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Peter Zijlstra
923510c88d
Clang likes to create conditional tail calls like: 0000000000000350 <amd_pmu_add_event>: 350: 0f 1f 44 00 00 nopl 0x0(%rax,%rax,1) 351: R_X86_64_NONE __fentry__-0x4 355: 48 83 bf 20 01 00 00 00 cmpq $0x0,0x120(%rdi) 35d: 0f 85 00 00 00 00 jne 363 <amd_pmu_add_event+0x13> 35f: R_X86_64_PLT32 __SCT__amd_pmu_branch_add-0x4 363: e9 00 00 00 00 jmp 368 <amd_pmu_add_event+0x18> 364: R_X86_64_PLT32 __x86_return_thunk-0x4 Where 0x35d is a static call site that's turned into a conditional tail-call using the Jcc class of instructions. Teach the in-line static call text patching about this. Notably, since there is no conditional-ret, in that case patch the Jcc to point at an empty stub function that does the ret -- or the return thunk when needed. Reported-by: "Erhard F." <[email protected]> Signed-off-by: Peter Zijlstra (Intel) <[email protected]> Signed-off-by: Ingo Molnar <[email protected]> Reviewed-by: Masami Hiramatsu (Google) <[email protected]> Link: https://lore.kernel.org/r/[email protected]