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Merge pull request #20822 from alexrp/start-mips-fixes

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`start`: A handful of MIPS fixes
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Andrew Kelley 2024-07-29 12:02:59 -07:00 committed by GitHub
commit 7342017404
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1 changed files with 35 additions and 6 deletions
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lib/std/start.zig
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@ -289,17 +289,42 @@ fn _start() callconv(.Naked) noreturn {
,
.mips, .mipsel =>
\\ move $fp, $0
\\ bal 1f
\\ .gpword .
\\ .gpword %[posixCallMainAndExit]
\\ 1:
\\ lw $gp, 0($ra)
\\ subu $gp, $ra, $gp
\\ lw $25, 4($ra)
\\ addu $25, $25, $gp
\\ move $ra, $0
\\ move $a0, $sp
\\ and $sp, -8
\\ j %[posixCallMainAndExit]
\\ subu $sp, $sp, 16
\\ jalr $25
,
.mips64, .mips64el =>
\\ move $fp, $0
// This is needed because early MIPS versions don't support misaligned loads. Without
// this directive, the hidden `nop` inserted to fill the delay slot after `bal` would
// cause the two doublewords to be aligned to 4 bytes instead of 8.
\\ .balign 8
\\ bal 1f
\\ .gpdword .
\\ .gpdword %[posixCallMainAndExit]
\\ 1:
// The `gp` register on MIPS serves a similar purpose to `r2` (ToC pointer) on PPC64.
// We need to set it up in order for dynamically-linked / position-independent code to
// work.
\\ ld $gp, 0($ra)
\\ dsubu $gp, $ra, $gp
\\ ld $25, 8($ra)
\\ daddu $25, $25, $gp
\\ move $ra, $0
\\ move $a0, $sp
\\ and $sp, -16
\\ j %[posixCallMainAndExit]
\\ dsubu $sp, $sp, 16
\\ jalr $25
,
.powerpc, .powerpcle =>
// Set up the initial stack frame, and clear the back chain pointer.
@ -389,7 +414,6 @@ fn posixCallMainAndExit(argc_argv_ptr: [*]usize) callconv(.C) noreturn {
if (native_os == .linux) {
// Find the beginning of the auxiliary vector
const auxv: [*]elf.Auxv = @ptrCast(@alignCast(envp.ptr + envp_count + 1));
std.os.linux.elf_aux_maybe = auxv;
var at_hwcap: usize = 0;
const phdrs = init: {
@ -407,12 +431,17 @@ fn posixCallMainAndExit(argc_argv_ptr: [*]usize) callconv(.C) noreturn {
break :init @as([*]elf.Phdr, @ptrFromInt(at_phdr))[0..at_phnum];
};
// Apply the initial relocations as early as possible in the startup
// process.
// Apply the initial relocations as early as possible in the startup process. We cannot
// make calls yet on some architectures (e.g. MIPS) *because* they haven't been applied yet,
// so this must be fully inlined.
if (builtin.position_independent_executable) {
std.os.linux.pie.relocate(phdrs);
@call(.always_inline, std.os.linux.pie.relocate, .{phdrs});
}
// This must be done after PIE relocations have been applied or we may crash
// while trying to access the global variable (happens on MIPS at least).
std.os.linux.elf_aux_maybe = auxv;
if (!builtin.single_threaded) {
// ARMv6 targets (and earlier) have no support for TLS in hardware.
// FIXME: Elide the check for targets >= ARMv7 when the target feature API