Merge pull request #16398 from ziglang/check-object-elf

std: add ELF parse'n'dump functionality to std.Build.Step.CheckObject
ziglang · Jul 14, 2023 · 546212f · 546212f
2 parents 3ec3374 + 77026c6
commit 546212f
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Showing 2 changed files with 292 additions and 4 deletions.
diff --git a/lib/std/Build/Step/CheckObject.zig b/lib/std/Build/Step/CheckObject.zig
@@ -1,5 +1,6 @@
 const std = @import("std");
 const assert = std.debug.assert;
+const elf = std.elf;
 const fs = std.fs;
 const macho = std.macho;
 const math = std.math;
@@ -338,7 +339,9 @@ fn make(step: *Step, prog_node: *std.Progress.Node) !void {
         .macho => try MachODumper.parseAndDump(step, contents, .{
             .dump_symtab = self.dump_symtab,
         }),
-        .elf => @panic("TODO elf parser"),
+        .elf => try ElfDumper.parseAndDump(step, contents, .{
+            .dump_symtab = self.dump_symtab,
+        }),
         .coff => @panic("TODO coff parser"),
         .wasm => try WasmDumper.parseAndDump(step, contents, .{
             .dump_symtab = self.dump_symtab,
@@ -695,6 +698,234 @@ const MachODumper = struct {
     }
 };
 
+const ElfDumper = struct {
+    const symtab_label = "symtab";
+
+    const Symtab = struct {
+        symbols: []align(1) const elf.Elf64_Sym,
+        strings: []const u8,
+
+        fn get(st: Symtab, index: usize) ?elf.Elf64_Sym {
+            if (index >= st.symbols.len) return null;
+            return st.symbols[index];
+        }
+
+        fn getName(st: Symtab, index: usize) ?[]const u8 {
+            const sym = st.get(index) orelse return null;
+            assert(sym.st_name < st.strings.len);
+            return mem.sliceTo(@ptrCast(st.strings.ptr + sym.st_name), 0);
+        }
+    };
+
+    const Context = struct {
+        gpa: Allocator,
+        data: []const u8,
+        hdr: elf.Elf64_Ehdr,
+        shdrs: []align(1) const elf.Elf64_Shdr,
+        phdrs: []align(1) const elf.Elf64_Phdr,
+        shstrtab: []const u8,
+        symtab: ?Symtab = null,
+        dysymtab: ?Symtab = null,
+    };
+
+    fn parseAndDump(step: *Step, bytes: []const u8, opts: Opts) ![]const u8 {
+        const gpa = step.owner.allocator;
+        var stream = std.io.fixedBufferStream(bytes);
+        const reader = stream.reader();
+
+        const hdr = try reader.readStruct(elf.Elf64_Ehdr);
+        if (!mem.eql(u8, hdr.e_ident[0..4], "\x7fELF")) {
+            return error.InvalidMagicNumber;
+        }
+
+        const shdrs = @as([*]align(1) const elf.Elf64_Shdr, @ptrCast(bytes.ptr + hdr.e_shoff))[0..hdr.e_shnum];
+        const phdrs = @as([*]align(1) const elf.Elf64_Phdr, @ptrCast(bytes.ptr + hdr.e_phoff))[0..hdr.e_phnum];
+
+        var ctx = Context{
+            .gpa = gpa,
+            .data = bytes,
+            .hdr = hdr,
+            .shdrs = shdrs,
+            .phdrs = phdrs,
+            .shstrtab = undefined,
+        };
+        ctx.shstrtab = getSectionContents(ctx, ctx.hdr.e_shstrndx);
+
+        if (opts.dump_symtab) {
+            for (ctx.shdrs, 0..) |shdr, i| switch (shdr.sh_type) {
+                elf.SHT_SYMTAB, elf.SHT_DYNSYM => {
+                    const raw = getSectionContents(ctx, i);
+                    const nsyms = @divExact(raw.len, @sizeOf(elf.Elf64_Sym));
+                    const symbols = @as([*]align(1) const elf.Elf64_Sym, @ptrCast(raw.ptr))[0..nsyms];
+                    const strings = getSectionContents(ctx, shdr.sh_link);
+
+                    switch (shdr.sh_type) {
+                        elf.SHT_SYMTAB => {
+                            ctx.symtab = .{
+                                .symbols = symbols,
+                                .strings = strings,
+                            };
+                        },
+                        elf.SHT_DYNSYM => {
+                            ctx.dysymtab = .{
+                                .symbols = symbols,
+                                .strings = strings,
+                            };
+                        },
+                        else => unreachable,
+                    }
+                },
+
+                else => {},
+            };
+        }
+
+        var output = std.ArrayList(u8).init(gpa);
+        const writer = output.writer();
+
+        try dumpHeader(ctx, writer);
+        try dumpShdrs(ctx, writer);
+        try dumpPhdrs(ctx, writer);
+
+        return output.toOwnedSlice();
+    }
+
+    fn getSectionName(ctx: Context, shndx: usize) []const u8 {
+        const shdr = ctx.shdrs[shndx];
+        assert(shdr.sh_name < ctx.shstrtab.len);
+        return mem.sliceTo(@as([*:0]const u8, @ptrCast(ctx.shstrtab.ptr + shdr.sh_name)), 0);
+    }
+
+    fn getSectionContents(ctx: Context, shndx: usize) []const u8 {
+        const shdr = ctx.shdrs[shndx];
+        assert(shdr.sh_offset < ctx.data.len);
+        assert(shdr.sh_offset + shdr.sh_size <= ctx.data.len);
+        return ctx.data[shdr.sh_offset..][0..shdr.sh_size];
+    }
+
+    fn dumpHeader(ctx: Context, writer: anytype) !void {
+        try writer.writeAll("header\n");
+        try writer.print("type {s}\n", .{@tagName(ctx.hdr.e_type)});
+        try writer.print("entry {x}\n", .{ctx.hdr.e_entry});
+    }
+
+    fn dumpShdrs(ctx: Context, writer: anytype) !void {
+        if (ctx.shdrs.len == 0) return;
+
+        for (ctx.shdrs, 0..) |shdr, shndx| {
+            try writer.print("shdr {d}\n", .{shndx});
+            try writer.print("name {s}\n", .{getSectionName(ctx, shndx)});
+            try writer.print("type {s}\n", .{fmtShType(shdr.sh_type)});
+            try writer.print("addr {x}\n", .{shdr.sh_addr});
+            try writer.print("offset {x}\n", .{shdr.sh_offset});
+            try writer.print("size {x}\n", .{shdr.sh_size});
+            try writer.print("addralign {x}\n", .{shdr.sh_addralign});
+            // TODO dump formatted sh_flags
+        }
+    }
+
+    fn fmtShType(sh_type: u32) std.fmt.Formatter(formatShType) {
+        return .{ .data = sh_type };
+    }
+
+    fn formatShType(
+        sh_type: u32,
+        comptime unused_fmt_string: []const u8,
+        options: std.fmt.FormatOptions,
+        writer: anytype,
+    ) !void {
+        _ = unused_fmt_string;
+        _ = options;
+        if (elf.SHT_LOOS <= sh_type and sh_type < elf.SHT_HIOS) {
+            try writer.print("LOOS+0x{x}", .{sh_type - elf.SHT_LOOS});
+        } else if (elf.SHT_LOPROC <= sh_type and sh_type < elf.SHT_HIPROC) {
+            try writer.print("LOPROC+0x{x}", .{sh_type - elf.SHT_LOPROC});
+        } else if (elf.SHT_LOUSER <= sh_type and sh_type < elf.SHT_HIUSER) {
+            try writer.print("LOUSER+0x{x}", .{sh_type - elf.SHT_LOUSER});
+        } else {
+            const name = switch (sh_type) {
+                elf.SHT_NULL => "NULL",
+                elf.SHT_PROGBITS => "PROGBITS",
+                elf.SHT_SYMTAB => "SYMTAB",
+                elf.SHT_STRTAB => "STRTAB",
+                elf.SHT_RELA => "RELA",
+                elf.SHT_HASH => "HASH",
+                elf.SHT_DYNAMIC => "DYNAMIC",
+                elf.SHT_NOTE => "NOTE",
+                elf.SHT_NOBITS => "NOBITS",
+                elf.SHT_REL => "REL",
+                elf.SHT_SHLIB => "SHLIB",
+                elf.SHT_DYNSYM => "DYNSYM",
+                elf.SHT_INIT_ARRAY => "INIT_ARRAY",
+                elf.SHT_FINI_ARRAY => "FINI_ARRAY",
+                elf.SHT_PREINIT_ARRAY => "PREINIT_ARRAY",
+                elf.SHT_GROUP => "GROUP",
+                elf.SHT_SYMTAB_SHNDX => "SYMTAB_SHNDX",
+                elf.SHT_X86_64_UNWIND => "X86_64_UNWIND",
+                elf.SHT_LLVM_ADDRSIG => "LLVM_ADDRSIG",
+                elf.SHT_GNU_HASH => "GNU_HASH",
+                elf.SHT_GNU_VERDEF => "VERDEF",
+                elf.SHT_GNU_VERNEED => "VERNEED",
+                elf.SHT_GNU_VERSYM => "VERSYM",
+                else => "UNKNOWN",
+            };
+            try writer.writeAll(name);
+        }
+    }
+
+    fn dumpPhdrs(ctx: Context, writer: anytype) !void {
+        if (ctx.phdrs.len == 0) return;
+
+        for (ctx.phdrs, 0..) |phdr, phndx| {
+            try writer.print("phdr {d}\n", .{phndx});
+            try writer.print("type {s}\n", .{fmtPhType(phdr.p_type)});
+            try writer.print("vaddr {x}\n", .{phdr.p_vaddr});
+            try writer.print("paddr {x}\n", .{phdr.p_paddr});
+            try writer.print("offset {x}\n", .{phdr.p_offset});
+            try writer.print("memsz {x}\n", .{phdr.p_memsz});
+            try writer.print("filesz {x}\n", .{phdr.p_filesz});
+            try writer.print("align {x}\n", .{phdr.p_align});
+            // TODO dump formatted p_flags
+        }
+    }
+
+    fn fmtPhType(ph_type: u32) std.fmt.Formatter(formatPhType) {
+        return .{ .data = ph_type };
+    }
+
+    fn formatPhType(
+        ph_type: u32,
+        comptime unused_fmt_string: []const u8,
+        options: std.fmt.FormatOptions,
+        writer: anytype,
+    ) !void {
+        _ = unused_fmt_string;
+        _ = options;
+        if (elf.PT_LOOS <= ph_type and ph_type < elf.PT_HIOS) {
+            try writer.print("LOOS+0x{x}", .{ph_type - elf.PT_LOOS});
+        } else if (elf.PT_LOPROC <= ph_type and ph_type < elf.PT_HIPROC) {
+            try writer.print("LOPROC+0x{x}", .{ph_type - elf.PT_LOPROC});
+        } else {
+            const p_type = switch (ph_type) {
+                elf.PT_NULL => "NULL",
+                elf.PT_LOAD => "LOAD",
+                elf.PT_DYNAMIC => "DYNAMIC",
+                elf.PT_INTERP => "INTERP",
+                elf.PT_NOTE => "NOTE",
+                elf.PT_SHLIB => "SHLIB",
+                elf.PT_PHDR => "PHDR",
+                elf.PT_TLS => "TLS",
+                elf.PT_NUM => "NUM",
+                elf.PT_GNU_EH_FRAME => "GNU_EH_FRAME",
+                elf.PT_GNU_STACK => "GNU_STACK",
+                elf.PT_GNU_RELRO => "GNU_RELRO",
+                else => "UNKNOWN",
+            };
+            try writer.writeAll(p_type);
+        }
+    }
+};
+
 const WasmDumper = struct {
     const symtab_label = "symbols";
 

diff --git a/lib/std/elf.zig b/lib/std/elf.zig
@@ -221,6 +221,58 @@ pub const DT_IA_64_NUM = 1;
 
 pub const DT_NIOS2_GP = 0x70000002;
 
+pub const DF_ORIGIN = 0x00000001;
+pub const DF_SYMBOLIC = 0x00000002;
+pub const DF_TEXTREL = 0x00000004;
+pub const DF_BIND_NOW = 0x00000008;
+pub const DF_STATIC_TLS = 0x00000010;
+
+pub const DF_1_NOW = 0x00000001;
+pub const DF_1_GLOBAL = 0x00000002;
+pub const DF_1_GROUP = 0x00000004;
+pub const DF_1_NODELETE = 0x00000008;
+pub const DF_1_LOADFLTR = 0x00000010;
+pub const DF_1_INITFIRST = 0x00000020;
+pub const DF_1_NOOPEN = 0x00000040;
+pub const DF_1_ORIGIN = 0x00000080;
+pub const DF_1_DIRECT = 0x00000100;
+pub const DF_1_TRANS = 0x00000200;
+pub const DF_1_INTERPOSE = 0x00000400;
+pub const DF_1_NODEFLIB = 0x00000800;
+pub const DF_1_NODUMP = 0x00001000;
+pub const DF_1_CONFALT = 0x00002000;
+pub const DF_1_ENDFILTEE = 0x00004000;
+pub const DF_1_DISPRELDNE = 0x00008000;
+pub const DF_1_DISPRELPND = 0x00010000;
+pub const DF_1_NODIRECT = 0x00020000;
+pub const DF_1_IGNMULDEF = 0x00040000;
+pub const DF_1_NOKSYMS = 0x00080000;
+pub const DF_1_NOHDR = 0x00100000;
+pub const DF_1_EDITED = 0x00200000;
+pub const DF_1_NORELOC = 0x00400000;
+pub const DF_1_SYMINTPOSE = 0x00800000;
+pub const DF_1_GLOBAUDIT = 0x01000000;
+pub const DF_1_SINGLETON = 0x02000000;
+pub const DF_1_STUB = 0x04000000;
+pub const DF_1_PIE = 0x08000000;
+
+pub const VERSYM_HIDDEN = 0x8000;
+pub const VERSYM_VERSION = 0x7fff;
+
+/// Symbol is local
+pub const VER_NDX_LOCAL = 0;
+/// Symbol is global
+pub const VER_NDX_GLOBAL = 1;
+/// Beginning of reserved entries
+pub const VER_NDX_LORESERVE = 0xff00;
+/// Symbol is to be eliminated
+pub const VER_NDX_ELIMINATE = 0xff01;
+
+/// Version definition of the file itself
+pub const VER_FLG_BASE = 1;
+/// Weak version identifier
+pub const VER_FLG_WEAK = 2;
+
 /// Program header table entry unused
 pub const PT_NULL = 0;
 /// Loadable program segment
@@ -298,6 +350,14 @@ pub const SHT_SYMTAB_SHNDX = 18;
 pub const SHT_LOOS = 0x60000000;
 /// LLVM address-significance table
 pub const SHT_LLVM_ADDRSIG = 0x6fff4c03;
+/// GNU hash table
+pub const SHT_GNU_HASH = 0x6ffffff6;
+/// GNU version definition table
+pub const SHT_GNU_VERDEF = 0x6ffffffd;
+/// GNU needed versions table
+pub const SHT_GNU_VERNEED = 0x6ffffffe;
+/// GNU symbol version table
+pub const SHT_GNU_VERSYM = 0x6fffffff;
 /// End of OS-specific
 pub const SHT_HIOS = 0x6fffffff;
 /// Start of processor-specific
@@ -369,9 +429,6 @@ pub const STT_HP_STUB = (STT_LOOS + 0x2);
 pub const STT_ARM_TFUNC = STT_LOPROC;
 pub const STT_ARM_16BIT = STT_HIPROC;
 
-pub const VER_FLG_BASE = 0x1;
-pub const VER_FLG_WEAK = 0x2;
-
 pub const MAGIC = "\x7fELF";
 
 /// File types