Some of the new Linux/Android tests were failing in 32-bit code where
pointers were being casted via reinterpret_cast<>() to LinuxVMAddress,
an unsigned 64-bit type. The behavior of such casts is
implementation-defined, and in this case, sign-extension was being used
to convert the 32-bit pointers to 64 bits, resulting in very large
(unsigned) LinuxVMAddress values that could not possibly refer to proper
addresses in a 32-bit process’ address space.
The offending reinterpret_cast<>() conversions have been replaced with
the new FromPointerCast<>(), which is careful to do sign-extension when
converting to a signed type, and zero-extension when converting to an
unsigned type like LinuxVMAddress.
Bug: crashpad:30
Test: crashpad_util_test FromPointerCast*:MemoryMap.*:ProcessMemory.*
Change-Id: I6f1408dc63369a8740ecd6015d657e4407a7c271
Reviewed-on: https://chromium-review.googlesource.com/488264
Reviewed-by: Joshua Peraza <jperaza@chromium.org>
This fixes ProcessMemory for 32-bit processes. All ProcessMemory tests
were failing on 32-bit ARM on Android like this:
[ RUN ] ProcessMemory.ReadSelf
[17345:17345:20170407,172222.579687:ERROR process_memory.cc:55] pread: Invalid argument (22)
../../../../util/linux/process_memory_test.cc:73: Failure
Value of: memory.Read(address, region_size_, result.get())
Actual: false
Expected: true
[ FAILED ] ProcessMemory.ReadSelf (5 ms)
Contemporary Linux doesn’t provide a pread() system call, it provides
pread64(), which operates on off64_t. pread() is a user-space wrapper
that accepts off_t. See Android 7.1.1
bionic/libc/bionic/legacy_32_bit_support.cpp pread().
Note that off_t is a signed type. With a 32-bit off_t, when the
“offset” parameter to pread() has its high bit set, it will be
sign-extended into the 64-bit off64_t, and when interpreted as a memory
address by virtue of being used as an offset into /proc/pid/mem, the
value will take on an incorrect meaning. In fact, the kernel will reject
it outright for its negativity. See linux-4.9.20/fs/read_write.c
[sys_]pread64().
Since ProcessMemory accepts its address parameter as a LinuxVMAddress,
which is wisely a uint64_t, it converts to off64_t properly, retaining
its original value.
Note, however, that the pread64() mechanism evidently cannot read memory
in the high half of a process’ address space even when pread64() is used
throughout. Most importantly, the (pos < 0) check in the kernel will be
tripped. Less importantly, the conversion of our unsigned LinuxVMAddress
to pread64’s signed off64_t, with the high bit set, is not defined. This
is not an immediate practical problem. With the exception of possible
shared pages mapped from kernel space (I only see this for the vsyscall
page on x86_64), Linux restricts 64-bit user process’ address space to
at least the lower half of the addressable range, with the high bit
clear. (The limit of the user address space is
linux-4.9.20/arch/x86/include/asm/processor.h TASK_SIZE_MAX =
0x7ffffffff000 for x86_64 and
linux-4.9.20/arch/arm64/include/asm/memory.h TASK_SIZE_64 =
0x1000000000000 at maximum for arm64.)
The 32-bit off_t may be a surprise, because
third_party/mini_chromium/mini_chromium/build/common.gypi sets
_FILE_OFFSET_BITS=64. Altough this macro is considered in the NDK’s
“unified headers”, in the classic NDK, this macro is never consulted.
Instead, off_t is always “long”, and pread() always gets the
compatibility shim in Bionic.
Bug: crashpad:30
Change-Id: Id00c882a3d521a46ef3fc0060d03ea0ab9493175
Reviewed-on: https://chromium-review.googlesource.com/472048
Reviewed-by: Joshua Peraza <jperaza@chromium.org>
When Yama is enabled and /proc/sys/kernel/yama/ptrace_scope is set to 1
(YAMA_SCOPE_RELATIONAL), for a child to ptrace() its parent, the parent
must first call prctl(PR_SET_PTRACER, child_pid, ...).
Bug: crashpad:30
Test: crashpad_util_test ScopedPtraceAttach.*
Change-Id: Ic85e8551259f17f372b2362887e7701b833b4cb4
Reviewed-on: https://chromium-review.googlesource.com/472006
Reviewed-by: Joshua Peraza <jperaza@chromium.org>
gtest used to require (expected, actual) ordering for arguments to
EXPECT_EQ and ASSERT_EQ, and in failed test assertions would identify
each side as “expected” or “actual.” Tests in Crashpad adhered to this
traditional ordering. After a gtest change in February 2016, it is now
agnostic with respect to the order of these arguments.
This change mechanically updates all uses of these macros to (actual,
expected) by reversing them. This provides consistency with our use of
the logging CHECK_EQ and DCHECK_EQ macros, and makes for better
readability by ordinary native speakers. The rough (but working!)
conversion tool is
https://chromium-review.googlesource.com/c/466727/1/rewrite_expectassert_eq.py,
and “git cl format” cleaned up its output.
EXPECT_NE and ASSERT_NE never had a preferred ordering. gtest never made
a judgment that one side or the other needed to provide an “unexpected”
value. Consequently, some code used (unexpected, actual) while other
code used (actual, unexpected). For consistency with the new EXPECT_EQ
and ASSERT_EQ usage, as well as consistency with CHECK_NE and DCHECK_NE,
this change also updates these use sites to (actual, unexpected) where
one side can be called “unexpected” as, for example, std::string::npos
can be. Unfortunately, this portion was a manual conversion.
References:
https://github.com/google/googletest/blob/master/googletest/docs/Primer.md#binary-comparison77d6b17338https://github.com/google/googletest/pull/713
Change-Id: I978fef7c94183b8b1ef63f12f5ab4d6693626be3
Reviewed-on: https://chromium-review.googlesource.com/466727
Reviewed-by: Scott Graham <scottmg@chromium.org>
Provides Read, ReadCString, and ReadCStringSizeLimited. Does not provide
ReadMapped because Linux does not support mmap on /proc/pid/mem.
Bug: crashpad:30
Change-Id: Ia319c0107b1f138aeb8e5d0ee480c77310df7202
Reviewed-on: https://chromium-review.googlesource.com/459700
Reviewed-by: Mark Mentovai <mark@chromium.org>
Commit-Queue: Joshua Peraza <jperaza@chromium.org>
