Commit 4e32edbff5d34dfc779797d73bb61d32ffa02953 | zig

author	Andrew Kelley <andrew@ziglang.org> 2024-08-07 21:05:26-07:00
committer	Andrew Kelley <andrew@ziglang.org> 2024-08-08 21:46:36-07:00
log	4e32edbff5d34dfc779797d73bb61d32ffa02953
tree	6641a92b99f5488d1891bfb7ef52f3104cc52053
parent	2cfad202045632945b5007e1d42c2f8a326be44a

fuzzing: comptime assertions to protect the ABI

compile errors are nice

3 files changed, 21 insertions(+), 1 deletions(-)

lib
- fuzzer.zig
- std
  - Build
    Fuzz
    WebServer.zig
    abi.zig

lib/fuzzer.zig+7

 @@ -214,6 +214,9 @@ const Fuzzer = struct {
         });
         defer coverage_file.close();
         const n_bitset_elems = (flagged_pcs.len + 7) / 8;
+        comptime assert(SeenPcsHeader.trailing[0] == .pc_addr);
+        comptime assert(SeenPcsHeader.trailing[1][0] == .pc_bits);
+        comptime assert(SeenPcsHeader.trailing[1][1] == u8);
         const bytes_len = @sizeOf(SeenPcsHeader) + flagged_pcs.len * @sizeOf(usize) + n_bitset_elems;
         const existing_len = coverage_file.getEndPos() catch |err| {
             fatal("unable to check len of coverage file: {s}", .{@errorName(err)});
 @@ -301,6 +304,10 @@ const Fuzzer = struct {
                 // Track code coverage from all runs.
                 {
+                    comptime assert(SeenPcsHeader.trailing[0] == .pc_addr);
+                    comptime assert(SeenPcsHeader.trailing[1][0] == .pc_bits);
+                    comptime assert(SeenPcsHeader.trailing[1][1] == u8);
                     const seen_pcs = f.seen_pcs.items[@sizeOf(SeenPcsHeader) + f.flagged_pcs.len * @sizeOf(usize) ..];
                     for (seen_pcs, 0..) |*elem, i| {
                         const byte_i = i * 8;

lib/std/Build/Fuzz/WebServer.zig+6

lib/std/Build/Fuzz/abi.zig+8-1

 @@ -8,12 +8,19 @@
 ///
 /// Trailing:
 /// * pc_addr: usize for each pcs_len
-/// * 1 bit per pc_addr, usize elements
+/// * 1 bit per pc_addr, u8 elements
 pub const SeenPcsHeader = extern struct {
     n_runs: usize,
     unique_runs: usize,
     pcs_len: usize,
     lowest_stack: usize,
+    /// Used for comptime assertions. Provides a mechanism for strategically
+    /// causing compile errors.
+    pub const trailing = .{
+        .pc_addr,
+        .{ .pc_bits, u8 },
+    };
 };
 pub const ToClientTag = enum(u8) {

...	@@ -7,6 +7,7 @@ const Step = std.Build.Step;	...	@@ -7,6 +7,7 @@ const Step = std.Build.Step;
7	const Coverage = std.debug.Coverage;	7	const Coverage = std.debug.Coverage;
8	const abi = std.Build.Fuzz.abi;	8	const abi = std.Build.Fuzz.abi;
9	const log = std.log;	9	const log = std.log;
		10	const assert = std.debug.assert;
10		11
11	const WebServer = @This();	12	const WebServer = @This();
12		13
...	@@ -383,7 +384,10 @@ fn sendCoverageContext(	...	@@ -383,7 +384,10 @@ fn sendCoverageContext(
383	// TODO: make each events URL correspond to one coverage map	384	// TODO: make each events URL correspond to one coverage map
384	const coverage_map = &coverage_maps[0];	385	const coverage_map = &coverage_maps[0];
385	const cov_header: *const abi.SeenPcsHeader = @ptrCast(coverage_map.mapped_memory[0..@sizeOf(abi.SeenPcsHeader)]);	386	const cov_header: *const abi.SeenPcsHeader = @ptrCast(coverage_map.mapped_memory[0..@sizeOf(abi.SeenPcsHeader)]);
		387	comptime assert(abi.SeenPcsHeader.trailing[0] == .pc_addr);
386	const seen_pcs = coverage_map.mapped_memory[@sizeOf(abi.SeenPcsHeader) + coverage_map.source_locations.len * @sizeOf(usize) ..];	388	const seen_pcs = coverage_map.mapped_memory[@sizeOf(abi.SeenPcsHeader) + coverage_map.source_locations.len * @sizeOf(usize) ..];
		389	comptime assert(abi.SeenPcsHeader.trailing[1][0] == .pc_bits);
		390	comptime assert(abi.SeenPcsHeader.trailing[1][1] == u8);
387	const n_runs = @atomicLoad(usize, &cov_header.n_runs, .monotonic);	391	const n_runs = @atomicLoad(usize, &cov_header.n_runs, .monotonic);
388	const unique_runs = @atomicLoad(usize, &cov_header.unique_runs, .monotonic);	392	const unique_runs = @atomicLoad(usize, &cov_header.unique_runs, .monotonic);
389	const lowest_stack = @atomicLoad(usize, &cov_header.lowest_stack, .monotonic);	393	const lowest_stack = @atomicLoad(usize, &cov_header.lowest_stack, .monotonic);
...	@@ -630,6 +634,7 @@ fn prepareTables(	...	@@ -630,6 +634,7 @@ fn prepareTables(
630	gop.value_ptr.mapped_memory = mapped_memory;	634	gop.value_ptr.mapped_memory = mapped_memory;
631		635
632	const header: *const abi.SeenPcsHeader = @ptrCast(mapped_memory[0..@sizeOf(abi.SeenPcsHeader)]);	636	const header: *const abi.SeenPcsHeader = @ptrCast(mapped_memory[0..@sizeOf(abi.SeenPcsHeader)]);
		637	comptime assert(abi.SeenPcsHeader.trailing[0] == .pc_addr);
633	const pcs_bytes = mapped_memory[@sizeOf(abi.SeenPcsHeader)..][0 .. header.pcs_len * @sizeOf(usize)];	638	const pcs_bytes = mapped_memory[@sizeOf(abi.SeenPcsHeader)..][0 .. header.pcs_len * @sizeOf(usize)];
634	const pcs = std.mem.bytesAsSlice(usize, pcs_bytes);	639	const pcs = std.mem.bytesAsSlice(usize, pcs_bytes);
635	const source_locations = try gpa.alloc(Coverage.SourceLocation, pcs.len);	640	const source_locations = try gpa.alloc(Coverage.SourceLocation, pcs.len);
...	@@ -649,6 +654,7 @@ fn addEntryPoint(ws: *WebServer, coverage_id: u64, addr: u64) error{ AlreadyRepo	...	@@ -649,6 +654,7 @@ fn addEntryPoint(ws: *WebServer, coverage_id: u64, addr: u64) error{ AlreadyRepo
649		654
650	const coverage_map = ws.coverage_files.getPtr(coverage_id).?;	655	const coverage_map = ws.coverage_files.getPtr(coverage_id).?;
651	const ptr = coverage_map.mapped_memory;	656	const ptr = coverage_map.mapped_memory;
		657	comptime assert(abi.SeenPcsHeader.trailing[0] == .pc_addr);
652	const pcs_bytes = ptr[@sizeOf(abi.SeenPcsHeader)..][0 .. coverage_map.source_locations.len * @sizeOf(usize)];	658	const pcs_bytes = ptr[@sizeOf(abi.SeenPcsHeader)..][0 .. coverage_map.source_locations.len * @sizeOf(usize)];
653	const pcs: []const usize = @alignCast(std.mem.bytesAsSlice(usize, pcs_bytes));	659	const pcs: []const usize = @alignCast(std.mem.bytesAsSlice(usize, pcs_bytes));
654	const index = std.sort.upperBound(usize, pcs, addr, struct {	660	const index = std.sort.upperBound(usize, pcs, addr, struct {