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Earle F. Philhower, III 7c4961e83c
Add basic canary check to BSSL stack thunk ()
On return from a BSSL call, check that the last element of the stack is
still untouched.  If it is modified, print an error and abort().

Will catch problems like  many times with an informative error
message instead of corrupting the heap and having a random crash
sometime later.
2019-05-27 20:51:27 -07:00

93 lines
3.2 KiB
C

/*
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();
extern void stack_thunk_fatal_overflow();
// 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\
.literal .LC_STACK_VALUE"#fcnToThunk", 0xdeadbeef\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\
/* Check the stack canary wasn't overwritten */\n\
movi a15, stack_thunk_ptr\n\
l32i.n a15, a15, 0 /* A15 now has the pointer to stack end*/ \n\
l32i.n a15, a15, 0 /* A15 now has contents of last stack entry */\n\
l32r a0, .LC_STACK_VALUE"#fcnToThunk" /* A0 now has the check value */\n\
beq a0, a15, .L1"#fcnToThunk"\n\
call0 stack_thunk_fatal_overflow\n\
.L1"#fcnToThunk":\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