Hi Timo, unfortunately your fix isn't exactly correct. 2010/5/11 Timo Teräs <[email protected]>: > GCC can emit prologue/epilogue code for the functions in various > different cases: > - frame pointers > - PIC build (to load ebx for indirect calls/jumps) > - forced stack smashing protection > > If we used jump in such cases, we'd corrupt the call stack and > crash.
Yes, but using call will push additional word on the stack and the called function will use wrong offset to access the parameter on stack. > --- a/libm/ldouble_wrappers.c > +++ b/libm/ldouble_wrappers.c > @@ -60,7 +60,9 @@ long long func##l(long double x) \ > * The return value is returned in st(0) per ABI in both cases (returning > * a long double or returning a double). So we can simply jump to func. > * Using __GI_func in jump to make optimized intra-library jump. > - * gcc will still generate a useless "ret" after asm. Oh well... > + * > + * We do need to use call (instead of tail jump) as gcc can create > + * stack frame, and push/modify/pop ebx during PIC build. > */ > # define WRAPPER1(func) \ > long double func##l(long double x) \ > @@ -69,7 +71,7 @@ long double func##l(long double x) \ > __asm ( \ > " fldt %1\n" \ > " fstpl %1\n" \ > - " jmp " __stringify(__GI_##func) "\n" \ > + " call " __stringify(__GI_##func) "\n" \ > : "=t" (st_top) \ > : "m" (x) \ > ); \ So instead of this, you need to update #if guard: #if defined __i386__ && defined __OPTIMIZE__ Add more conditions so that it kicks in only when safe. -- vda _______________________________________________ uClibc mailing list [email protected] http://lists.busybox.net/mailman/listinfo/uclibc
