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// Copyright 2015, ARM Limited
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are met:
//
// * Redistributions of source code must retain the above copyright notice,
// this list of conditions and the following disclaimer.
// * Redistributions in binary form must reproduce the above copyright notice,
// this list of conditions and the following disclaimer in the documentation
// and/or other materials provided with the distribution.
// * Neither the name of ARM Limited nor the names of its contributors may be
// used to endorse or promote products derived from this software without
// specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS CONTRIBUTORS "AS IS" AND
// ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
// WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
// DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE
// FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
// DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
// SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
// CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
// OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
#include "jit/arm64/vixl/Cpu-vixl.h"
#include "jit/arm64/vixl/Simulator-vixl.h"
#include "jit/arm64/vixl/Utils-vixl.h"
#include "util/Windows.h"
#if defined(XP_DARWIN)
# include <libkern/OSCacheControl.h>
#endif
#if defined(__aarch64__) && !defined(_MSC_VER) && !defined(XP_DARWIN)
# if defined(__linux__)
# include <linux/membarrier.h>
# include <sys/syscall.h>
# include <sys/utsname.h>
# include <unistd.h>
# elif defined(__ANDROID__)
# include <sys/syscall.h>
# include <unistd.h>
# else
# error "Missing platform-specific declarations for membarrier syscall!"
# endif // __linux__ / ANDROID
# include "vm/JSContext.h" // TlsContext
static int membarrier(int cmd, int flags) {
return syscall(__NR_membarrier, cmd, flags);
}
// These definitions come from the Linux kernel source, for kernels before 4.16
// which didn't have access to these membarrier commands.
# ifndef MEMBARRIER_CMD_PRIVATE_EXPEDITED_SYNC_CORE
# define MEMBARRIER_CMD_PRIVATE_EXPEDITED_SYNC_CORE (1 << 5)
# endif
# ifndef MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED_SYNC_CORE
# define MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED_SYNC_CORE (1 << 6)
# endif
#endif // __aarch64__
namespace vixl {
// Currently computes I and D cache line size.
void CPU::SetUp() {
uint32_t cache_type_register = GetCacheType();
// The cache type register holds information about the caches, including I
// D caches line size.
static const int kDCacheLineSizeShift = 16;
static const int kICacheLineSizeShift = 0;
static const uint32_t kDCacheLineSizeMask = 0xf << kDCacheLineSizeShift;
static const uint32_t kICacheLineSizeMask = 0xf << kICacheLineSizeShift;
// The cache type register holds the size of the I and D caches in words as
// a power of two.
uint32_t dcache_line_size_power_of_two =
(cache_type_register & kDCacheLineSizeMask) >> kDCacheLineSizeShift;
uint32_t icache_line_size_power_of_two =
(cache_type_register & kICacheLineSizeMask) >> kICacheLineSizeShift;
dcache_line_size_ = 4 << dcache_line_size_power_of_two;
icache_line_size_ = 4 << icache_line_size_power_of_two;
// Bug 1521158 suggests that having CPU with different cache line sizes could
// cause issues as we would only invalidate half of the cache line of we
// invalidate every 128 bytes, but other little cores have a different stride
// such as 64 bytes. To be conservative, we will try reducing the stride to 32
// bytes, which should be smaller than any known cache line.
const uint32_t conservative_line_size = 32;
dcache_line_size_ = std::min(dcache_line_size_, conservative_line_size);
icache_line_size_ = std::min(icache_line_size_, conservative_line_size);
}
uint32_t CPU::GetCacheType() {
#if defined(__aarch64__) && !defined(_MSC_VER) && !defined(XP_DARWIN)
uint64_t cache_type_register;
// Copy the content of the cache type register to a core register.
__asm__ __volatile__ ("mrs %[ctr], ctr_el0" // NOLINT
: [ctr] "=r" (cache_type_register));
VIXL_ASSERT(IsUint32(cache_type_register));
return static_cast<uint32_t>(cache_type_register);
#else
// This will lead to a cache with 1 byte long lines, which is fine since
// neither EnsureIAndDCacheCoherency nor the simulator will need this
// information.
return 0;
#endif
}
bool CPU::CanFlushICacheFromBackgroundThreads() {
#if defined(__aarch64__) && !defined(_MSC_VER) && !defined(XP_DARWIN)
// On linux, check the kernel supports membarrier(2), that is, it's a kernel
// above Linux 4.16 included.
//
// Note: this code has been extracted (August 2020) from
static constexpr int kRequiredMajor = 4;
static constexpr int kRequiredMinor = 16;
static bool computed = false;
static bool kernelHasMembarrier = false;
if (!computed) {
struct utsname uts;
int major, minor;
kernelHasMembarrier = uname(&uts) == 0 &&
strcmp(uts.sysname, "Linux") == 0 &&
sscanf(uts.release, "%d.%d", &major, &minor) == 2 &&
major >= kRequiredMajor && (major != kRequiredMajor || minor >= kRequiredMinor);
// As a test bed, try to run the syscall with the command registering the
// intent to use the actual membarrier we'll want to carry out later.
if (kernelHasMembarrier &&
membarrier(MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED_SYNC_CORE, 0) != 0) {
kernelHasMembarrier = false;
}
computed = true;
}
return kernelHasMembarrier;
#else
// On other platforms, we assume that the provided syscall does the right thing.
return true;
#endif
}
void CPU::EnsureIAndDCacheCoherency(void *address, size_t length, bool codeIsThreadLocal) {
#if defined(JS_SIMULATOR_ARM64) && defined(JS_CACHE_SIMULATOR_ARM64)
// This code attempts to emulate what the following assembly sequence is
// doing, which is sending the information to all cores that some cache line
// have to be invalidated and invalidating them only on the current core.
//
// This is done by recording the current range to be flushed to all
// simulators, then if there is a simulator associated with the current
// thread, applying all flushed ranges as the "isb" instruction would do.
//
// As we have no control over the CPU cores used by the code generator and the
// execution threads, this code assumes that each thread runs on its own core.
//
// See Bug 1529933 for more detailed explanation of this issue.
using js::jit::SimulatorProcess;
js::jit::AutoLockSimulatorCache alsc;
if (length > 0) {
SimulatorProcess::recordICacheFlush(address, length);
}
Simulator* sim = vixl::Simulator::Current();
if (sim) {
sim->FlushICache();
} else if (!codeIsThreadLocal) {
// We're on a background thread; emulate what the real hardware would do by
// emitting a membarrier that'll interrupt and cause an icache invalidation
// on all the threads.
SimulatorProcess::membarrier();
}
#elif defined(_MSC_VER) && defined(_M_ARM64)
FlushInstructionCache(GetCurrentProcess(), address, length);
#elif defined(XP_DARWIN)
sys_icache_invalidate(address, length);
#elif defined(__aarch64__)
// Implement the cache synchronisation for all targets where AArch64 is the
// host, even if we're building the simulator for an AAarch64 host. This
// allows for cases where the user wants to simulate code as well as run it
// natively.
if (length == 0) {
return;
}
// The code below assumes user space cache operations are allowed.
// Work out the line sizes for each cache, and use them to determine the
// start addresses.
uintptr_t start = reinterpret_cast<uintptr_t>(address);
uintptr_t dsize = static_cast<uintptr_t>(dcache_line_size_);
uintptr_t isize = static_cast<uintptr_t>(icache_line_size_);
uintptr_t dline = start & ~(dsize - 1);
uintptr_t iline = start & ~(isize - 1);
// Cache line sizes are always a power of 2.
VIXL_ASSERT(IsPowerOf2(dsize));
VIXL_ASSERT(IsPowerOf2(isize));
uintptr_t end = start + length;
do {
__asm__ __volatile__ (
// Clean each line of the D cache containing the target data.
//
// dc : Data Cache maintenance
// c : Clean
// i : Invalidate
// va : by (Virtual) Address
// c : to the point of Coherency
// Original implementation used cvau, but changed to civac due to
// errata on Cortex-A53 819472, 826319, 827319 and 824069.
// See ARM DDI 0406B page B2-12 for more information.
//
" dc civac, %[dline]\n"
:
: [dline] "r" (dline)
// This code does not write to memory, but the "memory" dependency
// prevents GCC from reordering the code.
: "memory");
dline += dsize;
} while (dline < end);
__asm__ __volatile__ (
// Make sure that the data cache operations (above) complete before the
// instruction cache operations (below).
//
// dsb : Data Synchronisation Barrier
// ish : Inner SHareable domain
//
// The point of unification for an Inner Shareable shareability domain is
// the point by which the instruction and data caches of all the processors
// in that Inner Shareable shareability domain are guaranteed to see the
// same copy of a memory location. See ARM DDI 0406B page B2-12 for more
// information.
" dsb ish\n"
: : : "memory");
do {
__asm__ __volatile__ (
// Invalidate each line of the I cache containing the target data.
//
// ic : Instruction Cache maintenance
// i : Invalidate
// va : by Address
// u : to the point of Unification
" ic ivau, %[iline]\n"
:
: [iline] "r" (iline)
: "memory");
iline += isize;
} while (iline < end);
__asm__ __volatile__ (
// Make sure that the instruction cache operations (above) take effect
// before the isb (below).
" dsb ish\n"
// Ensure that any instructions already in the pipeline are discarded and
// reloaded from the new data.
// isb : Instruction Synchronisation Barrier
" isb\n"
: : : "memory");
if (!codeIsThreadLocal) {
// If we're on a background thread, emit a membarrier that will synchronize
// all the executing threads with the new version of the code.
JSContext* cx = js::TlsContext.get();
if (!cx || !cx->isMainThreadContext()) {
MOZ_RELEASE_ASSERT(CPU::CanFlushICacheFromBackgroundThreads());
// The intent to use this command has been carried over in
// CanFlushICacheFromBackgroundThreads.
if (membarrier(MEMBARRIER_CMD_PRIVATE_EXPEDITED_SYNC_CORE, 0) != 0) {
// Better safe than sorry.
MOZ_CRASH("membarrier can't be executed");
}
}
}
#else
// If the host isn't AArch64, we must be using the simulator, so this function
// doesn't have to do anything.
USE(address, length);
#endif
}
} // namespace vixl