We must not scratch any registers in signal bottom half handlers
because jit code that triggered signal is unaware that these registers
are modified. We should save/restore all caller saved registers
before calling the bottom half handler. We do it in signal_bh_trampoline
assembly routine installed by install_signal_bh().
Signed-off-by: Tomek Grabiec <tgrab...@gmail.com>
---
arch/x86/Makefile_32 | 1 +
arch/x86/signal.c | 15 ++++++++++++---
arch/x86/signal_32.S | 42 ++++++++++++++++++++++++++++++++++++++++++
include/vm/signal.h | 7 ++++++-
vm/signal.c | 31 +++++++++++++++++++++++++++----
5 files changed, 88 insertions(+), 8 deletions(-)
create mode 100644 arch/x86/signal_32.S
diff --git a/arch/x86/Makefile_32 b/arch/x86/Makefile_32
index 8b37c34..7242102 100644
--- a/arch/x86/Makefile_32
+++ b/arch/x86/Makefile_32
@@ -10,5 +10,6 @@ ARCH_OBJS = \
arch/x86/signal.o \
arch/x86/stack-frame.o \
arch/x86/unwind_32.o \
+ arch/x86/signal_32.o \
arch/x86/use-def.o \
arch/x86/thread.o
diff --git a/arch/x86/signal.c b/arch/x86/signal.c
index f36464c..724ece8 100644
--- a/arch/x86/signal.c
+++ b/arch/x86/signal.c
@@ -32,6 +32,8 @@
#include <vm/signal.h>
+extern void signal_bh_trampoline(void *bh);
+
bool signal_from_native(void *ctx)
{
ucontext_t *uc;
@@ -65,12 +67,19 @@ int install_signal_bh(void *ctx, signal_bh_fn bh)
uc = ctx;
+ stack = (unsigned long*)uc->uc_mcontext.gregs[REG_SP];
+
/* push return address on stack */
- stack = (unsigned long*)uc->uc_mcontext.gregs[REG_SP] - 1;
+ stack--;
*stack = uc->uc_mcontext.gregs[REG_IP];
- uc->uc_mcontext.gregs[REG_SP] -= sizeof(unsigned long);
- uc->uc_mcontext.gregs[REG_IP] = (unsigned long)bh;
+ /* push bottom-half handler address on stack */
+ stack--;
+ *stack = bh;
+
+ uc->uc_mcontext.gregs[REG_SP] -= 2 * sizeof(unsigned long);
+
+ uc->uc_mcontext.gregs[REG_IP] = (unsigned long)signal_bh_trampoline;
return 0;
}
diff --git a/arch/x86/signal_32.S b/arch/x86/signal_32.S
new file mode 100644
index 0000000..af2d044
--- /dev/null
+++ b/arch/x86/signal_32.S
@@ -0,0 +1,42 @@
+.global signal_bh_trampoline
+.text
+
+/*
+ * signal_bh_trampoline - saves the caller saved registers and calls
+ * signal bottom half hanlder.
+ */
+signal_bh_trampoline:
+ push %ebp
+ mov %esp, %ebp
+
+ /* save caller saved registers */
+ pushl %eax
+ pushl %ecx
+ pushl %edx
+
+ /* push signal bottom half handler's argument - address of
+ faulting instruction. */
+ pushl 8(%ebp)
+
+ /* call the signal bottom half handler */
+ pushl $.bh_return
+ pushl 4(%ebp)
+ ret
+
+.bh_return:
+ /* cleanup call arguments */
+ addl $4,%esp
+
+ /* overwrite return address */
+ movl %eax, 8(%ebp)
+
+ /* restore caller saved registers */
+ popl %edx
+ popl %ecx
+ popl %eax
+
+ popl %ebp
+
+ /* Skip bottom half hanlder address pushed by signal_install_bh() */
+ addl $4,%esp
+ ret
diff --git a/include/vm/signal.h b/include/vm/signal.h
index dad9381..a188daf 100644
--- a/include/vm/signal.h
+++ b/include/vm/signal.h
@@ -1,7 +1,12 @@
#ifndef VM_SIGNAL_H
#define VM_SIGNAL_H
-typedef void (*signal_bh_fn)(void);
+/*
+ * Signal bottom half handler is called with the address of faulting
+ * instruction as argument. The address that handler returns is the
+ * address to which controll will be transfered when it returns.
+ */
+typedef unsigned long (*signal_bh_fn)(unsigned long);
void setup_signal_handlers(void);
int install_signal_bh(void *ctx, signal_bh_fn bh);
diff --git a/vm/signal.c b/vm/signal.c
index ea33596..c1dfdc7 100644
--- a/vm/signal.c
+++ b/vm/signal.c
@@ -37,17 +37,40 @@
#include <stddef.h>
#include <unistd.h>
-static void throw_arithmetic_exception(void)
+static unsigned long
+throw_from_signal_bh(unsigned long jit_addr)
+{
+ struct jit_stack_frame *frame;
+ struct compilation_unit *cu;
+
+ /*
+ * The frame chain looks like this here:
+ *
+ * 0 <throw_from_signal_bh>
+ * 1 <signal_bottom_half_handler>
+ * 2 <signal_bh_trampoline>
+ * 3 <jit_method>
+ * ...
+ */
+ frame = __builtin_frame_address(3);
+
+ cu = get_cu_from_native_addr(jit_addr);
+
+ return (unsigned long)throw_exception_from(cu, frame,
+ (unsigned char *)jit_addr);
+}
+
+static unsigned long throw_arithmetic_exception(unsigned long src_addr)
{
signal_new_exception("java/lang/ArithmeticException",
"division by zero");
- throw_from_native(0);
+ return throw_from_signal_bh(src_addr);
}
-static void throw_null_pointer_exception(void)
+static unsigned long throw_null_pointer_exception(unsigned long src_addr)
{
signal_new_exception("java/lang/NullPointerException", NULL);
- throw_from_native(0);
+ return throw_from_signal_bh(src_addr);
}
static void sigfpe_handler(int sig, siginfo_t *si, void *ctx)
--
1.6.0.6
------------------------------------------------------------------------------
_______________________________________________
Jatovm-devel mailing list
Jatovm-devel@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/jatovm-devel
