From: Guilherme G. Piccoli <gpiccoli@xxxxxxxxxx> Sent: Friday, March 17, 2023 9:06 AM > > Annotate the function prototype and definition as noreturn to prevent > objtool warnings like: > > vmlinux.o: warning: objtool: hyperv_init+0x55c: unreachable instruction > > Also, as per Josh's suggestion, add it to the global_noreturns list. > As a comparison, an objdump output without the annotation: > > [...] > 1b63: mov $0x1,%esi > 1b68: xor %edi,%edi > 1b6a: callq ffffffff8102f680 <hv_ghcb_terminate> > 1b6f: jmpq ffffffff82f217ec <hyperv_init+0x9c> # unreachable > 1b74: cmpq $0xffffffffffffffff,-0x702a24(%rip) > [...] > > Now, after adding the __noreturn to the function prototype: > > [...] > 17df: callq ffffffff8102f6d0 <hv_ghcb_negotiate_protocol> > 17e4: test %al,%al > 17e6: je ffffffff82f21bb9 <hyperv_init+0x469> > [...] <many insns> > 1bb9: mov $0x1,%esi > 1bbe: xor %edi,%edi > 1bc0: callq ffffffff8102f680 <hv_ghcb_terminate> > 1bc5: nopw %cs:0x0(%rax,%rax,1) # end of function > > Reported-by: Arnd Bergmann <arnd@xxxxxxxx> > Link: https://lore.kernel.org/all/9698eff1-9680-4f0a-94de-590eaa923e94@xxxxxxxxxxxxxxxx/ > Cc: Josh Poimboeuf <jpoimboe@xxxxxxxxxx> > Cc: Michael Kelley <mikelley@xxxxxxxxxxxxx> > Signed-off-by: Guilherme G. Piccoli <gpiccoli@xxxxxxxxxx> > --- > > > V3: > - As per Michael / Josh advice (thanks!), added __noreturn to the > function definition as well. > > V2: > - Per Josh's suggestion (thanks!), added the function name to the > objtool global table. > > Thanks in advance for reviews/comments! > Cheers, > > Guilherme > > > arch/x86/hyperv/ivm.c | 2 +- > arch/x86/include/asm/mshyperv.h | 2 +- > tools/objtool/check.c | 1 + > 3 files changed, 3 insertions(+), 2 deletions(-) > > diff --git a/arch/x86/hyperv/ivm.c b/arch/x86/hyperv/ivm.c > index 1dbcbd9da74d..4f79dc76042d 100644 > --- a/arch/x86/hyperv/ivm.c > +++ b/arch/x86/hyperv/ivm.c > @@ -127,7 +127,7 @@ static enum es_result hv_ghcb_hv_call(struct ghcb *ghcb, u64 > exit_code, > return ES_OK; > } > > -void hv_ghcb_terminate(unsigned int set, unsigned int reason) > +void __noreturn hv_ghcb_terminate(unsigned int set, unsigned int reason) > { > u64 val = GHCB_MSR_TERM_REQ; > > diff --git a/arch/x86/include/asm/mshyperv.h b/arch/x86/include/asm/mshyperv.h > index 4c4c0ec3b62e..09c26e658bcc 100644 > --- a/arch/x86/include/asm/mshyperv.h > +++ b/arch/x86/include/asm/mshyperv.h > @@ -212,7 +212,7 @@ int hv_set_mem_host_visibility(unsigned long addr, int > numpages, bool visible); > void hv_ghcb_msr_write(u64 msr, u64 value); > void hv_ghcb_msr_read(u64 msr, u64 *value); > bool hv_ghcb_negotiate_protocol(void); > -void hv_ghcb_terminate(unsigned int set, unsigned int reason); > +void __noreturn hv_ghcb_terminate(unsigned int set, unsigned int reason); > #else > static inline void hv_ghcb_msr_write(u64 msr, u64 value) {} > static inline void hv_ghcb_msr_read(u64 msr, u64 *value) {} > diff --git a/tools/objtool/check.c b/tools/objtool/check.c > index f937be1afe65..4b5e03f61f1f 100644 > --- a/tools/objtool/check.c > +++ b/tools/objtool/check.c > @@ -209,6 +209,7 @@ static bool __dead_end_function(struct objtool_file *file, struct > symbol *func, > "do_task_dead", > "ex_handler_msr_mce", > "fortify_panic", > + "hv_ghcb_terminate", > "kthread_complete_and_exit", > "kthread_exit", > "kunit_try_catch_throw", > -- > 2.39.2 Reviewed-by: Michael Kelley <mikelley@xxxxxxxxxxxxx>
