Stack overflow debugging support.

From Kanoj Sarcar.

arch/sparc64/Makefile

@@ -48,6 +48,11 @@ else
   AFLAGS += -m64 -mcpu=ultrasparc $(CC_UNDECL)
 endif
 
+ifeq ($(CONFIG_MCOUNT),y)
+  CFLAGS := $(subst -fomit-frame-pointer,,$(CFLAGS))
+  CFLAGS := $(CFLAGS) -pg
+endif
+
 LINKFLAGS = -T arch/sparc64/vmlinux.lds
 
 HEAD := arch/sparc64/kernel/head.o arch/sparc64/kernel/init_task.o

arch/sparc64/config.in

@@ -289,6 +289,10 @@ if [ "$CONFIG_DEBUG_KERNEL" != "n" ]; then
    bool '  Verbose BUG() reporting (adds 70K)' CONFIG_DEBUG_BUGVERBOSE
    bool '  D-cache flush debugging' CONFIG_DEBUG_DCFLUSH
 fi
+bool 'Stack Overflow Detection Support' CONFIG_STACK_DEBUG
+if [ "$CONFIG_STACK_DEBUG" = "y" ] ; then
+   define_bool CONFIG_MCOUNT y
+fi
 
 endmenu
 

arch/sparc64/kernel/sparc64_ksyms.c

@@ -139,6 +139,11 @@ EXPORT_SYMBOL(__global_sti);
 EXPORT_SYMBOL(__global_save_flags);
 EXPORT_SYMBOL(__global_restore_flags);
 
+#if defined(CONFIG_MCOUNT)
+extern void mcount(void);
+EXPORT_SYMBOL(mcount);
+#endif
+
 /* Per-CPU information table */
 EXPORT_SYMBOL(cpu_data);
 

arch/sparc64/lib/Makefile

@@ -16,6 +16,6 @@ obj-y := PeeCeeI.o blockops.o debuglocks.o strlen.o strncmp.o \
 	 VIScopy.o VISbzero.o VISmemset.o VIScsum.o VIScsumcopy.o \
 	 VIScsumcopyusr.o VISsave.o atomic.o rwlock.o bitops.o \
 	 dec_and_lock.o U3memcpy.o U3copy_from_user.o U3copy_to_user.o \
-	 U3copy_in_user.o
+	 U3copy_in_user.o mcount.o
 
 include $(TOPDIR)/Rules.make

arch/sparc64/lib/mcount.S

+/*
+ * Copyright (C) 2000 Anton Blanchard (anton@linuxcare.com)
+ *
+ * This file implements mcount(), which is used to collect profiling data.
+ * This can also be tweaked for kernel stack overflow detection.
+ */
+
+#include <linux/config.h>
+#include <linux/linkage.h>
+
+#include <asm/ptrace.h>
+#include <asm/thread_info.h>
+
+/*
+ * This is the main variant and is called by C code.  GCC's -pg option
+ * automatically instruments every C function with a call to this.
+ */
+
+#ifdef CONFIG_STACK_DEBUG
+
+#define OVSTACKSIZE	4096		/* lets hope this is enough */
+
+	.data
+	.align		8
+panicstring:
+	.asciz		"Stack overflow\n"
+	.align		8
+ovstack:
+	.skip		OVSTACKSIZE
+#endif
+	.text
+	.align 32
+	.globl mcount
+mcount:
+#ifdef CONFIG_STACK_DEBUG
+	/*
+	 * Check whether %sp is dangerously low.
+	 */
+	add		%g6, (TI_FPREGS + 256 + 192), %g5! where does task_struct+frame end?
+	sub		%g5, STACK_BIAS, %g5
+	cmp		%sp, %g5
+	bg,pt		%xcc, 1f
+	 sethi		%hi(panicstring), %g5
+	sethi		%hi(ovstack), %g7		! cant move to panic stack fast enough
+	 or		%g7, %lo(ovstack), %g7
+	add		%g7, OVSTACKSIZE, %g7
+	sub		%g7, STACK_BIAS, %g7
+	mov		%g7, %sp
+	call		prom_printf
+	 or		%g5, %lo(panicstring), %o0
+	call		prom_halt
+	 nop
+#endif
+1:	retl
+	 nop

arch/sparc64/prom/Makefile

@@ -19,3 +19,6 @@ obj-y   := bootstr.o devops.o init.o memory.o misc.o \
 	$(CC) $(AFLAGS) -ansi -c $< -o $*.o
 
 include $(TOPDIR)/Rules.make
+
+%.o: %.c
+	$(CC) $(subst -pg,,$(CFLAGS)) -c $<