Change ARG_MAX/_SC_ARG_MAX back to a constant.
As per the lkml thread https://lkml.org/lkml/2017/11/1/946.
Bug: http://b/65818597
Test: ran tests
Change-Id: I7a0610e6903e6761f2b31416e2f5017bd7a60659
diff --git a/libc/bionic/sysconf.cpp b/libc/bionic/sysconf.cpp
index d45cb38..2442fd9 100644
--- a/libc/bionic/sysconf.cpp
+++ b/libc/bionic/sysconf.cpp
@@ -52,9 +52,16 @@
// 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);
+ // https://lkml.org/lkml/2017/11/15/813...
+ //
+ // I suspect a 128kB sysconf(_SC_ARG_MAX) is the sanest bet, simply
+ // because of that "conservative is better than aggressive".
+ //
+ // Especially since _technically_ we're still limiting things to that
+ // 128kB due to the single-string limit.
+ //
+ // Linus
+ return ARG_MAX;
case _SC_AVPHYS_PAGES: return get_avphys_pages();
case _SC_CHILD_MAX: return __sysconf_rlimit(RLIMIT_NPROC);
diff --git a/libc/kernel/tools/defaults.py b/libc/kernel/tools/defaults.py
index b0fb95f..586cb02 100644
--- a/libc/kernel/tools/defaults.py
+++ b/libc/kernel/tools/defaults.py
@@ -58,8 +58,6 @@
# Replace tokens in the output according to this mapping.
kernel_token_replacements = {
- # 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 usage of C++ keywords causes problems for C++ code so rename.
diff --git a/libc/kernel/uapi/linux/limits.h b/libc/kernel/uapi/linux/limits.h
index 41108f9..ad0e33e 100644
--- a/libc/kernel/uapi/linux/limits.h
+++ b/libc/kernel/uapi/linux/limits.h
@@ -20,7 +20,7 @@
#define _LINUX_LIMITS_H
#define NR_OPEN 1024
#define NGROUPS_MAX 65536
-#define _KERNEL_ARG_MAX 131072
+#define ARG_MAX 131072
#define LINK_MAX 127
#define MAX_CANON 255
#define MAX_INPUT 255
diff --git a/libc/upstream-freebsd/android/include/freebsd-compat.h b/libc/upstream-freebsd/android/include/freebsd-compat.h
index 8f0a307..e646e23 100644
--- a/libc/upstream-freebsd/android/include/freebsd-compat.h
+++ b/libc/upstream-freebsd/android/include/freebsd-compat.h
@@ -50,6 +50,4 @@
/* FreeBSD has this, but we can't really implement it correctly on Linux. */
#define issetugid() 0
-#define ARG_MAX sysconf(_SC_ARG_MAX)
-
#endif
diff --git a/tests/unistd_test.cpp b/tests/unistd_test.cpp
index 456ddde..022da4d 100644
--- a/tests/unistd_test.cpp
+++ b/tests/unistd_test.cpp
@@ -1017,36 +1017,11 @@
}
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 = android::base::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));
+ // https://lkml.org/lkml/2017/11/15/813.
+#if !defined(ARG_MAX)
+#define ARG_MAX 131072
+#endif
+ ASSERT_EQ(ARG_MAX, sysconf(_SC_ARG_MAX));
}
TEST(UNISTD_TEST, dup2_same) {