sh: Provide diagnostic kernel stack checks
Enable kernel stack checking code in both the dynamic ftrace and mcount
code paths. Check the stack to see if it's overflowing and make sure
that the stack pointer contains an address that's either in init_stack
or after the bss.
Signed-off-by: Matt Fleming <matt@console-pimps.org>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>
diff --git a/arch/sh/Kconfig.debug b/arch/sh/Kconfig.debug
index 39224b5..52a132c 100644
--- a/arch/sh/Kconfig.debug
+++ b/arch/sh/Kconfig.debug
@@ -123,4 +123,15 @@
bool "Debug: set SR.WATCH to enable hardware watchpoints and trace"
depends on SUPERH64
+config STACK_DEBUG
+ bool "Enable diagnostic checks of the kernel stack"
+ depends on FUNCTION_TRACER
+ select DEBUG_STACKOVERFLOW
+ default n
+ help
+ This option allows checks to be performed on the kernel stack
+ at runtime. Saying Y here will add overhead to every function
+ call and will therefore incur a major performance hit. Most
+ users should say N.
+
endmenu
diff --git a/arch/sh/kernel/asm-offsets.c b/arch/sh/kernel/asm-offsets.c
index 99aceb28..d218e80 100644
--- a/arch/sh/kernel/asm-offsets.c
+++ b/arch/sh/kernel/asm-offsets.c
@@ -26,6 +26,7 @@
DEFINE(TI_CPU, offsetof(struct thread_info, cpu));
DEFINE(TI_PRE_COUNT, offsetof(struct thread_info, preempt_count));
DEFINE(TI_RESTART_BLOCK,offsetof(struct thread_info, restart_block));
+ DEFINE(TI_SIZE, sizeof(struct thread_info));
#ifdef CONFIG_HIBERNATION
DEFINE(PBE_ADDRESS, offsetof(struct pbe, address));
diff --git a/arch/sh/lib/mcount.S b/arch/sh/lib/mcount.S
index 71e87f9..8596483 100644
--- a/arch/sh/lib/mcount.S
+++ b/arch/sh/lib/mcount.S
@@ -9,6 +9,8 @@
* for more details.
*/
#include <asm/ftrace.h>
+#include <asm/thread_info.h>
+#include <asm/asm-offsets.h>
#define MCOUNT_ENTER() \
mov.l r4, @-r15; \
@@ -28,6 +30,55 @@
rts; \
mov.l @r15+, r4
+#ifdef CONFIG_STACK_DEBUG
+/*
+ * Perform diagnostic checks on the state of the kernel stack.
+ *
+ * Check for stack overflow. If there is less than 1KB free
+ * then it has overflowed.
+ *
+ * Make sure the stack pointer contains a valid address. Valid
+ * addresses for kernel stacks are anywhere after the bss
+ * (after _ebss) and anywhere in init_thread_union (init_stack).
+ */
+#define STACK_CHECK() \
+ mov #(THREAD_SIZE >> 10), r0; \
+ shll8 r0; \
+ shll2 r0; \
+ \
+ /* r1 = sp & (THREAD_SIZE - 1) */ \
+ mov #-1, r1; \
+ add r0, r1; \
+ and r15, r1; \
+ \
+ mov #TI_SIZE, r3; \
+ mov #(STACK_WARN >> 8), r2; \
+ shll8 r2; \
+ add r3, r2; \
+ \
+ /* Is the stack overflowing? */ \
+ cmp/hi r2, r1; \
+ bf stack_panic; \
+ \
+ /* If sp > _ebss then we're OK. */ \
+ mov.l .L_ebss, r1; \
+ cmp/hi r1, r15; \
+ bt 1f; \
+ \
+ /* If sp < init_stack, we're not OK. */ \
+ mov.l .L_init_thread_union, r1; \
+ cmp/hs r1, r15; \
+ bf stack_panic; \
+ \
+ /* If sp > init_stack && sp < _ebss, not OK. */ \
+ add r0, r1; \
+ cmp/hs r1, r15; \
+ bt stack_panic; \
+1:
+#else
+#define STACK_CHECK()
+#endif /* CONFIG_STACK_DEBUG */
+
.align 2
.globl _mcount
.type _mcount,@function
@@ -41,6 +92,8 @@
tst r0, r0
bf ftrace_stub
#endif
+ STACK_CHECK()
+
MCOUNT_ENTER()
#ifdef CONFIG_DYNAMIC_FTRACE
@@ -73,6 +126,8 @@
tst r0, r0
bf ftrace_stub
+ STACK_CHECK()
+
MCOUNT_ENTER()
.globl ftrace_call
@@ -100,6 +155,36 @@
rts
nop
+#ifdef CONFIG_STACK_DEBUG
+ .globl stack_panic
+stack_panic:
+ mov.l .Ldump_stack, r0
+ jsr @r0
+ nop
+
+ mov.l .Lpanic, r0
+ jsr @r0
+ mov.l .Lpanic_s, r4
+
+ rts
+ nop
+
.align 2
.Lfunction_trace_stop:
.long function_trace_stop
+.L_ebss:
+ .long _ebss
+.L_init_thread_union:
+ .long init_thread_union
+.Lpanic:
+ .long panic
+.Lpanic_s:
+ .long .Lpanic_str
+.Ldump_stack:
+ .long dump_stack
+
+ .section .rodata
+ .align 2
+.Lpanic_str:
+ .string "Stack error"
+#endif /* CONFIG_STACK_DEBUG */