The situation where the caller uses a TOC and the callee does not
but is marked as clobbers the TOC (st_other=1) was not being compiled
correctly if both functions where in the same object file.
The call site where we had `callee` was missing a nop after the call.
This is because it was assumed that since the two functions where in
the same DSO they would be sharing a TOC. This is not the case if the
callee uses PC Relative because in that case it may clobber the TOC.
This patch makes sure that we add the cnop correctly so that the
linker has a place to restore the TOC.
Reviewers: sfertile, NeHuang, saghir
Differential Revision: https://reviews.llvm.org/D81126
static void *ifunc(void) __attribute__((ifunc("resolver")));
void foo() { ifunc(); }
The relocation produced by the ifunc() call:
1. gcc -msecure-plt -fPIC => R_PPC_PLTREL24 r_addend=0x8000
2. gcc -msecure-plt -PIE => R_PPC_PLTREL24 r_addend=0x8000
3. clang -msecure-plt -fPIC => R_PPC_PLTREL24 r_addend=0x8000
4. clang -msecure-plt -fPIE => R_PPC_REL24
4 is incorrect. The R_PPC_REL24 needs a call stub due to ifunc. If this
relocation is mixed with other R_PPC_PLTREL24(r_addend=0x8000) in a
function, both GNU ld and lld (after D71621 fix) may produce a wrong
result.
This patch fixes 4 to use R_PPC_PLTREL24, which matches GCC.
Both GNU ld and lld (after D71621) will be happy.
Reviewed By: sfertile
Differential Revision: https://reviews.llvm.org/D71649
