8000 Stack Thunk - check saved a1 before using and zero after using by mcspr · Pull Request #9252 · esp8266/Arduino · GitHub
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Stack Thunk - check saved a1 before using and zero after using #9252

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Merged
merged 2 commits into from
May 29, 2025
Merged

Stack Thunk - check saved a1 before using and zero after using #9252

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Stack Thunk - check saved a1 before using and zero after using
mcspr May 15, 2025
b43c4fb
skip invalid a1 load, but not yielding
mcspr May 29, 2025
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Stack Thunk - check saved a1 before using and zero after using 
Post #9224, allow to call 'stack_thunk_yield()' outside of bssl context
Reset 'stack_thunk_save' before returning from 'thunk_...'ed function
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@mcspr
mcspr committed May 29, 2025
commit 630aa880ad220df00fde7dd27cb9be92731aad44
6 changes: 6 additions & 0 deletions cores/esp8266/StackThunk.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -73,6 +73,7 @@ void stack_thunk_add_ref()
}
stack_thunk_top = stack_thunk_ptr + _stackSize - 1;
stack_thunk_save = NULL;
stack_thunk_yield_save = NULL;
stack_thunk_repaint();
}
}
Expand All @@ -90,6 +91,7 @@ void stack_thunk_del_ref()
stack_thunk_ptr = NULL;
stack_thunk_top = NULL;
stack_thunk_save = NULL;
stack_thunk_yield_save = NULL;
}
}

Expand Down Expand Up @@ -175,12 +177,16 @@ asm(
"movi a2, stack_thunk_yield_save\n\t"
"s32i.n a1, a2, 0\n\t"
"movi a2, stack_thunk_save\n\t"
/* But, only when inside of bssl stack (saved a1 != 0) */
"l32i.n a3, a2, 0\n\t"
"beqz a3, stack_thunk_yield_restore\n\t"
"l32i.n a1, a2, 0\n\t"
/* optimistic_yield(10000) without extra l32r */
"movi a2, 0x10\n\t"
"addmi a2, a2, 0x2700\n\t"
"call0 optimistic_yield\n\t"
/* Swap bearssl <-> cont stacks, again */
"stack_thunk_yield_restore:\n\t"
"movi a2, stack_thunk_yield_save\n\t"
"l32i.n a1, a2, 0\n\t"
"\n"
Expand Down
10 changes: 7 additions & 3 deletions cores/esp8266/StackThunk.h
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Original file line number Diff line number Diff line change
Expand Up @@ -27,6 +27,8 @@
#ifndef _STACKTHUNK_H
#define _STACKTHUNK_H

#include <stdint.h>

#ifdef __cplusplus
extern "C" {
#endif
Expand Down Expand Up @@ -80,9 +82,11 @@ thunk_"#fcnToThunk":\n\
call0 stack_thunk_fatal_smashing\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\
l32i.n a1, a15, 0/* Restore A1(SP) */\n\
movi a0, 0 /* Purge temporary storage */\n\
s32i.n a0, a15, 0\n\
l32i.n a15, a1, 8/* Restore A15 */\n\
l32i.n a0, a1, 12/* Restore A0 */\n\
addi a1, a1, 16 /* Free up stack and return to caller */\n\
ret\n\
.size thunk_"#fcnToThunk", . - thunk_"#fcnToThunk"\n");
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