tools/nolibc: add support for program_invocation_{,short_}name

Add support for the GNU extensions 'program_invocation_name' and
'program_invocation_short_name'. These are useful to print error
messages, which by convention include the program name.

As these are global variables which take up memory even if not used,
similar to 'errno', gate them behind NOLIBC_IGNORE_ERRNO.

Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
Acked-by: Willy Tarreau <w@1wt.eu>
Link: https://patch.msgid.link/20260318-nolibc-err-h-v4-1-08247a694bd9@weissschuh.net

1 files changed, 34 insertions, 0 deletions

diff --git a/tools/testing/selftests/nolibc/nolibc-test.c b/tools/testing/selftests/nolibc/nolibc-test.c
index 0ca695acbc44..1efd10152e83 100644
--- a/tools/testing/selftests/nolibc/nolibc-test.c
+++ b/tools/testing/selftests/nolibc/nolibc-test.c
@@ -42,6 +42,7 @@
 #include <unistd.h>
 #include <limits.h>
 #include <ctype.h>
+#include <stdbool.h>
 
 #pragma GCC diagnostic ignored "-Wmissing-prototypes"
 
@@ -710,6 +711,37 @@ static void constructor2(int argc, char **argv, char **envp)
 		constructor_test_value |= 1 << 1;
 }
 
+int test_program_invocation_name(void)
+{
+	char buf[100];
+	char *dirsep;
+	ssize_t r;
+	int fd;
+
+	fd = open("/proc/self/cmdline", O_RDONLY);
+	if (fd == -1)
+		return 1;
+
+	r = read(fd, buf, sizeof(buf));
+	close(fd);
+	if (r < 1 || r == sizeof(buf))
+		return 1;
+
+	buf[r - 1] = '\0';
+
+	if (strcmp(program_invocation_name, buf) != 0)
+		return 1;
+
+	dirsep = strrchr(buf, '/');
+	if (!dirsep || dirsep[1] == '\0')
+		return 1;
+
+	if (strcmp(program_invocation_short_name, dirsep + 1) != 0)
+		return 1;
+
+	return 0;
+}
+
 int run_startup(int min, int max)
 {
 	int test;
@@ -724,6 +756,7 @@ int run_startup(int min, int max)
 #ifdef NOLIBC
 	test_auxv = _auxv;
 #endif
+	bool proc = access("/proc", R_OK) == 0;
 
 	for (test = min; test >= 0 && test <= max; test++) {
 		int llen = 0; /* line length */
@@ -749,6 +782,7 @@ int run_startup(int min, int max)
 		CASE_TEST(constructor);      EXPECT_EQ(is_nolibc, constructor_test_value, 0x3); break;
 		CASE_TEST(linkage_errno);    EXPECT_PTREQ(1, linkage_test_errno_addr(), &errno); break;
 		CASE_TEST(linkage_constr);   EXPECT_EQ(1, linkage_test_constructor_test_value, 0x3); break;
+		CASE_TEST(prog_name);        EXPECT_ZR(proc, test_program_invocation_name()); break;
 		case __LINE__:
 			return ret; /* must be last */
 		/* note: do not set any defaults so as to permit holes above */