kexec jump: fix for ftrace

Restore ftrace after jumping back from kexeced kernel.

Signed-off-by Huang Ying <[email protected]>

---
 arch/x86/kernel/machine_kexec_32.c |   19 +++++++++++++++++++
 kernel/kexec.c                     |    2 --
 2 files changed, 19 insertions(+), 2 deletions(-)

arch/x86/kernel/machine_kexec_32.c +2 -0

@@ -124,7 +126,15 @@ void machine_kexec(struct kimage *image)
 				       unsigned int has_pae,
 				       unsigned int preserve_context);
 
+#ifdef CONFIG_KEXEC_JUMP
+	if (kexec_image->preserve_context)

arch/x86/kernel/machine_kexec_32.c +9 -0

@@ -182,6 +192,15 @@ void machine_kexec(struct kimage *image)
 					   (unsigned long)page_list,
 					   image->start, cpu_has_pae,
 					   image->preserve_context);
+
+#ifdef CONFIG_KEXEC_JUMP
+	if (kexec_image->preserve_context)
+		restore_processor_state();
+#endif
+
+#ifdef CONFIG_FTRACE
+	ftrace_enabled = save_ftrace_enabled;
+#endif
 }
 
 void arch_crash_save_vmcoreinfo(void)

kernel/kexec.c +0 -2

@@ -1469,7 +1469,6 @@ int kernel_kexec(void)
 		error = device_power_down(PMSG_FREEZE);
 		if (error)
 			goto Enable_irqs;
-		save_processor_state();
 	} else
 #endif
 	{

@@ -1482,7 +1481,6 @@ int kernel_kexec(void)
 
 #ifdef CONFIG_KEXEC_JUMP
 	if (kexec_image->preserve_context) {
-		restore_processor_state();
 		device_power_up(PMSG_RESTORE);
  Enable_irqs:
 		local_irq_enable();

Restore ftrace after jumping back from kexeced kernel.

Signed-off-by Huang Ying <[email protected]>

---
 arch/x86/kernel/machine_kexec_32.c |   19 +++++++++++++++++++
 kernel/kexec.c                     |    2 --
 2 files changed, 19 insertions(+), 2 deletions(-)

arch/x86/kernel/machine_kexec_32.c +11 -0

@@ -12,6 +12,7 @@
 #include <linux/init.h>
 #include <linux/numa.h>
 #include <linux/ftrace.h>
+#include <linux/suspend.h>
 
 #include <asm/pgtable.h>
 #include <asm/pgalloc.h>

@@ -117,6 +118,7 @@ void machine_kexec(struct kimage *image)
 {
 	unsigned long page_list[PAGES_NR];
 	void *control_page;
+	int save_ftrace_enabled;
 	asmlinkage unsigned long
 		(*relocate_kernel_ptr)(unsigned long indirection_page,
 				       unsigned long control_page,

@@ -124,7 +126,15 @@ void machine_kexec(struct kimage *image)
 				       unsigned int has_pae,
 				       unsigned int preserve_context);
 
+#ifdef CONFIG_KEXEC_JUMP
+	if (kexec_image->preserve_context)
+		save_processor_state();
+#endif
+
+#ifdef CONFIG_FTRACE
+	save_ftrace_enabled = ftrace_enabled;
 	tracer_disable();
+#endif
 
 	/* Interrupts aren't acceptable while we reboot */
 	raw_local_irq_disable();

@@ -182,6 +192,15 @@ void machine_kexec(struct kimage *image)
 					   (unsigned long)page_list,
 					   image->start, cpu_has_pae,
 					   image->preserve_context);
+

What kind of problem we run into if we don't disable the ftracer?

I think there are too many #ifdefs now and probably we can at least get rid if #ifdef CONFIG_FTRACE thing.

I think ftracer needs to export the function to enable the tracer back (tracer_enable()) so that we don't directly play with ftrace_enabled variable. tracer_enable() can be do {} while{0} in case of CONFIG_FTRACE=n so that we can get rid of #ifdefs here.