Merge pull request #8683 from LemonBoy/thumblinux

Initial bringup for Linux/Thumb2

4 files changed, 173 insertions, 4 deletions

diff --git a/lib/std/os/bits/linux.zig b/lib/std/os/bits/linux.zig
index 74f9b14ca2..61a432673a 100644
--- a/lib/std/os/bits/linux.zig
+++ b/lib/std/os/bits/linux.zig
@@ -18,7 +18,7 @@ pub usingnamespace switch (builtin.arch) {
     .i386 => @import("linux/i386.zig"),
     .x86_64 => @import("linux/x86_64.zig"),
     .aarch64 => @import("linux/arm64.zig"),
-    .arm => @import("linux/arm-eabi.zig"),
+    .arm, .thumb => @import("linux/arm-eabi.zig"),
     .riscv64 => @import("linux/riscv64.zig"),
     .sparcv9 => @import("linux/sparc64.zig"),
     .mips, .mipsel => @import("linux/mips.zig"),
diff --git a/lib/std/os/linux.zig b/lib/std/os/linux.zig
index 4a67ca7685..6c88d9eae1 100644
--- a/lib/std/os/linux.zig
+++ b/lib/std/os/linux.zig
@@ -23,6 +23,7 @@ pub usingnamespace switch (builtin.arch) {
     .x86_64 => @import("linux/x86_64.zig"),
     .aarch64 => @import("linux/arm64.zig"),
     .arm => @import("linux/arm-eabi.zig"),
+    .thumb => @import("linux/thumb.zig"),
     .riscv64 => @import("linux/riscv64.zig"),
     .sparcv9 => @import("linux/sparc64.zig"),
     .mips, .mipsel => @import("linux/mips.zig"),
diff --git a/lib/std/os/linux/thumb.zig b/lib/std/os/linux/thumb.zig
new file mode 100644
index 0000000000..5db9d2cbf4
--- /dev/null
+++ b/lib/std/os/linux/thumb.zig
@@ -0,0 +1,168 @@
+// SPDX-License-Identifier: MIT
+// Copyright (c) 2015-2021 Zig Contributors
+// This file is part of [zig](https://ziglang.org/), which is MIT licensed.
+// The MIT license requires this copyright notice to be included in all copies
+// and substantial portions of the software.
+usingnamespace @import("../bits.zig");
+
+// The syscall interface is identical to the ARM one but we're facing an extra
+// challenge: r7, the register where the syscall number is stored, may be
+// reserved for the frame pointer.
+// Save and restore r7 around the syscall without touching the stack pointer not
+// to break the frame chain.
+
+pub fn syscall0(number: SYS) usize {
+    @setRuntimeSafety(false);
+
+    var buf: [2]usize = .{ @enumToInt(number), undefined };
+    return asm volatile (
+        \\ str r7, [%[tmp], #4]
+        \\ ldr r7, [%[tmp]]
+        \\ svc #0
+        \\ ldr r7, [%[tmp], #4]
+        : [ret] "={r0}" (-> usize)
+        : [tmp] "{r1}" (buf)
+        : "memory"
+    );
+}
+
+pub fn syscall1(number: SYS, arg1: usize) usize {
+    @setRuntimeSafety(false);
+
+    var buf: [2]usize = .{ @enumToInt(number), undefined };
+    return asm volatile (
+        \\ str r7, [%[tmp], #4]
+        \\ ldr r7, [%[tmp]]
+        \\ svc #0
+        \\ ldr r7, [%[tmp], #4]
+        : [ret] "={r0}" (-> usize)
+        : [tmp] "{r1}" (buf),
+          [arg1] "{r0}" (arg1)
+        : "memory"
+    );
+}
+
+pub fn syscall2(number: SYS, arg1: usize, arg2: usize) usize {
+    @setRuntimeSafety(false);
+
+    var buf: [2]usize = .{ @enumToInt(number), undefined };
+    return asm volatile (
+        \\ str r7, [%[tmp], #4]
+        \\ ldr r7, [%[tmp]]
+        \\ svc #0
+        \\ ldr r7, [%[tmp], #4]
+        : [ret] "={r0}" (-> usize)
+        : [tmp] "{r2}" (buf),
+          [arg1] "{r0}" (arg1),
+          [arg2] "{r1}" (arg2)
+        : "memory"
+    );
+}
+
+pub fn syscall3(number: SYS, arg1: usize, arg2: usize, arg3: usize) usize {
+    @setRuntimeSafety(false);
+
+    var buf: [2]usize = .{ @enumToInt(number), undefined };
+    return asm volatile (
+        \\ str r7, [%[tmp], #4]
+        \\ ldr r7, [%[tmp]]
+        \\ svc #0
+        \\ ldr r7, [%[tmp], #4]
+        : [ret] "={r0}" (-> usize)
+        : [tmp] "{r3}" (buf),
+          [arg1] "{r0}" (arg1),
+          [arg2] "{r1}" (arg2),
+          [arg3] "{r2}" (arg3)
+        : "memory"
+    );
+}
+
+pub fn syscall4(number: SYS, arg1: usize, arg2: usize, arg3: usize, arg4: usize) usize {
+    @setRuntimeSafety(false);
+
+    var buf: [2]usize = .{ @enumToInt(number), undefined };
+    return asm volatile (
+        \\ str r7, [%[tmp], #4]
+        \\ ldr r7, [%[tmp]]
+        \\ svc #0
+        \\ ldr r7, [%[tmp], #4]
+        : [ret] "={r0}" (-> usize)
+        : [tmp] "{r4}" (buf),
+          [arg1] "{r0}" (arg1),
+          [arg2] "{r1}" (arg2),
+          [arg3] "{r2}" (arg3),
+          [arg4] "{r3}" (arg4)
+        : "memory"
+    );
+}
+
+pub fn syscall5(number: SYS, arg1: usize, arg2: usize, arg3: usize, arg4: usize, arg5: usize) usize {
+    @setRuntimeSafety(false);
+
+    var buf: [2]usize = .{ @enumToInt(number), undefined };
+    return asm volatile (
+        \\ str r7, [%[tmp], #4]
+        \\ ldr r7, [%[tmp]]
+        \\ svc #0
+        \\ ldr r7, [%[tmp], #4]
+        : [ret] "={r0}" (-> usize)
+        : [tmp] "{r5}" (buf),
+          [arg1] "{r0}" (arg1),
+          [arg2] "{r1}" (arg2),
+          [arg3] "{r2}" (arg3),
+          [arg4] "{r3}" (arg4),
+          [arg5] "{r4}" (arg5)
+        : "memory"
+    );
+}
+
+pub fn syscall6(
+    number: SYS,
+    arg1: usize,
+    arg2: usize,
+    arg3: usize,
+    arg4: usize,
+    arg5: usize,
+    arg6: usize,
+) usize {
+    @setRuntimeSafety(false);
+
+    var buf: [2]usize = .{ @enumToInt(number), undefined };
+    return asm volatile (
+        \\ str r7, [%[tmp], #4]
+        \\ ldr r7, [%[tmp]]
+        \\ svc #0
+        \\ ldr r7, [%[tmp], #4]
+        : [ret] "={r0}" (-> usize)
+        : [tmp] "{r6}" (buf),
+          [arg1] "{r0}" (arg1),
+          [arg2] "{r1}" (arg2),
+          [arg3] "{r2}" (arg3),
+          [arg4] "{r3}" (arg4),
+          [arg5] "{r4}" (arg5),
+          [arg6] "{r5}" (arg6)
+        : "memory"
+    );
+}
+
+/// This matches the libc clone function.
+pub extern fn clone(func: fn (arg: usize) callconv(.C) u8, stack: usize, flags: u32, arg: usize, ptid: *i32, tls: usize, ctid: *i32) usize;
+
+pub fn restore() callconv(.Naked) void {
+    return asm volatile (
+        \\ mov r7, %[number]
+        \\ svc #0
+        :
+        : [number] "I" (@enumToInt(SYS.sigreturn))
+    );
+}
+
+pub fn restore_rt() callconv(.Naked) void {
+    return asm volatile (
+        \\ mov r7, %[number]
+        \\ svc #0
+        :
+        : [number] "I" (@enumToInt(SYS.rt_sigreturn))
+        : "memory"
+    );
+}
diff --git a/lib/std/os/linux/tls.zig b/lib/std/os/linux/tls.zig
index 4a36b0d485..0830dcbfda 100644
--- a/lib/std/os/linux/tls.zig
+++ b/lib/std/os/linux/tls.zig
@@ -53,7 +53,7 @@ const TLSVariant = enum {
 };
 
 const tls_variant = switch (builtin.arch) {
-    .arm, .armeb, .aarch64, .aarch64_be, .riscv32, .riscv64, .mips, .mipsel, .powerpc, .powerpc64, .powerpc64le => TLSVariant.VariantI,
+    .arm, .armeb, .thumb, .aarch64, .aarch64_be, .riscv32, .riscv64, .mips, .mipsel, .powerpc, .powerpc64, .powerpc64le => TLSVariant.VariantI,
     .x86_64, .i386, .sparcv9 => TLSVariant.VariantII,
     else => @compileError("undefined tls_variant for this architecture"),
 };
@@ -62,7 +62,7 @@ const tls_variant = switch (builtin.arch) {
 const tls_tcb_size = switch (builtin.arch) {
     // ARM EABI mandates enough space for two pointers: the first one points to
     // the DTV while the second one is unspecified but reserved
-    .arm, .armeb, .aarch64, .aarch64_be => 2 * @sizeOf(usize),
+    .arm, .armeb, .thumb, .aarch64, .aarch64_be => 2 * @sizeOf(usize),
     // One pointer-sized word that points either to the DTV or the TCB itself
     else => @sizeOf(usize),
 };
@@ -150,7 +150,7 @@ pub fn setThreadPointer(addr: usize) void {
                 : [addr] "r" (addr)
             );
         },
-        .arm => {
+        .arm, .thumb => {
             const rc = std.os.linux.syscall1(.set_tls, addr);
             assert(rc == 0);
         },