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[ion][python] Implement an architecture-dependant collect_registers.

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setjmp is not guaranteed to collect all registers without modification
on all platforms.

This fixes the following bug: when the pointer of a newly allocated
object on the Python heap is stored in rpb registers on x86_64 arch, it
was not collected by the garbarge collector.
This commit is contained in:
Émilie Feral
2020-05-14 16:22:51 +02:00
committed by LeaNumworks
parent 5a32006dcd
commit 3f6647f3ae
13 changed files with 98 additions and 31 deletions
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51
python/port/port.cpp
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@@ -1,6 +1,6 @@
#include "port.h"
#include <ion/keyboard.h>
#include <ion.h>
#include <math.h>
#include <stdint.h>
@@ -231,63 +231,54 @@ KDColor MicroPython::ColorParser::ParseColor(mp_obj_t input, ColorMode ColorMode
mp_raise_TypeError("Color couldn't be parsed");
}
/* Forbid inlining to ensure regs to be at the top of the stack. Otherwise,
* LTO inlining can make regs lower on the stack than some just-allocated
* pointers. */
__attribute__((noinline)) void gc_collect(void) {
void gc_collect_regs_and_stack(void) {
// get the registers and the sp
jmp_buf regs;
uintptr_t sp = Ion::collectRegisters(regs);
void * python_stack_top = MP_STATE_THREAD(stack_top);
assert(python_stack_top != NULL);
gc_collect_start();
modturtle_gc_collect();
modpyplot_gc_collect();
/* get the registers.
* regs is the also the last object on the stack so the stack is bound by
* &regs and python_stack_top. */
jmp_buf regs;
/* TODO: we use setjmp to get the registers values to look for python heap
* root. However, the 'setjmp' does not guarantee that it gets all registers
* values. We should check our setjmp implementation for the device and
* ensure that it also works for other platforms. */
setjmp(regs);
void **regs_ptr = (void**)&regs;
/* On the device, the stack is stored in reverse order, but it might not be
* the case on a computer. We thus have to take the absolute value of the
* addresses difference. */
size_t stackLengthInByte;
void ** scanStart;
if ((uintptr_t)python_stack_top > (uintptr_t)regs_ptr) {
if ((uintptr_t)python_stack_top > sp) {
/* To compute the stack length:
* regs
* registers
* <----------->
* STACK <- ...| | | | | |--|--|--|--| | | | | | |
* ^&regs ^python_stack_top
* ^sp ^python_stack_top
* */
stackLengthInByte = (uintptr_t)python_stack_top - (uintptr_t)regs_ptr;
scanStart = regs_ptr;
stackLengthInByte = (uintptr_t)python_stack_top - sp;
scanStart = (void **)sp;
} else {
/* When computing the stack length, take into account regs' size.
* regs
* registers
* <----------->
* STACK -> | | | | | | | | | | | |--|--|--|--| | | |...
* ^python_stack_top ^&regs
* ^python_stack_top ^sp
* */
stackLengthInByte = (uintptr_t)regs_ptr - (uintptr_t)python_stack_top + sizeof(regs);
stackLengthInByte = sp - (uintptr_t)python_stack_top + sizeof(regs);
scanStart = (void **)python_stack_top;
}
/* Memory error detectors might find an error here as they might split regs
* and stack memory zones. */
MicroPython::collectRootsAtAddress((char *)scanStart, stackLengthInByte);
}
void gc_collect(void) {
gc_collect_start();
modturtle_gc_collect();
modpyplot_gc_collect();
gc_collect_regs_and_stack();
gc_collect_end();
}