baremetal: get exit status working with on_exit :-)

README.adoc

@@ -11916,7 +11916,7 @@ svc 0x00123456
 
 and we can see from the docs that `0x18` stands for the `SYS_EXIT` command.
 
-This is also how we implement the `exit(0)` system call in C for QEMU for link:baremetal/exit.c[] through the Newlib via the function `_exit` at link:baremetal/lib/kwargs['c'][].
+This is also how we implement the `exit(0)` system call in C for QEMU for link:baremetal/exit0.c[] through the Newlib via the function `_exit` at link:baremetal/lib/kwargs['c'][].
 
 Other magic operations we can do with semihosting besides exiting the on the host include:
 
@@ -11990,7 +11990,7 @@ sudo apt-get install gcc-arm-none-eabi qemu-system-arm
 
 However, there are as usual limitations to using prebuilts:
 
-* certain examples fail to build with the Ubuntu packaged toolchain. E.g.: link:baremetal/exit.c[] fails with:
+* certain examples fail to build with the Ubuntu packaged toolchain. E.g.: link:baremetal/exit0.c[] fails with:
 +
 ....
 /usr/lib/gcc/arm-none-eabi/6.3.1/../../../arm-none-eabi/lib/libg.a(lib_a-fini.o): In function `__libc_fini_array':
@@ -14001,20 +14001,42 @@ For other arch / emulator combinations, we know how to do it:
 * gem5: <<m5-fail>> works on all archs
 * user mode: QEMU forwards exit status, gem5 we do some log parsing: <<gem5-syscall-emulation-exit-status>>
 
-For this reason, we just parse the terminal output for a magic failure string to check if tests failed.
+Since we can't do it for QEMU arm, the only reliable solution is to just parse the guest serial output for a magic failure string to check if tests failed.
 
-In order to cover all archs, our run scripts parse the serial output looking for a line line containing only exactly the magic regular expression:
+Our run scripts parse the serial output looking for a line line containing only exactly the magic regular expression:
 
 ....
 lkmc_exit_status_(\d+)
 ....
 
-and then exit with the given regular expression.
+and then exit with the given regular expression, e.g.:
+
+....
+./run --arch aarch64 baremetal
+....
 
 This magic output string is notably generated by:
 
-* the `exit()` baremetal function when `status != 1`. This is in turn called by failed assertions for example from `lkmc_assert_fail`, which is used by <<baremetal-tests>>
 * link:rootfs_overlay/lkmc/test_fail.sh[], which is used by <<test-userland-in-full-system>>
+* the `exit()` baremetal function when `status != 1`.
++
+Unfortunately the only way we found to set this up was with `on_exit`: link:https://github.com/cirosantilli/linux-kernel-module-cheat/issues/59[].
++
+Trying to patch `_exit` directly fails since at that point some de-initialization has already happened which prevents the print.
++
+So setup this `on_exit` automatically from all our <<baremetal-bootloaders>>, so it just works automatically for the examples that use the bootloaders: https://stackoverflow.com/questions/44097610/pass-parameter-to-atexit/49659697#49659697
++
+The following examples end up testing that our setup is working:
++
+* link:baremetal/lkmc_assert_fail.c[]
+* link:baremetal/return1.c[]
+* link:baremetal/return2.c[]
+* link:baremetal/exit0.c[]
+* link:baremetal/exit1.c[]
+* link:baremetal/arch/arm/return1.S[]
+* link:baremetal/arch/aarch64/return1.S[]
+
+Beware that on Linux kernel simulations, you cannot even echo that string from userland, since userland stdout shows up on the serial.
 
 ==== Non-automated tests
 

baremetal/arch/aarch64/return1.S

@@ -0,0 +1,5 @@
+/* https://github.com/cirosantilli/linux-kernel-module-cheat#magic-failure-string */
+.global main
+main:
+    mov x0, 1
+    ret

baremetal/arch/arm/return1.S

@@ -0,0 +1,5 @@
+/* https://github.com/cirosantilli/linux-kernel-module-cheat#magic-failure-string */
+.global main
+main:
+    mov r0, #1
+    bx lr

baremetal/exit.c

@@ -1,6 +0,0 @@
-#include <stdio.h>
-#include <stdlib.h>
-
-int main(void) {
-    exit(0);
-}

baremetal/exit0.c

@@ -0,0 +1,7 @@
+/* https://github.com/cirosantilli/linux-kernel-module-cheat#magic-failure-string */
+
+#include <stdlib.h>
+
+int main(void) {
+    exit(0);
+}

baremetal/exit1.c

@@ -1,4 +1,5 @@
-#include <stdio.h>
+/* https://github.com/cirosantilli/linux-kernel-module-cheat#magic-failure-string */
+
 #include <stdlib.h>
 
 int main(void) {

baremetal/lib/aarch64.S

@@ -14,6 +14,12 @@ mystart:
     /* Prepare the stack for main, mandatory for C code. */
     ldr x0, =stack_top
     mov sp, x0
+
+    /* https://github.com/cirosantilli/linux-kernel-module-cheat#magic-failure-string */
+    adr x0, lkmc_baremetal_on_exit_callback
+    bl on_exit
+
+    /* Run main. */
     bl main
 
     /* If main returns, exit. */

baremetal/lib/arm.S

@@ -1,5 +1,16 @@
+#include <lkmc.h>
+
 .global mystart
 mystart:
+    /* Prepare the stack for main, mandatory for C code. */
     ldr sp, =stack_top
+
+    /* https://github.com/cirosantilli/linux-kernel-module-cheat#magic-failure-string */
+    ldr r0, =lkmc_baremetal_on_exit_callback
+    bl on_exit
+
+    /* Run main. */
     bl main
+
+    /* If main returns, exit. */
     bl exit

baremetal/return1.c

@@ -1 +1,2 @@
+/* https://github.com/cirosantilli/linux-kernel-module-cheat#magic-failure-string */
 int main(void) { return 1; }

baremetal/return2.c

@@ -1 +1,2 @@
+/* https://github.com/cirosantilli/linux-kernel-module-cheat#magic-failure-string */
 int main(void) { return 2; }

lkmc.c

@@ -12,11 +12,16 @@ void lkmc_assert(bool condition) {
 }
 
 void lkmc_assert_fail(void) {
-    printf("%s\n", __func__);
-    puts("lkmc_exit_status_1");
     exit(1);
 }
 
+void lkmc_baremetal_on_exit_callback(int status, void *arg) {
+    (void)arg;
+    if (status != 0) {
+        printf("lkmc_exit_status_%d\n", status);
+    }
+}
+
 #if defined(__aarch64__)
 #define LKMC_SYSREG_READ_WRITE(type, name) \
     type LKMC_CONCAT(LKMC_CONCAT(LKMC_SYSREG_SYMBOL_PREFIX, name), _read(void)) { \

lkmc.h

@@ -11,6 +11,7 @@
 
 void lkmc_assert(bool);
 void lkmc_assert_fail();
+void lkmc_baremetal_on_exit_callback(int status, void *arg);
 #endif
 
 /* https://stackoverflow.com/questions/1489932/how-to-concatenate-twice-with-the-c-preprocessor-and-expand-a-macro-as-in-arg */

lkmc/assert_fail.c

@@ -1,21 +1,5 @@
 #include <lkmc.h>
 
-#include <stdio.h>
-
-void atexit_cb(void) {
-    puts("atexit");
-}
-
-void onexit_cb(int status, void *arg) {
-    printf("status %d\n", status);
-}
-
-void __attribute__ ((constructor)) premain() {
-    printf("premain2()\n");
-}
-
 int main(void) {
-    atexit(atexit_cb);
-    on_exit(onexit_cb, NULL);
     lkmc_assert_fail();
 }

path_properties.py

@@ -220,6 +220,7 @@ path_properties_tuples = (
                                         'semihost_exit.S': {'requires_semihosting': True},
                                     }
                                 ),
+                                'return1.S': {'exit_status': 1},
                                 'semihost_exit.S': {'requires_semihosting': True},
                             },
 
@@ -235,12 +236,13 @@ path_properties_tuples = (
                                         'semihost_exit.S': {'requires_semihosting': True},
                                     }
                                 ),
+                                'return1.S': {'exit_status': 1},
                                 'semihost_exit.S': {'requires_semihosting': True},
                             },
                         )
                     }
                 ),
-                'assert_fail.c': {'exit_status': 1},
+                'lkmc_assert_fail.c': {'exit_status': 1},
                 'exit1.c': {'exit_status': 1},
                 'infinite_loop.c': {'more_than_1s': True},
                 'lib': (

test-baremetal

@@ -55,9 +55,9 @@ If given, run only the given tests. Otherwise, run all tests.
                                         'run_obj': self.import_path_main('run'),
                                         'test_id': path_relative_root,
                                     }
-                                    if path_relative_root != os.path.join('baremetal', 'assert_fail.c'):
+                                    # if path_relative_root != os.path.join('baremetal', 'lkmc_assert_fail.c'):
                                         # Workaround fro: https://github.com/cirosantilli/linux-kernel-module-cheat/issues/59
-                                        test_args['expected_exit_status'] = 0
+                                        # test_args['expected_exit_status'] = 0
                                     error = thread_pool.submit(test_args)
                                     if error is not None:
                                         if self.env['quit_on_fail']: