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author | Paul Lind <paul.lind@imgtec.com> | 2013-05-06 16:09:29 -0700 |
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committer | Paul Lind <paul.lind@imgtec.com> | 2013-05-06 16:10:07 -0700 |
commit | 3ee90b0f201427268e35d86d7ad95e45aa7491a8 (patch) | |
tree | 58c5c0c83fd997ff172dd47fc7d148fc3baa2e1b | |
parent | 7b6942b5f764ef3f146954bef70458db6a71e25d (diff) | |
download | android_external_v8-3ee90b0f201427268e35d86d7ad95e45aa7491a8.tar.gz android_external_v8-3ee90b0f201427268e35d86d7ad95e45aa7491a8.tar.bz2 android_external_v8-3ee90b0f201427268e35d86d7ad95e45aa7491a8.zip |
Use kernel cacheflush for large sizes on MIPS.
This is a workaround to a deserializer bug. The bug was exposed
with a recent optimization to use user-mode cache-flushing on
MIPS. To reduce risk, we're doing a workaround in mips-specific
code so that other arch's cannot be affected.
The deserializer does this FlushICache:
CPU::FlushICache(last_object_address_, Page::kPageSize);
However, that region includes OS guard-pages with no access
privilege. The MIPS kernel cacheflush routines work OK in this
case, but the Bionic cacheflush recently enabled user-mode flushing
using the synci instruction, which causes a segfault on MIPS when
the guard pages are reached.
(change I48fd6f2b0cbe80c3cd90f453ced97a2f154f7ad3)
The workaround just reverts to the kernel flush when the size
is Page::kPageSize or bigger.
A better fix would be to alter the deserializer so that only the
executable pages are flushed:
CPU::FlushICache(last_object_address_,
isolate_->memory_allocator()->CodePageAreaSize());
However, that changes common code for all supported architectures.
There is no evidence that this bug affects the other arch's, so we
are doing a MIPS-specific workaround.
Change-Id: I30b62eb579feab1453d3ae85a5fb9b408f91756b
Signed-off-by: Paul Lind <paul.lind@imgtec.com>
-rw-r--r-- | src/mips/cpu-mips.cc | 21 |
1 files changed, 17 insertions, 4 deletions
diff --git a/src/mips/cpu-mips.cc b/src/mips/cpu-mips.cc index 93ebeda8..b8200007 100644 --- a/src/mips/cpu-mips.cc +++ b/src/mips/cpu-mips.cc @@ -65,10 +65,23 @@ void CPU::FlushICache(void* start, size_t size) { #if !defined (USE_SIMULATOR) #if defined(ANDROID) - // Bionic cacheflush can typically run in userland, avoiding kernel call. - char *end = reinterpret_cast<char *>(start) + size; - cacheflush( - reinterpret_cast<intptr_t>(start), reinterpret_cast<intptr_t>(end), 0); + // Workaround for a deserializer bug. Bionic usermode cacheflush + // fails in deserializer for a size of Page::kPageSize (1MB), + // because that region contains protected pages. Switch to kernel + // cacheflush in this case. + if (size >= static_cast<size_t>(Page::kPageSize)) { + int res; + // See http://www.linux-mips.org/wiki/Cacheflush_Syscall. + res = syscall(__NR_cacheflush, start, size, ICACHE); + if (res) { + V8_Fatal(__FILE__, __LINE__, "Failed to flush the instruction cache"); + } + } else { + // Bionic cacheflush can typically run in userland, avoiding kernel call. + char *end = reinterpret_cast<char *>(start) + size; + cacheflush( + reinterpret_cast<intptr_t>(start), reinterpret_cast<intptr_t>(end), 0); + } #else // ANDROID int res; // See http://www.linux-mips.org/wiki/Cacheflush_Syscall. |