Fix sysconf(_SC_ARG_MAX).
ARG_MAX hasn't been a constant since Linux 2.6.23.
Bug: http://lists.landley.net/pipermail/toybox-landley.net/2016-August/008592.html
Change-Id: I1eddb562751604c75b89fa610d79be0655c53693
Test: ran the bionic tests on device and against glibc
diff --git a/libc/bionic/sysconf.cpp b/libc/bionic/sysconf.cpp
index 7be0ab7..4a23fec 100644
--- a/libc/bionic/sysconf.cpp
+++ b/libc/bionic/sysconf.cpp
@@ -29,10 +29,10 @@
#include <errno.h>
#include <fcntl.h>
#include <limits.h>
-#include <linux/uio.h> // For UIO_MAXIOV.
#include <pthread.h>
#include <stdio.h> // For FOPEN_MAX.
#include <sys/auxv.h>
+#include <sys/param.h>
#include <sys/resource.h>
#include <sys/sysinfo.h>
#include <time.h>
@@ -48,18 +48,39 @@
long sysconf(int name) {
switch (name) {
- case _SC_ARG_MAX: return ARG_MAX;
+ //
+ // Things we actually have to calculate...
+ //
+ case _SC_ARG_MAX:
+ // Not a constant since Linux 2.6.23; see fs/exec.c for details.
+ // At least 32 pages, otherwise a quarter of the stack limit.
+ return MAX(__sysconf_rlimit(RLIMIT_STACK) / 4, _KERNEL_ARG_MAX);
+
+ case _SC_AVPHYS_PAGES: return get_avphys_pages();
+ case _SC_CHILD_MAX: return __sysconf_rlimit(RLIMIT_NPROC);
+ case _SC_CLK_TCK: return static_cast<long>(getauxval(AT_CLKTCK));
+ case _SC_NPROCESSORS_CONF: return get_nprocs_conf();
+ case _SC_NPROCESSORS_ONLN: return get_nprocs();
+ case _SC_OPEN_MAX: return __sysconf_rlimit(RLIMIT_NOFILE);
+
+ case _SC_PAGESIZE:
+ case _SC_PAGE_SIZE:
+ // _SC_PAGESIZE and _SC_PAGE_SIZE are distinct, but return the same value.
+ return static_cast<long>(getauxval(AT_PAGESZ));
+
+ case _SC_PHYS_PAGES: return get_phys_pages();
+
+ //
+ // Constants...
+ //
case _SC_BC_BASE_MAX: return _POSIX2_BC_BASE_MAX; // Minimum requirement.
case _SC_BC_DIM_MAX: return _POSIX2_BC_DIM_MAX; // Minimum requirement.
case _SC_BC_SCALE_MAX: return _POSIX2_BC_SCALE_MAX; // Minimum requirement.
case _SC_BC_STRING_MAX: return _POSIX2_BC_STRING_MAX; // Minimum requirement.
- case _SC_CHILD_MAX: return __sysconf_rlimit(RLIMIT_NPROC);
- case _SC_CLK_TCK: return static_cast<long>(getauxval(AT_CLKTCK));
case _SC_COLL_WEIGHTS_MAX: return _POSIX2_COLL_WEIGHTS_MAX; // Minimum requirement.
case _SC_EXPR_NEST_MAX: return _POSIX2_EXPR_NEST_MAX; // Minimum requirement.
case _SC_LINE_MAX: return _POSIX2_LINE_MAX; // Minimum requirement.
case _SC_NGROUPS_MAX: return NGROUPS_MAX;
- case _SC_OPEN_MAX: return __sysconf_rlimit(RLIMIT_NOFILE);
case _SC_PASS_MAX: return PASS_MAX;
case _SC_2_C_BIND: return _POSIX2_C_BIND;
case _SC_2_C_DEV: return _POSIX2_C_DEV;
@@ -84,12 +105,7 @@
case _SC_XOPEN_REALTIME_THREADS: return _XOPEN_REALTIME_THREADS;
case _SC_XOPEN_LEGACY: return _XOPEN_LEGACY;
case _SC_ATEXIT_MAX: return LONG_MAX; // Unlimited.
- case _SC_IOV_MAX: return UIO_MAXIOV;
-
- // _SC_PAGESIZE and _SC_PAGE_SIZE are distinct, but return the same value.
- case _SC_PAGESIZE:
- case _SC_PAGE_SIZE:
- return static_cast<long>(getauxval(AT_PAGESZ));
+ case _SC_IOV_MAX: return IOV_MAX;
case _SC_XOPEN_UNIX: return _XOPEN_UNIX;
case _SC_AIO_LISTIO_MAX: return _POSIX_AIO_LISTIO_MAX; // Minimum requirement.
@@ -132,10 +148,6 @@
case _SC_THREAD_PRIO_INHERIT: return _POSIX_THREAD_PRIO_INHERIT;
case _SC_THREAD_PRIO_PROTECT: return _POSIX_THREAD_PRIO_PROTECT;
case _SC_THREAD_SAFE_FUNCTIONS: return _POSIX_THREAD_SAFE_FUNCTIONS;
- case _SC_NPROCESSORS_CONF: return get_nprocs_conf();
- case _SC_NPROCESSORS_ONLN: return get_nprocs();
- case _SC_PHYS_PAGES: return get_phys_pages();
- case _SC_AVPHYS_PAGES: return get_avphys_pages();
case _SC_MONOTONIC_CLOCK: return _POSIX_VERSION;
case _SC_2_PBS: return -1; // Obsolescent in POSIX.1-2008.
diff --git a/libc/kernel/tools/defaults.py b/libc/kernel/tools/defaults.py
index 773d22f..340af13 100644
--- a/libc/kernel/tools/defaults.py
+++ b/libc/kernel/tools/defaults.py
@@ -53,9 +53,10 @@
"x86": {},
}
-# Replace tokens in the output according to this mapping
+# Replace tokens in the output according to this mapping.
kernel_token_replacements = {
- "asm": "__asm__",
+ # The kernel's ARG_MAX is actually the "minimum" maximum (see fs/exec.c).
+ "ARG_MAX": "_KERNEL_ARG_MAX",
# The kernel usage of __unused for unused struct fields conflicts with the macro defined in <sys/cdefs.h>.
"__unused": "__linux_unused",
# The kernel's _NSIG/NSIG are one less than the userspace value, so we need to move them aside.
diff --git a/libc/kernel/uapi/linux/limits.h b/libc/kernel/uapi/linux/limits.h
index 406d175..4441592 100644
--- a/libc/kernel/uapi/linux/limits.h
+++ b/libc/kernel/uapi/linux/limits.h
@@ -21,7 +21,7 @@
#define NR_OPEN 1024
#define NGROUPS_MAX 65536
/* WARNING: DO NOT EDIT, AUTO-GENERATED CODE - SEE TOP FOR INSTRUCTIONS */
-#define ARG_MAX 131072
+#define _KERNEL_ARG_MAX 131072
#define LINK_MAX 127
#define MAX_CANON 255
#define MAX_INPUT 255
diff --git a/tests/unistd_test.cpp b/tests/unistd_test.cpp
index 3a87e88..32b1626 100644
--- a/tests/unistd_test.cpp
+++ b/tests/unistd_test.cpp
@@ -857,6 +857,39 @@
ASSERT_EQ(online_cpus, sysconf(_SC_NPROCESSORS_ONLN));
}
+TEST(UNISTD_TEST, sysconf_SC_ARG_MAX) {
+ // Since Linux 2.6.23, ARG_MAX isn't a constant and depends on RLIMIT_STACK.
+
+ // Get our current limit, and set things up so we restore the limit.
+ rlimit rl;
+ ASSERT_EQ(0, getrlimit(RLIMIT_STACK, &rl));
+ uint64_t original_rlim_cur = rl.rlim_cur;
+ if (rl.rlim_cur == RLIM_INFINITY) {
+ rl.rlim_cur = 8 * 1024 * 1024; // Bionic reports unlimited stacks as 8MiB.
+ }
+ auto guard = make_scope_guard([&rl, original_rlim_cur]() {
+ rl.rlim_cur = original_rlim_cur;
+ ASSERT_EQ(0, setrlimit(RLIMIT_STACK, &rl));
+ });
+
+ // _SC_ARG_MAX should be 1/4 the stack size.
+ EXPECT_EQ(static_cast<long>(rl.rlim_cur / 4), sysconf(_SC_ARG_MAX));
+
+ // If you have a really small stack, the kernel still guarantees "32 pages" (fs/exec.c).
+ rl.rlim_cur = 1024;
+ rl.rlim_max = RLIM_INFINITY;
+ ASSERT_EQ(0, setrlimit(RLIMIT_STACK, &rl));
+
+ EXPECT_EQ(static_cast<long>(32 * sysconf(_SC_PAGE_SIZE)), sysconf(_SC_ARG_MAX));
+
+ // With a 128-page stack limit, we know exactly what _SC_ARG_MAX should be...
+ rl.rlim_cur = 128 * sysconf(_SC_PAGE_SIZE);
+ rl.rlim_max = RLIM_INFINITY;
+ ASSERT_EQ(0, setrlimit(RLIMIT_STACK, &rl));
+
+ EXPECT_EQ(static_cast<long>((128 * sysconf(_SC_PAGE_SIZE)) / 4), sysconf(_SC_ARG_MAX));
+}
+
TEST(UNISTD_TEST, dup2_same) {
// POSIX says of dup2:
// If fildes2 is already a valid open file descriptor ...