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aarch64: Re-implement setcontext without rt_sigreturn syscall
The current implementation of setcontext uses rt_sigreturn to restore the contents of registers. This contrasts with the way most other architectures implement setcontext: powerpc64, mips, tile: Call rt_sigreturn if context was created by a call to a signal handler, otherwise restore in user code. powerpc32: Call swapcontext system call and don't call sigreturn or rt_sigreturn. x86_64, sparc, hppa, sh, ia64, m68k, s390, arm: Only support restoring "synchronous" contexts, that is contexts created by getcontext, and restoring in user code and don't call sigreturn or rt_sigreturn. alpha: Call sigreturn (but not rt_sigreturn) in all cases to do the restore. The text of the setcontext manpage suggests that the requirement to be able to restore a signal handler created context has been dropped from SUSv2: If the context was obtained by a call to a signal handler, then old standard text says that "program execution continues with the program instruction following the instruction interrupted by the signal". However, this sentence was removed in SUSv2, and the present verdict is "the result is unspecified". Implementing setcontext by calling rt_sigreturn unconditionally causes problems when used with sigaltstack as in BZ #16629. On this basis it seems that aarch64 is broken and that new ports should only support restoring contexts created with getcontext and do not need to call rt_sigreturn at all. This patch re-implements the aarch64 setcontext function to restore the context in user code in a similar manner to x86_64 and other ports. ChangeLog: 2014-04-17 Will Newton <will.newton@linaro.org> [BZ #16629] * sysdeps/unix/sysv/linux/aarch64/setcontext.S (__setcontext): Re-implement to restore registers in user code and avoid rt_sigreturn system call.
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Will Newton
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423a7160af
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@ -1,3 +1,10 @@
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2014-04-17 Will Newton <will.newton@linaro.org>
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[BZ #16629]
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* sysdeps/unix/sysv/linux/aarch64/setcontext.S (__setcontext):
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Re-implement to restore registers in user code and avoid
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rt_sigreturn system call.
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2014-04-17 Wilco <wdijkstr@arm.com>
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* sysdeps/arm/math-tests.h: New file: Set ARM math-test settings.
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10
NEWS
10
NEWS
@ -11,11 +11,11 @@ Version 2.20
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6804, 13347, 14770, 15347, 15514, 15804, 15894, 16002, 16198, 16284,
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16348, 16349, 16357, 16362, 16447, 16532, 16545, 16574, 16599, 16600,
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16609, 16610, 16611, 16613, 16619, 16623, 16632, 16634, 16639, 16642,
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16648, 16649, 16670, 16674, 16677, 16680, 16683, 16689, 16695, 16701,
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16706, 16707, 16712, 16713, 16714, 16731, 16739, 16740, 16743, 16758,
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16759, 16760, 16770, 16786, 16789, 16799, 16800, 16815, 16824, 16831,
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16838.
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16609, 16610, 16611, 16613, 16619, 16623, 16629, 16632, 16634, 16639,
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16642, 16648, 16649, 16670, 16674, 16677, 16680, 16683, 16689, 16695,
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16701, 16706, 16707, 16712, 16713, 16714, 16731, 16739, 16740, 16743,
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16758, 16759, 16760, 16770, 16786, 16789, 16799, 16800, 16815, 16824,
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16831, 16838.
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* Running the testsuite no longer terminates as soon as a test fails.
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Instead, a file tests.sum (xtests.sum from "make xcheck") is generated,
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@ -22,68 +22,108 @@
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#include "ucontext_i.h"
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#include "ucontext-internal.h"
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/* int setcontext (const ucontext_t *ucp) */
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/* int __setcontext (const ucontext_t *ucp)
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Restores the machine context in UCP and thereby resumes execution
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in that context.
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This implementation is intended to be used for *synchronous* context
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switches only. Therefore, it does not have to restore anything
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other than the PRESERVED state. */
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.text
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ENTRY(__setcontext)
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ENTRY (__setcontext)
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/* Save a copy of UCP. */
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mov x9, x0
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/* Create a signal frame on the stack:
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fp
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lr
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...
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sp-> rt_sigframe
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*/
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stp x29, x30, [sp, -16]!
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cfi_adjust_cfa_offset (16)
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cfi_rel_offset (x29, 0)
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cfi_rel_offset (x30, 8)
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mov x29, sp
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cfi_def_cfa_register (x29)
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/* Allocate space for the sigcontext. */
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mov w3, #((RT_SIGFRAME_SIZE + SP_ALIGN_SIZE) & SP_ALIGN_MASK)
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sub sp, sp, x3
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/* Compute the base address of the ucontext structure. */
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add x1, sp, #RT_SIGFRAME_UCONTEXT
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/* Only ucontext is required in the frame, *copy* it in. */
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#if UCONTEXT_SIZE % 16
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#error The implementation of setcontext.S assumes sizeof(ucontext_t) % 16 == 0
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#endif
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mov x2, #UCONTEXT_SIZE / 16
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0:
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ldp x3, x4, [x0], #16
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stp x3, x4, [x1], #16
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sub x2, x2, 1
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cbnz x2, 0b
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/* rt_sigreturn () -- no arguments, sp points to struct rt_sigframe. */
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mov x8, SYS_ify (rt_sigreturn)
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/* Set the signal mask with
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rt_sigprocmask (SIG_SETMASK, mask, NULL, _NSIG/8). */
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mov x0, #SIG_SETMASK
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add x1, x9, #UCONTEXT_SIGMASK
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mov x2, #0
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mov x3, #_NSIG8
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mov x8, SYS_ify (rt_sigprocmask)
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svc 0
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cbz x0, 1f
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b C_SYMBOL_NAME (__syscall_error)
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1:
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/* Restore the general purpose registers. */
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mov x0, x9
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cfi_def_cfa (x0, 0)
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cfi_offset (x18, oX0 + 18 * SZREG)
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cfi_offset (x19, oX0 + 19 * SZREG)
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cfi_offset (x20, oX0 + 20 * SZREG)
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cfi_offset (x21, oX0 + 21 * SZREG)
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cfi_offset (x22, oX0 + 22 * SZREG)
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cfi_offset (x23, oX0 + 23 * SZREG)
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cfi_offset (x24, oX0 + 24 * SZREG)
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cfi_offset (x25, oX0 + 25 * SZREG)
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cfi_offset (x26, oX0 + 26 * SZREG)
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cfi_offset (x27, oX0 + 27 * SZREG)
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cfi_offset (x28, oX0 + 28 * SZREG)
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cfi_offset (x29, oX0 + 29 * SZREG)
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cfi_offset (x30, oX0 + 30 * SZREG)
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/* Ooops we failed. Recover the stack */
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cfi_offset ( d8, oV0 + 8 * SZVREG)
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cfi_offset ( d9, oV0 + 9 * SZVREG)
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cfi_offset (d10, oV0 + 10 * SZVREG)
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cfi_offset (d11, oV0 + 11 * SZVREG)
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cfi_offset (d12, oV0 + 12 * SZVREG)
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cfi_offset (d13, oV0 + 13 * SZVREG)
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cfi_offset (d14, oV0 + 14 * SZVREG)
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cfi_offset (d15, oV0 + 15 * SZVREG)
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ldp x18, x19, [x0, oX0 + 18 * SZREG]
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ldp x20, x21, [x0, oX0 + 20 * SZREG]
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ldp x22, x23, [x0, oX0 + 22 * SZREG]
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ldp x24, x25, [x0, oX0 + 24 * SZREG]
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ldp x26, x27, [x0, oX0 + 26 * SZREG]
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ldp x28, x29, [x0, oX0 + 28 * SZREG]
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ldr x30, [x0, oX0 + 30 * SZREG]
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ldr x2, [x0, oSP]
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mov sp, x2
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mov sp, x29
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cfi_def_cfa_register (sp)
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/* Check for FP SIMD context. We don't support restoring
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contexts created by the kernel, so this context must have
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been created by getcontext. Hence we can rely on the
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first extension block being the FP SIMD context. */
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add x2, x0, #oEXTENSION
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ldp x29, x30, [sp], 16
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cfi_adjust_cfa_offset (16)
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cfi_restore (x29)
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cfi_restore (x30)
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b C_SYMBOL_NAME(__syscall_error)
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mov w3, #(FPSIMD_MAGIC & 0xffff)
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movk w3, #(FPSIMD_MAGIC >> 16), lsl #16
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ldr w1, [x2, #oHEAD + oMAGIC]
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cmp w1, w3
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b.ne 2f
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/* Restore the FP SIMD context. */
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add x3, x2, #oV0 + 8 * SZVREG
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ldp d8, d9, [x3], #2 * SZVREG
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ldp d10, d11, [x3], #2 * SZVREG
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ldp d12, d13, [x3], #2 * SZVREG
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ldp d14, d15, [x3], #2 * SZVREG
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add x3, x2, oFPSR
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ldr w4, [x3]
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msr fpsr, x4
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ldr w4, [x3, oFPCR - oFPSR]
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msr fpcr, x4
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2:
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ldr x16, [x0, oPC]
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/* Restore arg registers. */
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ldp x2, x3, [x0, oX0 + 2 * SZREG]
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ldp x4, x5, [x0, oX0 + 4 * SZREG]
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ldp x6, x7, [x0, oX0 + 6 * SZREG]
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ldp x0, x1, [x0, oX0 + 0 * SZREG]
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/* Jump to the new pc value. */
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br x16
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PSEUDO_END (__setcontext)
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weak_alias (__setcontext, setcontext)
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ENTRY(__startcontext)
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ENTRY (__startcontext)
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mov x0, x19
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cbnz x0, __setcontext
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1: b HIDDEN_JUMPTARGET(_exit)
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END(__startcontext)
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1: b HIDDEN_JUMPTARGET (_exit)
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END (__startcontext)
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