ww/test/wwc/810_dyn.c

/*
 * 810_dyn — end-to-end test of 6l's dynamic linker.
 *
 * Drives `ww build -L /usr/lib -l c` over a small ww program that
 * binds libc symbols via @symbol, then runs the produced binary and
 * checks the exit status. Verifies:
 *
 *   - the .so loader (dyn.c) reads ET_DYN and extracts exports
 *   - PLT/GOT generation and the JUMP_SLOT relocation
 *   - PT_INTERP/PT_DYNAMIC emission
 *   - symbol versioning (.gnu.version + .gnu.version_r) — clock_gettime
 *     has both GLIBC_2.2.5 (compat) and GLIBC_2.17 (default) on glibc;
 *     the loader requires the right .gnu.version_r entry to bind
 *     the default vDSO-aware impl.
 *
 * Skipped (passing trivially) on systems without /usr/lib/libc.so.6.
 */
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/stat.h>
#include <sys/wait.h>

static int
runwait(const char *cmd)
{
	int rc = system(cmd);
	if (rc == -1) return -1;
	if (WIFEXITED(rc)) return WEXITSTATUS(rc);
	return 1;
}

struct row {
	const char *src;
	int want_exit;
};

static const struct row rows[] = {
	/* 1. _exit via dynamically-linked libc. Exit code is the plumbing
	 * of choice — proves the PLT entry calls into libc.so.6. */
	{ "@symbol(\"_exit\") fn libc_exit(c: i32) void;\n"
	  "export fn main() i32 = { libc_exit(42); return 0; };", 42 },

	/* 2. Multiple dyn syms in one binary: write + _exit. */
	{ "@symbol(\"write\") fn libc_write(fd: i32, b: *u8, n: u64) i64;\n"
	  "@symbol(\"_exit\") fn libc_exit(c: i32) void;\n"
	  "export fn main() i32 = {\n"
	  "  libc_write(1, \"x\".ptr, 1u64);\n"
	  "  libc_exit(7);\n"
	  "  return 0;\n"
	  "};", 7 },

	/* 3. Symbol versioning: clock_gettime. Without DT_VERSYM/VERNEED
	 * pointing at a Vernaux entry for GLIBC_2.17, the loader either
	 * picks the wrong impl or fails outright on modern glibc. */
	{ "@symbol(\"clock_gettime\") fn clock_gettime(c: i32, ts: *u8) i32;\n"
	  "@symbol(\"_exit\")         fn libc_exit(c: i32) void;\n"
	  "export fn main() i32 = {\n"
	  "  let ts: [16]u8;\n"
	  "  let r: i32 = clock_gettime(1, ts.ptr);\n"  /* CLOCK_MONOTONIC */
	  "  libc_exit(r);\n"
	  "  return 0;\n"
	  "};", 0 },

	/* 4. Take the address of an FFI binding and call it indirectly.
	 * Codegen must apply @symbol resolution at the LEAQ site (so the
	 * stub address is `write`, not the ww-side ident `libc_write`),
	 * and the local-variable call must be CALL *AX, not CALL fp(SB). */
	{ "@symbol(\"write\") fn libc_write(fd: i32, b: *u8, n: u64) i64;\n"
	  "@symbol(\"_exit\") fn libc_exit(c: i32) void;\n"
	  "export fn main() i32 = {\n"
	  "  let fp: fn(fd: i32, b: *u8, n: u64) i64 = libc_write;\n"
	  "  fp(1, \"X\".ptr, 1u64);\n"
	  "  libc_exit(5);\n"
	  "  return 0;\n"
	  "};", 5 },

	{ NULL, 0 }
};

int
main(void)
{
	if (access("/usr/lib/libc.so.6", 0) != 0
	    && access("/lib/x86_64-linux-gnu/libc.so.6", 0) != 0
	    && access("/lib64/libc.so.6", 0) != 0) {
		puts("dyn: no libc.so.6 on this system — skipping");
		return 0;
	}

	const char *bin = getenv("BIN");
	if (!bin) bin = "out/bin";
	char absbin[1024];
	if (bin[0] != '/') {
		char cwd[1024];
		if (getcwd(cwd, sizeof cwd) == NULL) return 1;
		snprintf(absbin, sizeof absbin, "%s/%s", cwd, bin);
		bin = absbin;
	}

	/* Probe each common libc dir to find the right -L. */
	const char *libdir = NULL;
	if (access("/usr/lib/libc.so.6", 0) == 0) libdir = "/usr/lib";
	else if (access("/lib/x86_64-linux-gnu/libc.so.6", 0) == 0) libdir = "/lib/x86_64-linux-gnu";
	else if (access("/lib64/libc.so.6", 0) == 0) libdir = "/lib64";

	int n = 0, fail = 0;
	for (int i = 0; rows[i].src; i++, n++) {
		char src[80], exe[80], tmpdir[80];
		snprintf(src, sizeof src, "/tmp/wwdyn_%d_%d.ww", getpid(), i);
		snprintf(exe, sizeof exe, "/tmp/wwdyn_%d_%d", getpid(), i);
		snprintf(tmpdir, sizeof tmpdir, "/tmp/wwdyn_%d_d_%d", getpid(), i);
		mkdir(tmpdir, 0755);

		FILE *f = fopen(src, "wb");
		fputs(rows[i].src, f);
		fclose(f);

		char cmd[1024];
		snprintf(cmd, sizeof cmd,
		    "cd %s && %s/ww build %s -L %s -l c",
		    tmpdir, bin, src, libdir);
		if (runwait(cmd) != 0) {
			fprintf(stderr, "dyn row %d: build failed\n", i);
			fail++;
			unlink(src); rmdir(tmpdir);
			continue;
		}

		char outbin[160];
		const char *base = strrchr(src, '/');
		base = base ? base + 1 : src;
		snprintf(outbin, sizeof outbin, "%s/%s", tmpdir, base);
		char *dot = strrchr(outbin, '.');
		if (dot && strcmp(dot, ".ww") == 0) *dot = '\0';

		int got = runwait(outbin);
		if (got != rows[i].want_exit) {
			fprintf(stderr, "dyn row %d: exit %d, want %d\n",
			    i, got, rows[i].want_exit);
			fail++;
		}
		unlink(src); unlink(outbin); rmdir(tmpdir);
	}
	if (fail) {
		fprintf(stderr, "%d/%d dyn tests failed\n", fail, n);
		return 1;
	}
	printf("dyn: %d/%d ok\n", n, n);
	return 0;
}