| Commit message (Collapse) | Author | Age | Files | Lines |
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This is a workaround (hack) for a gcc optimization issue (PR 99551).
Without this the generated code may evaluate the expression in the
cold path which causes performance regression for small allocations
in the memory tagging disabled (common) case.
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The internal _mid_memalign already returns newly tagged memory.
(__libc_memalign and posix_memalign already relied on this, this
patch fixes the other call sites.)
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The previous patch ensured that all chunk to mem computations use
chunk2rawmem, so now we can rename it to chunk2mem, and in the few
cases where the tag of mem is relevant chunk2mem_tag can be used.
Replaced tag_at (chunk2rawmem (x)) with chunk2mem_tag (x).
Renamed chunk2rawmem to chunk2mem.
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The difference between chunk2mem and chunk2rawmem is that the latter
does not get the memory tag for the returned pointer. It turns out
chunk2rawmem almost always works:
The input of chunk2mem is a chunk pointer that is untagged so it can
access the chunk header. All memory that is not user allocated heap
memory is untagged, which in the current implementation means that it
has the 0 tag, but this patch does not rely on the tag value. The
patch relies on that chunk operations are either done on untagged
chunks or without doing memory access to the user owned part.
Internal interface contracts:
sysmalloc: Returns untagged memory.
_int_malloc: Returns untagged memory.
_int_free: Takes untagged memory.
_int_memalign: Returns untagged memory.
_int_realloc: Takes and returns tagged memory.
So only _int_realloc and functions outside this list need care.
Alignment checks do not need the right tag and tcache works with
untagged memory.
tag_at was kept in realloc after an mremap, which is not strictly
necessary, since the pointer is only used to retag the memory, but this
way the tag is guaranteed to be different from the old tag.
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The comment explained why different tag is used after mremap, but
for that correctly tagged pointer should be passed to tag_new_usable.
Use chunk2mem to get the tag.
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This is a pure refactoring change that does not affect behaviour.
The CHUNK_AVAILABLE_SIZE name was unclear, the memsize name tries to
follow the existing convention of mem denoting the allocation that is
handed out to the user, while chunk is its internally used container.
The user owned memory for a given chunk starts at chunk2mem(p) and
the size is memsize(p). It is not valid to use on dumped heap chunks.
Moved the definition next to other chunk and mem related macros.
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This is a target hook for memory tagging, the original was a naive
implementation. Uses the same algorithm as __libc_mtag_tag_region,
but with instructions that also zero the memory. This was not
benchmarked on real cpu, but expected to be faster than the naive
implementation.
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This is a target hook for memory tagging, the original was a naive
implementation. The optimized version relies on "dc gva" to tag 64
bytes at a time for large allocations and optimizes small cases without
adding too many branches. This was not benchmarked on real cpu, but
expected to be faster than the naive implementation.
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This is a common operation when heap tagging is enabled, so inline the
instructions instead of using an extern call.
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This is a common operation when heap tagging is enabled, so inline the
instruction instead of using an extern call.
The .inst directive is used instead of the name of the instruction (or
acle intrinsics) because malloc.c is not compiled for armv8.5-a+memtag
architecture, runtime cpu support detection is used.
Prototypes are removed from the comments as they were not always
correct.
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Use the runtime check where possible: it should not cause slow down in
the !USE_MTAG case since then mtag_enabled is constant false, but it
allows compiling the tagging logic so it's less likely to break or
diverge when developers only test the !USE_MTAG case.
Reviewed-by: DJ Delorie <dj@redhat.com>
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The branches may be better optimized since mtag_enabled is widely used.
Granule size larger than a chunk header is not supported since then we
cannot have both the chunk header and user area granule aligned. To
fix that for targets with large granule, the chunk layout has to change.
So code that attempted to handle the granule mask generally was changed.
This simplified CHUNK_AVAILABLE_SIZE and the logic in malloc_usable_size.
Reviewed-by: DJ Delorie <dj@redhat.com>
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When glibc is built with memory tagging support (USE_MTAG) but it is not
enabled at runtime (mtag_enabled) then unconditional memset was used
even though that can be often avoided.
This is for performance when tagging is supported but not enabled.
The extra check should have no overhead: tag_new_zero_region already
had a runtime check which the compiler can now optimize away.
Reviewed-by: DJ Delorie <dj@redhat.com>
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The memset api is suboptimal and does not provide much benefit. Memory
tagging only needs a zeroing memset (and only for memory that's sized
and aligned to multiples of the tag granule), so change the internal
api and the target hooks accordingly. This is to simplify the
implementation of the target hook.
Reviewed-by: DJ Delorie <dj@redhat.com>
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A flag check can be faster than function pointers because of how
branch prediction and speculation works and it can also remove a layer
of indirection when there is a mismatch between the malloc internal
tag_* api and __libc_mtag_* target hooks.
Memory tagging wrapper functions are moved to malloc.c from arena.c and
the logic now checks mmap_enabled. The definition of tag_new_usable is
moved after chunk related definitions.
This refactoring also allows using mtag_enabled checks instead of
USE_MTAG ifdefs when memory tagging support only changes code logic
when memory tagging is enabled at runtime. Note: an "if (false)" code
block is optimized away even at -O0 by gcc.
Reviewed-by: DJ Delorie <dj@redhat.com>
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This does not change behaviour, just removes one layer of indirection
in the internal memory tagging logic.
Use tag_ and mtag_ prefixes instead of __tag_ and __mtag_ since these
are all symbols with internal linkage, private to malloc.c, so there
is no user namespace pollution issue.
Reviewed-by: DJ Delorie <dj@redhat.com>
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Use inline functions instead of macros, because macros can cause unused
variable warnings and type conversion issues. We assume these functions
may appear in the code but only in dead code paths (hidden by a runtime
check), so it's important that they can compile with correct types, but
if they are actually used that should be an error.
Currently the hooks are only used when USE_MTAG is true which only
happens on aarch64 and then the aarch64 specific code is used not this
generic header. However followup refactoring will allow the hooks to
be used with !USE_MTAG.
Note: the const qualifier in the comment was wrong: changing tags is a
write operation.
Reviewed-by: DJ Delorie <dj@redhat.com>
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Either the memory belongs to the dumped area, in which case we don't
want to tag (the dumped area has the same tag as malloc internal data
so tagging is unnecessary, but chunks there may not have the right
alignment for the tag granule), or the memory will be unmapped
immediately (and thus tagging is not useful).
Reviewed-by: DJ Delorie <dj@redhat.com>
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The chunk cannot be a dumped one here. The only non-obvious cases
are free and realloc which may be called on a dumped area chunk,
but in both cases it can be verified that tagging is already
avoided for dumped area chunks.
Reviewed-by: DJ Delorie <dj@redhat.com>
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This is only used internally in malloc.c, the extern declaration
was wrong, __mtag_mmap_flags has internal linkage.
Reviewed-by: DJ Delorie <dj@redhat.com>
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The value of PR_TAGGED_ADDR_ENABLE was incorrect in the installed
headers and the prctl command macros were missing that are needed
for it to be useful (PR_SET_TAGGED_ADDR_CTRL). Linux headers have
the definitions since 5.4 so it's widely available, we don't need
to repeat these definitions. The remaining definitions are from
Linux 5.10.
To build glibc with --enable-memory-tagging, Linux 5.4 headers and
binutils 2.33.1 or newer is needed.
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At an _int_free call site in realloc the wrong size was used for tag
clearing: the chunk header of the next chunk was also cleared which
in practice may work, but logically wrong.
The tag clearing is moved before the memcpy to save a tag computation,
this avoids a chunk2mem. Another chunk2mem is removed because newmem
does not have to be recomputed. Whitespaces got fixed too.
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_int_free must be called with a chunk that has its tag reset. This was
missing in a rare case that could crash when heap tagging is enabled:
when in a multi-threaded process the current arena runs out of memory
during realloc, but another arena still has space to finish the realloc
then _int_free was called without clearing the user allocation tags.
Fixes bug 27468.
Reviewed-by: DJ Delorie <dj@redhat.com>
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It fixes the build on ARM in thumb mode that requires an out of the
line helper (__libc_do_syscall) to issue the syscall.
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The generic implementation basically handle the system agnostic logic
(filtering out the invalid signals) while the __libc_sigaction is
the function with implements the system and architecture bits.
Checked on x86_64-linux-gnu and i686-linux-gnu.
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The libc version is identical and built with same flags.
Checked on x86_64-linux-gnu.
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The libc version is identical and built with same flags.
Checked on x86_64-linux-gnu.
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The libc version is identical and built with same flags.
Checked on x86_64-linux-gnu.
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The libc version is identical and built with same flags.
Checked on x86_64-linux-gnu.
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The libc version is identical and built with same flags.
Checked on x86_64-linux-gnu.
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The libc version is identical and built with same flags.
Checked on x86_64-linux-gnu.
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The libc version is identical and built with same flags.
Checked on x86_64-linux-gnu.
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The libc version is identical and built with same flags.
Checked on x86_64-linux-gnu.
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The libc version is identical and built with same flags.
Checked on x86_64-linux-gnu.
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The libc version is identical and built with same flags.
Checked on x86_64-linux-gnu.
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The libc version is identical and built with same flags.
Checked on x86_64-linux-gnu.
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The libc version is identical and built with same flags.
Checked on x86_64-linux-gnu.
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The libc version is identical and built with same flags.
Checked on x86_64-linux-gnu.
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The libc version is identical and built with same flags.
Checked on x86_64-linux-gnu.
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The libc version is identical and built with same flags.
Checked on x86_64-linux-gnu.
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The libc version is identical and built with same flags.
Checked on x86_64-linux-gnu.
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The libc version is identical and built with same flags.
Checked on x86_64-linux-gnu.
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Add a benchtest to ilogb, ilogbf and ilogbf128 based on the logb* benchtests.
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The POWER9 builtins used to improve the ilogb* functions can be
used in the llogb* functions as well.
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The instructions xsxexpdp and xsxexpqp introduced on POWER9 extract
the exponent from a double-precision and quad-precision floating-point
respectively, thus they can be used to improve ilogb, ilogbf and ilogbf128.
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This detects some bogus abilist files.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
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Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
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It is not actually used by the legacy unwinder linked into
libc.so, and it conflicts with the unwind-link functionality
in libpthread.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
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Pass environ to posix_spawn so that the child process can inherit
environment of the test.
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Generated with 'make regen-ulps' on POWER8.
Tested on powerpc, powerpc64, and powerpc64le
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