diff options
| -rw-r--r-- | Config.in | 42 | ||||
| -rwxr-xr-x | scripts/genconfig.sh | 2 |
2 files changed, 28 insertions, 16 deletions
@@ -165,22 +165,34 @@ config TOYBOX_UID_USR help When commands like useradd/groupadd allocate user IDs, start here. -config TOYBOX_MUSL_NOMMU_IS_BROKEN - bool "Workaround for musl-libc breakage on nommu systems." +config TOYBOX_FORCE_NOMMU + bool "Enable nommu support when the build can't detect it." default n help - When using musl-libc on a nommu system, you'll need to say "y" here. - - Although uclibc lets you detect support for things like fork() and - daemon() at compile time, musl intentionally includes broken versions - that always return -ENOSYS on nommu systems, and goes out of its way - to prevent any cross-compile compatible compile-time probes for a - nommu system. (It doesn't even #define __MUSL__ in features.h.) - - Musl does this despite the fact that a nommu system can't even run - standard ELF binaries, and requires specially packaged executables. - So our only choice is to manually provide a musl nommu bug workaround - you can manually select to enable (larger, slower) nommu support with - musl. + When using musl-libc on a nommu system, you'll need to say "y" here + unless you used the patch in the mcm-buildall.sh script. You can also + say "y" here to test the nommu codepaths on an mmu system. + + A nommu system can't use fork(), it can only vfork() which suspends + the parent until the child calls exec() or exits. When a program + needs a second instance of itself to run specific code at the same + time as the parent, it must use a more complicated approach (such as + exec("/proc/self/exe") then pass data to the new child through a pipe) + which is larger and slower, especially for things like toysh subshells + that need to duplicate a lot of internal state in the child process + fork() gives you for free. + + Libraries like uclibc omit fork() on nommu systems, allowing + compile-time probes to select which codepath to use. But musl + intentionally includes a broken version of fork() that always returns + -ENOSYS on nommu systems, and goes out of its way to prevent any + cross-compile compatible compile-time probes for a nommu system. + (It doesn't even #define __MUSL__ in features.h.) Musl does this + despite the fact that a nommu system can't even run standard ELF + binaries (requiring specially packaged executables) because it wants + to force every program to either include all nommu code in every + instance ever built, or drop nommu support altogether. + + Building a toolchain scripts/mcm-buildall.sh patches musl to fix this. endmenu diff --git a/scripts/genconfig.sh b/scripts/genconfig.sh index cc2bd764..b5637f86 100755 --- a/scripts/genconfig.sh +++ b/scripts/genconfig.sh @@ -92,7 +92,7 @@ EOF #include <unistd.h> int main(int argc, char *argv[]) { return fork(); } EOF - echo -e '\tdepends on !TOYBOX_MUSL_NOMMU_IS_BROKEN' + echo -e '\tdepends on !TOYBOX_FORCE_NOMMU' probesymbol TOYBOX_PRLIMIT << EOF #include <sys/types.h> |