Merge branch 'for-next/stacktrace' into for-next/kasan

Merge in stack unwinding work to cater for 8-byte aligned stack frames
which may be generated following optimisations to CONFIG_KASAN_OUTLINE.

* for-next/stacktrace:
  arm64: stacktrace: Relax frame record alignment requirement to 8 bytes
  arm64: Change the on_*stack functions to take a size argument
  arm64: Implement stack trace termination record

Author: willdeacon

arch/arm64/include/asm/processor.h

@@ -329,13 +329,13 @@ long get_tagged_addr_ctrl(struct task_struct *task);
  * of header definitions for the use of task_stack_page.
  */
 
-#define current_top_of_stack()							\
-({										\
-	struct stack_info _info;						\
-	BUG_ON(!on_accessible_stack(current, current_stack_pointer, &_info));	\
-	_info.high;								\
+#define current_top_of_stack()								\
+({											\
+	struct stack_info _info;							\
+	BUG_ON(!on_accessible_stack(current, current_stack_pointer, 1, &_info));	\
+	_info.high;									\
 })
-#define on_thread_stack()	(on_task_stack(current, current_stack_pointer, NULL))
+#define on_thread_stack()	(on_task_stack(current, current_stack_pointer, 1, NULL))
 
 #endif /* __ASSEMBLY__ */
 #endif /* __ASM_PROCESSOR_H */

arch/arm64/include/asm/sdei.h

@@ -42,16 +42,17 @@ unsigned long sdei_arch_get_entry_point(int conduit);
 
 struct stack_info;
 
-bool _on_sdei_stack(unsigned long sp, struct stack_info *info);
-static inline bool on_sdei_stack(unsigned long sp,
+bool _on_sdei_stack(unsigned long sp, unsigned long size,
+		    struct stack_info *info);
+static inline bool on_sdei_stack(unsigned long sp, unsigned long size,
 				struct stack_info *info)
 {
 	if (!IS_ENABLED(CONFIG_VMAP_STACK))
 		return false;
 	if (!IS_ENABLED(CONFIG_ARM_SDE_INTERFACE))
 		return false;
 	if (in_nmi())
-		return _on_sdei_stack(sp, info);
+		return _on_sdei_stack(sp, size, info);
 
 	return false;
 }

arch/arm64/include/asm/stacktrace.h

@@ -69,14 +69,14 @@ extern void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk,
 
 DECLARE_PER_CPU(unsigned long *, irq_stack_ptr);
 
-static inline bool on_stack(unsigned long sp, unsigned long low,
-				unsigned long high, enum stack_type type,
-				struct stack_info *info)
+static inline bool on_stack(unsigned long sp, unsigned long size,
+			    unsigned long low, unsigned long high,
+			    enum stack_type type, struct stack_info *info)
 {
 	if (!low)
 		return false;
 
-	if (sp < low || sp >= high)
+	if (sp < low || sp + size < sp || sp + size > high)
 		return false;
 
 	if (info) {
@@ -87,38 +87,38 @@ static inline bool on_stack(unsigned long sp, unsigned long low,
 	return true;
 }
 
-static inline bool on_irq_stack(unsigned long sp,
+static inline bool on_irq_stack(unsigned long sp, unsigned long size,
 				struct stack_info *info)
 {
 	unsigned long low = (unsigned long)raw_cpu_read(irq_stack_ptr);
 	unsigned long high = low + IRQ_STACK_SIZE;
 
-	return on_stack(sp, low, high, STACK_TYPE_IRQ, info);
+	return on_stack(sp, size, low, high, STACK_TYPE_IRQ, info);
 }
 
 static inline bool on_task_stack(const struct task_struct *tsk,
-				 unsigned long sp,
+				 unsigned long sp, unsigned long size,
 				 struct stack_info *info)
 {
 	unsigned long low = (unsigned long)task_stack_page(tsk);
 	unsigned long high = low + THREAD_SIZE;
 
-	return on_stack(sp, low, high, STACK_TYPE_TASK, info);
+	return on_stack(sp, size, low, high, STACK_TYPE_TASK, info);
 }
 
 #ifdef CONFIG_VMAP_STACK
 DECLARE_PER_CPU(unsigned long [OVERFLOW_STACK_SIZE/sizeof(long)], overflow_stack);
 
-static inline bool on_overflow_stack(unsigned long sp,
+static inline bool on_overflow_stack(unsigned long sp, unsigned long size,
 				struct stack_info *info)
 {
 	unsigned long low = (unsigned long)raw_cpu_ptr(overflow_stack);
 	unsigned long high = low + OVERFLOW_STACK_SIZE;
 
-	return on_stack(sp, low, high, STACK_TYPE_OVERFLOW, info);
+	return on_stack(sp, size, low, high, STACK_TYPE_OVERFLOW, info);
 }
 #else
-static inline bool on_overflow_stack(unsigned long sp,
+static inline bool on_overflow_stack(unsigned long sp, unsigned long size,
 			struct stack_info *info) { return false; }
 #endif
 
@@ -128,21 +128,21 @@ static inline bool on_overflow_stack(unsigned long sp,
  * context.
  */
 static inline bool on_accessible_stack(const struct task_struct *tsk,
-				       unsigned long sp,
+				       unsigned long sp, unsigned long size,
 				       struct stack_info *info)
 {
 	if (info)
 		info->type = STACK_TYPE_UNKNOWN;
 
-	if (on_task_stack(tsk, sp, info))
+	if (on_task_stack(tsk, sp, size, info))
 		return true;
 	if (tsk != current || preemptible())
 		return false;
-	if (on_irq_stack(sp, info))
+	if (on_irq_stack(sp, size, info))
 		return true;
-	if (on_overflow_stack(sp, info))
+	if (on_overflow_stack(sp, size, info))
 		return true;
-	if (on_sdei_stack(sp, info))
+	if (on_sdei_stack(sp, size, info))
 		return true;
 
 	return false;

arch/arm64/kernel/entry.S

@@ -285,7 +285,7 @@ alternative_else_nop_endif
 	stp	lr, x21, [sp, #S_LR]
 
 	/*
-	 * For exceptions from EL0, create a terminal frame record.
+	 * For exceptions from EL0, create a final frame record.
 	 * For exceptions from EL1, create a synthetic frame record so the
 	 * interrupted code shows up in the backtrace.
 	 */

arch/arm64/kernel/head.S

@@ -16,6 +16,7 @@
 #include <asm/asm_pointer_auth.h>
 #include <asm/assembler.h>
 #include <asm/boot.h>
+#include <asm/bug.h>
 #include <asm/ptrace.h>
 #include <asm/asm-offsets.h>
 #include <asm/cache.h>
@@ -393,6 +394,18 @@ SYM_FUNC_START_LOCAL(__create_page_tables)
 	ret	x28
 SYM_FUNC_END(__create_page_tables)
 
+	/*
+	 * Create a final frame record at task_pt_regs(current)->stackframe, so
+	 * that the unwinder can identify the final frame record of any task by
+	 * its location in the task stack. We reserve the entire pt_regs space
+	 * for consistency with user tasks and kthreads.
+	 */
+	.macro setup_final_frame
+	sub	sp, sp, #PT_REGS_SIZE
+	stp	xzr, xzr, [sp, #S_STACKFRAME]
+	add	x29, sp, #S_STACKFRAME
+	.endm
+
 /*
  * The following fragment of code is executed with the MMU enabled.
  *
@@ -447,9 +460,9 @@ SYM_FUNC_START_LOCAL(__primary_switched)
 #endif
 	bl	switch_to_vhe			// Prefer VHE if possible
 	add	sp, sp, #16
-	mov	x29, #0
-	mov	x30, #0
-	b	start_kernel
+	setup_final_frame
+	bl	start_kernel
+	ASM_BUG()
 SYM_FUNC_END(__primary_switched)
 
 	.pushsection ".rodata", "a"
@@ -639,14 +652,14 @@ SYM_FUNC_START_LOCAL(__secondary_switched)
 	cbz	x2, __secondary_too_slow
 	msr	sp_el0, x2
 	scs_load x2, x3
-	mov	x29, #0
-	mov	x30, #0
+	setup_final_frame
 
 #ifdef CONFIG_ARM64_PTR_AUTH
 	ptrauth_keys_init_cpu x2, x3, x4, x5
 #endif
 
-	b	secondary_start_kernel
+	bl	secondary_start_kernel
+	ASM_BUG()
 SYM_FUNC_END(__secondary_switched)
 
 SYM_FUNC_START_LOCAL(__secondary_too_slow)

arch/arm64/kernel/perf_callchain.c

@@ -116,7 +116,7 @@ void perf_callchain_user(struct perf_callchain_entry_ctx *entry,
 		tail = (struct frame_tail __user *)regs->regs[29];
 
 		while (entry->nr < entry->max_stack &&
-		       tail && !((unsigned long)tail & 0xf))
+		       tail && !((unsigned long)tail & 0x7))
 			tail = user_backtrace(tail, entry);
 	} else {
 #ifdef CONFIG_COMPAT

arch/arm64/kernel/process.c

@@ -435,6 +435,11 @@ int copy_thread(unsigned long clone_flags, unsigned long stack_start,
 	}
 	p->thread.cpu_context.pc = (unsigned long)ret_from_fork;
 	p->thread.cpu_context.sp = (unsigned long)childregs;
+	/*
+	 * For the benefit of the unwinder, set up childregs->stackframe
+	 * as the final frame for the new task.
+	 */
+	p->thread.cpu_context.fp = (unsigned long)childregs->stackframe;
 
 	ptrace_hw_copy_thread(p);
 

arch/arm64/kernel/ptrace.c

@@ -122,7 +122,7 @@ static bool regs_within_kernel_stack(struct pt_regs *regs, unsigned long addr)
 {
 	return ((addr & ~(THREAD_SIZE - 1))  ==
 		(kernel_stack_pointer(regs) & ~(THREAD_SIZE - 1))) ||
-		on_irq_stack(addr, NULL);
+		on_irq_stack(addr, sizeof(unsigned long), NULL);
 }
 
 /**

arch/arm64/kernel/sdei.c

@@ -162,31 +162,33 @@ static int init_sdei_scs(void)
 	return err;
 }
 
-static bool on_sdei_normal_stack(unsigned long sp, struct stack_info *info)
+static bool on_sdei_normal_stack(unsigned long sp, unsigned long size,
+				 struct stack_info *info)
 {
 	unsigned long low = (unsigned long)raw_cpu_read(sdei_stack_normal_ptr);
 	unsigned long high = low + SDEI_STACK_SIZE;
 
-	return on_stack(sp, low, high, STACK_TYPE_SDEI_NORMAL, info);
+	return on_stack(sp, size, low, high, STACK_TYPE_SDEI_NORMAL, info);
 }
 
-static bool on_sdei_critical_stack(unsigned long sp, struct stack_info *info)
+static bool on_sdei_critical_stack(unsigned long sp, unsigned long size,
+				   struct stack_info *info)
 {
 	unsigned long low = (unsigned long)raw_cpu_read(sdei_stack_critical_ptr);
 	unsigned long high = low + SDEI_STACK_SIZE;
 
-	return on_stack(sp, low, high, STACK_TYPE_SDEI_CRITICAL, info);
+	return on_stack(sp, size, low, high, STACK_TYPE_SDEI_CRITICAL, info);
 }
 
-bool _on_sdei_stack(unsigned long sp, struct stack_info *info)
+bool _on_sdei_stack(unsigned long sp, unsigned long size, struct stack_info *info)
 {
 	if (!IS_ENABLED(CONFIG_VMAP_STACK))
 		return false;
 
-	if (on_sdei_critical_stack(sp, info))
+	if (on_sdei_critical_stack(sp, size, info))
 		return true;
 
-	if (on_sdei_normal_stack(sp, info))
+	if (on_sdei_normal_stack(sp, size, info))
 		return true;
 
 	return false;

arch/arm64/kernel/stacktrace.c

@@ -68,13 +68,17 @@ int notrace unwind_frame(struct task_struct *tsk, struct stackframe *frame)
 	unsigned long fp = frame->fp;
 	struct stack_info info;
 
-	if (fp & 0xf)
-		return -EINVAL;
-
 	if (!tsk)
 		tsk = current;
 
-	if (!on_accessible_stack(tsk, fp, &info))
+	/* Final frame; nothing to unwind */
+	if (fp == (unsigned long)task_pt_regs(tsk)->stackframe)
+		return -ENOENT;
+
+	if (fp & 0x7)
+		return -EINVAL;
+
+	if (!on_accessible_stack(tsk, fp, 16, &info))
 		return -EINVAL;
 
 	if (test_bit(info.type, frame->stacks_done))
@@ -128,12 +132,6 @@ int notrace unwind_frame(struct task_struct *tsk, struct stackframe *frame)
 
 	frame->pc = ptrauth_strip_insn_pac(frame->pc);
 
-	/*
-	 * This is a terminal record, so we have finished unwinding.
-	 */
-	if (!frame->fp && !frame->pc)
-		return -ENOENT;
-
 	return 0;
 }
 NOKPROBE_SYMBOL(unwind_frame);