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Revert "Merge pull request #4807 from LemonBoy/tls-touchups" 

This reverts commit ee6fda2297, reversing
changes made to f313ab18ae.

This caused a test failure:

```
behavior.misc.test "behavior-arm-linux-none-Debug-bare-multi thread local variable"...test failure
/home/vsts/work/1/s/lib/std/testing.zig:191:14: 0x4608f in std.testing.expect (test)
    if (!ok) @panic("test failure");
             ^
/home/vsts/work/1/s/test/stage1/behavior/misc.zig:616:11: 0x53e93 in behavior.misc.test "behavior-arm-linux-none-Debug-bare-multi thread local variable" (test)
    expect(S.t == 1235);
          ^
```
master
Andrew Kelley 2020-03-25 21:12:24 -04:00
parent 5ec6a0ea02
commit f7f563ea53
No known key found for this signature in database
GPG Key ID: 7C5F548F728501A9
3 changed files with 136 additions and 142 deletions
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237
lib/std/os/linux/tls.zig
View File

@ -1,9 +1,8 @@
const std = @import("std");
const builtin = std.builtin;
const os = std.os;
const mem = std.mem;
const elf = std.elf;
const math = std.math;
const builtin = @import("builtin");
const assert = std.debug.assert;
// This file implements the two TLS variants [1] used by ELF-based systems.
@ -61,11 +60,10 @@ const tls_tcb_size = switch (builtin.arch) {
else => @sizeOf(usize),
};
// Controls the minimum alignment of the TCB end address. The effective value
// used by the code is min(this_value, tls_segment.p_align)
// Controls if the TCB should be aligned according to the TLS segment p_align
const tls_tcb_align_size = switch (builtin.arch) {
.arm, .armeb, .aarch64, .aarch64_be => 16,
else => 1,
.arm, .armeb, .aarch64, .aarch64_be => true,
else => false,
};
// Controls if the TP points to the end of the TCB instead of its beginning
@ -74,6 +72,13 @@ const tls_tp_points_past_tcb = switch (builtin.arch) {
else => false,
};
// Check if the architecture-specific parameters look correct
comptime {
if (tls_tcb_align_size and tls_variant != TLSVariant.VariantI) {
@compileError("tls_tcb_align_size is only meaningful for variant I TLS");
}
}
// Some architectures add some offset to the tp and dtv addresses in order to
// make the generated code more efficient
@ -89,19 +94,17 @@ const tls_dtv_offset = switch (builtin.arch) {
};
// Per-thread storage for Zig's use
const CustomData = struct {
padding: [16]usize,
};
const CustomData = packed struct {};
// Dynamic Thread Vector
const DTV = extern struct {
const DTV = packed struct {
entries: usize,
tls_block: [1][*]u8,
tls_block: [1]usize,
};
// Holds all the information about the process TLS image
const TLSImage = struct {
data_src: []const u8,
data_src: []u8,
alloc_size: usize,
tcb_offset: usize,
dtv_offset: usize,
@ -110,13 +113,13 @@ const TLSImage = struct {
gdt_entry_number: usize,
};
pub var tls_image: TLSImage = undefined;
pub var tls_image: ?TLSImage = null;
pub fn setThreadPointer(addr: usize) void {
switch (builtin.arch) {
.i386 => {
var user_desc = std.os.linux.user_desc{
.entry_number = tls_image.gdt_entry_number,
.entry_number = tls_image.?.gdt_entry_number,
.base_addr = addr,
.limit = 0xfffff,
.seg_32bit = 1,
@ -131,7 +134,7 @@ pub fn setThreadPointer(addr: usize) void {
const gdt_entry_number = user_desc.entry_number;
// We have to keep track of our slot as it's also needed for clone()
tls_image.gdt_entry_number = gdt_entry_number;
tls_image.?.gdt_entry_number = gdt_entry_number;
// Update the %gs selector
asm volatile ("movl %[gs_val], %%gs"
:
@ -168,7 +171,7 @@ pub fn setThreadPointer(addr: usize) void {
}
}
fn initTLS() void {
pub fn initTLS() ?*elf.Phdr {
var tls_phdr: ?*elf.Phdr = null;
var img_base: usize = 0;
@ -192,138 +195,124 @@ fn initTLS() void {
// Sanity check
assert(at_phent == @sizeOf(elf.Phdr));
// Find the TLS section
// Search the TLS section
const phdrs = (@intToPtr([*]elf.Phdr, at_phdr))[0..at_phnum];
var gnu_stack: ?*elf.Phdr = null;
for (phdrs) |*phdr| {
switch (phdr.p_type) {
elf.PT_PHDR => img_base = at_phdr - phdr.p_vaddr,
elf.PT_TLS => tls_phdr = phdr,
else => {},
elf.PT_GNU_STACK => gnu_stack = phdr,
else => continue,
}
}
// If the cpu is ARM-based, check if it supports the TLS register
if (comptime builtin.arch.isARM() and at_hwcap & std.os.linux.HWCAP_TLS == 0) {
// If the CPU does not support TLS via a coprocessor register,
// a kernel helper function can be used instead on certain linux kernels.
// See linux/arch/arm/include/asm/tls.h and musl/src/thread/arm/__set_thread_area.c.
@panic("TODO: Implement ARM fallback TLS functionality");
}
var tls_align_factor: usize = undefined;
var tls_data: []const u8 = undefined;
if (tls_phdr) |phdr| {
tls_align_factor = phdr.p_align;
tls_data = @intToPtr([*]u8, img_base + phdr.p_vaddr)[0..phdr.p_memsz];
} else {
tls_align_factor = @alignOf(*usize);
tls_data = &[_]u8{};
// If the cpu is arm-based, check if it supports the TLS register
if (builtin.arch == .arm and at_hwcap & std.os.linux.HWCAP_TLS == 0) {
// If the CPU does not support TLS via a coprocessor register,
// a kernel helper function can be used instead on certain linux kernels.
// See linux/arch/arm/include/asm/tls.h and musl/src/thread/arm/__set_thread_area.c.
@panic("TODO: Implement ARM fallback TLS functionality");
}
// Offsets into the allocated TLS area
var tcb_offset: usize = undefined;
var dtv_offset: usize = undefined;
var data_offset: usize = undefined;
var thread_data_offset: usize = undefined;
// Compute the total size of the ABI-specific data plus our own control
// structures
const alloc_size = switch (tls_variant) {
.VariantI => blk: {
var l: usize = 0;
dtv_offset = l;
l += @sizeOf(DTV);
thread_data_offset = l;
l += @sizeOf(CustomData);
l = mem.alignForward(l, phdr.p_align);
tcb_offset = l;
if (tls_tcb_align_size) {
l += mem.alignForward(tls_tcb_size, phdr.p_align);
} else {
l += tls_tcb_size;
}
data_offset = l;
l += phdr.p_memsz;
break :blk l;
},
.VariantII => blk: {
var l: usize = 0;
data_offset = l;
l += phdr.p_memsz;
l = mem.alignForward(l, phdr.p_align);
tcb_offset = l;
l += tls_tcb_size;
thread_data_offset = l;
l += @sizeOf(CustomData);
dtv_offset = l;
l += @sizeOf(DTV);
break :blk l;
},
};
tls_image = TLSImage{
.data_src = @intToPtr([*]u8, phdr.p_vaddr + img_base)[0..phdr.p_filesz],
.alloc_size = alloc_size,
.tcb_offset = tcb_offset,
.dtv_offset = dtv_offset,
.data_offset = data_offset,
.gdt_entry_number = @bitCast(usize, @as(isize, -1)),
};
}
// Offsets into the allocated TLS area
var tcb_offset: usize = undefined;
var dtv_offset: usize = undefined;
var data_offset: usize = undefined;
var thread_data_offset: usize = undefined;
// Compute the total size of the ABI-specific data plus our own control
// structures
const alloc_size = switch (tls_variant) {
.VariantI => blk: {
var l: usize = 0;
// Unneeded because l is zero
// l = mem.alignForward(l, @alignOf(DTV));
dtv_offset = l;
l += @sizeOf(DTV);
l = mem.alignForward(l, @alignOf(CustomData));
thread_data_offset = l;
l += @sizeOf(CustomData);
// Make sure the TP is aligned
l = mem.alignForward(l, tls_align_factor);
tcb_offset = l;
// Ensure there are at least tls_tcb_align_size bytes of padding
const min_align = math.max(tls_tcb_align_size, tls_align_factor);
l += mem.alignForward(tls_tcb_size, min_align);
data_offset = l;
l += mem.alignForward(tls_data.len, tls_align_factor);
break :blk l;
},
.VariantII => blk: {
var l: usize = 0;
data_offset = l;
l = mem.alignForward(tls_data.len, tls_align_factor);
// The TP is aligned to p_align
tcb_offset = l;
l += tls_tcb_size;
l = mem.alignForward(l, @alignOf(CustomData));
thread_data_offset = l;
l += @sizeOf(CustomData);
l = mem.alignForward(l, @alignOf(DTV));
dtv_offset = l;
l += @sizeOf(DTV);
break :blk l;
},
};
tls_image = TLSImage{
.data_src = tls_data,
.alloc_size = alloc_size,
.tcb_offset = tcb_offset,
.dtv_offset = dtv_offset,
.data_offset = data_offset,
.gdt_entry_number = @bitCast(usize, @as(isize, -1)),
};
return gnu_stack;
}
inline fn alignPtrCast(comptime T: type, ptr: [*]u8) *T {
return @ptrCast(*T, @alignCast(@alignOf(*T), ptr));
}
pub fn copyTLS(addr: usize) usize {
const tls_img = tls_image.?;
/// Initializes all the fields of the static TLS area and returns the computed
/// architecture-specific value of the thread-pointer register
pub fn prepareTLS(area: []u8) usize {
// Clear the area we're going to use, just to be safe
mem.set(u8, area, 0);
// Be paranoid, clear the area we're going to use
@memset(@intToPtr([*]u8, addr), 0, tls_img.alloc_size);
// Prepare the DTV
const dtv = alignPtrCast(DTV, area.ptr + tls_image.dtv_offset);
const dtv = @intToPtr(*DTV, addr + tls_img.dtv_offset);
dtv.entries = 1;
dtv.tls_block[0] = area.ptr + tls_dtv_offset + tls_image.data_offset;
// Prepare the TCB
const tcb_ptr = alignPtrCast([*]u8, area.ptr + tls_image.tcb_offset);
tcb_ptr.* = switch (tls_variant) {
.VariantI => area.ptr + tls_image.dtv_offset,
.VariantII => area.ptr + tls_image.tcb_offset,
};
dtv.tls_block[0] = addr + tls_img.data_offset + tls_dtv_offset;
// Set-up the TCB
// Force the alignment to 1 byte as the TCB may start from a non-aligned
// address under the variant II model
const tcb_ptr = @intToPtr(*align(1) usize, addr + tls_img.tcb_offset);
if (tls_variant == TLSVariant.VariantI) {
tcb_ptr.* = addr + tls_img.dtv_offset;
} else {
tcb_ptr.* = addr + tls_img.tcb_offset;
}
// Copy the data
mem.copy(u8, area[tls_image.data_offset..], tls_image.data_src);
@memcpy(@intToPtr([*]u8, addr + tls_img.data_offset), tls_img.data_src.ptr, tls_img.data_src.len);
// Return the corrected (if needed) value for the tp register
return @ptrToInt(area.ptr) + tls_tp_offset +
if (tls_tp_points_past_tcb) tls_image.data_offset else tls_image.tcb_offset;
return addr + tls_tp_offset +
if (tls_tp_points_past_tcb) tls_img.data_offset else tls_img.tcb_offset;
}
var main_thread_tls_buffer: [256]u8 align(32) = undefined;
pub fn initStaticTLS() void {
initTLS();
pub fn allocateTLS(size: usize) usize {
// Small TLS allocation, use our local buffer
if (size < main_thread_tls_buffer.len) {
return @ptrToInt(&main_thread_tls_buffer);
}
var tls_area = blk: {
// Fast path for the common case where the TLS data is really small,
// avoid an allocation and use our local buffer
if (tls_image.alloc_size < main_thread_tls_buffer.len) {
break :blk main_thread_tls_buffer[0..tls_image.alloc_size];
}
const slice = os.mmap(
null,
size,
os.PROT_READ | os.PROT_WRITE,
os.MAP_PRIVATE | os.MAP_ANONYMOUS,
-1,
0,
) catch @panic("out of memory");
break :blk os.mmap(
null,
tls_image.alloc_size,
os.PROT_READ | os.PROT_WRITE,
os.MAP_PRIVATE | os.MAP_ANONYMOUS,
-1,
0,
) catch @panic("out of memory");
};
const tp_value = prepareTLS(tls_area);
setThreadPointer(tp_value);
return @ptrToInt(slice.ptr);
}

8
lib/std/start.zig
View File

@ -152,7 +152,13 @@ fn posixCallMainAndExit() noreturn {
const auxv = @ptrCast([*]std.elf.Auxv, @alignCast(@alignOf(usize), envp.ptr + envp_count + 1));
std.os.linux.elf_aux_maybe = auxv;
// Initialize the TLS area
std.os.linux.tls.initStaticTLS();
const gnu_stack_phdr = std.os.linux.tls.initTLS() orelse @panic("ELF missing stack size");
if (std.os.linux.tls.tls_image) |tls_img| {
const tls_addr = std.os.linux.tls.allocateTLS(tls_img.alloc_size);
const tp = std.os.linux.tls.copyTLS(tls_addr);
std.os.linux.tls.setThreadPointer(tp);
}
// TODO This is disabled because what should we do when linking libc and this code
// does not execute? And also it's causing a test failure in stack traces in release modes.

33
lib/std/thread.zig
View File

@ -286,10 +286,11 @@ pub const Thread = struct {
}
// Finally, the Thread Local Storage, if any.
if (!Thread.use_pthreads) {
// XXX: Is this alignment enough?
l = mem.alignForward(l, @alignOf(usize));
tls_start_offset = l;
l += os.linux.tls.tls_image.alloc_size;
if (os.linux.tls.tls_image) |tls_img| {
l = mem.alignForward(l, @alignOf(usize));
tls_start_offset = l;
l += tls_img.alloc_size;
}
}
// Round the size to the page size.
break :blk mem.alignForward(l, mem.page_size);
@ -395,21 +396,18 @@ pub const Thread = struct {
else => return os.unexpectedErrno(@intCast(usize, err)),
}
} else if (std.Target.current.os.tag == .linux) {
const flags: u32 = os.CLONE_VM | os.CLONE_FS | os.CLONE_FILES |
os.CLONE_SIGHAND | os.CLONE_THREAD | os.CLONE_SYSVSEM |
os.CLONE_PARENT_SETTID | os.CLONE_CHILD_CLEARTID |
os.CLONE_DETACHED | os.CLONE_SETTLS;
var flags: u32 = os.CLONE_VM | os.CLONE_FS | os.CLONE_FILES | os.CLONE_SIGHAND |
os.CLONE_THREAD | os.CLONE_SYSVSEM | os.CLONE_PARENT_SETTID | os.CLONE_CHILD_CLEARTID |
os.CLONE_DETACHED;
var newtls: usize = undefined;
// This structure is only needed when targeting i386
var user_desc: if (std.Target.current.cpu.arch == .i386) os.linux.user_desc else void = undefined;
const tls_area = mmap_slice[tls_start_offset..];
const tp_value = os.linux.tls.prepareTLS(tls_area);
const newtls = blk: {
if (os.linux.tls.tls_image) |tls_img| {
if (std.Target.current.cpu.arch == .i386) {
user_desc = os.linux.user_desc{
.entry_number = os.linux.tls.tls_image.gdt_entry_number,
.base_addr = tp_value,
.entry_number = tls_img.gdt_entry_number,
.base_addr = os.linux.tls.copyTLS(mmap_addr + tls_start_offset),
.limit = 0xfffff,
.seg_32bit = 1,
.contents = 0, // Data
@ -418,11 +416,12 @@ pub const Thread = struct {
.seg_not_present = 0,
.useable = 1,
};
break :blk @ptrToInt(&user_desc);
newtls = @ptrToInt(&user_desc);
} else {
break :blk tp_value;
newtls = os.linux.tls.copyTLS(mmap_addr + tls_start_offset);
}
};
flags |= os.CLONE_SETTLS;
}
const rc = os.linux.clone(
MainFuncs.linuxThreadMain,