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linux/include/asm-generic/percpu.h
Nathan Chancellor 093d9b240a percpu: Fix self-assignment of __old in raw_cpu_generic_try_cmpxchg() 
After commit c5c0ba953b ("percpu: Add {raw,this}_cpu_try_cmpxchg()"),
clang built ARCH=arm and ARCH=arm64 kernels with CONFIG_INIT_STACK_NONE
started panicking on boot in alloc_vmap_area():

  [    0.000000] kernel BUG at mm/vmalloc.c:1638!
  [    0.000000] Internal error: Oops - BUG: 00000000f2000800 [#1] PREEMPT SMP
  [    0.000000] Modules linked in:
  [    0.000000] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 6.4.0-rc2-ARCH+ #1
  [    0.000000] Hardware name: linux,dummy-virt (DT)
  [    0.000000] pstate: 200000c9 (nzCv daIF -PAN -UAO -TCO -DIT -SSBS BTYPE=--)
  [    0.000000] pc : alloc_vmap_area+0x7ec/0x7f8
  [    0.000000] lr : alloc_vmap_area+0x7e8/0x7f8

Compiling mm/vmalloc.c with W=2 reveals an instance of -Wshadow, which
helps uncover that through macro expansion, '__old = *(ovalp)' in
raw_cpu_generic_try_cmpxchg() can become '__old = *(&__old)' through
raw_cpu_generic_cmpxchg(), which results in garbage being assigned to
the inner __old and the cmpxchg not working properly.

Add an extra underscore to __old in raw_cpu_generic_try_cmpxchg() so
that there is no more self-assignment, which resolves the panics.

Closes: https://github.com/ClangBuiltLinux/linux/issues/1868
Fixes: c5c0ba953b ("percpu: Add {raw,this}_cpu_try_cmpxchg()")
Debugged-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20230607-fix-shadowing-in-raw_cpu_generic_try_cmpxchg-v1-1-8f0a3d930d43@kernel.org
2023-06-08 10:28:39 +02:00

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/* SPDX-License-Identifier: GPL-2.0 */
#ifndef _ASM_GENERIC_PERCPU_H_
#define _ASM_GENERIC_PERCPU_H_
#include <linux/compiler.h>
#include <linux/threads.h>
#include <linux/percpu-defs.h>
#ifdef CONFIG_SMP
/*
* per_cpu_offset() is the offset that has to be added to a
* percpu variable to get to the instance for a certain processor.
*
* Most arches use the __per_cpu_offset array for those offsets but
* some arches have their own ways of determining the offset (x86_64, s390).
*/
#ifndef __per_cpu_offset
extern unsigned long __per_cpu_offset[NR_CPUS];
#define per_cpu_offset(x) (__per_cpu_offset[x])
#endif
/*
* Determine the offset for the currently active processor.
* An arch may define __my_cpu_offset to provide a more effective
* means of obtaining the offset to the per cpu variables of the
* current processor.
*/
#ifndef __my_cpu_offset
#define __my_cpu_offset per_cpu_offset(raw_smp_processor_id())
#endif
#ifdef CONFIG_DEBUG_PREEMPT
#define my_cpu_offset per_cpu_offset(smp_processor_id())
#else
#define my_cpu_offset __my_cpu_offset
#endif
/*
* Arch may define arch_raw_cpu_ptr() to provide more efficient address
* translations for raw_cpu_ptr().
*/
#ifndef arch_raw_cpu_ptr
#define arch_raw_cpu_ptr(ptr) SHIFT_PERCPU_PTR(ptr, __my_cpu_offset)
#endif
#ifdef CONFIG_HAVE_SETUP_PER_CPU_AREA
extern void setup_per_cpu_areas(void);
#endif
#endif /* SMP */
#ifndef PER_CPU_BASE_SECTION
#ifdef CONFIG_SMP
#define PER_CPU_BASE_SECTION ".data..percpu"
#else
#define PER_CPU_BASE_SECTION ".data"
#endif
#endif
#ifndef PER_CPU_ATTRIBUTES
#define PER_CPU_ATTRIBUTES
#endif
#define raw_cpu_generic_read(pcp) \
({ \
*raw_cpu_ptr(&(pcp)); \
})
#define raw_cpu_generic_to_op(pcp, val, op) \
do { \
*raw_cpu_ptr(&(pcp)) op val; \
} while (0)
#define raw_cpu_generic_add_return(pcp, val) \
({ \
typeof(pcp) *__p = raw_cpu_ptr(&(pcp)); \
\
*__p += val; \
*__p; \
})
#define raw_cpu_generic_xchg(pcp, nval) \
({ \
typeof(pcp) *__p = raw_cpu_ptr(&(pcp)); \
typeof(pcp) __ret; \
__ret = *__p; \
*__p = nval; \
__ret; \
})
#define __cpu_fallback_try_cmpxchg(pcp, ovalp, nval, _cmpxchg) \
({ \
typeof(pcp) __val, __old = *(ovalp); \
__val = _cmpxchg(pcp, __old, nval); \
if (__val != __old) \
*(ovalp) = __val; \
__val == __old; \
})
#define raw_cpu_generic_try_cmpxchg(pcp, ovalp, nval) \
({ \
typeof(pcp) *__p = raw_cpu_ptr(&(pcp)); \
typeof(pcp) __val = *__p, ___old = *(ovalp); \
bool __ret; \
if (__val == ___old) { \
*__p = nval; \
__ret = true; \
} else { \
*(ovalp) = __val; \
__ret = false; \
} \
__ret; \
})
#define raw_cpu_generic_cmpxchg(pcp, oval, nval) \
({ \
typeof(pcp) __old = (oval); \
raw_cpu_generic_try_cmpxchg(pcp, &__old, nval); \
__old; \
})
#define __this_cpu_generic_read_nopreempt(pcp) \
({ \
typeof(pcp) ___ret; \
preempt_disable_notrace(); \
___ret = READ_ONCE(*raw_cpu_ptr(&(pcp))); \
preempt_enable_notrace(); \
___ret; \
})
#define __this_cpu_generic_read_noirq(pcp) \
({ \
typeof(pcp) ___ret; \
unsigned long ___flags; \
raw_local_irq_save(___flags); \
___ret = raw_cpu_generic_read(pcp); \
raw_local_irq_restore(___flags); \
___ret; \
})
#define this_cpu_generic_read(pcp) \
({ \
typeof(pcp) __ret; \
if (__native_word(pcp)) \
__ret = __this_cpu_generic_read_nopreempt(pcp); \
else \
__ret = __this_cpu_generic_read_noirq(pcp); \
__ret; \
})
#define this_cpu_generic_to_op(pcp, val, op) \
do { \
unsigned long __flags; \
raw_local_irq_save(__flags); \
raw_cpu_generic_to_op(pcp, val, op); \
raw_local_irq_restore(__flags); \
} while (0)
#define this_cpu_generic_add_return(pcp, val) \
({ \
typeof(pcp) __ret; \
unsigned long __flags; \
raw_local_irq_save(__flags); \
__ret = raw_cpu_generic_add_return(pcp, val); \
raw_local_irq_restore(__flags); \
__ret; \
})
#define this_cpu_generic_xchg(pcp, nval) \
({ \
typeof(pcp) __ret; \
unsigned long __flags; \
raw_local_irq_save(__flags); \
__ret = raw_cpu_generic_xchg(pcp, nval); \
raw_local_irq_restore(__flags); \
__ret; \
})
#define this_cpu_generic_try_cmpxchg(pcp, ovalp, nval) \
({ \
bool __ret; \
unsigned long __flags; \
raw_local_irq_save(__flags); \
__ret = raw_cpu_generic_try_cmpxchg(pcp, ovalp, nval); \
raw_local_irq_restore(__flags); \
__ret; \
})
#define this_cpu_generic_cmpxchg(pcp, oval, nval) \
({ \
typeof(pcp) __ret; \
unsigned long __flags; \
raw_local_irq_save(__flags); \
__ret = raw_cpu_generic_cmpxchg(pcp, oval, nval); \
raw_local_irq_restore(__flags); \
__ret; \
})
#ifndef raw_cpu_read_1
#define raw_cpu_read_1(pcp) raw_cpu_generic_read(pcp)
#endif
#ifndef raw_cpu_read_2
#define raw_cpu_read_2(pcp) raw_cpu_generic_read(pcp)
#endif
#ifndef raw_cpu_read_4
#define raw_cpu_read_4(pcp) raw_cpu_generic_read(pcp)
#endif
#ifndef raw_cpu_read_8
#define raw_cpu_read_8(pcp) raw_cpu_generic_read(pcp)
#endif
#ifndef raw_cpu_write_1
#define raw_cpu_write_1(pcp, val) raw_cpu_generic_to_op(pcp, val, =)
#endif
#ifndef raw_cpu_write_2
#define raw_cpu_write_2(pcp, val) raw_cpu_generic_to_op(pcp, val, =)
#endif
#ifndef raw_cpu_write_4
#define raw_cpu_write_4(pcp, val) raw_cpu_generic_to_op(pcp, val, =)
#endif
#ifndef raw_cpu_write_8
#define raw_cpu_write_8(pcp, val) raw_cpu_generic_to_op(pcp, val, =)
#endif
#ifndef raw_cpu_add_1
#define raw_cpu_add_1(pcp, val) raw_cpu_generic_to_op(pcp, val, +=)
#endif
#ifndef raw_cpu_add_2
#define raw_cpu_add_2(pcp, val) raw_cpu_generic_to_op(pcp, val, +=)
#endif
#ifndef raw_cpu_add_4
#define raw_cpu_add_4(pcp, val) raw_cpu_generic_to_op(pcp, val, +=)
#endif
#ifndef raw_cpu_add_8
#define raw_cpu_add_8(pcp, val) raw_cpu_generic_to_op(pcp, val, +=)
#endif
#ifndef raw_cpu_and_1
#define raw_cpu_and_1(pcp, val) raw_cpu_generic_to_op(pcp, val, &=)
#endif
#ifndef raw_cpu_and_2
#define raw_cpu_and_2(pcp, val) raw_cpu_generic_to_op(pcp, val, &=)
#endif
#ifndef raw_cpu_and_4
#define raw_cpu_and_4(pcp, val) raw_cpu_generic_to_op(pcp, val, &=)
#endif
#ifndef raw_cpu_and_8
#define raw_cpu_and_8(pcp, val) raw_cpu_generic_to_op(pcp, val, &=)
#endif
#ifndef raw_cpu_or_1
#define raw_cpu_or_1(pcp, val) raw_cpu_generic_to_op(pcp, val, |=)
#endif
#ifndef raw_cpu_or_2
#define raw_cpu_or_2(pcp, val) raw_cpu_generic_to_op(pcp, val, |=)
#endif
#ifndef raw_cpu_or_4
#define raw_cpu_or_4(pcp, val) raw_cpu_generic_to_op(pcp, val, |=)
#endif
#ifndef raw_cpu_or_8
#define raw_cpu_or_8(pcp, val) raw_cpu_generic_to_op(pcp, val, |=)
#endif
#ifndef raw_cpu_add_return_1
#define raw_cpu_add_return_1(pcp, val) raw_cpu_generic_add_return(pcp, val)
#endif
#ifndef raw_cpu_add_return_2
#define raw_cpu_add_return_2(pcp, val) raw_cpu_generic_add_return(pcp, val)
#endif
#ifndef raw_cpu_add_return_4
#define raw_cpu_add_return_4(pcp, val) raw_cpu_generic_add_return(pcp, val)
#endif
#ifndef raw_cpu_add_return_8
#define raw_cpu_add_return_8(pcp, val) raw_cpu_generic_add_return(pcp, val)
#endif
#ifndef raw_cpu_xchg_1
#define raw_cpu_xchg_1(pcp, nval) raw_cpu_generic_xchg(pcp, nval)
#endif
#ifndef raw_cpu_xchg_2
#define raw_cpu_xchg_2(pcp, nval) raw_cpu_generic_xchg(pcp, nval)
#endif
#ifndef raw_cpu_xchg_4
#define raw_cpu_xchg_4(pcp, nval) raw_cpu_generic_xchg(pcp, nval)
#endif
#ifndef raw_cpu_xchg_8
#define raw_cpu_xchg_8(pcp, nval) raw_cpu_generic_xchg(pcp, nval)
#endif
#ifndef raw_cpu_try_cmpxchg_1
#ifdef raw_cpu_cmpxchg_1
#define raw_cpu_try_cmpxchg_1(pcp, ovalp, nval) \
__cpu_fallback_try_cmpxchg(pcp, ovalp, nval, raw_cpu_cmpxchg_1)
#else
#define raw_cpu_try_cmpxchg_1(pcp, ovalp, nval) \
raw_cpu_generic_try_cmpxchg(pcp, ovalp, nval)
#endif
#endif
#ifndef raw_cpu_try_cmpxchg_2
#ifdef raw_cpu_cmpxchg_2
#define raw_cpu_try_cmpxchg_2(pcp, ovalp, nval) \
__cpu_fallback_try_cmpxchg(pcp, ovalp, nval, raw_cpu_cmpxchg_2)
#else
#define raw_cpu_try_cmpxchg_2(pcp, ovalp, nval) \
raw_cpu_generic_try_cmpxchg(pcp, ovalp, nval)
#endif
#endif
#ifndef raw_cpu_try_cmpxchg_4
#ifdef raw_cpu_cmpxchg_4
#define raw_cpu_try_cmpxchg_4(pcp, ovalp, nval) \
__cpu_fallback_try_cmpxchg(pcp, ovalp, nval, raw_cpu_cmpxchg_4)
#else
#define raw_cpu_try_cmpxchg_4(pcp, ovalp, nval) \
raw_cpu_generic_try_cmpxchg(pcp, ovalp, nval)
#endif
#endif
#ifndef raw_cpu_try_cmpxchg_8
#ifdef raw_cpu_cmpxchg_8
#define raw_cpu_try_cmpxchg_8(pcp, ovalp, nval) \
__cpu_fallback_try_cmpxchg(pcp, ovalp, nval, raw_cpu_cmpxchg_8)
#else
#define raw_cpu_try_cmpxchg_8(pcp, ovalp, nval) \
raw_cpu_generic_try_cmpxchg(pcp, ovalp, nval)
#endif
#endif
#ifndef raw_cpu_try_cmpxchg64
#ifdef raw_cpu_cmpxchg64
#define raw_cpu_try_cmpxchg64(pcp, ovalp, nval) \
__cpu_fallback_try_cmpxchg(pcp, ovalp, nval, raw_cpu_cmpxchg64)
#else
#define raw_cpu_try_cmpxchg64(pcp, ovalp, nval) \
raw_cpu_generic_try_cmpxchg(pcp, ovalp, nval)
#endif
#endif
#ifndef raw_cpu_try_cmpxchg128
#ifdef raw_cpu_cmpxchg128
#define raw_cpu_try_cmpxchg128(pcp, ovalp, nval) \
__cpu_fallback_try_cmpxchg(pcp, ovalp, nval, raw_cpu_cmpxchg128)
#else
#define raw_cpu_try_cmpxchg128(pcp, ovalp, nval) \
raw_cpu_generic_try_cmpxchg(pcp, ovalp, nval)
#endif
#endif
#ifndef raw_cpu_cmpxchg_1
#define raw_cpu_cmpxchg_1(pcp, oval, nval) \
raw_cpu_generic_cmpxchg(pcp, oval, nval)
#endif
#ifndef raw_cpu_cmpxchg_2
#define raw_cpu_cmpxchg_2(pcp, oval, nval) \
raw_cpu_generic_cmpxchg(pcp, oval, nval)
#endif
#ifndef raw_cpu_cmpxchg_4
#define raw_cpu_cmpxchg_4(pcp, oval, nval) \
raw_cpu_generic_cmpxchg(pcp, oval, nval)
#endif
#ifndef raw_cpu_cmpxchg_8
#define raw_cpu_cmpxchg_8(pcp, oval, nval) \
raw_cpu_generic_cmpxchg(pcp, oval, nval)
#endif
#ifndef raw_cpu_cmpxchg64
#define raw_cpu_cmpxchg64(pcp, oval, nval) \
raw_cpu_generic_cmpxchg(pcp, oval, nval)
#endif
#ifndef raw_cpu_cmpxchg128
#define raw_cpu_cmpxchg128(pcp, oval, nval) \
raw_cpu_generic_cmpxchg(pcp, oval, nval)
#endif
#ifndef this_cpu_read_1
#define this_cpu_read_1(pcp) this_cpu_generic_read(pcp)
#endif
#ifndef this_cpu_read_2
#define this_cpu_read_2(pcp) this_cpu_generic_read(pcp)
#endif
#ifndef this_cpu_read_4
#define this_cpu_read_4(pcp) this_cpu_generic_read(pcp)
#endif
#ifndef this_cpu_read_8
#define this_cpu_read_8(pcp) this_cpu_generic_read(pcp)
#endif
#ifndef this_cpu_write_1
#define this_cpu_write_1(pcp, val) this_cpu_generic_to_op(pcp, val, =)
#endif
#ifndef this_cpu_write_2
#define this_cpu_write_2(pcp, val) this_cpu_generic_to_op(pcp, val, =)
#endif
#ifndef this_cpu_write_4
#define this_cpu_write_4(pcp, val) this_cpu_generic_to_op(pcp, val, =)
#endif
#ifndef this_cpu_write_8
#define this_cpu_write_8(pcp, val) this_cpu_generic_to_op(pcp, val, =)
#endif
#ifndef this_cpu_add_1
#define this_cpu_add_1(pcp, val) this_cpu_generic_to_op(pcp, val, +=)
#endif
#ifndef this_cpu_add_2
#define this_cpu_add_2(pcp, val) this_cpu_generic_to_op(pcp, val, +=)
#endif
#ifndef this_cpu_add_4
#define this_cpu_add_4(pcp, val) this_cpu_generic_to_op(pcp, val, +=)
#endif
#ifndef this_cpu_add_8
#define this_cpu_add_8(pcp, val) this_cpu_generic_to_op(pcp, val, +=)
#endif
#ifndef this_cpu_and_1
#define this_cpu_and_1(pcp, val) this_cpu_generic_to_op(pcp, val, &=)
#endif
#ifndef this_cpu_and_2
#define this_cpu_and_2(pcp, val) this_cpu_generic_to_op(pcp, val, &=)
#endif
#ifndef this_cpu_and_4
#define this_cpu_and_4(pcp, val) this_cpu_generic_to_op(pcp, val, &=)
#endif
#ifndef this_cpu_and_8
#define this_cpu_and_8(pcp, val) this_cpu_generic_to_op(pcp, val, &=)
#endif
#ifndef this_cpu_or_1
#define this_cpu_or_1(pcp, val) this_cpu_generic_to_op(pcp, val, |=)
#endif
#ifndef this_cpu_or_2
#define this_cpu_or_2(pcp, val) this_cpu_generic_to_op(pcp, val, |=)
#endif
#ifndef this_cpu_or_4
#define this_cpu_or_4(pcp, val) this_cpu_generic_to_op(pcp, val, |=)
#endif
#ifndef this_cpu_or_8
#define this_cpu_or_8(pcp, val) this_cpu_generic_to_op(pcp, val, |=)
#endif
#ifndef this_cpu_add_return_1
#define this_cpu_add_return_1(pcp, val) this_cpu_generic_add_return(pcp, val)
#endif
#ifndef this_cpu_add_return_2
#define this_cpu_add_return_2(pcp, val) this_cpu_generic_add_return(pcp, val)
#endif
#ifndef this_cpu_add_return_4
#define this_cpu_add_return_4(pcp, val) this_cpu_generic_add_return(pcp, val)
#endif
#ifndef this_cpu_add_return_8
#define this_cpu_add_return_8(pcp, val) this_cpu_generic_add_return(pcp, val)
#endif
#ifndef this_cpu_xchg_1
#define this_cpu_xchg_1(pcp, nval) this_cpu_generic_xchg(pcp, nval)
#endif
#ifndef this_cpu_xchg_2
#define this_cpu_xchg_2(pcp, nval) this_cpu_generic_xchg(pcp, nval)
#endif
#ifndef this_cpu_xchg_4
#define this_cpu_xchg_4(pcp, nval) this_cpu_generic_xchg(pcp, nval)
#endif
#ifndef this_cpu_xchg_8
#define this_cpu_xchg_8(pcp, nval) this_cpu_generic_xchg(pcp, nval)
#endif
#ifndef this_cpu_try_cmpxchg_1
#ifdef this_cpu_cmpxchg_1
#define this_cpu_try_cmpxchg_1(pcp, ovalp, nval) \
__cpu_fallback_try_cmpxchg(pcp, ovalp, nval, this_cpu_cmpxchg_1)
#else
#define this_cpu_try_cmpxchg_1(pcp, ovalp, nval) \
this_cpu_generic_try_cmpxchg(pcp, ovalp, nval)
#endif
#endif
#ifndef this_cpu_try_cmpxchg_2
#ifdef this_cpu_cmpxchg_2
#define this_cpu_try_cmpxchg_2(pcp, ovalp, nval) \
__cpu_fallback_try_cmpxchg(pcp, ovalp, nval, this_cpu_cmpxchg_2)
#else
#define this_cpu_try_cmpxchg_2(pcp, ovalp, nval) \
this_cpu_generic_try_cmpxchg(pcp, ovalp, nval)
#endif
#endif
#ifndef this_cpu_try_cmpxchg_4
#ifdef this_cpu_cmpxchg_4
#define this_cpu_try_cmpxchg_4(pcp, ovalp, nval) \
__cpu_fallback_try_cmpxchg(pcp, ovalp, nval, this_cpu_cmpxchg_4)
#else
#define this_cpu_try_cmpxchg_4(pcp, ovalp, nval) \
this_cpu_generic_try_cmpxchg(pcp, ovalp, nval)
#endif
#endif
#ifndef this_cpu_try_cmpxchg_8
#ifdef this_cpu_cmpxchg_8
#define this_cpu_try_cmpxchg_8(pcp, ovalp, nval) \
__cpu_fallback_try_cmpxchg(pcp, ovalp, nval, this_cpu_cmpxchg_8)
#else
#define this_cpu_try_cmpxchg_8(pcp, ovalp, nval) \
this_cpu_generic_try_cmpxchg(pcp, ovalp, nval)
#endif
#endif
#ifndef this_cpu_try_cmpxchg64
#ifdef this_cpu_cmpxchg64
#define this_cpu_try_cmpxchg64(pcp, ovalp, nval) \
__cpu_fallback_try_cmpxchg(pcp, ovalp, nval, this_cpu_cmpxchg64)
#else
#define this_cpu_try_cmpxchg64(pcp, ovalp, nval) \
this_cpu_generic_try_cmpxchg(pcp, ovalp, nval)
#endif
#endif
#ifndef this_cpu_try_cmpxchg128
#ifdef this_cpu_cmpxchg128
#define this_cpu_try_cmpxchg128(pcp, ovalp, nval) \
__cpu_fallback_try_cmpxchg(pcp, ovalp, nval, this_cpu_cmpxchg128)
#else
#define this_cpu_try_cmpxchg128(pcp, ovalp, nval) \
this_cpu_generic_try_cmpxchg(pcp, ovalp, nval)
#endif
#endif
#ifndef this_cpu_cmpxchg_1
#define this_cpu_cmpxchg_1(pcp, oval, nval) \
this_cpu_generic_cmpxchg(pcp, oval, nval)
#endif
#ifndef this_cpu_cmpxchg_2
#define this_cpu_cmpxchg_2(pcp, oval, nval) \
this_cpu_generic_cmpxchg(pcp, oval, nval)
#endif
#ifndef this_cpu_cmpxchg_4
#define this_cpu_cmpxchg_4(pcp, oval, nval) \
this_cpu_generic_cmpxchg(pcp, oval, nval)
#endif
#ifndef this_cpu_cmpxchg_8
#define this_cpu_cmpxchg_8(pcp, oval, nval) \
this_cpu_generic_cmpxchg(pcp, oval, nval)
#endif
#ifndef this_cpu_cmpxchg64
#define this_cpu_cmpxchg64(pcp, oval, nval) \
this_cpu_generic_cmpxchg(pcp, oval, nval)
#endif
#ifndef this_cpu_cmpxchg128
#define this_cpu_cmpxchg128(pcp, oval, nval) \
this_cpu_generic_cmpxchg(pcp, oval, nval)
#endif
#endif /* _ASM_GENERIC_PERCPU_H_ */
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