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93 lines
2.7 KiB
C
93 lines
2.7 KiB
C
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/* Used by the elf ifunc tests. */
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#ifndef ELF_IFUNC_SEL_H
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#define ELF_IFUNC_SEL_H 1
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extern int global;
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static inline __attribute__ ((always_inline)) void *
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ifunc_sel (int (*f1) (void), int (*f2) (void), int (*f3) (void))
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{
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#ifdef __powerpc__
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/* When generating PIC, powerpc gcc loads the address of "global"
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from the GOT, but the GOT may not have been relocated.
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Similarly, "f1", "f2" and "f3" may be loaded from non-relocated
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GOT entries.
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There is NO WAY to make this ill conceived IFUNC misfeature
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reliably work on targets that use a GOT for function or variable
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addresses, short of implementing two passes over relocations in
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ld.so, with ifunc relocations being applied after all other
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relocations, globally.
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Cheat. Don't use the GOT. Rely on this function being inlined
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and calculate all variable and function addresses relative to pc.
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Using the 'X' constraint is risky, but that's the only way to
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make the asm here see the function names for %4, %5 and %6.
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Sadly, powerpc64 gcc doesn't accept use of %3 here with 'X' for
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some reason, so we expand it ourselves. */
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register void *ret __asm__ ("r3");
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void *temp1, *temp2;
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__asm__ ("mflr %1\n\t"
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"bcl 20,31,1f\n"
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"1:\tmflr %2\n\t"
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"mtlr %1\n\t"
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"addis %1,%2,global-1b@ha\n\t"
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"lwz %1,global-1b@l(%1)\n\t"
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"addis %0,%2,%4-1b@ha\n\t"
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"addi %0,%0,%4-1b@l\n\t"
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"cmpwi %1,1\n\t"
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"beqlr\n\t"
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"addis %0,%2,%5-1b@ha\n\t"
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"addi %0,%0,%5-1b@l\n\t"
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"cmpwi %1,-1\n\t"
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"beqlr\n\t"
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"addis %0,%2,%6-1b@ha\n\t"
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"addi %0,%0,%6-1b@l"
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: "=&b" (ret), "=&b" (temp1), "=&b" (temp2)
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: "X" (&global), "X" (f1), "X" (f2), "X" (f3));
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return ret;
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#else
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switch (global)
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{
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case 1:
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return f1;
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case -1:
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return f2;
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default:
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return f3;
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}
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#endif
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}
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static inline __attribute__ ((always_inline)) void *
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ifunc_one (int (*f1) (void))
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{
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#ifdef __powerpc__
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/* As above, PIC may use an unrelocated GOT entry for f1.
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Case study: ifuncmain6pie's shared library, ifuncmod6.so, wants
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the address of "foo" in function get_foo(). So there is a GOT
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entry for "foo" in ifuncmod6.so. ld.so relocates ifuncmod6.so
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*before* ifuncmain6pie, and on finding "foo" to be STT_GNU_IFUNC,
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calls this function with f1 set to "one". But the address of
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"one" is loaded from ifuncmain6pie's GOT, which hasn't been
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relocated yet.
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Cheat as for ifunc-sel. */
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register void *ret __asm__ ("r3");
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void *temp;
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__asm__ ("mflr %1\n\t"
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"bcl 20,31,1f\n"
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"1:\tmflr %0\n\t"
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"mtlr %1\n\t"
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"addis %0,%0,%2-1b@ha\n\t"
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"addi %0,%0,%2-1b@l"
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: "=&b" (ret), "=&r" (temp)
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: "X" (f1));
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return ret;
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#else
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return f1;
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#endif
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}
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#endif
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