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Subject[PATCH] (3/3) stack overflow checking for x86
* stack checking (3/3)
- use gcc's profiling features to check for stack overflows upon
entry to functions.
- Warn if the task goes over 4k.
- Panic if the stack gets within 512 bytes of overflowing.
- use kksymoops information, if available

This won't apply cleanly without the irqstack patch, but the conflict
is easy to resolve. It requires the thread_info cleanup.
--
Dave Hansen
haveblue@us.ibm.com
# This is a BitKeeper generated patch for the following project:
# Project Name: Linux kernel tree
# This patch format is intended for GNU patch command version 2.5 or higher.
# This patch includes the following deltas:
# ChangeSet 1.858.1.2 -> 1.863
# arch/i386/kernel/process.c 1.32.1.1 -> 1.36
# arch/i386/Config.help 1.21.1.2 -> 1.24
# Makefile 1.320.1.1 -> 1.322
# include/asm-i386/thread_info.h 1.10 -> 1.11
# arch/i386/kernel/entry.S 1.38.1.2 -> 1.45
# arch/i386/config.in 1.56.1.4 -> 1.59
# arch/i386/Makefile 1.21.1.1 -> 1.23
# arch/i386/boot/compressed/misc.c 1.9 -> 1.10
# arch/i386/kernel/init_task.c 1.6.1.1 -> 1.8
# arch/i386/kernel/i386_ksyms.c 1.34.1.2 -> 1.36
#
# The following is the BitKeeper ChangeSet Log
# --------------------------------------------
# 02/10/16 haveblue@elm3b96.(none) 1.861
# change warning semantics
# --------------------------------------------
# 02/10/16 haveblue@elm3b96.(none) 1.862
# entry.S:
# don't need stack_warn_lock anymore
# --------------------------------------------
# 02/10/16 haveblue@elm3b96.(none) 1.863
# merge
# --------------------------------------------
#
diff -Nru a/Makefile b/Makefile
--- a/Makefile Wed Oct 16 14:14:00 2002
+++ b/Makefile Wed Oct 16 14:14:00 2002
@@ -156,7 +156,8 @@

CPPFLAGS := -D__KERNEL__ -Iinclude
CFLAGS := $(CPPFLAGS) -Wall -Wstrict-prototypes -Wno-trigraphs -O2 \
- -fomit-frame-pointer -fno-strict-aliasing -fno-common
+ -fno-strict-aliasing -fno-common
+
AFLAGS := -D__ASSEMBLY__ $(CPPFLAGS)

export VERSION PATCHLEVEL SUBLEVEL EXTRAVERSION KERNELRELEASE ARCH \
@@ -255,6 +256,10 @@

ifdef CONFIG_MODULES
export EXPORT_FLAGS := -DEXPORT_SYMTAB
+endif
+
+ifneq ($(CONFIG_FRAME_POINTER),y)
+CFLAGS += -fomit-frame-pointer
endif

#
diff -Nru a/arch/i386/Config.help b/arch/i386/Config.help
--- a/arch/i386/Config.help Wed Oct 16 14:14:00 2002
+++ b/arch/i386/Config.help Wed Oct 16 14:14:00 2002
@@ -1050,6 +1050,20 @@
symbolic stack backtraces. This increases the size of the kernel
somewhat, as all symbols have to be loaded into the kernel image.

+CONFIG_X86_STACK_CHECK
+ Say Y here to have the kernel attempt to detect when the per-task
+ kernel stack overflows.
+
+ Some older versions of gcc don't handle the -p option correctly.
+ Kernprof is affected by the same problem, which is described here:
+ http://oss.sgi.com/projects/kernprof/faq.html#Q9
+
+ Basically, if you get oopses in __free_pages_ok during boot when
+ you have this turned on, you need to fix gcc. The Redhat 2.96
+ version and gcc-3.x seem to work.
+
+ If not debugging a stack overflow problem, say N
+
CONFIG_DEBUG_OBSOLETE
Say Y here if you want to reduce the chances of the tree compiling,
and are prepared to dig into driver internals to fix compile errors.
diff -Nru a/arch/i386/Makefile b/arch/i386/Makefile
--- a/arch/i386/Makefile Wed Oct 16 14:14:00 2002
+++ b/arch/i386/Makefile Wed Oct 16 14:14:00 2002
@@ -49,6 +49,10 @@
MACHINE := mach-generic
endif

+ifdef CONFIG_X86_STACK_CHECK
+CFLAGS += -p
+endif
+
HEAD := arch/i386/kernel/head.o arch/i386/kernel/init_task.o

libs-y += arch/i386/lib/
diff -Nru a/arch/i386/boot/compressed/misc.c b/arch/i386/boot/compressed/misc.c
--- a/arch/i386/boot/compressed/misc.c Wed Oct 16 14:14:00 2002
+++ b/arch/i386/boot/compressed/misc.c Wed Oct 16 14:14:00 2002
@@ -377,3 +377,7 @@
if (high_loaded) close_output_buffer_if_we_run_high(mv);
return high_loaded;
}
+
+/* We don't actually check for stack overflows this early. */
+__asm__(".globl mcount ; mcount: ret\n");
+
diff -Nru a/arch/i386/config.in b/arch/i386/config.in
--- a/arch/i386/config.in Wed Oct 16 14:14:00 2002
+++ b/arch/i386/config.in Wed Oct 16 14:14:00 2002
@@ -467,6 +467,11 @@
bool ' Highmem debugging' CONFIG_DEBUG_HIGHMEM
fi
bool ' Load all symbols for debugging/kksymoops' CONFIG_KALLSYMS
+ bool ' Check for stack overflows' CONFIG_X86_STACK_CHECK
+ if [ "$CONFIG_X86_STACK_CHECK" = "y" ]; then
+ define_bool CONFIG_FRAME_POINTER y
+ fi
+
fi

if [ "$CONFIG_X86_LOCAL_APIC" = "y" ]; then
diff -Nru a/arch/i386/kernel/entry.S b/arch/i386/kernel/entry.S
--- a/arch/i386/kernel/entry.S Wed Oct 16 14:14:00 2002
+++ b/arch/i386/kernel/entry.S Wed Oct 16 14:14:00 2002
@@ -519,6 +519,61 @@
pushl $do_spurious_interrupt_bug
jmp error_code

+
+#ifdef CONFIG_X86_STACK_CHECK
+.data
+ .globl stack_overflowed
+stack_overflowed:
+ .long 0
+.text
+
+ENTRY(mcount)
+ push %eax
+ movl $(THREAD_SIZE - 1),%eax
+ andl %esp,%eax
+ cmpl $STACK_WARN,%eax /* more than half the stack is used*/
+ jle 1f
+2:
+ popl %eax
+ ret
+1:
+ lock; btsl $0,stack_overflowed
+ jc 2b
+
+ # switch to overflow stack
+ movl %esp,%eax
+ movl $(stack_overflow_stack + THREAD_SIZE - 4),%esp
+
+ pushf
+ cli
+ pushl %eax
+
+ # push eip then esp of error for stack_overflow_panic
+ pushl 4(%eax)
+ pushl %eax
+
+ # update the task pointer and cpu in the overflow stack's thread_info.
+ GET_THREAD_INFO_WITH_ESP(%eax)
+ movl TI_TASK(%eax),%ebx
+ movl %ebx,stack_overflow_stack+TI_TASK
+ movl TI_CPU(%eax),%ebx
+ movl %ebx,stack_overflow_stack+TI_CPU
+
+ call stack_overflow
+
+ # pop off call arguments
+ addl $8,%esp
+
+ popl %eax
+ popf
+ movl %eax,%esp
+ popl %eax
+ movl $0,stack_overflowed
+ ret
+
+#warning stack check enabled
+#endif
+
.data
ENTRY(sys_call_table)
.long sys_ni_syscall /* 0 - old "setup()" system call*/
diff -Nru a/arch/i386/kernel/i386_ksyms.c b/arch/i386/kernel/i386_ksyms.c
--- a/arch/i386/kernel/i386_ksyms.c Wed Oct 16 14:14:00 2002
+++ b/arch/i386/kernel/i386_ksyms.c Wed Oct 16 14:14:00 2002
@@ -192,3 +192,8 @@
EXPORT_SYMBOL(is_sony_vaio_laptop);

EXPORT_SYMBOL(__PAGE_KERNEL);
+
+#ifdef CONFIG_X86_STACK_CHECK
+extern void mcount(void);
+EXPORT_SYMBOL(mcount);
+#endif
diff -Nru a/arch/i386/kernel/init_task.c b/arch/i386/kernel/init_task.c
--- a/arch/i386/kernel/init_task.c Wed Oct 16 14:14:00 2002
+++ b/arch/i386/kernel/init_task.c Wed Oct 16 14:14:00 2002
@@ -16,6 +16,10 @@
union thread_union init_irq_union
__attribute__((__section__(".data.init_task")));

+#ifdef CONFIG_X86_STACK_CHECK
+union thread_union stack_overflow_stack
+ __attribute__((__section__(".data.init_task")));
+#endif

/*
* Initial thread structure.
diff -Nru a/arch/i386/kernel/process.c b/arch/i386/kernel/process.c
--- a/arch/i386/kernel/process.c Wed Oct 16 14:14:00 2002
+++ b/arch/i386/kernel/process.c Wed Oct 16 14:14:00 2002
@@ -156,7 +156,25 @@

__setup("idle=", idle_setup);

-void show_regs(struct pt_regs * regs)
+void stack_overflow(unsigned long esp, unsigned long eip)
+{
+ int panicing = ((esp&(THREAD_SIZE-1)) <= STACK_PANIC);
+
+ printk( "esp: 0x%x masked: 0x%x STACK_PANIC:0x%x %d %d\n",
+ esp, (esp&(THREAD_SIZE-1)), STACK_PANIC, (((esp&(THREAD_SIZE-1)) <= STACK_PANIC)), panicing );
+
+ if (panicing)
+ print_symbol("stack overflow from %s\n", eip);
+ else
+ print_symbol("excessive stack use from %s\n", eip);
+ printk("esp: %p\n", (void*)esp);
+ show_trace((void*)esp);
+
+ if (panicing)
+ panic("stack overflow\n");
+}
+
+asmlinkage void show_regs(struct pt_regs * regs)
{
unsigned long cr0 = 0L, cr2 = 0L, cr3 = 0L, cr4 = 0L;

diff -Nru a/include/asm-i386/thread_info.h b/include/asm-i386/thread_info.h
--- a/include/asm-i386/thread_info.h Wed Oct 16 14:14:00 2002
+++ b/include/asm-i386/thread_info.h Wed Oct 16 14:14:00 2002
@@ -60,6 +60,8 @@
*/
#define THREAD_ORDER 1
#define INIT_THREAD_SIZE THREAD_SIZE
+#define STACK_PANIC 0x200ul
+#define STACK_WARN ((THREAD_SIZE)>>1)

#ifndef __ASSEMBLY__
#define INIT_THREAD_INFO(tsk) \
\
 
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