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// -*- mode: c++ -*-
#ifndef CONTEXT_H
#define CONTEXT_H
#include <cstdlib>
#include <inttypes.h>
#include <stdint.h>
#include <xmmintrin.h>
#include "vg/memcheck.h"
template<typename T>
T align_down(T sp)
{
// There is no platform we care about that needs more than a
// 16-byte alignment.
return (T)((uint64_t)sp & ~(16 - 1));
}
// The struct in which we store the saved data. This is mostly the
// volatile registers and instruction pointer, but it also includes
// RCX/RDI which are used to pass arguments. The indices for each
// register are found in "regs.h". Note that the alignment must be
// 16 bytes so that SSE instructions can be used.
#include "regs.h"
struct registers_t {
uint64_t data[RUSTRT_MAX];
} __attribute__((aligned(16)));
extern "C" void __morestack(void *args, void *fn_ptr, uintptr_t stack_ptr);
class context {
public:
registers_t regs;
context();
context *next;
void swap(context &out);
void call(void *f, void *arg, void *sp);
void call(void *f, void *sp);
// Note that this doesn't actually adjust esp. Instead, we adjust esp when
// we actually do the call. This is needed for exception safety -- if the
// function being called causes the task to fail, then we have to avoid
// leaking space on the C stack.
inline void *alloc_stack(size_t nbytes) {
uint64_t bot = regs.data[RUSTRT_RSP];
uint64_t top = align_down(bot - nbytes);
(void)VALGRIND_MAKE_MEM_UNDEFINED(top - 4, bot - top + 4);
return reinterpret_cast<void *>(top);
}
void call_shim_on_c_stack(void *args, void *fn_ptr) {
__morestack(args, fn_ptr, regs.data[RUSTRT_RSP]);
}
};
#endif
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