ceph/src/seastar/dpdk/examples/performance-thread/common/arch/arm64/stack.h

   1 /* SPDX-License-Identifier: BSD-3-Clause
   2  * Copyright(c) 2017 Cavium, Inc
   3  */
   4
   5 #ifndef STACK_H
   6 #define STACK_H
   7
   8 #ifdef __cplusplus
   9 extern "C" {
  10 #endif
  11
  12 #include "lthread_int.h"
  13
  14 /*
  15  * Sets up the initial stack for the lthread.
  16  */
  17 static inline void
  18 arch_set_stack(struct lthread *lt, void *func)
  19 {
  20         void **stack_top = (void *)((char *)(lt->stack) + lt->stack_size);
  21
  22         /*
  23          * Align stack_top to 16 bytes. Arm64 has the constraint that the
  24          * stack pointer must always be quad-word aligned.
  25          */
  26         stack_top = (void **)(((unsigned long)(stack_top)) & ~0xfUL);
  27
  28         /*
  29          * First Stack Frame
  30          */
  31         stack_top[0] = NULL;
  32         stack_top[-1] = NULL;
  33
  34         /*
  35          * Initialize the context
  36          */
  37         lt->ctx.fp = &stack_top[-1];
  38         lt->ctx.sp = &stack_top[-2];
  39
  40         /*
  41          * Here only the address of _lthread_exec is saved as the link
  42          * register value. The argument to _lthread_exec i.e the address of
  43          * the lthread struct is not saved. This is because the first
  44          * argument to ctx_switch is the address of the new context,
  45          * which also happens to be the address of required lthread struct.
  46          * So while returning from ctx_switch into _thread_exec, parameter
  47          * register x0 will always contain the required value.
  48          */
  49         lt->ctx.lr = func;
  50 }
  51
  52 #ifdef __cplusplus
  53 }
  54 #endif
  55
  56 #endif /* STACK_H_ */