Add implicit null pointer and stack overflow checks for Mips.
Bug: 21555893
Change-Id: I2a995be128a5603d08753c14956dd8c8240ac63c
diff --git a/runtime/arch/mips/fault_handler_mips.cc b/runtime/arch/mips/fault_handler_mips.cc
index abe495b..8ea78eb 100644
--- a/runtime/arch/mips/fault_handler_mips.cc
+++ b/runtime/arch/mips/fault_handler_mips.cc
@@ -17,11 +17,17 @@
#include "fault_handler.h"
#include <sys/ucontext.h>
+#include "art_method-inl.h"
#include "base/macros.h"
#include "globals.h"
#include "base/logging.h"
#include "base/hex_dump.h"
+#include "registers_mips.h"
+#include "thread.h"
+#include "thread-inl.h"
+extern "C" void art_quick_throw_stack_overflow();
+extern "C" void art_quick_throw_null_pointer_exception();
//
// Mips specific fault handler functions.
@@ -33,16 +39,52 @@
void* context ATTRIBUTE_UNUSED) {
}
-void FaultManager::GetMethodAndReturnPcAndSp(siginfo_t* siginfo ATTRIBUTE_UNUSED,
- void* context ATTRIBUTE_UNUSED,
- ArtMethod** out_method ATTRIBUTE_UNUSED,
- uintptr_t* out_return_pc ATTRIBUTE_UNUSED,
- uintptr_t* out_sp ATTRIBUTE_UNUSED) {
+void FaultManager::GetMethodAndReturnPcAndSp(siginfo_t* siginfo, void* context,
+ ArtMethod** out_method,
+ uintptr_t* out_return_pc, uintptr_t* out_sp) {
+ struct ucontext* uc = reinterpret_cast<struct ucontext*>(context);
+ struct sigcontext *sc = reinterpret_cast<struct sigcontext*>(&uc->uc_mcontext);
+ *out_sp = static_cast<uintptr_t>(sc->sc_regs[29]); // SP register
+ VLOG(signals) << "sp: " << *out_sp;
+ if (*out_sp == 0) {
+ return;
+ }
+
+ // In the case of a stack overflow, the stack is not valid and we can't
+ // get the method from the top of the stack. However it's in r0.
+ uintptr_t* fault_addr = reinterpret_cast<uintptr_t*>(siginfo->si_addr); // BVA addr
+ uintptr_t* overflow_addr = reinterpret_cast<uintptr_t*>(
+ reinterpret_cast<uint8_t*>(*out_sp) - GetStackOverflowReservedBytes(kMips));
+ if (overflow_addr == fault_addr) {
+ *out_method = reinterpret_cast<ArtMethod*>(sc->sc_regs[4]); // A0 register
+ } else {
+ // The method is at the top of the stack.
+ *out_method = *reinterpret_cast<ArtMethod**>(*out_sp);
+ }
+
+ // Work out the return PC. This will be the address of the instruction
+ // following the faulting ldr/str instruction.
+
+ VLOG(signals) << "pc: " << std::hex
+ << static_cast<void*>(reinterpret_cast<uint8_t*>(sc->sc_pc));
+
+ *out_return_pc = sc->sc_pc + 4;
}
bool NullPointerHandler::Action(int sig ATTRIBUTE_UNUSED, siginfo_t* info ATTRIBUTE_UNUSED,
- void* context ATTRIBUTE_UNUSED) {
- return false;
+ void* context) {
+ // The code that looks for the catch location needs to know the value of the
+ // PC at the point of call. For Null checks we insert a GC map that is immediately after
+ // the load/store instruction that might cause the fault.
+
+ struct ucontext *uc = reinterpret_cast<struct ucontext*>(context);
+ struct sigcontext *sc = reinterpret_cast<struct sigcontext*>(&uc->uc_mcontext);
+
+ sc->sc_regs[31] = sc->sc_pc + 4; // RA needs to point to gc map location
+ sc->sc_pc = reinterpret_cast<uintptr_t>(art_quick_throw_null_pointer_exception);
+ sc->sc_regs[25] = sc->sc_pc; // make sure T9 points to the function
+ VLOG(signals) << "Generating null pointer exception";
+ return true;
}
bool SuspensionHandler::Action(int sig ATTRIBUTE_UNUSED, siginfo_t* info ATTRIBUTE_UNUSED,
@@ -50,8 +92,51 @@
return false;
}
-bool StackOverflowHandler::Action(int sig ATTRIBUTE_UNUSED, siginfo_t* info ATTRIBUTE_UNUSED,
- void* context ATTRIBUTE_UNUSED) {
- return false;
+// Stack overflow fault handler.
+//
+// This checks that the fault address is equal to the current stack pointer
+// minus the overflow region size (16K typically). The instruction that
+// generates this signal is:
+//
+// lw zero, -16384(sp)
+//
+// It will fault if sp is inside the protected region on the stack.
+//
+// If we determine this is a stack overflow we need to move the stack pointer
+// to the overflow region below the protected region.
+
+bool StackOverflowHandler::Action(int sig ATTRIBUTE_UNUSED, siginfo_t* info, void* context) {
+ struct ucontext* uc = reinterpret_cast<struct ucontext*>(context);
+ struct sigcontext *sc = reinterpret_cast<struct sigcontext*>(&uc->uc_mcontext);
+ VLOG(signals) << "stack overflow handler with sp at " << std::hex << &uc;
+ VLOG(signals) << "sigcontext: " << std::hex << sc;
+
+ uintptr_t sp = sc->sc_regs[29]; // SP register
+ VLOG(signals) << "sp: " << std::hex << sp;
+
+ uintptr_t fault_addr = reinterpret_cast<uintptr_t>(info->si_addr); // BVA addr
+ VLOG(signals) << "fault_addr: " << std::hex << fault_addr;
+ VLOG(signals) << "checking for stack overflow, sp: " << std::hex << sp <<
+ ", fault_addr: " << fault_addr;
+
+ uintptr_t overflow_addr = sp - GetStackOverflowReservedBytes(kMips);
+
+ // Check that the fault address is the value expected for a stack overflow.
+ if (fault_addr != overflow_addr) {
+ VLOG(signals) << "Not a stack overflow";
+ return false;
+ }
+
+ VLOG(signals) << "Stack overflow found";
+
+ // Now arrange for the signal handler to return to art_quick_throw_stack_overflow_from.
+ // The value of RA must be the same as it was when we entered the code that
+ // caused this fault. This will be inserted into a callee save frame by
+ // the function to which this handler returns (art_quick_throw_stack_overflow).
+ sc->sc_pc = reinterpret_cast<uintptr_t>(art_quick_throw_stack_overflow);
+ sc->sc_regs[25] = sc->sc_pc; // make sure T9 points to the function
+
+ // The kernel will now return to the address in sc->arm_pc.
+ return true;
}
} // namespace art