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StackThunk.h
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StackThunk.h
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/*
StackThunk.h - Allow use second stack for BearSSL calls
BearSSL uses a significant amount of stack space, much larger than
the default Arduino core stack. These routines handle swapping
between a secondary, user-allocated stack on the heap and the real
stack.
Copyright (c) 2017 Earle F. Philhower, III. All rights reserved.
This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
This library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with this library; if not, write to the Free Software
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
Modified 8 May 2015 by Hristo Gochkov (proper post and file upload handling)
*/
#ifndef _STACKTHUNK_H
#define _STACKTHUNK_H
#ifdef __cplusplus
extern "C" {
#endif
extern void stack_thunk_add_ref();
extern void stack_thunk_del_ref();
extern void stack_thunk_repaint();
extern uint32_t stack_thunk_get_refcnt();
extern uint32_t stack_thunk_get_stack_top();
extern uint32_t stack_thunk_get_stack_bot();
extern uint32_t stack_thunk_get_cont_sp();
extern uint32_t stack_thunk_get_max_usage();
extern void stack_thunk_dump_stack();
// Globals required for thunking operation
extern uint32_t *stack_thunk_ptr;
extern uint32_t *stack_thunk_top;
extern uint32_t *stack_thunk_save;
extern uint32_t stack_thunk_refcnt;
// Thunking macro
#define make_stack_thunk(fcnToThunk) \
__asm("\n\
.text\n\
.literal_position\n\
\n\
.text\n\
.global thunk_"#fcnToThunk"\n\
.type thunk_"#fcnToThunk", @function\n\
.align 4\n\
thunk_"#fcnToThunk":\n\
addi a1, a1, -16 /* Allocate space for saved registers on stack */\n\
s32i a0, a1, 12 /* Store A0, trounced by calls */\n\
s32i a15, a1, 8 /* Store A15 (our temporary one) */\n\
movi a15, stack_thunk_save /* Store A1(SP) in temp space */\n\
s32i a1, a15, 0\n\
movi a15, stack_thunk_top /* Load A1(SP) with thunk stack */\n\
l32i.n a1, a15, 0\n\
call0 "#fcnToThunk" /* Do the call */\n\
movi a15, stack_thunk_save /* Restore A1(SP) */\n\
l32i.n a1, a15, 0\n\
l32i.n a15, a1, 8 /* Restore the saved registers */\n\
l32i.n a0, a1, 12\n\
addi a1, a1, 16 /* Free up stack and return to caller */\n\
ret\n\
.size thunk_"#fcnToThunk", . - thunk_"#fcnToThunk"\n");
#ifdef __cplusplus
}
#endif
#endif