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Will Deacon 412fcb6ceb arm64: entry: always restore x0 from the stack on syscall return 
We have a micro-optimisation on the fast syscall return path where we
take care to keep x0 live with the return value from the syscall so that
we can avoid restoring it from the stack. The benefit of doing this is
fairly suspect, since we will be restoring x1 from the stack anyway
(which lives adjacent in the pt_regs structure) and the only additional
cost is saving x0 back to pt_regs after the syscall handler, which could
be seen as a poor man's prefetch.

More importantly, this causes issues with the context tracking code.

The ct_user_enter macro ends up branching into C code, which is free to
use x0 as a scratch register and consequently leads to us returning junk
back to userspace as the syscall return value. Rather than special case
the context-tracking code, this patch removes the questionable
optimisation entirely.

Cc: <stable@vger.kernel.org>
Cc: Larry Bassel <larry.bassel@linaro.org>
Cc: Kevin Hilman <khilman@linaro.org>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Reported-by: Hanjun Guo <hanjun.guo@linaro.org>
Tested-by: Hanjun Guo <hanjun.guo@linaro.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>
 		2015-08-21 15:11:43 +01:00
..
vdso arm64: vdso: work-around broken ELF toolchains in Makefile 2015-06-19 14:54:10 +01:00
.gitignore arm64: Build infrastructure 2012-09-17 13:42:21 +01:00
Makefile arm64: remove redundant object file list 2015-07-29 18:32:09 +01:00
acpi.c arm64: psci: remove ACPI coupling 2015-05-27 13:22:24 +01:00
alternative.c arm64: alternatives: ensure secondary CPUs execute ISB after patching 2015-08-04 18:52:09 +01:00
arm64ksyms.c arm64: Add ftrace support 2014-05-29 09:08:08 +01:00
armv8_deprecated.c arm64: kernel: Add support for Privileged Access Never 2015-07-27 11:08:41 +01:00
asm-offsets.c arm64: KVM: Switch vgic save/restore to alternative_insn 2015-06-12 15:12:08 +01:00
cacheinfo.c arm64: kernel: add support for cpu cache information 2015-01-15 11:55:07 +00:00
cpu_errata.c arm64: fix midr range for Cortex-A57 erratum 832075 2015-04-01 11:12:03 +01:00
cpu_ops.c arm64: force CONFIG_SMP=y and remove redundant #ifdefs 2015-07-27 11:08:40 +01:00
cpufeature.c arm64: lse: use generic cpufeature detection for LSE atomics 2015-07-27 16:37:14 +01:00
cpuidle.c arm64: cpuidle: add __init section marker to arm_cpuidle_init 2015-07-02 17:44:27 +01:00
cpuinfo.c arm64: Extract feature parsing code from cpu_errata.c 2015-03-30 11:03:43 +01:00
debug-monitors.c arm64: debug: rename enum debug_el to avoid symbol collision 2015-07-27 18:36:54 +01:00
efi-entry.S arm64 updates for 3.19 2014-12-09 13:12:47 -08:00
efi-stub.c arm64: efi: prefer AllocatePages() over efi_low_alloc() for vmlinux 2015-07-27 11:08:41 +01:00
efi.c e820, efi: add ACPI 6.0 persistent memory types 2015-05-27 21:46:05 -04:00
entry-fpsimd.S arm64: fpsimd: fix a typo in fpsimd_save_partial_state ENDPROC 2014-07-31 11:42:42 +01:00
entry-ftrace.S arm64: ftrace: eliminate literal pool entries 2014-11-07 15:04:49 +00:00
entry.S arm64: entry: always restore x0 from the stack on syscall return 2015-08-21 15:11:43 +01:00
entry32.S arm64: entry32: remove pointless register assignment 2015-07-10 16:47:13 +01:00
fpsimd.c arm64: fix bug for reloading FPSIMD state after CPU hotplug. 2015-06-11 17:08:11 +01:00
ftrace.c arm64: ftrace: fix ftrace_modify_graph_caller for branch replace 2015-02-23 09:13:45 +00:00
head.S arm64: mm: ensure patched kernel text is fetched from PoU 2015-08-05 10:05:20 +01:00
hw_breakpoint.c arm64: debug: rename enum debug_el to avoid symbol collision 2015-07-27 18:36:54 +01:00
hyp-stub.S irqchip: gic-v3: Initial support for GICv3 2014-07-08 22:11:47 +00:00
image.h arm64: Update the Image header 2014-07-10 12:36:40 +01:00
insn.c arm64: insn: use set_fixmap_offset to make it more clear 2015-07-27 11:08:41 +01:00
io.c arm64: optimize memcpy_{from,to}io() and memset_io() 2014-11-06 17:25:27 +00:00
irq.c arm64: force CONFIG_SMP=y and remove redundant #ifdefs 2015-07-27 11:08:40 +01:00
jump_label.c arm64: jump labels: NOP out NOP -> NOP replacement 2014-11-26 17:19:47 +00:00
kgdb.c arm64/debug: Simplify BRK insn opcode declarations 2015-07-27 11:08:42 +01:00
kuser32.S arm64: Add __NR_* definitions for compat syscalls 2014-07-10 11:02:40 +01:00
module.c mm: vmalloc: pass additional vm_flags to __vmalloc_node_range() 2015-02-13 21:21:42 -08:00
pci.c ARM64: PCI: do not enable resources on PROBE_ONLY systems 2015-07-30 20:17:07 +01:00
perf_callchain.c arm64: perf: factor out callchain code 2015-07-27 11:08:39 +01:00
perf_event.c arm64: perf: condense event number maps 2015-07-27 11:08:40 +01:00
perf_regs.c perf: Move task_pt_regs sampling into arch code 2015-01-09 11:12:28 +01:00
process.c arm64: kernel thread don't need to save fpsimd context. 2015-06-11 15:35:23 +01:00
psci-call.S arm64: psci: move psci firmware calls out of line 2015-02-26 18:23:53 +00:00
psci.c Merge branch 'aarch64/psci/drivers' into aarch64/for-next/core 2015-08-05 14:14:06 +01:00
ptrace.c arm64: Better native ptrace support for compat tasks 2015-07-27 11:08:39 +01:00
return_address.c arm64: LLVMLinux: Use global stack pointer in return_address() 2014-09-08 14:39:19 +01:00
setup.c Merge branch 'aarch64/psci/drivers' into aarch64/for-next/core 2015-08-05 14:14:06 +01:00
signal.c arm64: Removed unused variable 2015-04-13 20:40:10 +02:00
signal32.c arm64: compat: print compat_sp instead of sp 2015-06-17 14:30:53 +01:00
sleep.S arm64: mm: ensure patched kernel text is fetched from PoU 2015-08-05 10:05:20 +01:00
smp.c arm64: remove dead-code depending on CONFIG_UP_LATE_INIT 2015-07-29 18:32:09 +01:00
smp_spin_table.c ARM64: kernel: make cpu_ops hooks DT agnostic 2015-05-19 16:09:29 +01:00
stacktrace.c arm64: LLVMLinux: Use current_stack_pointer in save_stack_trace_tsk 2014-09-08 14:39:19 +01:00
suspend.c arm64: kernel: rename __cpu_suspend to keep it aligned with arm 2015-06-19 14:46:39 +01:00
sys.c arm64: make sys_call_table const 2015-01-27 09:38:08 +00:00
sys32.c arm64: fix implementation of mmap2 compat syscall 2015-03-19 10:43:51 +00:00
sys_compat.c arm64: compat: align cacheflush syscall with arch/arm 2014-12-01 13:31:12 +00:00
time.c arm64: force CONFIG_SMP=y and remove redundant #ifdefs 2015-07-27 11:08:40 +01:00
topology.c arm64: kernel: remove non-legit DT warnings when booting using ACPI 2015-07-27 11:08:41 +01:00
trace-events-emulation.h arm64: Trace emulation of AArch32 legacy instructions 2014-11-20 16:35:02 +00:00
traps.c arm64/BUG: Show explicit backtrace for WARNs 2015-07-27 11:08:42 +01:00
vdso.c time: Rename timekeeper::tkr to timekeeper::tkr_mono 2015-03-27 09:45:06 +01:00
vmlinux.lds.S arm64: reduce ID map to a single page 2015-06-02 17:44:51 +01:00