--- /dev/null
+From ff7a167961d1b97e0e205f245f806e564d3505e7 Mon Sep 17 00:00:00 2001
+From: Ard Biesheuvel <ardb@kernel.org>
+Date: Mon, 5 Dec 2022 11:31:25 +0100
+Subject: arm64: efi: Execute runtime services from a dedicated stack
+
+From: Ard Biesheuvel <ardb@kernel.org>
+
+commit ff7a167961d1b97e0e205f245f806e564d3505e7 upstream.
+
+With the introduction of PRMT in the ACPI subsystem, the EFI rts
+workqueue is no longer the only caller of efi_call_virt_pointer() in the
+kernel. This means the EFI runtime services lock is no longer sufficient
+to manage concurrent calls into firmware, but also that firmware calls
+may occur that are not marshalled via the workqueue mechanism, but
+originate directly from the caller context.
+
+For added robustness, and to ensure that the runtime services have 8 KiB
+of stack space available as per the EFI spec, introduce a spinlock
+protected EFI runtime stack of 8 KiB, where the spinlock also ensures
+serialization between the EFI rts workqueue (which itself serializes EFI
+runtime calls) and other callers of efi_call_virt_pointer().
+
+While at it, use the stack pivot to avoid reloading the shadow call
+stack pointer from the ordinary stack, as doing so could produce a
+gadget to defeat it.
+
+Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
+Cc: Lee Jones <lee@kernel.org>
+Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
+---
+ arch/arm64/include/asm/efi.h | 3 +++
+ arch/arm64/kernel/efi-rt-wrapper.S | 13 ++++++++++++-
+ arch/arm64/kernel/efi.c | 27 +++++++++++++++++++++++++++
+ 3 files changed, 42 insertions(+), 1 deletion(-)
+
+--- a/arch/arm64/include/asm/efi.h
++++ b/arch/arm64/include/asm/efi.h
+@@ -25,6 +25,7 @@ int efi_set_mapping_permissions(struct m
+ ({ \
+ efi_virtmap_load(); \
+ __efi_fpsimd_begin(); \
++ spin_lock(&efi_rt_lock); \
+ })
+
+ #define arch_efi_call_virt(p, f, args...) \
+@@ -36,10 +37,12 @@ int efi_set_mapping_permissions(struct m
+
+ #define arch_efi_call_virt_teardown() \
+ ({ \
++ spin_unlock(&efi_rt_lock); \
+ __efi_fpsimd_end(); \
+ efi_virtmap_unload(); \
+ })
+
++extern spinlock_t efi_rt_lock;
+ efi_status_t __efi_rt_asm_wrapper(void *, const char *, ...);
+
+ #define ARCH_EFI_IRQ_FLAGS_MASK (PSR_D_BIT | PSR_A_BIT | PSR_I_BIT | PSR_F_BIT)
+--- a/arch/arm64/kernel/efi-rt-wrapper.S
++++ b/arch/arm64/kernel/efi-rt-wrapper.S
+@@ -16,6 +16,12 @@ SYM_FUNC_START(__efi_rt_asm_wrapper)
+ */
+ stp x1, x18, [sp, #16]
+
++ ldr_l x16, efi_rt_stack_top
++ mov sp, x16
++#ifdef CONFIG_SHADOW_CALL_STACK
++ str x18, [sp, #-16]!
++#endif
++
+ /*
+ * We are lucky enough that no EFI runtime services take more than
+ * 5 arguments, so all are passed in registers rather than via the
+@@ -29,6 +35,7 @@ SYM_FUNC_START(__efi_rt_asm_wrapper)
+ mov x4, x6
+ blr x8
+
++ mov sp, x29
+ ldp x1, x2, [sp, #16]
+ cmp x2, x18
+ ldp x29, x30, [sp], #32
+@@ -42,6 +49,10 @@ SYM_FUNC_START(__efi_rt_asm_wrapper)
+ * called with preemption disabled and a separate shadow stack is used
+ * for interrupts.
+ */
+- mov x18, x2
++#ifdef CONFIG_SHADOW_CALL_STACK
++ ldr_l x18, efi_rt_stack_top
++ ldr x18, [x18, #-16]
++#endif
++
+ b efi_handle_corrupted_x18 // tail call
+ SYM_FUNC_END(__efi_rt_asm_wrapper)
+--- a/arch/arm64/kernel/efi.c
++++ b/arch/arm64/kernel/efi.c
+@@ -143,3 +143,30 @@ asmlinkage efi_status_t efi_handle_corru
+ pr_err_ratelimited(FW_BUG "register x18 corrupted by EFI %s\n", f);
+ return s;
+ }
++
++DEFINE_SPINLOCK(efi_rt_lock);
++
++asmlinkage u64 *efi_rt_stack_top __ro_after_init;
++
++/* EFI requires 8 KiB of stack space for runtime services */
++static_assert(THREAD_SIZE >= SZ_8K);
++
++static int __init arm64_efi_rt_init(void)
++{
++ void *p;
++
++ if (!efi_enabled(EFI_RUNTIME_SERVICES))
++ return 0;
++
++ p = __vmalloc_node(THREAD_SIZE, THREAD_ALIGN, GFP_KERNEL,
++ NUMA_NO_NODE, &&l);
++l: if (!p) {
++ pr_warn("Failed to allocate EFI runtime stack\n");
++ clear_bit(EFI_RUNTIME_SERVICES, &efi.flags);
++ return -ENOMEM;
++ }
++
++ efi_rt_stack_top = p + THREAD_SIZE;
++ return 0;
++}
++core_initcall(arm64_efi_rt_init);
--- /dev/null
+From 18bba1843fc7f264f58c9345d00827d082f9c558 Mon Sep 17 00:00:00 2001
+From: Ard Biesheuvel <ardb@kernel.org>
+Date: Mon, 9 Jan 2023 12:41:46 +0100
+Subject: efi: rt-wrapper: Add missing include
+
+From: Ard Biesheuvel <ardb@kernel.org>
+
+commit 18bba1843fc7f264f58c9345d00827d082f9c558 upstream.
+
+Add the missing #include of asm/assembler.h, which is where the ldr_l
+macro is defined.
+
+Fixes: ff7a167961d1b97e ("arm64: efi: Execute runtime services from a dedicated stack")
+Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
+Cc: Lee Jones <lee@kernel.org>
+Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
+---
+ arch/arm64/kernel/efi-rt-wrapper.S | 1 +
+ 1 file changed, 1 insertion(+)
+
+--- a/arch/arm64/kernel/efi-rt-wrapper.S
++++ b/arch/arm64/kernel/efi-rt-wrapper.S
+@@ -4,6 +4,7 @@
+ */
+
+ #include <linux/linkage.h>
++#include <asm/assembler.h>
+
+ SYM_FUNC_START(__efi_rt_asm_wrapper)
+ stp x29, x30, [sp, #-32]!
projects / thirdparty / kernel / stable-queue.git / commitdiff
