1 + add \tmp, \tmp, #(SWAPPER_DIR_SIZE + RESERVED_TTBR0_SIZE) + orr \tmp, \tmp, #USER_ASID_FLAG + msr ttbr1_el1, \tmp + /* + * We avoid running the post_ttbr_update_workaround here because the + * user and kernel ASIDs don't have conflicting mappings, so any + * "blessing" as described in: + * + * http://lkml.kernel.org/r/56BB848A.6060603@caviumnetworks.com + * + * will not hurt correctness. Whilst this may partially defeat the + * point of using split ASIDs in the first place, it avoids + * the hit of invalidating the entire I-cache on every return to + * userspace. + */ + .endm + + .macro tramp_ventry, regsize = 64 + .align 7 +1: + .if \regsize == 64 + msr tpidrro_el0, x30 // Restored in kernel_ventry + .endif + tramp_map_kernel x30 + ldr x30, =vectors + prfm plil1strm, [x30, #(1b - tramp_vectors)] + msr vbar_el1, x30 + add x30, x30, #(1b - tramp_vectors) + isb + br x30 + .endm + + .macro tramp_exit, regsize = 64 + adr x30, tramp_vectors + msr vbar_el1, x30 + tramp_unmap_kernel x30 + .if \regsize == 64 + mrs x30, far_el1 + .endif + eret + .endm + + .align 11 +ENTRY(tramp_vectors) + .space 0x400 + + tramp_ventry + tramp_ventry + tramp_ventry + tramp_ventry + + tramp_ventry 32 + tramp_ventry 32 + tramp_ventry 32 + tramp_ventry 32 +END(tramp_vectors) + +ENTRY(tramp_exit_native) + tramp_exit +END(tramp_exit_native) + +ENTRY(tramp_exit_compat) + tramp_exit 32 +END(tramp_exit_compat) + + .ltorg + .popsection // .entry.tramp.text +#endif /* CONFIG_UNMAP_KERNEL_AT_EL0 */ + /* * Special system call wrappers. */ diff --git a/arch/arm64/kernel/vmlinux.lds.S b/arch/arm64/kernel/vmlinux.lds.S index 9572844c57a5..a0432ab720cd 100644 --- a/arch/arm64/kernel/vmlinux.lds.S +++ b/arch/arm64/kernel/vmlinux.lds.S @@ -46,6 +46,17 @@ jiffies = jiffies_64; *(.idmap.text) \ VMLINUX_SYMBOL(__idmap_text_end) = .; +#ifdef CONFIG_UNMAP_KERNEL_AT_EL0 +#define TRAMP_TEXT \ + . = ALIGN(PAGE_SIZE); \ + VMLINUX_SYMBOL(__entry_tramp_text_start) = .; \ + *(.entry.tramp.text) \ + . = ALIGN(PAGE_SIZE); \ + VMLINUX_SYMBOL(__entry_tramp_text_end) = .; +#else +#define TRAMP_TEXT +#endif + /* * The size of the PE/COFF section that covers the kernel image, which * runs from stext to _edata, must be a round multiple of the PE/COFF @@ -109,6 +120,7 @@ SECTIONS LOCK_TEXT HYPERVISOR_TEXT IDMAP_TEXT + TRAMP_TEXT *(.fixup) *(.gnu.warning) . = ALIGN(16); @@ -191,6 +203,11 @@ SECTIONS . += RESERVED_TTBR0_SIZE; #endif +#ifdef CONFIG_UNMAP_KERNEL_AT_EL0 + tramp_pg_dir = .; + . += PAGE_SIZE; +#endif + _end = .; STABS_DEBUG -- 2.20.1