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fix(v4t/v5te): resolve critical error in ldm/stm obscure behaviour

This commit is contained in:
Rekai Nyangadzayi Musuka 2023-09-21 01:18:18 -05:00
parent 2c5d474c56
commit ccaf0d6715
1 changed files with 73 additions and 55 deletions
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100
src/arm/cpu/arm/block_data_transfer.zig
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@ -12,18 +12,18 @@ pub fn blockDataTransfer(comptime InstrFn: type, comptime P: bool, comptime U: b
// U determines whether the LDM/STM transfer is made upwards (U == 1)
// or downwards (U == 0).
const base_addr = cpu.r[rn];
const start_addr: u32 = if (U) blk: {
break :blk cpu.r[rn] + if (P) 4 else 0;
break :blk base_addr + if (P) 4 else 0;
} else blk: {
break :blk cpu.r[rn] - (4 * reg_count) + if (!P) 4 else 0;
break :blk base_addr - (4 * reg_count) + if (!P) 4 else 0;
};
// FIXME : why 4 * reg_count?
const new_base_addr: u32 = if (U) blk: {
break :blk cpu.r[rn] + 4 * reg_count;
break :blk base_addr + 4 * reg_count;
} else blk: {
break :blk cpu.r[rn] - 4 * reg_count;
break :blk base_addr - 4 * reg_count;
};
var address = start_addr;
@ -36,9 +36,9 @@ pub fn blockDataTransfer(comptime InstrFn: type, comptime P: bool, comptime U: b
if (rlist == 0) {
if (Arm32.arch == .v4t) {
const undefined_addr: u32 = if (U) blk: {
break :blk cpu.r[rn] + if (P) 4 else 0;
break :blk base_addr + if (P) 4 else 0;
} else blk: {
break :blk cpu.r[rn] - (0x40 - if (!P) 4 else 0);
break :blk base_addr - (0x40 - if (!P) 4 else 0);
};
if (L) {
@ -49,41 +49,34 @@ pub fn blockDataTransfer(comptime InstrFn: type, comptime P: bool, comptime U: b
}
}
cpu.r[rn] = if (U) cpu.r[rn] + 0x40 else cpu.r[rn] - 0x40;
cpu.r[rn] = if (U) base_addr + 0x40 else base_addr - 0x40;
return;
}
// What happens when W is set and Rn is in the rlist? (STM)
//
// Armv4: Store OLD Base if Rb is FIRST entry in Rlist, otherwise store NEW base
// Armv5: Always store OLD Base
// FIXME: This absolutely needs revisiting :skull:
const r15_present = rlist >> 15 & 1 == 1;
var write_to_base = true;
for (first_in_list..16) |idx| {
const i: u4 = @intCast(idx);
if (rlist >> i & 1 == 1) {
transfer(cpu, r15_present, i, address);
if (L) {
load(cpu, i, rlist, address);
} else {
store(cpu, rn, i, rlist, address, .{ .old_addr = base_addr, .new_addr = new_base_addr });
}
address += 4;
}
}
if (W and !L and write_to_base) {
if (W and !L)
cpu.r[rn] = new_base_addr;
write_to_base = false;
}
}
}
if (W and L) {
// What happens when W is set and Rn is in the rlist? (LDM)
//
// ARMv4: No writeback
// ARMv5: writeback if Rn is "the ONLY register" or NOT the LAST register
if (W and L) {
if (rlist >> rn & 1 == 0) {
if (rlist >> rn & 1 == 0) { // rn is not in rlist
cpu.r[rn] = new_base_addr;
return;
}
@ -101,18 +94,19 @@ pub fn blockDataTransfer(comptime InstrFn: type, comptime P: bool, comptime U: b
}
}
fn transfer(cpu: *Arm32, r15_present: bool, i: u5, address: u32) void {
if (L) {
if (S and !r15_present) {
fn load(cpu: *Arm32, ri: u4, rlist: u16, address: u32) void {
const has_r15 = rlist >> 15 & 1 == 1;
if (S and !has_r15) {
// Always Transfer User mode Registers
cpu.setUserModeRegister(i, cpu.read(u32, address));
cpu.setUserModeRegister(ri, cpu.read(u32, address));
} else {
const value = cpu.read(u32, address);
cpu.r[ri] = value;
cpu.r[i] = value;
if (i == 0xF) {
if (ri == 0xF) {
const mask: u32 = if (Arm32.arch == .v5te) 1 else 3;
cpu.r[i] &= ~mask;
cpu.r[ri] &= ~mask;
if (Arm32.arch == .v5te) cpu.cpsr.t.write(value & 1 == 1);
if (S) cpu.setCpsr(cpu.spsr.raw); // FIXME: before or after the reload?
@ -120,16 +114,40 @@ pub fn blockDataTransfer(comptime InstrFn: type, comptime P: bool, comptime U: b
cpu.pipe.reload(cpu);
}
}
} else {
if (S) {
}
const BaseAddrs = struct { old_addr: u32, new_addr: u32 };
fn store(cpu: *Arm32, rn: u4, ri: u4, rlist: u16, address: u32, base: BaseAddrs) void {
const value = if (S) blk: {
// if S == true:
// Always Transfer User mode Registers
// This happens regardless if r15 is in the list
const value = cpu.getUserModeRegister(i);
cpu.write(u32, address, value + if (i == 0xF) 4 else @as(u32, 0)); // PC is already 8 ahead to make 12
} else {
cpu.write(u32, address, cpu.r[i] + if (i == 0xF) 4 else @as(u32, 0));
}
break :blk cpu.getUserModeRegister(ri);
} else blk: {
if (ri == rn) {
// What happens when W is set and Rn is in the rlist? (STM)
//
// Armv4: Store OLD Base if Rb is FIRST entry in Rlist, otherwise store NEW base
// Armv5: Always store OLD Base
if (rlist >> rn & 1 == 0)
break :blk base.new_addr;
const mask = @as(u16, 1) << rn;
const is_first = @popCount(rlist & (mask - 1)) == 0;
break :blk switch (Arm32.arch) {
.v4t => if (is_first) base.old_addr else base.new_addr,
.v5te => base.old_addr,
};
}
break :blk cpu.r[ri];
};
cpu.write(u32, address + if (ri == 0xF) 4 else @as(u32, 0), value);
}
}.inner;
}