arm64: scs: use vmapped IRQ and SDEI shadow stacks

Use scs_alloc() to allocate also IRQ and SDEI shadow stacks instead of
using statically allocated stacks.

Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Acked-by: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20201130233442.2562064-3-samitolvanen@google.com
[will: Move CONFIG_SHADOW_CALL_STACK check into init_irq_scs()]
Signed-off-by: Will Deacon <will@kernel.org>

diff --git a/arch/arm64/kernel/Makefile b/arch/arm64/kernel/Makefile
index bbaf0bc..86364ab 100644 (file)
--- a/arch/arm64/kernel/Makefile
+++ b/arch/arm64/kernel/Makefile
@@ -58,7 +58,6 @@ obj-$(CONFIG_CRASH_DUMP)              += crash_dump.o
 obj-$(CONFIG_CRASH_CORE)               += crash_core.o
 obj-$(CONFIG_ARM_SDE_INTERFACE)                += sdei.o
 obj-$(CONFIG_ARM64_PTR_AUTH)           += pointer_auth.o
-obj-$(CONFIG_SHADOW_CALL_STACK)                += scs.o
 obj-$(CONFIG_ARM64_MTE)                        += mte.o
 
 obj-y                                  += vdso/ probes/

diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
index b295fb9..5c2ac4b 100644 (file)
--- a/arch/arm64/kernel/entry.S
+++ b/arch/arm64/kernel/entry.S
@@ -441,7 +441,7 @@ SYM_CODE_END(__swpan_exit_el0)
 
 #ifdef CONFIG_SHADOW_CALL_STACK
        /* also switch to the irq shadow stack */
-       adr_this_cpu scs_sp, irq_shadow_call_stack, x26
+       ldr_this_cpu scs_sp, irq_shadow_call_stack_ptr, x26
 #endif
 
 9998:
@@ -1097,9 +1097,9 @@ SYM_CODE_START(__sdei_asm_handler)
 #ifdef CONFIG_SHADOW_CALL_STACK
        /* Use a separate shadow call stack for normal and critical events */
        cbnz    w4, 3f
-       adr_this_cpu dst=scs_sp, sym=sdei_shadow_call_stack_normal, tmp=x6
+       ldr_this_cpu dst=scs_sp, sym=sdei_shadow_call_stack_normal_ptr, tmp=x6
        b       4f
-3:     adr_this_cpu dst=scs_sp, sym=sdei_shadow_call_stack_critical, tmp=x6
+3:     ldr_this_cpu dst=scs_sp, sym=sdei_shadow_call_stack_critical_ptr, tmp=x6
 4:
 #endif
 

diff --git a/arch/arm64/kernel/irq.c b/arch/arm64/kernel/irq.c
index 9cf2fb8..ac54c21 100644 (file)
--- a/arch/arm64/kernel/irq.c
+++ b/arch/arm64/kernel/irq.c
@@ -17,6 +17,7 @@
 #include <linux/init.h>
 #include <linux/irqchip.h>
 #include <linux/kprobes.h>
+#include <linux/scs.h>
 #include <linux/seq_file.h>
 #include <linux/vmalloc.h>
 #include <asm/daifflags.h>
@@ -27,6 +28,25 @@ DEFINE_PER_CPU(struct nmi_ctx, nmi_contexts);
 
 DEFINE_PER_CPU(unsigned long *, irq_stack_ptr);
 
+
+DECLARE_PER_CPU(unsigned long *, irq_shadow_call_stack_ptr);
+
+#ifdef CONFIG_SHADOW_CALL_STACK
+DEFINE_PER_CPU(unsigned long *, irq_shadow_call_stack_ptr);
+#endif
+
+static void init_irq_scs(void)
+{
+       int cpu;
+
+       if (!IS_ENABLED(CONFIG_SHADOW_CALL_STACK))
+               return;
+
+       for_each_possible_cpu(cpu)
+               per_cpu(irq_shadow_call_stack_ptr, cpu) =
+                       scs_alloc(cpu_to_node(cpu));
+}
+
 #ifdef CONFIG_VMAP_STACK
 static void init_irq_stacks(void)
 {
@@ -54,6 +74,7 @@ static void init_irq_stacks(void)
 void __init init_IRQ(void)
 {
        init_irq_stacks();
+       init_irq_scs();
        irqchip_init();
        if (!handle_arch_irq)
                panic("No interrupt controller found.");

diff --git a/arch/arm64/kernel/scs.c b/arch/arm64/kernel/scs.c
deleted file mode 100644 (file)
index e8f7ff4..0000000
--- a/arch/arm64/kernel/scs.c
+++ /dev/null
@@ -1,16 +0,0 @@
-// SPDX-License-Identifier: GPL-2.0
-/*
- * Shadow Call Stack support.
- *
- * Copyright (C) 2019 Google LLC
- */
-
-#include <linux/percpu.h>
-#include <linux/scs.h>
-
-DEFINE_SCS(irq_shadow_call_stack);
-
-#ifdef CONFIG_ARM_SDE_INTERFACE
-DEFINE_SCS(sdei_shadow_call_stack_normal);
-DEFINE_SCS(sdei_shadow_call_stack_critical);
-#endif

diff --git a/arch/arm64/kernel/sdei.c b/arch/arm64/kernel/sdei.c
index 7689f20..d12fd78 100644 (file)
--- a/arch/arm64/kernel/sdei.c
+++ b/arch/arm64/kernel/sdei.c
@@ -7,6 +7,7 @@
 #include <linux/hardirq.h>
 #include <linux/irqflags.h>
 #include <linux/sched/task_stack.h>
+#include <linux/scs.h>
 #include <linux/uaccess.h>
 
 #include <asm/alternative.h>
@@ -37,6 +38,14 @@ DEFINE_PER_CPU(unsigned long *, sdei_stack_normal_ptr);
 DEFINE_PER_CPU(unsigned long *, sdei_stack_critical_ptr);
 #endif
 
+DECLARE_PER_CPU(unsigned long *, sdei_shadow_call_stack_normal_ptr);
+DECLARE_PER_CPU(unsigned long *, sdei_shadow_call_stack_critical_ptr);
+
+#ifdef CONFIG_SHADOW_CALL_STACK
+DEFINE_PER_CPU(unsigned long *, sdei_shadow_call_stack_normal_ptr);
+DEFINE_PER_CPU(unsigned long *, sdei_shadow_call_stack_critical_ptr);
+#endif
+
 static void _free_sdei_stack(unsigned long * __percpu *ptr, int cpu)
 {
        unsigned long *p;
@@ -90,6 +99,59 @@ static int init_sdei_stacks(void)
        return err;
 }
 
+static void _free_sdei_scs(unsigned long * __percpu *ptr, int cpu)
+{
+       void *s;
+
+       s = per_cpu(*ptr, cpu);
+       if (s) {
+               per_cpu(*ptr, cpu) = NULL;
+               scs_free(s);
+       }
+}
+
+static void free_sdei_scs(void)
+{
+       int cpu;
+
+       for_each_possible_cpu(cpu) {
+               _free_sdei_scs(&sdei_shadow_call_stack_normal_ptr, cpu);
+               _free_sdei_scs(&sdei_shadow_call_stack_critical_ptr, cpu);
+       }
+}
+
+static int _init_sdei_scs(unsigned long * __percpu *ptr, int cpu)
+{
+       void *s;
+
+       s = scs_alloc(cpu_to_node(cpu));
+       if (!s)
+               return -ENOMEM;
+       per_cpu(*ptr, cpu) = s;
+
+       return 0;
+}
+
+static int init_sdei_scs(void)
+{
+       int cpu;
+       int err = 0;
+
+       for_each_possible_cpu(cpu) {
+               err = _init_sdei_scs(&sdei_shadow_call_stack_normal_ptr, cpu);
+               if (err)
+                       break;
+               err = _init_sdei_scs(&sdei_shadow_call_stack_critical_ptr, cpu);
+               if (err)
+                       break;
+       }
+
+       if (err)
+               free_sdei_scs();
+
+       return err;
+}
+
 static bool on_sdei_normal_stack(unsigned long sp, struct stack_info *info)
 {
        unsigned long low = (unsigned long)raw_cpu_read(sdei_stack_normal_ptr);
@@ -138,6 +200,14 @@ unsigned long sdei_arch_get_entry_point(int conduit)
                        return 0;
        }
 
+       if (IS_ENABLED(CONFIG_SHADOW_CALL_STACK)) {
+               if (init_sdei_scs()) {
+                       if (IS_ENABLED(CONFIG_VMAP_STACK))
+                               free_sdei_stacks();
+                       return 0;
+               }
+       }
+
        sdei_exit_mode = (conduit == SMCCC_CONDUIT_HVC) ? SDEI_EXIT_HVC : SDEI_EXIT_SMC;
 
 #ifdef CONFIG_UNMAP_KERNEL_AT_EL0

diff --git a/include/linux/scs.h b/include/linux/scs.h
index 2a506c2..18122d9 100644 (file)
--- a/include/linux/scs.h
+++ b/include/linux/scs.h
@@ -22,10 +22,6 @@
 /* An illegal pointer value to mark the end of the shadow stack. */
 #define SCS_END_MAGIC          (0x5f6UL + POISON_POINTER_DELTA)
 
-/* Allocate a static per-CPU shadow stack */
-#define DEFINE_SCS(name)                                               \
-       DEFINE_PER_CPU(unsigned long [SCS_SIZE/sizeof(long)], name)     \
-
 #define task_scs(tsk)          (task_thread_info(tsk)->scs_base)
 #define task_scs_sp(tsk)       (task_thread_info(tsk)->scs_sp)