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fix(armv5te): implement obscure behaviour on invalid LDM writeback 

All I have to do is implement ARMv5TE specific instructions, and then
we're finished with ARMWRESTLER!
This commit is contained in:
Rekai Nyangadzayi Musuka 2023-09-06 00:19:25 -05:00
parent 591352a65b
commit e6863e7a9b
2 changed files with 77 additions and 53 deletions
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11
src/arm.zig
View File

@ -27,11 +27,12 @@ const condition_lut = [_]u16{
0x0000, // NV - never
};
pub fn Arm32(comptime arch: Architecture) type {
const is_v5te = arch == .v5te;
pub fn Arm32(comptime isa: Architecture) type {
const is_v5te = isa == .v5te;
return struct {
const Self = @This();
pub const arch = isa;
r: [16]u32 = [_]u32{0x00} ** 16,
pipe: Pipeline = Pipeline.init(),
@ -46,12 +47,12 @@ pub fn Arm32(comptime arch: Architecture) type {
itcm: if (is_v5te) Itcm else void,
dtcm: if (is_v5te) Dtcm else void,
const arm = switch (arch) {
const arm = switch (isa) {
.v4t => @import("arm/v4t.zig").arm,
.v5te => @import("arm/v5te.zig").arm,
};
const thumb = switch (arch) {
const thumb = switch (isa) {
.v4t => @import("arm/v4t.zig").thumb,
.v5te => @import("arm/v5te.zig").thumb,
};
@ -388,7 +389,7 @@ pub fn Arm32(comptime arch: Architecture) type {
}
pub fn interface(self: *Self) Interpreter {
return switch (arch) {
return switch (isa) {
.v4t => .{ .v4t = self },
.v5te => .{ .v5te = self },
};

113
src/arm/cpu/arm/block_data_transfer.zig
View File

@ -4,78 +4,101 @@ pub fn blockDataTransfer(comptime InstrFn: type, comptime P: bool, comptime U: b
return struct {
fn inner(cpu: *Arm32, opcode: u32) void {
const rn: u4 = @truncate(opcode >> 16 & 0xF);
const rlist = opcode & 0xFFFF;
const r15 = rlist >> 15 & 1 == 1;
const rlist: u16 = @intCast(opcode & 0xFFFF);
var count: u32 = 0;
var i: u5 = 0;
var first: u4 = 0;
var write_to_base = true;
const reg_count: u32 = @popCount(rlist);
const first_in_list: u4 = @truncate(@ctz(rlist)); // note that @ctz(0x0000) and @ctz(0x0001) collide
while (i < 16) : (i += 1) {
const r: u4 = @truncate(15 - i);
if (rlist >> r & 1 == 1) {
first = r;
count += 1;
}
}
// U determines whether the LDM/STM transfer is made upwards (U == 1)
// or downwards (U == 0).
var start = cpu.r[rn];
if (U) {
start += if (P) 4 else 0;
} else {
start = start - (4 * count) + if (!P) 4 else 0;
}
const start_addr: u32 = if (U) blk: {
break :blk cpu.r[rn] + if (P) 4 else 0;
} else blk: {
break :blk cpu.r[rn] - (4 * reg_count) + if (!P) 4 else 0;
};
var end = cpu.r[rn];
if (U) {
end = end + (4 * count) - if (!P) 4 else 0;
} else {
end -= if (P) 4 else 0;
}
// FIXME : why 4 * reg_count?
var new_base = cpu.r[rn];
if (U) {
new_base += 4 * count;
} else {
new_base -= 4 * count;
}
const new_base_addr: u32 = if (U) blk: {
break :blk cpu.r[rn] + 4 * reg_count;
} else blk: {
break :blk cpu.r[rn] - 4 * reg_count;
};
var address = start;
var address = start_addr;
// On Empty List:
//
// ARMv4 Only: R15 is Loaded/Stored
// ARMv4/Armv5: Rn = Rn +/- 0x40
if (rlist == 0) {
var und_addr = cpu.r[rn];
if (U) {
und_addr += if (P) 4 else 0;
} else {
und_addr -= 0x40 - if (!P) 4 else 0;
}
if (Arm32.arch == .v4t) {
const undefined_addr: u32 = if (U) blk: {
break :blk cpu.r[rn] + if (P) 4 else 0;
} else blk: {
break :blk cpu.r[rn] - 0x40 - if (!P) 4 else 0;
};
if (L) {
cpu.r[15] = cpu.read(u32, und_addr);
cpu.r[15] = cpu.read(u32, undefined_addr);
cpu.pipe.reload(cpu);
} else {
cpu.write(u32, und_addr, cpu.r[15] + 4);
cpu.write(u32, undefined_addr, cpu.r[15] + 4);
}
}
cpu.r[rn] = if (U) cpu.r[rn] + 0x40 else cpu.r[rn] - 0x40;
return;
}
i = first;
while (i < 16) : (i += 1) {
// 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, i, address);
transfer(cpu, r15_present, i, address);
address += 4;
if (W and !L and write_to_base) {
cpu.r[rn] = new_base;
cpu.r[rn] = new_base_addr;
write_to_base = false;
}
}
}
if (W and L and rlist >> rn & 1 == 0) cpu.r[rn] = new_base;
// 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) {
cpu.r[rn] = new_base_addr;
return;
}
switch (Arm32.arch) {
.v4t => {}, // No Writeback
.v5te => {
const rn_is_last = (15 - @clz(rlist)) <= rn;
if (reg_count == 1 or !rn_is_last) {
cpu.r[rn] = new_base_addr;
}
},
}
}
}
fn transfer(cpu: *Arm32, r15_present: bool, i: u5, address: u32) void {