Merge pull request #24960 from ziglang/MemoryAccessor

andrewrk · web-flow · commit 83f773fc6497 · 2025-08-23T18:54:32.000-07:00
std.debug: delete MemoryAccessor
diff --git a/lib/std/debug.zig b/lib/std/debug.zig
@@ -14,7 +14,6 @@ const native_os = builtin.os.tag;
 const native_endian = native_arch.endian();
 const Writer = std.io.Writer;
 
-pub const MemoryAccessor = @import("debug/MemoryAccessor.zig");
 pub const FixedBufferReader = @import("debug/FixedBufferReader.zig");
 pub const Dwarf = @import("debug/Dwarf.zig");
 pub const Pdb = @import("debug/Pdb.zig");
@@ -501,6 +500,11 @@ pub fn captureStackTrace(first_address: ?usize, stack_trace: *std.builtin.StackT
         // TODO: This should use the DWARF unwinder if .eh_frame_hdr is available (so that full debug info parsing isn't required).
         //       A new path for loading SelfInfo needs to be created which will only attempt to parse in-memory sections, because
         //       stopping to load other debug info (ie. source line info) from disk here is not required for unwinding.
+        if (builtin.cpu.arch == .powerpc64) {
+            // https://github.com/ziglang/zig/issues/24970
+            stack_trace.index = 0;
+            return;
+        }
         var it = StackIterator.init(first_address, null);
         defer it.deinit();
         for (stack_trace.instruction_addresses, 0..) |*addr, i| {
@@ -773,7 +777,6 @@ pub const StackIterator = struct {
     first_address: ?usize,
     // Last known value of the frame pointer register.
     fp: usize,
-    ma: MemoryAccessor = MemoryAccessor.init,
 
     // When SelfInfo and a register context is available, this iterator can unwind
     // stacks with frames that don't use a frame pointer (ie. -fomit-frame-pointer),
@@ -795,7 +798,7 @@ pub const StackIterator = struct {
                 ::: .{ .memory = true });
         }
 
-        return StackIterator{
+        return .{
             .first_address = first_address,
             // TODO: this is a workaround for #16876
             //.fp = fp orelse @frameAddress(),
@@ -825,7 +828,6 @@ pub const StackIterator = struct {
     }
 
     pub fn deinit(it: *StackIterator) void {
-        it.ma.deinit();
         if (have_ucontext and it.unwind_state != null) it.unwind_state.?.dwarf_context.deinit();
     }
 
@@ -896,7 +898,6 @@ pub const StackIterator = struct {
                         unwind_state.debug_info.allocator,
                         module.base_address,
                         &unwind_state.dwarf_context,
-                        &it.ma,
                         unwind_info,
                         module.eh_frame,
                     )) |return_address| {
@@ -915,7 +916,6 @@ pub const StackIterator = struct {
                 di,
                 module.base_address,
                 &unwind_state.dwarf_context,
-                &it.ma,
                 null,
             );
         } else return error.MissingDebugInfo;
@@ -951,16 +951,15 @@ pub const StackIterator = struct {
 
         // Sanity check.
         if (fp == 0 or !mem.isAligned(fp, @alignOf(usize))) return null;
-        const new_fp = math.add(usize, it.ma.load(usize, fp) orelse return null, fp_bias) catch
+        const new_fp = math.add(usize, @as(*usize, @ptrFromInt(fp)).*, fp_bias) catch
             return null;
 
         // Sanity check: the stack grows down thus all the parent frames must be
         // be at addresses that are greater (or equal) than the previous one.
         // A zero frame pointer often signals this is the last frame, that case
         // is gracefully handled by the next call to next_internal.
         if (new_fp != 0 and new_fp < it.fp) return null;
-        const new_pc = it.ma.load(usize, math.add(usize, fp, pc_offset) catch return null) orelse
-            return null;
+        const new_pc = @as(*usize, @ptrFromInt(math.add(usize, fp, pc_offset) catch return null)).*;
 
         it.fp = new_fp;
 
@@ -1774,7 +1773,6 @@ pub inline fn inValgrind() bool {
 
 test {
     _ = &Dwarf;
-    _ = &MemoryAccessor;
     _ = &FixedBufferReader;
     _ = &Pdb;
     _ = &SelfInfo;
diff --git a/lib/std/debug/Dwarf.zig b/lib/std/debug/Dwarf.zig
@@ -24,7 +24,6 @@ const UT = DW.UT;
 const assert = std.debug.assert;
 const cast = std.math.cast;
 const maxInt = std.math.maxInt;
-const MemoryAccessor = std.debug.MemoryAccessor;
 const Path = std.Build.Cache.Path;
 const FixedBufferReader = std.debug.FixedBufferReader;
 const ArrayList = std.ArrayList;
@@ -349,29 +348,9 @@ pub const ExceptionFrameHeader = struct {
         };
     }
 
-    fn isValidPtr(
-        self: ExceptionFrameHeader,
-        comptime T: type,
-        ptr: usize,
-        ma: *MemoryAccessor,
-        eh_frame_len: ?usize,
-    ) bool {
-        if (eh_frame_len) |len| {
-            return ptr >= self.eh_frame_ptr and ptr <= self.eh_frame_ptr + len - @sizeOf(T);
-        } else {
-            return ma.load(T, ptr) != null;
-        }
-    }
-
-    /// Find an entry by binary searching the eh_frame_hdr section.
-    ///
-    /// Since the length of the eh_frame section (`eh_frame_len`) may not be known by the caller,
-    /// MemoryAccessor will be used to verify readability of the header entries.
-    /// If `eh_frame_len` is provided, then these checks can be skipped.
     pub fn findEntry(
         self: ExceptionFrameHeader,
-        ma: *MemoryAccessor,
-        eh_frame_len: ?usize,
+        eh_frame_len: usize,
         eh_frame_hdr_ptr: usize,
         pc: usize,
         cie: *CommonInformationEntry,
@@ -421,8 +400,7 @@ pub const ExceptionFrameHeader = struct {
 
         if (fde_ptr < self.eh_frame_ptr) return bad();
 
-        // Even if eh_frame_len is not specified, all ranges accssed are checked via MemoryAccessor
-        const eh_frame = @as([*]const u8, @ptrFromInt(self.eh_frame_ptr))[0 .. eh_frame_len orelse maxInt(u32)];
+        const eh_frame = @as([*]const u8, @ptrFromInt(self.eh_frame_ptr))[0..eh_frame_len];
 
         const fde_offset = fde_ptr - self.eh_frame_ptr;
         var eh_frame_fbr: FixedBufferReader = .{
@@ -431,15 +409,13 @@ pub const ExceptionFrameHeader = struct {
             .endian = native_endian,
         };
 
-        const fde_entry_header = try EntryHeader.read(&eh_frame_fbr, if (eh_frame_len == null) ma else null, .eh_frame);
-        if (fde_entry_header.entry_bytes.len > 0 and !self.isValidPtr(u8, @intFromPtr(&fde_entry_header.entry_bytes[fde_entry_header.entry_bytes.len - 1]), ma, eh_frame_len)) return bad();
+        const fde_entry_header = try EntryHeader.read(&eh_frame_fbr, .eh_frame);
         if (fde_entry_header.type != .fde) return bad();
 
         // CIEs always come before FDEs (the offset is a subtraction), so we can assume this memory is readable
         const cie_offset = fde_entry_header.type.fde;
         try eh_frame_fbr.seekTo(cie_offset);
-        const cie_entry_header = try EntryHeader.read(&eh_frame_fbr, if (eh_frame_len == null) ma else null, .eh_frame);
-        if (cie_entry_header.entry_bytes.len > 0 and !self.isValidPtr(u8, @intFromPtr(&cie_entry_header.entry_bytes[cie_entry_header.entry_bytes.len - 1]), ma, eh_frame_len)) return bad();
+        const cie_entry_header = try EntryHeader.read(&eh_frame_fbr, .eh_frame);
         if (cie_entry_header.type != .cie) return bad();
 
         cie.* = try CommonInformationEntry.parse(
@@ -486,15 +462,11 @@ pub const EntryHeader = struct {
 
     /// Reads a header for either an FDE or a CIE, then advances the fbr to the position after the trailing structure.
     /// `fbr` must be a FixedBufferReader backed by either the .eh_frame or .debug_frame sections.
-    pub fn read(
-        fbr: *FixedBufferReader,
-        opt_ma: ?*MemoryAccessor,
-        dwarf_section: Section.Id,
-    ) !EntryHeader {
+    pub fn read(fbr: *FixedBufferReader, dwarf_section: Section.Id) !EntryHeader {
         assert(dwarf_section == .eh_frame or dwarf_section == .debug_frame);
 
         const length_offset = fbr.pos;
-        const unit_header = try readUnitHeader(fbr, opt_ma);
+        const unit_header = try readUnitHeader(fbr);
         const unit_length = cast(usize, unit_header.unit_length) orelse return bad();
         if (unit_length == 0) return .{
             .length_offset = length_offset,
@@ -506,10 +478,7 @@ pub const EntryHeader = struct {
         const end_offset = start_offset + unit_length;
         defer fbr.pos = end_offset;
 
-        const id = try if (opt_ma) |ma|
-            fbr.readAddressChecked(unit_header.format, ma)
-        else
-            fbr.readAddress(unit_header.format);
+        const id = try fbr.readAddress(unit_header.format);
         const entry_bytes = fbr.buf[fbr.pos..end_offset];
         const cie_id: u64 = switch (dwarf_section) {
             .eh_frame => CommonInformationEntry.eh_id,
@@ -856,7 +825,7 @@ fn scanAllFunctions(di: *Dwarf, allocator: Allocator) ScanError!void {
     while (this_unit_offset < fbr.buf.len) {
         try fbr.seekTo(this_unit_offset);
 
-        const unit_header = try readUnitHeader(&fbr, null);
+        const unit_header = try readUnitHeader(&fbr);
         if (unit_header.unit_length == 0) return;
         const next_offset = unit_header.header_length + unit_header.unit_length;
 
@@ -1045,7 +1014,7 @@ fn scanAllCompileUnits(di: *Dwarf, allocator: Allocator) ScanError!void {
     while (this_unit_offset < fbr.buf.len) {
         try fbr.seekTo(this_unit_offset);
 
-        const unit_header = try readUnitHeader(&fbr, null);
+        const unit_header = try readUnitHeader(&fbr);
         if (unit_header.unit_length == 0) return;
         const next_offset = unit_header.header_length + unit_header.unit_length;
 
@@ -1427,7 +1396,7 @@ fn runLineNumberProgram(d: *Dwarf, gpa: Allocator, compile_unit: *CompileUnit) !
     };
     try fbr.seekTo(line_info_offset);
 
-    const unit_header = try readUnitHeader(&fbr, null);
+    const unit_header = try readUnitHeader(&fbr);
     if (unit_header.unit_length == 0) return missing();
 
     const next_offset = unit_header.header_length + unit_header.unit_length;
@@ -1815,7 +1784,7 @@ pub fn scanCieFdeInfo(di: *Dwarf, allocator: Allocator, base_address: usize) !vo
         if (di.section(frame_section)) |section_data| {
             var fbr: FixedBufferReader = .{ .buf = section_data, .endian = di.endian };
             while (fbr.pos < fbr.buf.len) {
-                const entry_header = try EntryHeader.read(&fbr, null, frame_section);
+                const entry_header = try EntryHeader.read(&fbr, frame_section);
                 switch (entry_header.type) {
                     .cie => {
                         const cie = try CommonInformationEntry.parse(
@@ -1988,8 +1957,8 @@ const UnitHeader = struct {
     unit_length: u64,
 };
 
-fn readUnitHeader(fbr: *FixedBufferReader, opt_ma: ?*MemoryAccessor) ScanError!UnitHeader {
-    return switch (try if (opt_ma) |ma| fbr.readIntChecked(u32, ma) else fbr.readInt(u32)) {
+fn readUnitHeader(fbr: *FixedBufferReader) ScanError!UnitHeader {
+    return switch (try fbr.readInt(u32)) {
         0...0xfffffff0 - 1 => |unit_length| .{
             .format = .@"32",
             .header_length = 4,
@@ -1999,7 +1968,7 @@ fn readUnitHeader(fbr: *FixedBufferReader, opt_ma: ?*MemoryAccessor) ScanError!U
         0xffffffff => .{
             .format = .@"64",
             .header_length = 12,
-            .unit_length = try if (opt_ma) |ma| fbr.readIntChecked(u64, ma) else fbr.readInt(u64),
+            .unit_length = try fbr.readInt(u64),
         },
     };
 }
diff --git a/lib/std/debug/Dwarf/expression.zig b/lib/std/debug/Dwarf/expression.zig
@@ -15,8 +15,6 @@ const assert = std.debug.assert;
 pub const Context = struct {
     /// The dwarf format of the section this expression is in
     format: std.dwarf.Format = .@"32",
-    /// If specified, any addresses will pass through before being accessed
-    memory_accessor: ?*std.debug.MemoryAccessor = null,
     /// The compilation unit this expression relates to, if any
     compile_unit: ?*const std.debug.Dwarf.CompileUnit = null,
     /// When evaluating a user-presented expression, this is the address of the object being evaluated
@@ -465,16 +463,6 @@ pub fn StackMachine(comptime options: Options) type {
                         else => unreachable,
                     };
 
-                    if (context.memory_accessor) |memory_accessor| {
-                        if (!switch (size) {
-                            1 => memory_accessor.load(u8, addr) != null,
-                            2 => memory_accessor.load(u16, addr) != null,
-                            4 => memory_accessor.load(u32, addr) != null,
-                            8 => memory_accessor.load(u64, addr) != null,
-                            else => return error.InvalidExpression,
-                        }) return error.InvalidExpression;
-                    }
-
                     const value: addr_type = std.math.cast(addr_type, @as(u64, switch (size) {
                         1 => @as(*const u8, @ptrFromInt(addr)).*,
                         2 => @as(*const u16, @ptrFromInt(addr)).*,
diff --git a/lib/std/debug/FixedBufferReader.zig b/lib/std/debug/FixedBufferReader.zig
@@ -1,7 +1,6 @@
 //! Optimized for performance in debug builds.
 
 const std = @import("../std.zig");
-const MemoryAccessor = std.debug.MemoryAccessor;
 
 const FixedBufferReader = @This();
 
@@ -38,17 +37,6 @@ pub fn readInt(fbr: *FixedBufferReader, comptime T: type) Error!T {
     return std.mem.readInt(T, fbr.buf[fbr.pos..][0..size], fbr.endian);
 }
 
-pub fn readIntChecked(
-    fbr: *FixedBufferReader,
-    comptime T: type,
-    ma: *MemoryAccessor,
-) Error!T {
-    if (ma.load(T, @intFromPtr(fbr.buf[fbr.pos..].ptr)) == null)
-        return error.InvalidBuffer;
-
-    return fbr.readInt(T);
-}
-
 pub fn readUleb128(fbr: *FixedBufferReader, comptime T: type) Error!T {
     return std.leb.readUleb128(T, fbr);
 }
@@ -64,17 +52,6 @@ pub fn readAddress(fbr: *FixedBufferReader, format: std.dwarf.Format) Error!u64
     };
 }
 
-pub fn readAddressChecked(
-    fbr: *FixedBufferReader,
-    format: std.dwarf.Format,
-    ma: *MemoryAccessor,
-) Error!u64 {
-    return switch (format) {
-        .@"32" => try fbr.readIntChecked(u32, ma),
-        .@"64" => try fbr.readIntChecked(u64, ma),
-    };
-}
-
 pub fn readBytes(fbr: *FixedBufferReader, len: usize) Error![]const u8 {
     if (fbr.buf.len - fbr.pos < len) return error.EndOfBuffer;
     defer fbr.pos += len;
diff --git a/lib/std/debug/MemoryAccessor.zig b/lib/std/debug/MemoryAccessor.zig
diff --git a/lib/std/debug/SelfInfo.zig b/lib/std/debug/SelfInfo.zig
