DoxigAlpha
std › debug › Dwarf.readEhPointer

readEhPointer

Function parameters

Parameters

#
fbr:*FixedBufferReader
enc:u8
addr_size_bytes:u8

Type definitions in this namespace

Types

#
ExceptionFrameHeader
This represents the decoded .eh_frame_hdr header

Initialize DWARF info.

Functions

#
open
Initialize DWARF info.
findCompileUnit
TODO: change this to binary searching the sorted compile unit list
scanAllUnwindInfo
If `.eh_frame_hdr` is present, then only the header needs to be parsed.
scanCieFdeInfo
Scan `.eh_frame` and `.debug_frame` and build a sorted list of FDEs for binary searching during
compactUnwindToDwarfRegNumber
Returns the DWARF register number for an x86_64 register number found in compact unwind info
bad
This function is to make it handy to comment out the return and make it

Error sets in this namespace

Error Sets

#

= [_]?Section{null} ** num_sections

Values

#
null_section_array
= [_]?Section{null} ** num_sections

Source

Implementation

#
fn readEhPointer(fbr: *FixedBufferReader, enc: u8, addr_size_bytes: u8, ctx: EhPointerContext) !?u64 {
    if (enc == EH.PE.omit) return null;

    const value: union(enum) {
        signed: i64,
        unsigned: u64,
    } = switch (enc & EH.PE.type_mask) {
        EH.PE.absptr => .{
            .unsigned = switch (addr_size_bytes) {
                2 => try fbr.readInt(u16),
                4 => try fbr.readInt(u32),
                8 => try fbr.readInt(u64),
                else => return error.InvalidAddrSize,
            },
        },
        EH.PE.uleb128 => .{ .unsigned = try fbr.readUleb128(u64) },
        EH.PE.udata2 => .{ .unsigned = try fbr.readInt(u16) },
        EH.PE.udata4 => .{ .unsigned = try fbr.readInt(u32) },
        EH.PE.udata8 => .{ .unsigned = try fbr.readInt(u64) },
        EH.PE.sleb128 => .{ .signed = try fbr.readIleb128(i64) },
        EH.PE.sdata2 => .{ .signed = try fbr.readInt(i16) },
        EH.PE.sdata4 => .{ .signed = try fbr.readInt(i32) },
        EH.PE.sdata8 => .{ .signed = try fbr.readInt(i64) },
        else => return bad(),
    };

    const base = switch (enc & EH.PE.rel_mask) {
        EH.PE.pcrel => ctx.pc_rel_base,
        EH.PE.textrel => ctx.text_rel_base orelse return error.PointerBaseNotSpecified,
        EH.PE.datarel => ctx.data_rel_base orelse return error.PointerBaseNotSpecified,
        EH.PE.funcrel => ctx.function_rel_base orelse return error.PointerBaseNotSpecified,
        else => null,
    };

    const ptr: u64 = if (base) |b| switch (value) {
        .signed => |s| @intCast(try std.math.add(i64, s, @as(i64, @intCast(b)))),
        // absptr can actually contain signed values in some cases (aarch64 MachO)
        .unsigned => |u| u +% b,
    } else switch (value) {
        .signed => |s| @as(u64, @intCast(s)),
        .unsigned => |u| u,
    };

    if ((enc & EH.PE.indirect) > 0 and ctx.follow_indirect) {
        if (@sizeOf(usize) != addr_size_bytes) {
            // See the documentation for `follow_indirect`
            return error.NonNativeIndirection;
        }

        const native_ptr = cast(usize, ptr) orelse return error.PointerOverflow;
        return switch (addr_size_bytes) {
            2, 4, 8 => return @as(*const usize, @ptrFromInt(native_ptr)).*,
            else => return error.UnsupportedAddrSize,
        };
    } else {
        return ptr;
    }
}