[PATCH v2 3/6] x86: Add struct inactive_task_frame

Brian Gerst
2016-06-18T20:56:57Z

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 <brgerst@gmail.com>
---
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 7c247e7..fb4a078 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>

extern int kstack_depth_to_print;

@@ -70,8 +71,7 @@ stack_frame(struct task_struct *task, struct pt_regs *regs)
return bp;
}

- /* bp is the last reg pushed by switch_to */
- return *(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 8f321a1..02de86e 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 5e3f294..8e36f24 100644
--- a/arch/x86/kernel/kgdb.c
+++ b/arch/x86/kernel/kgdb.c
@@ -50,6 +50,7 @@
#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] =
{
@@ -166,7 +167,7 @@ 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 96becbb..00ebab0 100644
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -31,6 +31,7 @@
#include <asm/tlbflush.h>
#include <asm/mce.h>
#include <asm/vm86.h>
+#include <asm/switch_to.h>

/*
* per-CPU TSS segments. Threads are completely 'soft' on Linux,
@@ -555,7 +556,7 @@ 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;
--
2.5.5