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Subject[PATCH -tip V3] [BUGFIX] kprobes/x86: Do not jump-optimize kprobes on irq entry code
Date
Since the kernel segment registers are not prepared at the
entry of irq-entry code, if a kprobe on such code is
jump-optimized, accessing per-cpu variables may cause
kernel panic.
However, if the kprobe is not optimized, it kicks int3
exception and set segment registers correctly.

This checks probe-address and if it is in irq-entry code,
it prohibits optimizing such kprobes. This means we can
continuously probing such interrupt handlers by kprobes
but it is not optimized anymore.

Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Reported-by: Francis Deslauriers <francis.deslauriers@efficios.com>
Tested-by: Francis Deslauriers <francis.deslauriers@efficios.com>
---
Changes in V3:
- Define __irqentry_text_start/end symbols when CONFIG_OPTPROBES=y.
---
arch/x86/kernel/kprobes/opt.c | 9 ++++++---
include/asm-generic/vmlinux.lds.h | 6 ++++--
include/linux/interrupt.h | 3 ++-
3 files changed, 12 insertions(+), 6 deletions(-)

diff --git a/arch/x86/kernel/kprobes/opt.c b/arch/x86/kernel/kprobes/opt.c
index 69ea0bc..c26e7f9 100644
--- a/arch/x86/kernel/kprobes/opt.c
+++ b/arch/x86/kernel/kprobes/opt.c
@@ -29,6 +29,7 @@
#include <linux/kallsyms.h>
#include <linux/ftrace.h>
#include <linux/frame.h>
+#include <linux/interrupt.h>

#include <asm/text-patching.h>
#include <asm/cacheflush.h>
@@ -251,10 +252,12 @@ static int can_optimize(unsigned long paddr)

/*
* Do not optimize in the entry code due to the unstable
- * stack handling.
+ * stack handling and registers setup.
*/
- if ((paddr >= (unsigned long)__entry_text_start) &&
- (paddr < (unsigned long)__entry_text_end))
+ if (((paddr >= (unsigned long)__entry_text_start) &&
+ (paddr < (unsigned long)__entry_text_end)) ||
+ ((paddr >= (unsigned long)__irqentry_text_start) &&
+ (paddr < (unsigned long)__irqentry_text_end)))
return 0;

/* Check there is enough space for a relative jump. */
diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index da0be9a..3092a1f 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -483,7 +483,8 @@
*(.entry.text) \
VMLINUX_SYMBOL(__entry_text_end) = .;

-#if defined(CONFIG_FUNCTION_GRAPH_TRACER) || defined(CONFIG_KASAN)
+#if defined(CONFIG_FUNCTION_GRAPH_TRACER) || defined(CONFIG_KASAN) || \
+ defined(CONFIG_OPTPROBES)
#define IRQENTRY_TEXT \
ALIGN_FUNCTION(); \
VMLINUX_SYMBOL(__irqentry_text_start) = .; \
@@ -493,7 +494,8 @@
#define IRQENTRY_TEXT
#endif

-#if defined(CONFIG_FUNCTION_GRAPH_TRACER) || defined(CONFIG_KASAN)
+#if defined(CONFIG_FUNCTION_GRAPH_TRACER) || defined(CONFIG_KASAN) || \
+ defined(CONFIG_OPTPROBES)
#define SOFTIRQENTRY_TEXT \
ALIGN_FUNCTION(); \
VMLINUX_SYMBOL(__softirqentry_text_start) = .; \
diff --git a/include/linux/interrupt.h b/include/linux/interrupt.h
index a2fdddd..a1b78f4 100644
--- a/include/linux/interrupt.h
+++ b/include/linux/interrupt.h
@@ -726,7 +726,8 @@ extern int early_irq_init(void);
extern int arch_probe_nr_irqs(void);
extern int arch_early_irq_init(void);

-#if defined(CONFIG_FUNCTION_GRAPH_TRACER) || defined(CONFIG_KASAN)
+#if defined(CONFIG_FUNCTION_GRAPH_TRACER) || defined(CONFIG_KASAN) || \
+ defined(CONFIG_KPROBES)
/*
* We want to know which function is an entrypoint of a hardirq or a softirq.
*/
\
 
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