This is caused by the CONFIG_RETHUNK option. In the disassembly from objdump you are seeing the result of RET being replaced with JMP __x86_return_thunk.
https://github.com/torvalds/linux/blob/v6.1/arch/x86/include...
https://github.com/torvalds/linux/blob/v6.1/arch/x86/lib/ret...
> The NOP instructions at the beginning and at the end of the function allow ftrace to insert tracing instructions when needed.
These are from the ASM_CLAC and ASM_STAC macros, which make space for the CLAC and STAC instructions (both of them three bytes in length, same as the number of NOPs) to be filled in at runtime if X86_FEATURE_SMAP is detected.
https://github.com/torvalds/linux/blob/v6.1/arch/x86/include...
https://github.com/torvalds/linux/blob/v6.1/arch/x86/include...
https://github.com/torvalds/linux/blob/v6.1/arch/x86/kernel/...