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Description: Work around problem of atexit() functions accessing the TCB
atexit() functions might want to access the TCB (such as libpthread's
own internal atexit function), and they might be called from the
startup code after the end of stackgap(), on whose stack the TCB is
allocated.
.
This is a temporary workaround to make this work for most use cases,
but this needs to be followed up with a proper fix.
Author: Christian Seiler <christian@iwakd.de>
Last-Update: 2017-01-05
--- a/lib/stackgap-common.h
+++ b/lib/stackgap-common.h
@@ -583,7 +583,21 @@ int stackgap(int argc,char* argv[],char*
__unlikely(__tmemsize>512*1024*1024) ||
__unlikely(__tmemsize<__tdatasize))
return 111;
- tlsdata=alloca(__tmemsize+sizeof(tcbhead_t));
+ /* Ugly temporary workaround until a proper fix is available:
+
+ The TCB is allocated on the stack in stackgap (called by the
+ startup code). However, exit() will be called by the startup
+ code after the end of main, and some atexit functions might
+ still want to access the current TCB.
+
+ The workaround for now is to allocate 512 bytes more so that
+ a small stack within atexit() functions will not overwrite the
+ TCB. This is not a permanent solution, and we should probably
+ mmap() the real TCB - but for that we need to have an mmap
+ implementation that doesn't set errno, because that might be a
+ TLS variable.
+ */
+ tlsdata=alloca(__tmemsize+sizeof(tcbhead_t)+512);
memcpy(tlsdata,__tdataptr,__tdatasize);
memset(tlsdata+__tdatasize,0,__tmemsize-__tdatasize);
__setup_tls(__tcb_mainthread=(tcbhead_t*)(tlsdata+__tmemsize));
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