search for: __x86_thunk_indirect

...t final 'ret' still leaves the target address on the stack, so there would also need to be a complicated dance, without using any registers, to pop that too. I expected the emitted code for a *call* using the thunk to look more like    jmp 2f  1: pushl -0x20(%ebp)        # cmp_func    jmp __x86_thunk_indirect # jmp, not call 2: call 1b                  # set up address for cmp_func to return to -------------- next part -------------- A non-text attachment was scrubbed... Name: smime.p7s Type: application/x-pkcs7-signature Size: 5213 bytes Desc: not available URL: <http://lists.llvm.org/pipermail/llvm...

On Fri, 2018-02-09 at 01:18 +0000, David Woodhouse wrote: > > For now I'm just going to attempt to work around it like this in the > kernel, so I can concentrate on the retpoline bits: >  http://david.woodhou.se/clang-percpu-hack.patch 32-bit doesn't boot. Built without CONFIG_RETPOLINE and with Clang 5.0 (and the above patch) it does. I'm rebuilding a Release build of

...mments here: https://github.com/llvm-project/llvm-project-20170507/blob/master/llvm/lib/Target/X86/X86RetpolineThunks.cpp#L179-L194 > > I expected the emitted code for a *call* using the thunk to look more > like > > jmp 2f > 1: pushl -0x20(%ebp) # cmp_func > jmp __x86_thunk_indirect # jmp, not call > 2: call 1b # set up address for cmp_func to return to > Yeah, the specific goal was to minimize the code size footprint at the call site even though it means a few more instructions in the thunk. Our pattern also has a minor reduction in the dynamic branche...