Improvements for UEFI

[RossComputerGuy]

Just run: zig build -Dtarget=x86_64-uefi -Dsingle-threaded --zig-lib-dir lib

This PR introduces several improvements for UEFI, so far:

• std.process.ArgvIterator support
• std.process.totalSystemMemory support
• UEFI Shell Protocol
• Merged @truemedian's uefi-rework branch

Planned:

• std.process.EnvMap support

[squeek502]

Correct me if I'm wrong, but my assumption would be that UEFI should be using WTF-16 <-> WTF-8 conversion instead of UTF-16 <-> UTF-8 (see #19005 for context).

(links to any resources about these sorts of UEFI details would be appreciated if anyone has them handy)

Either way, the doc comments of either the InvalidUtf8 or InvalidWtf8 error in ChangeCurDirError will need to be updated accordingly.

[RossComputerGuy]

@squeek502 The UEFI spec mentions UTF-16 and UTF-8 but not WTF-8 or WTF-16.

[llogick]

https://uefi.org/specs/UEFI/2.10/02_Overview.html?highlight=char16#data-types

CHAR16

2-byte Character.

Unless otherwise specified all characters and strings are stored in the UCS-2 encoding format as defined by Unicode 2.1 and ISO/IEC 10646 standards.

UCS-2 is a fixed width encoding that uses two bytes for each character; meaning, it can represent up to a total of 216 characters or slightly over 65 thousand. On the other hand, UTF-16 is a variable width encoding scheme that uses a minimum of 2 bytes and a maximum of 4 bytes for each character. This lets UTF-16 represent any character in Unicode while using minimal space for the most commonly used characters. For majority of the 65,000+ characters, UCS-2 and UTF-16 have identical [code](http://www.differencebetween.net/business/structure-systems/difference-between-universal-product-code-upc-and-stock-keeping-unit-sku/) points; so they are largely equivalent. This lets UTF-16 capable applications to correctly interpret UCS-2 codes. But the other way around would not work due to the many enhancements in UTF-16.

[RossComputerGuy]

https://www.ibm.com/docs/en/i/7.4?topic=unicode-ucs-2-its-relationship-utf-16

The UCS-2 standard, an early version of Unicode, is limited to 65 535 characters. However, the data processing industry needs over 94 000 characters; the UCS-2 standard has been superseded by the Unicode UTF-16 standard.

So should we implement UCS-2 specific functions in the Unicode module or stick with the UTF-16 methods?

[squeek502]

The situation with UEFI sounds like it is the same as the situation with Windows (arbitrary sequences of u16), so I think the right way to go is WTF-16 <-> WTF-8.

(WTF-16 is an informal name for potentially ill-formed UTF-16, or UTF-16 with potentially unpaired surrogates).

See the motivation section of the WTF-8 spec: https://simonsapin.github.io/wtf-8/#motivation and the description of #19005

[RossComputerGuy]

The situation with UEFI sounds like it is the same as the situation with Windows

Yeah, well UEFI takes similarities from Windows so no surprise there.

so I think the right way to go is WTF-16 <-> WTF-8.

Has anyone tried WTF-8/16 encodings on UEFI? I've only seen UTF-8/16.

[squeek502]

From the linked specs, UEFI uses UCS-2 which is essentially just sequences of u16. The only difference to UTF-16 is that well-formed UTF-16 disallows unpaired surrogate codepoints, meaning the code units 0xD800 through 0xDFFF. Because UCS-2 allows any u16 (including 0xD800 through 0xDFFF), this means that not all valid UCS-2 can be represented as UTF-16 (and also that not all valid UCS-2 can be represented as UTF-8).

WTF-16 is functionally equivalent to UCS-2 for our purposes, and WTF-8 is a superset of UTF-8 that allows the codepoints U+D800 to U+DFFF (surrogate codepoints) to be encoded using the normal UTF-8 encoding algorithm. Since U+D800 to U+DFFF are the only WTF-16 code units that are normally unrepresentable in UTF-8, this alone is sufficient to be able to losslessly roundtrip from WTF-8 to WTF-16.

If you'd like to test whether or not WTF-16 is needed, the way to go would be to create a file with any value from 0xD800 to 0xDFFF as one of the u16s in the filename. If the filesystem supports creating a file with such a name (which I'm assuming it does), then UTF-16 <-> UTF-8 is not going to cut it.

[RossComputerGuy]

If you'd like to test this, the way to go would be to create a file with any value from 0xD800 to 0xDFFF as one of the u16s. If the filesystem supports creating a file with such a name (which I'm assuming it does), then UTF-16 <-> UTF-8 is not going to cut it.

Well, I can give it a try. I'm currently porting over @truemedian's UEFI stuff from their own fork so this PR will include file system operations.

[RossComputerGuy]

I've merged @truemedian's Zig branch for the uefi-rework into this one and added a couple of improvements along the way.

[RossComputerGuy]

Ok, so I got the compiler to build for UEFI

This PR still needs a lot of work though.

[RossComputerGuy]

This method is causing an integer overflow panic.

const std = @import("std");

pub fn main() !void {
    const stat = try std.posix.fstat(std.fs.cwd().fd);

    std.debug.print("{} ", .{stat.atim});
    std.debug.print("{}\n", .{stat.atime()});

    std.debug.print("{} ", .{stat.mtim});
    std.debug.print("{}\n", .{stat.mtime()});

    std.debug.print("{} ", .{stat.ctim});
    std.debug.print("{}\n", .{stat.ctime()});
}

os.uefi.bits.Time{ .year = 2024, .month = 3, .day = 31, .hour = 0, .minute = 0, .second = 0, .nanosecond = 0, .timezone = 2047, .daylight = os.uefi.bits.Time.Time__struct_1282{ ._pad1 = 0, .in_daylight = false, .adjust_daylight = false } } 3920832000
os.uefi.bits.Time{ .year = 2024, .month = 3, .day = 31, .hour = 22, .minute = 28, .second = 8, .nanosecond = 0, .timezone = 2047, .daylight = os.uefi.bits.Time.Time__struct_1282{ ._pad1 = 0, .in_daylight = false, .adjust_daylight = false } } 3920912888
os.uefi.bits.Time{ .year = 1980, .month = 0, .day = 0, .hour = 0, .minute = 0, .second = 0, .nanosecond = 0, .timezone = 2047, .daylight = os.uefi.bits.Time.Time__struct_1282{ ._pad1 = 0, .in_daylight = false, .adjust_daylight = false } } panic: integer overflow 3186494919

[RossComputerGuy]

Correction: this is with toEpochSeconds and not toEpochNanoseconds

[ianprime0509]

My suspicion would be days += self.day - 1;. Based on the doc comment for day, it should be between 1 and 31, but you're passing a struct with .day = 0, so something looks to be out of sync.

[RossComputerGuy]

Yeah, I am not sure why it is like that. My implementation didn't do this (the one currently in upstream). This comes from @truemedian's branch which I incorporated.

[RossComputerGuy]

Going further with this test program, I get this output:

os.uefi.bits.Time{ .year = 2024, .month = 3, .day = 31, .hour = 0, .minute = 0, .second = 0, .nanosecond = 0, .timezone = 2047, .daylight = os.uefi.bits.Time.Time__struct_1283{ ._pad1 = 0, .in_daylight = false, .adjust_daylight = false } } 3920832000
os.uefi.bits.Time{ .year = 2024, .month = 3, .day = 31, .hour = 22, .minute = 51, .second = 46, .nanosecond = 0, .timezone = 2047, .daylight = os.uefi.bits.Time.Time__struct_1283{ ._pad1 = 0, .in_daylight = false, .adjust_daylight = false } } 3920914306
os.uefi.bits.Time{ .year = 1980, .month = 0, .day = 0, .hour = 0, .minute = 0, .second = 0, .nanosecond = 0, .timezone = 2047, .daylight = os.uefi.bits.Time.Time__struct_1283{ ._pad1 = 0, .in_daylight = false, .adjust_daylight = false } }
Days in years: 29219

Days in months: 29219
panic: integer overflow 3186465173
Panicked during a panic. Aborting

const std = @import("std");

fn toEpochSeconds(self: std.os.uefi.bits.Time) u64 {
    var year: u16 = 1900;
    var days: u32 = 0;

    while (year < self.year) : (year += 1) {
        days += std.time.epoch.getDaysInYear(year);
    }
    std.debug.print("\nDays in years: {}\n", .{days});

    var month: u8 = 1;
    while (month < self.month) : (month += 1) {
        const leap_kind: std.time.epoch.YearLeapKind = if (std.time.epoch.isLeapYear(self.year)) .leap else .not_leap;

        days += std.time.epoch.getDaysInMonth(leap_kind, @enumFromInt(month));
    }
    std.debug.print("\nDays in months: {}\n", .{days});

    days += self.day - 1;
    std.debug.print("Days: {}\n", .{days});

    const hours = @as(u32, self.hour) * std.time.s_per_hour;
    std.debug.print("Hours: {}\n", .{hours});

    const minutes = @as(u16, self.minute) * std.time.s_per_min;
    std.debug.print("Minutes: {}\n", .{minutes});

    const days_as_sec = days * std.time.s_per_day;
    std.debug.print("Days as seconds: {}\n", .{days_as_sec});

    return days_as_sec +
        hours +
        minutes +
        self.second;
}

pub fn main() !void {
    const stat = try std.posix.fstat(std.fs.cwd().fd);

    std.debug.print("{} ", .{stat.atim});
    std.debug.print("{}\n", .{stat.atime()});

    std.debug.print("{} ", .{stat.mtim});
    std.debug.print("{}\n", .{stat.mtime()});

    std.debug.print("{} ", .{stat.ctim});
    std.debug.print("{}\n", .{toEpochSeconds(stat.ctim)});
}

So I think @ianprime0509 is right on this one.

[clickingbuttons]

@RossComputerGuy You don't even have to @intCast() to convert from u64 to u128:

pub fn main() void {
    const v: u64 = std.math.maxInt(u64);
    std.debug.print("{d}\n", .{ @as(u128, v) });
}

If you give a full stack trace I can help debug.

You may be able to avoid some integer casts if you refactor all your second and subsecond methods to be in terms of nanoseconds.

[truemedian]

If you give a full stack trace I can help debug.

Word of warning: we still cannot produce stack traces on UEFI, we're missing the information required to walk the stack backwards.

[RossComputerGuy]

I'm not even int casting. @nektro has tried helping me with this problem as well on Discord. I traced the issue to the @as(u128, v) call with print calls.

[clickingbuttons]

Hm, that's very strange. Is there a way to run behavior and stdlib tests on UEFI?

[RossComputerGuy]

Kinda, however there are more important issues we need to get through first. Like zig actually being able to find itself in UEFI.

[RossComputerGuy]

Some progress has been made. zig env works (libc hangs) but crashes at the end, zig targets prints but crashes which an OOB error.

[andrewrk]

draft status for > 30 days