140 lines
5.4 KiB
C++
140 lines
5.4 KiB
C++
/* -*- Mode: C; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
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/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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// Platform specific code to invoke XPCOM methods on native objects
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#include "xptcprivate.h"
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// The purpose of NS_InvokeByIndex() is to map a platform
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// independent call to the platform ABI. To do that,
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// NS_InvokeByIndex() has to determine the method to call via vtable
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// access. The parameters for the method are read from the
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// nsXPTCVariant* and prepared for the native ABI.
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//
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// Prior to POWER8, all 64-bit Power ISA systems used ELF v1 ABI, found
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// here:
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// https://refspecs.linuxfoundation.org/ELF/ppc64/PPC-elf64abi.html
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// and in particular:
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// https://refspecs.linuxfoundation.org/ELF/ppc64/PPC-elf64abi.html#FUNC-CALL
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// Little-endian ppc64le, however, uses ELF v2 ABI, which is here:
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// http://openpowerfoundation.org/wp-content/uploads/resources/leabi/leabi-20170510.pdf
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// and in particular section 2.2, page 22. However, most big-endian ppc64
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// systems still use ELF v1, so this file should support both.
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// 7 integral parameters are passed in registers, not including |this|
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// (i.e., r3-r10, with r3 being |this|).
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const uint32_t GPR_COUNT = 7;
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// 13 floating point parameters are passed in registers, either single or
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// double precision (i.e., f1-f13).
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const uint32_t FPR_COUNT = 13;
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// Both ABIs use the same register assignment strategy, as per this
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// example from V1 ABI section 3.2.3 and V2 ABI section 2.2.3.2 [page 43]:
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//
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// typedef struct {
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// int a;
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// double dd;
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// } sparm;
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// sparm s, t;
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// int c, d, e;
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// long double ld;
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// double ff, gg, hh;
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//
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// x = func(c, ff, d, ld, s, gg, t, e, hh);
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//
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// Parameter Register Offset in parameter save area
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// c r3 0-7 (not stored in parameter save area)
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// ff f1 8-15 (not stored)
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// d r5 16-23 (not stored)
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// ld f2,f3 24-39 (not stored)
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// s r8,r9 40-55 (not stored)
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// gg f4 56-63 (not stored)
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// t (none) 64-79 (stored in parameter save area)
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// e (none) 80-87 (stored)
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// hh f5 88-95 (not stored)
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//
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// i.e., each successive FPR usage skips a GPR, but not the other way around.
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extern "C" void invoke_copy_to_stack(uint64_t* gpregs, double* fpregs,
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uint32_t paramCount, nsXPTCVariant* s,
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uint64_t* d)
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{
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uint32_t nr_gpr = 0u;
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uint32_t nr_fpr = 0u;
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uint64_t value = 0u;
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for (uint32_t i = 0; i < paramCount; i++, s++) {
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if (s->IsIndirect())
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value = (uint64_t) &s->val;
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else {
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switch (s->type) {
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case nsXPTType::T_FLOAT: break;
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case nsXPTType::T_DOUBLE: break;
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case nsXPTType::T_I8: value = s->val.i8; break;
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case nsXPTType::T_I16: value = s->val.i16; break;
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case nsXPTType::T_I32: value = s->val.i32; break;
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case nsXPTType::T_I64: value = s->val.i64; break;
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case nsXPTType::T_U8: value = s->val.u8; break;
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case nsXPTType::T_U16: value = s->val.u16; break;
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case nsXPTType::T_U32: value = s->val.u32; break;
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case nsXPTType::T_U64: value = s->val.u64; break;
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case nsXPTType::T_BOOL: value = s->val.b; break;
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case nsXPTType::T_CHAR: value = s->val.c; break;
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case nsXPTType::T_WCHAR: value = s->val.wc; break;
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default: value = (uint64_t) s->val.p; break;
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}
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}
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if (!s->IsIndirect() && s->type == nsXPTType::T_DOUBLE) {
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if (nr_fpr < FPR_COUNT) {
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fpregs[nr_fpr++] = s->val.d;
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// Even if we have enough FPRs, still skip space in
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// the parameter area if we ran out of placeholder GPRs.
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if (nr_gpr < GPR_COUNT) {
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nr_gpr++;
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} else {
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d++;
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}
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} else {
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*((double *)d) = s->val.d;
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d++;
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}
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}
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else if (!s->IsIndirect() && s->type == nsXPTType::T_FLOAT) {
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if (nr_fpr < FPR_COUNT) {
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// Single-precision floats are passed in FPRs too.
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fpregs[nr_fpr++] = s->val.f;
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if (nr_gpr < GPR_COUNT) {
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nr_gpr++;
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} else {
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d++;
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}
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} else {
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#ifdef __LITTLE_ENDIAN__
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*((float *)d) = s->val.f;
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#else
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// Big endian needs adjustment to point to the least
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// significant word.
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float* p = (float*)d;
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p++;
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*p = s->val.f;
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#endif
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d++;
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}
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}
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else {
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if (nr_gpr < GPR_COUNT) {
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gpregs[nr_gpr++] = value;
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} else {
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*d++ = value;
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}
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}
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}
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}
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EXPORT_XPCOM_API(nsresult)
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NS_InvokeByIndex(nsISupports* that, uint32_t methodIndex, uint32_t paramCount,
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nsXPTCVariant* params);
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