As raw_cpu_generic_read() is a plain read from a raw_cpu_ptr() address,
it's possible (albeit unlikely) that the compiler will split the access
across multiple instructions.
In this_cpu_generic_read() we disable preemption but not interrupts
before calling raw_cpu_generic_read(). Thus, an interrupt could be taken
in the middle of the split load instructions. If a this_cpu_write() or
RMW this_cpu_*() op is made to the same variable in the interrupt
handling path, this_cpu_read() will return a torn value.
For native word types, we can avoid tearing using READ_ONCE(), but this
won't work in all cases (e.g. 64-bit types on most 32-bit platforms).
This patch reworks this_cpu_generic_read() to use READ_ONCE() where
possible, otherwise falling back to disabling interrupts.
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Christoph Lameter <cl@linux.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Pranith Kumar <bobby.prani@gmail.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-arch@vger.kernel.org
Cc: stable@vger.kernel.org
Signed-off-by: Tejun Heo <tj@kernel.org>
Pull misc leftovers from Al Viro.
* 'work.misc' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
fix the __user misannotations in asm-generic get_user/put_user
fput: Don't reinvent the wheel but use existing llist API
namespace.c: Don't reinvent the wheel but use existing llist API
Pull MTD updates from Boris Brezillon:
"General updates:
- Constify pci_device_id in various drivers
- Constify device_type
- Remove pad control code from the Gemini driver
- Use %pOF to print OF node full_name
- Various fixes in the physmap_of driver
- Remove unused vars in mtdswap
- Check devm_kzalloc() return value in the spear_smi driver
- Check clk_prepare_enable() return code in the st_spi_fsm driver
- Create per MTD device debugfs enties
NAND updates, from Boris Brezillon:
- Fix memory leaks in the core
- Remove unused NAND locking support
- Rename nand.h into rawnand.h (preparing support for spi NANDs)
- Use NAND_MAX_ID_LEN where appropriate
- Fix support for 20nm Hynix chips
- Fix support for Samsung and Hynix SLC NANDs
- Various cleanup, improvements and fixes in the qcom driver
- Fixes for bugs detected by various static code analysis tools
- Fix mxc ooblayout definition
- Add a new part_parsers to tmio and sharpsl platform data in order
to define a custom list of partition parsers
- Request the reset line in exclusive mode in the sunxi driver
- Fix a build error in the orion-nand driver when compiled for ARMv4
- Allow 64-bit mvebu platforms to select the PXA3XX driver
SPI NOR updates, from Cyrille Pitchen and Marek Vasut:
- add support to the JEDEC JESD216B specification (SFDP tables).
- add support to the Intel Denverton SPI flash controller.
- fix error recovery for Spansion/Cypress SPI NOR memories.
- fix 4-byte address management for the Aspeed SPI controller.
- add support to some Microchip SST26 memory parts
- remove unneeded pinctrl header Write a message for tag:"
* tag 'for-linus-20170904' of git://git.infradead.org/linux-mtd: (74 commits)
mtd: nand: complain loudly when chip->bits_per_cell is not correctly initialized
mtd: nand: make Samsung SLC NAND usable again
mtd: nand: tmio: Register partitions using the parsers
mfd: tmio: Add partition parsers platform data
mtd: nand: sharpsl: Register partitions using the parsers
mtd: nand: sharpsl: Add partition parsers platform data
mtd: nand: qcom: Support for IPQ8074 QPIC NAND controller
mtd: nand: qcom: support for IPQ4019 QPIC NAND controller
dt-bindings: qcom_nandc: IPQ8074 QPIC NAND documentation
dt-bindings: qcom_nandc: IPQ4019 QPIC NAND documentation
dt-bindings: qcom_nandc: fix the ipq806x device tree example
mtd: nand: qcom: support for different DEV_CMD register offsets
mtd: nand: qcom: QPIC data descriptors handling
mtd: nand: qcom: enable BAM or ADM mode
mtd: nand: qcom: erased codeword detection configuration
mtd: nand: qcom: support for read location registers
mtd: nand: qcom: support for passing flags in DMA helper functions
mtd: nand: qcom: add BAM DMA descriptor handling
mtd: nand: qcom: allocate BAM transaction
mtd: nand: qcom: DMA mapping support for register read buffer
...
When THP migration is being used, memory management code needs to handle
pmd migration entries properly. This patch uses !pmd_present() or
is_swap_pmd() (depending on whether pmd_none() needs separate code or
not) to check pmd migration entries at the places where a pmd entry is
present.
Since pmd-related code uses split_huge_page(), split_huge_pmd(),
pmd_trans_huge(), pmd_trans_unstable(), or
pmd_none_or_trans_huge_or_clear_bad(), this patch:
1. adds pmd migration entry split code in split_huge_pmd(),
2. takes care of pmd migration entries whenever pmd_trans_huge() is present,
3. makes pmd_none_or_trans_huge_or_clear_bad() pmd migration entry aware.
Since split_huge_page() uses split_huge_pmd() and pmd_trans_unstable()
is equivalent to pmd_none_or_trans_huge_or_clear_bad(), we do not change
them.
Until this commit, a pmd entry should be:
1. pointing to a pte page,
2. is_swap_pmd(),
3. pmd_trans_huge(),
4. pmd_devmap(), or
5. pmd_none().
Signed-off-by: Zi Yan <zi.yan@cs.rutgers.edu>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Anshuman Khandual <khandual@linux.vnet.ibm.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: David Nellans <dnellans@nvidia.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Michal Hocko <mhocko@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Pull x86 mm changes from Ingo Molnar:
"PCID support, 5-level paging support, Secure Memory Encryption support
The main changes in this cycle are support for three new, complex
hardware features of x86 CPUs:
- Add 5-level paging support, which is a new hardware feature on
upcoming Intel CPUs allowing up to 128 PB of virtual address space
and 4 PB of physical RAM space - a 512-fold increase over the old
limits. (Supercomputers of the future forecasting hurricanes on an
ever warming planet can certainly make good use of more RAM.)
Many of the necessary changes went upstream in previous cycles,
v4.14 is the first kernel that can enable 5-level paging.
This feature is activated via CONFIG_X86_5LEVEL=y - disabled by
default.
(By Kirill A. Shutemov)
- Add 'encrypted memory' support, which is a new hardware feature on
upcoming AMD CPUs ('Secure Memory Encryption', SME) allowing system
RAM to be encrypted and decrypted (mostly) transparently by the
CPU, with a little help from the kernel to transition to/from
encrypted RAM. Such RAM should be more secure against various
attacks like RAM access via the memory bus and should make the
radio signature of memory bus traffic harder to intercept (and
decrypt) as well.
This feature is activated via CONFIG_AMD_MEM_ENCRYPT=y - disabled
by default.
(By Tom Lendacky)
- Enable PCID optimized TLB flushing on newer Intel CPUs: PCID is a
hardware feature that attaches an address space tag to TLB entries
and thus allows to skip TLB flushing in many cases, even if we
switch mm's.
(By Andy Lutomirski)
All three of these features were in the works for a long time, and
it's coincidence of the three independent development paths that they
are all enabled in v4.14 at once"
* 'x86-mm-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (65 commits)
x86/mm: Enable RCU based page table freeing (CONFIG_HAVE_RCU_TABLE_FREE=y)
x86/mm: Use pr_cont() in dump_pagetable()
x86/mm: Fix SME encryption stack ptr handling
kvm/x86: Avoid clearing the C-bit in rsvd_bits()
x86/CPU: Align CR3 defines
x86/mm, mm/hwpoison: Clear PRESENT bit for kernel 1:1 mappings of poison pages
acpi, x86/mm: Remove encryption mask from ACPI page protection type
x86/mm, kexec: Fix memory corruption with SME on successive kexecs
x86/mm/pkeys: Fix typo in Documentation/x86/protection-keys.txt
x86/mm/dump_pagetables: Speed up page tables dump for CONFIG_KASAN=y
x86/mm: Implement PCID based optimization: try to preserve old TLB entries using PCID
x86: Enable 5-level paging support via CONFIG_X86_5LEVEL=y
x86/mm: Allow userspace have mappings above 47-bit
x86/mm: Prepare to expose larger address space to userspace
x86/mpx: Do not allow MPX if we have mappings above 47-bit
x86/mm: Rename tasksize_32bit/64bit to task_size_32bit/64bit()
x86/xen: Redefine XEN_ELFNOTE_INIT_P2M using PUD_SIZE * PTRS_PER_PUD
x86/mm/dump_pagetables: Fix printout of p4d level
x86/mm/dump_pagetables: Generalize address normalization
x86/boot: Fix memremap() related build failure
...
Pull locking updates from Ingo Molnar:
- Add 'cross-release' support to lockdep, which allows APIs like
completions, where it's not the 'owner' who releases the lock, to be
tracked. It's all activated automatically under
CONFIG_PROVE_LOCKING=y.
- Clean up (restructure) the x86 atomics op implementation to be more
readable, in preparation of KASAN annotations. (Dmitry Vyukov)
- Fix static keys (Paolo Bonzini)
- Add killable versions of down_read() et al (Kirill Tkhai)
- Rework and fix jump_label locking (Marc Zyngier, Paolo Bonzini)
- Rework (and fix) tlb_flush_pending() barriers (Peter Zijlstra)
- Remove smp_mb__before_spinlock() and convert its usages, introduce
smp_mb__after_spinlock() (Peter Zijlstra)
* 'locking-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (56 commits)
locking/lockdep/selftests: Fix mixed read-write ABBA tests
sched/completion: Avoid unnecessary stack allocation for COMPLETION_INITIALIZER_ONSTACK()
acpi/nfit: Fix COMPLETION_INITIALIZER_ONSTACK() abuse
locking/pvqspinlock: Relax cmpxchg's to improve performance on some architectures
smp: Avoid using two cache lines for struct call_single_data
locking/lockdep: Untangle xhlock history save/restore from task independence
locking/refcounts, x86/asm: Disable CONFIG_ARCH_HAS_REFCOUNT for the time being
futex: Remove duplicated code and fix undefined behaviour
Documentation/locking/atomic: Finish the document...
locking/lockdep: Fix workqueue crossrelease annotation
workqueue/lockdep: 'Fix' flush_work() annotation
locking/lockdep/selftests: Add mixed read-write ABBA tests
mm, locking/barriers: Clarify tlb_flush_pending() barriers
locking/lockdep: Make CONFIG_LOCKDEP_CROSSRELEASE and CONFIG_LOCKDEP_COMPLETIONS truly non-interactive
locking/lockdep: Explicitly initialize wq_barrier::done::map
locking/lockdep: Rename CONFIG_LOCKDEP_COMPLETE to CONFIG_LOCKDEP_COMPLETIONS
locking/lockdep: Reword title of LOCKDEP_CROSSRELEASE config
locking/lockdep: Make CONFIG_LOCKDEP_CROSSRELEASE part of CONFIG_PROVE_LOCKING
locking/refcounts, x86/asm: Implement fast refcount overflow protection
locking/lockdep: Fix the rollback and overwrite detection logic in crossrelease
...
Pull x86 asm updates from Ingo Molnar:
- Introduce the ORC unwinder, which can be enabled via
CONFIG_ORC_UNWINDER=y.
The ORC unwinder is a lightweight, Linux kernel specific debuginfo
implementation, which aims to be DWARF done right for unwinding.
Objtool is used to generate the ORC unwinder tables during build, so
the data format is flexible and kernel internal: there's no
dependency on debuginfo created by an external toolchain.
The ORC unwinder is almost two orders of magnitude faster than the
(out of tree) DWARF unwinder - which is important for perf call graph
profiling. It is also significantly simpler and is coded defensively:
there has not been a single ORC related kernel crash so far, even
with early versions. (knock on wood!)
But the main advantage is that enabling the ORC unwinder allows
CONFIG_FRAME_POINTERS to be turned off - which speeds up the kernel
measurably:
With frame pointers disabled, GCC does not have to add frame pointer
instrumentation code to every function in the kernel. The kernel's
.text size decreases by about 3.2%, resulting in better cache
utilization and fewer instructions executed, resulting in a broad
kernel-wide speedup. Average speedup of system calls should be
roughly in the 1-3% range - measurements by Mel Gorman [1] have shown
a speedup of 5-10% for some function execution intense workloads.
The main cost of the unwinder is that the unwinder data has to be
stored in RAM: the memory cost is 2-4MB of RAM, depending on kernel
config - which is a modest cost on modern x86 systems.
Given how young the ORC unwinder code is it's not enabled by default
- but given the performance advantages the plan is to eventually make
it the default unwinder on x86.
See Documentation/x86/orc-unwinder.txt for more details.
- Remove lguest support: its intended role was that of a temporary
proof of concept for virtualization, plus its removal will enable the
reduction (removal) of the paravirt API as well, so Rusty agreed to
its removal. (Juergen Gross)
- Clean up and fix FSGS related functionality (Andy Lutomirski)
- Clean up IO access APIs (Andy Shevchenko)
- Enhance the symbol namespace (Jiri Slaby)
* 'x86-asm-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (47 commits)
objtool: Handle GCC stack pointer adjustment bug
x86/entry/64: Use ENTRY() instead of ALIGN+GLOBAL for stub32_clone()
x86/fpu/math-emu: Add ENDPROC to functions
x86/boot/64: Extract efi_pe_entry() from startup_64()
x86/boot/32: Extract efi_pe_entry() from startup_32()
x86/lguest: Remove lguest support
x86/paravirt/xen: Remove xen_patch()
objtool: Fix objtool fallthrough detection with function padding
x86/xen/64: Fix the reported SS and CS in SYSCALL
objtool: Track DRAP separately from callee-saved registers
objtool: Fix validate_branch() return codes
x86: Clarify/fix no-op barriers for text_poke_bp()
x86/switch_to/64: Rewrite FS/GS switching yet again to fix AMD CPUs
selftests/x86/fsgsbase: Test selectors 1, 2, and 3
x86/fsgsbase/64: Report FSBASE and GSBASE correctly in core dumps
x86/fsgsbase/64: Fully initialize FS and GS state in start_thread_common
x86/asm: Fix UNWIND_HINT_REGS macro for older binutils
x86/asm/32: Fix regs_get_register() on segment registers
x86/xen/64: Rearrange the SYSCALL entries
x86/asm/32: Remove a bunch of '& 0xffff' from pt_regs segment reads
...
Pull perf updates from Ingo Molnar:
"Kernel side changes:
- Add branch type profiling/tracing support. (Jin Yao)
- Add the PERF_SAMPLE_PHYS_ADDR ABI to allow the tracing/profiling of
physical memory addresses, where the PMU supports it. (Kan Liang)
- Export some PMU capability details in the new
/sys/bus/event_source/devices/cpu/caps/ sysfs directory. (Andi
Kleen)
- Aux data fixes and updates (Will Deacon)
- kprobes fixes and updates (Masami Hiramatsu)
- AMD uncore PMU driver fixes and updates (Janakarajan Natarajan)
On the tooling side, here's a (limited!) list of highlights - there
were many other changes that I could not list, see the shortlog and
git history for details:
UI improvements:
- Implement a visual marker for fused x86 instructions in the
annotate TUI browser, available now in 'perf report', more work
needed to have it available as well in 'perf top' (Jin Yao)
Further explanation from one of Jin's patches:
│ ┌──cmpl $0x0,argp_program_version_hook
81.93 │ ├──je 20
│ │ lock cmpxchg %esi,0x38a9a4(%rip)
│ │↓ jne 29
│ │↓ jmp 43
11.47 │20:└─→cmpxch %esi,0x38a999(%rip)
That means the cmpl+je is a fused instruction pair and they should
be considered together.
- Record the branch type and then show statistics and info about in
callchain entries (Jin Yao)
Example from one of Jin's patches:
# perf record -g -j any,save_type
# perf report --branch-history --stdio --no-children
38.50% div.c:45 [.] main div
|
---main div.c:42 (RET CROSS_2M cycles:2)
compute_flag div.c:28 (cycles:2)
compute_flag div.c:27 (RET CROSS_2M cycles:1)
rand rand.c:28 (cycles:1)
rand rand.c:28 (RET CROSS_2M cycles:1)
__random random.c:298 (cycles:1)
__random random.c:297 (COND_BWD CROSS_2M cycles:1)
__random random.c:295 (cycles:1)
__random random.c:295 (COND_BWD CROSS_2M cycles:1)
__random random.c:295 (cycles:1)
__random random.c:295 (RET CROSS_2M cycles:9)
namespaces support:
- Add initial support for namespaces, using setns to access files in
namespaces, grabbing their build-ids, etc. (Krister Johansen)
perf trace enhancements:
- Beautify pkey_{alloc,free,mprotect} arguments in 'perf trace'
(Arnaldo Carvalho de Melo)
- Add initial 'clone' syscall args beautifier in 'perf trace'
(Arnaldo Carvalho de Melo)
- Ignore 'fd' and 'offset' args for MAP_ANONYMOUS in 'perf trace'
(Arnaldo Carvalho de Melo)
- Beautifiers for the 'cmd' arg of several ioctl types, including:
sound, DRM, KVM, vhost virtio and perf_events. (Arnaldo Carvalho de
Melo)
- Add PERF_SAMPLE_CALLCHAIN and PERF_RECORD_MMAP[2] to 'perf data'
CTF conversion, allowing CTF trace visualization tools to show
callchains and to resolve symbols (Geneviève Bastien)
- Beautify the fcntl syscall, which is an interesting one in the
sense that infrastructure had to be put in place to change the
formatters of some arguments according to the value in a previous
one, i.e. cmd dictates how arg and the syscall return will be
formatted. (Arnaldo Carvalho de Melo
perf stat enhancements:
- Use group read for event groups in 'perf stat', reducing overhead
when groups are defined in the event specification, i.e. when using
{} to enclose a list of events, asking them to be read at the same
time, e.g.: "perf stat -e '{cycles,instructions}'" (Jiri Olsa)
pipe mode improvements:
- Process tracing data in 'perf annotate' pipe mode (David
Carrillo-Cisneros)
- Add header record types to pipe-mode, now this command:
$ perf record -o - -e cycles sleep 1 | perf report --stdio --header
Will show the same as in non-pipe mode, i.e. involving a perf.data
file (David Carrillo-Cisneros)
Vendor specific hardware event support updates/enhancements:
- Update POWER9 vendor events tables (Sukadev Bhattiprolu)
- Add POWER9 PMU events Sukadev (Bhattiprolu)
- Support additional POWER8+ PVR in PMU mapfile (Shriya)
- Add Skylake server uncore JSON vendor events (Andi Kleen)
- Support exporting Intel PT data to sqlite3 with python perf
scripts, this is in addition to the postgresql support that was
already there (Adrian Hunter)"
* 'perf-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (253 commits)
perf symbols: Fix plt entry calculation for ARM and AARCH64
perf probe: Fix kprobe blacklist checking condition
perf/x86: Fix caps/ for !Intel
perf/core, x86: Add PERF_SAMPLE_PHYS_ADDR
perf/core, pt, bts: Get rid of itrace_started
perf trace beauty: Beautify pkey_{alloc,free,mprotect} arguments
tools headers: Sync cpu features kernel ABI headers with tooling headers
perf tools: Pass full path of FEATURES_DUMP
perf tools: Robustify detection of clang binary
tools lib: Allow external definition of CC, AR and LD
perf tools: Allow external definition of flex and bison binary names
tools build tests: Don't hardcode gcc name
perf report: Group stat values on global event id
perf values: Zero value buffers
perf values: Fix allocation check
perf values: Fix thread index bug
perf report: Add dump_read function
perf record: Set read_format for inherit_stat
perf c2c: Fix remote HITM detection for Skylake
perf tools: Fix static build with newer toolchains
...
Pull RCU updates from Ingo Molnad:
"The main RCU related changes in this cycle were:
- Removal of spin_unlock_wait()
- SRCU updates
- RCU torture-test updates
- RCU Documentation updates
- Extend the sys_membarrier() ABI with the MEMBARRIER_CMD_PRIVATE_EXPEDITED variant
- Miscellaneous RCU fixes
- CPU-hotplug fixes"
* 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (63 commits)
arch: Remove spin_unlock_wait() arch-specific definitions
locking: Remove spin_unlock_wait() generic definitions
drivers/ata: Replace spin_unlock_wait() with lock/unlock pair
ipc: Replace spin_unlock_wait() with lock/unlock pair
exit: Replace spin_unlock_wait() with lock/unlock pair
completion: Replace spin_unlock_wait() with lock/unlock pair
doc: Set down RCU's scheduling-clock-interrupt needs
doc: No longer allowed to use rcu_dereference on non-pointers
doc: Add RCU files to docbook-generation files
doc: Update memory-barriers.txt for read-to-write dependencies
doc: Update RCU documentation
membarrier: Provide expedited private command
rcu: Remove exports from rcu_idle_exit() and rcu_idle_enter()
rcu: Add warning to rcu_idle_enter() for irqs enabled
rcu: Make rcu_idle_enter() rely on callers disabling irqs
rcu: Add assertions verifying blocked-tasks list
rcu/tracing: Set disable_rcu_irq_enter on rcu_eqs_exit()
rcu: Add TPS() protection for _rcu_barrier_trace strings
rcu: Use idle versions of swait to make idle-hack clear
swait: Add idle variants which don't contribute to load average
...
When !NUMA, cpumask_of_node(@node) equals cpu_online_mask regardless of
@node. The assumption seems that if !NUMA, there shouldn't be more than
one node and thus reporting cpu_online_mask regardless of @node is
correct. However, that assumption was broken years ago to support
DISCONTIGMEM and whether a system has multiple nodes or not is
separately controlled by NEED_MULTIPLE_NODES.
This means that, on a system with !NUMA && NEED_MULTIPLE_NODES,
cpumask_of_node() will report cpu_online_mask for all possible nodes,
indicating that the CPUs are associated with multiple nodes which is an
impossible configuration.
This bug has been around forever but doesn't look like it has caused any
noticeable symptoms. However, it triggers a WARN recently added to
workqueue to verify NUMA affinity configuration.
Fix it by reporting empty cpumask on non-zero nodes if !NUMA.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-and-tested-by: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: stable@vger.kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Pull Kbuild fixes from Masahiro Yamada:
- fix linker script regression caused by dead code elimination support
- fix typos and outdated comments
- specify kselftest-clean as a PHONY target
- fix "make dtbs_install" when $(srctree) includes shell special
characters like '~'
- Move -fshort-wchar to the global option list because defining it
partially emits warnings
* tag 'kbuild-fixes-v4.13' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild:
kbuild: update comments of Makefile.asm-generic
kbuild: Do not use hyphen in exported variable name
Makefile: add kselftest-clean to PHONY target list
Kbuild: use -fshort-wchar globally
fixdep: trivial: typo fix and correction
kbuild: trivial cleanups on the comments
kbuild: linker script do not match C names unless LD_DEAD_CODE_DATA_ELIMINATION is configured
When XIP_KERNEL is enabled, some functions are defined in the .data
ELF section because we require them to be in RAM whenever we communicate
with the flash chip. However this causes problems when FTRACE is
enabled and gcc emits calls to __gnu_mcount_nc in the function
prolog:
drivers/built-in.o: In function `cfi_chip_setup':
:(.data+0x272fc): relocation truncated to fit: R_ARM_CALL against symbol `__gnu_mcount_nc' defined in .text section in arch/arm/kernel/built-in.o
drivers/built-in.o: In function `cfi_probe_chip':
:(.data+0x27de8): relocation truncated to fit: R_ARM_CALL against symbol `__gnu_mcount_nc' defined in .text section in arch/arm/kernel/built-in.o
/tmp/ccY172rP.s: Assembler messages:
/tmp/ccY172rP.s:70: Warning: ignoring changed section attributes for .data
/tmp/ccY172rP.s: Error: 1 warning, treating warnings as errors
make[5]: *** [drivers/mtd/chips/cfi_probe.o] Error 1
/tmp/ccK4rjeO.s: Assembler messages:
/tmp/ccK4rjeO.s:421: Warning: ignoring changed section attributes for .data
/tmp/ccK4rjeO.s: Error: 1 warning, treating warnings as errors
make[5]: *** [drivers/mtd/chips/cfi_util.o] Error 1
/tmp/ccUvhCYR.s: Assembler messages:
/tmp/ccUvhCYR.s:1895: Warning: ignoring changed section attributes for .data
/tmp/ccUvhCYR.s: Error: 1 warning, treating warnings as errors
Specifically, this does not work because the .data section is not
marked executable, which leads LD to not generate trampolines for
long calls.
This moves the __xipram functions into their own .xiptext section instead.
The section is still placed next to .data and located in RAM but is marked
executable, which avoids the build errors.
Also, we only need to place the XIP functions into a separate section
if both CONFIG_XIP_KERNEL and CONFIG_MTD_XIP are set: When only MTD_XIP
is used, the whole kernel is still in RAM and we do not need to worry
about pulling out the rug under it. When only XIP_KERNEL but not MTD_XIP
is set, the kernel is in some form of ROM, but we never write to it.
Note that MTD_XIP has been broken on ARM since around 2011 or 2012. I
have sent another patch[2] to fix compilation, which I plan to merge
through arm-soc unless there are objections. The obvious alternative
to that would be to completely rip out the MTD_XIP support from the
kernel, since obviously nobody has been using it in a long while.
Link: [1] https://patchwork.kernel.org/patch/8109771/
Link: [2] https://patchwork.kernel.org/patch/9855225/
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
