util: avoid calling kcmp on Android

On some combinations of Android version and kernel version, calling kcmp
results in seccomp killing the process.

As there doesn't seem to be a way to query for that in advance, skip
this check altogether on Android.

Signed-off-by: Eric Engestrom <eric@igalia.com>
Reviewed-by: Rob Clark <robclark@freedesktop.org>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/20180>

meson.build

@@ -851,6 +851,16 @@ if with_platform_android
   ]
 endif
 
+# On Android, seccomp kills the process on kernels without
+# CONFIG_KCMP/CONFIG_CHECKPOINT_RESTORE if it attemps to use KCMP.
+# Since we can't detect that, err on the side of caution and disable
+# KCMP by default on Android.
+if get_option('allow-kcmp') \
+    .disable_auto_if(with_platform_android) \
+    .allowed()
+  pre_args += '-DALLOW_KCMP'
+endif
+
 prog_python = import('python').find_installation('python3')
 has_mako = run_command(
   prog_python, '-c',

meson_options.txt

@@ -427,6 +427,11 @@ option(
   value : 25,
   description : 'Android Platform SDK version. Default: Nougat version.'
 )
+option(
+   'allow-kcmp',
+   type : 'feature',
+   description : 'Allow using KCMP_FILE to compare file descriptions. auto = allowed everywhere except on Android'
+)
 option(
   'zstd',
   type : 'feature',

src/util/os_file.c

@@ -194,7 +194,7 @@ os_read_file(const char *filename, size_t *size)
    return buf;
 }
 
-#if DETECT_OS_LINUX
+#if DETECT_OS_LINUX && ALLOW_KCMP
 
 #include <sys/syscall.h>
 #include <unistd.h>