Commit 29bcd2d54376f6b15a6900b264e8b4d99e7b186a | zig

author	Matthew Lugg <mlugg@mlugg.co.uk> 2026-08-15 09:04:07+01:00
committer	Matthew Lugg <mlugg@mlugg.co.uk> 2026-08-16 10:37:20+01:00
log	29bcd2d54376f6b15a6900b264e8b4d99e7b186a
tree	61a654a3729424bf2f67589221cc440489c1092a
parent	ede0017eb9e72cb5a799ad000ebe45cf326524d6
signature	Commit is signed but in an unrecognized format.

std.posix.test: fix `dl_iterate_phdr` test

The old test was relying on the following properties:

* There is a segment containing the ehdr, i.e. whose file offset is 0

* That segment is the first phdr with type `PT_LOAD`; because `PT_LOAD`
  segments are sorted on `p_vaddr`, this means its virtual address is
  the lowest of all loadable segments

The first assumption, although not standard, is somewhat reasonable, and
the commit prior to this one makes `Elf2` obey it. However, the second
assumption is not based on anything, and to my knowledge the linker is
entirely welcome to lay out the virtual address space as it sees fit.
Therefore, refactor this test to eliminate that bad assumption.

1 files changed, 16 insertions(+), 25 deletions(-)

lib
- std
  - posix
    test.zig

lib/std/posix/test.zig+16-25

...	...	@@ -64,42 +64,33 @@ const have_dl_phdr_info = posix.system.dl_phdr_info != void;
64	64	const dl_phdr_info = if (have_dl_phdr_info) posix.dl_phdr_info else anyopaque;
65	65
66	66	const IterFnError = error{
67		MissingPtLoadSegment,
68		MissingLoad,
	67	MissingLoadSegment,
	68	MissingEhdrLoadSegment,
69	69	BadElfMagic,
70		FailedConsistencyCheck,
	70	PhnumMismatch,
71	71	};
72	72
73	73	fn iter_fn(info: dl_phdr_info, size: usize, counter: usize) IterFnError!void {
74	74	_ = size;
75	75	// Count how many libraries are loaded
76		counter.* += @as(usize, 1);
	76	counter.* += 1;
77	77
78		// The image should contain at least a PT.LOAD segment
79		if (info.phnum < 1) return error.MissingPtLoadSegment;
80
81		// Quick & dirty validation of the phdr pointers, make sure we're not
82		// pointing to some random gibberish
83		var i: usize = 0;
84		var found_load = false;
85		while (i < info.phnum) : (i += 1) {
86		const phdr = info.phdr[i];
	78	// The image should contain at least one loadable segment
	79	if (info.phnum < 1) return error.MissingLoadSegment;
87	80
	81	// For some quick and dirty validation, find the phdr which contains the ELF
	82	// header, and check it makes sense.
	83	for (info.phdr[0..info.phnum]) \|phdr\| {
88	84	if (phdr.type != .LOAD) continue;
89
90		const reloc_addr = info.addr + phdr.vaddr;
91		// Find the ELF header
92		const elf_header = @as(*elf.Ehdr, @ptrFromInt(reloc_addr - phdr.offset));
93		// Validate the magic
94		if (!mem.eql(u8, elf_header.e_ident[0..4], elf.MAGIC)) return error.BadElfMagic;
95		// Consistency check
96		if (elf_header.e_phnum != info.phnum) return error.FailedConsistencyCheck;
97
98		found_load = true;
	85	if (phdr.offset != 0) continue;
	86	// This segment holds the ELF header at the start
	87	const ehdr: *elf.Ehdr = @ptrFromInt(info.addr + phdr.vaddr);
	88	if (!mem.eql(u8, ehdr.e_ident[0..4], elf.MAGIC)) return error.BadElfMagic;
	89	if (ehdr.e_phnum != info.phnum) return error.PhnumMismatch;
99	90	break;
	91	} else {
	92	return error.MissingEhdrLoadSegment;
100	93	}
101
102		if (!found_load) return error.MissingLoad;
103	94	}
104	95
105	96	test "dl_iterate_phdr" {