From: Brian Gerst <[email protected]>

Add 'struct inactive_task_frame', which defines the layout of the stack for
a sleeping process.  For now, the only defined field is the BP register
(frame pointer).

Signed-off-by: Brian Gerst <[email protected]>
Reviewed-by: Josh Poimboeuf <[email protected]>
Cc: Andy Lutomirski <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: Denys Vlasenko <[email protected]>
Cc: H. Peter Anvin <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Link: 
http://lkml.kernel.org/r/[email protected]
Signed-off-by: Ingo Molnar <[email protected]>

(cherry picked from commit 7b32aeadbc95d4a41402c1c0da6aa3ab51af4c10)
In the scope of https://jira.sw.ru/browse/HCI-171

Signed-off-by: Konstantin Khorenko <[email protected]>
---
 arch/x86/include/asm/stacktrace.h | 4 ++--
 arch/x86/include/asm/switch_to.h  | 5 +++++
 arch/x86/kernel/kgdb.c            | 3 ++-
 arch/x86/kernel/process.c         | 3 ++-
 4 files changed, 11 insertions(+), 4 deletions(-)

diff --git a/arch/x86/include/asm/stacktrace.h 
b/arch/x86/include/asm/stacktrace.h
index f8a383338352..a4fe84fd293c 100644
--- a/arch/x86/include/asm/stacktrace.h
+++ b/arch/x86/include/asm/stacktrace.h
@@ -8,6 +8,7 @@
 
 #include <linux/uaccess.h>
 #include <linux/ptrace.h>
+#include <asm/switch_to.h>
 
 enum stack_type {
        STACK_TYPE_UNKNOWN,
@@ -58,8 +59,7 @@ get_frame_pointer(struct task_struct *task, struct pt_regs 
*regs)
        if (task == current)
                return __builtin_frame_address(0);
 
-       /* bp is the last reg pushed by switch_to */
-       return (unsigned long *)*(unsigned long *)task->thread.sp;
+       return ((struct inactive_task_frame *)task->thread.sp)->bp;
 }
 #else
 static inline unsigned long *
diff --git a/arch/x86/include/asm/switch_to.h b/arch/x86/include/asm/switch_to.h
index 4ec45b3abba1..c8950d57a8f3 100644
--- a/arch/x86/include/asm/switch_to.h
+++ b/arch/x86/include/asm/switch_to.h
@@ -8,6 +8,11 @@ struct tss_struct;
 void __switch_to_xtra(struct task_struct *prev_p, struct task_struct *next_p,
                      struct tss_struct *tss);
 
+/* data that is pointed to by thread.sp */
+struct inactive_task_frame {
+       unsigned long bp;
+};
+
 #ifdef CONFIG_X86_32
 
 #ifdef CONFIG_CC_STACKPROTECTOR
diff --git a/arch/x86/kernel/kgdb.c b/arch/x86/kernel/kgdb.c
index 7ec1d5f8d283..9b4e1dd2e3aa 100644
--- a/arch/x86/kernel/kgdb.c
+++ b/arch/x86/kernel/kgdb.c
@@ -49,6 +49,7 @@
 #include <asm/apicdef.h>
 #include <asm/apic.h>
 #include <asm/nmi.h>
+#include <asm/switch_to.h>
 
 struct dbg_reg_def_t dbg_reg_def[DBG_MAX_REG_NUM] =
 {
@@ -165,7 +166,7 @@ void sleeping_thread_to_gdb_regs(unsigned long *gdb_regs, 
struct task_struct *p)
        gdb_regs[GDB_DX]        = 0;
        gdb_regs[GDB_SI]        = 0;
        gdb_regs[GDB_DI]        = 0;
-       gdb_regs[GDB_BP]        = *(unsigned long *)p->thread.sp;
+       gdb_regs[GDB_BP]        = ((struct inactive_task_frame 
*)p->thread.sp)->bp;
 #ifdef CONFIG_X86_32
        gdb_regs[GDB_DS]        = __KERNEL_DS;
        gdb_regs[GDB_ES]        = __KERNEL_DS;
diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index 1f2f0d1545bc..79c941f4c72c 100644
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -31,6 +31,7 @@
 #include <asm/nmi.h>
 #include <asm/mce.h>
 #include <asm/spec_ctrl.h>
+#include <asm/switch_to.h>
 
 /*
  * per-CPU TSS segments. Threads are completely 'soft' on Linux,
@@ -688,7 +689,7 @@ unsigned long get_wchan(struct task_struct *p)
        if (sp < bottom || sp > top)
                return 0;
 
-       fp = READ_ONCE_NOCHECK(*(unsigned long *)sp);
+       fp = READ_ONCE_NOCHECK(((struct inactive_task_frame *)sp)->bp);
        do {
                if (fp < bottom || fp > top)
                        return 0;
-- 
2.15.1

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