From: "Guilherme G. Piccoli" <gpiccoli@igalia.com>
Date: Wed, 12 Apr 2023 16:49:41 -0700
Patch-mainline: v6.4-rc1
Subject: x86/hyperv: Mark hv_ghcb_terminate() as noreturn
Git-commit: 611d4c716db0141cfc436994dc5aff1d69c924ad
References: bsc#1206453
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@arndb.de>
Signed-off-by: Guilherme G. Piccoli <gpiccoli@igalia.com>
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Michael Kelley <mikelley@microsoft.com>
Link: https://lore.kernel.org/r/32453a703dfcf0d007b473c9acbf70718222b74b.1681342859.git.jpoimboe@kernel.org
Acked-by: Olaf Hering <ohering@suse.de>
---
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(-)
--- a/arch/x86/hyperv/ivm.c
+++ b/arch/x86/hyperv/ivm.c
@@ -129,7 +129,7 @@ static enum es_result hv_ghcb_hv_call(st
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;
--- a/arch/x86/include/asm/mshyperv.h
+++ b/arch/x86/include/asm/mshyperv.h
@@ -221,7 +221,7 @@ int hv_unmap_ioapic_interrupt(int ioapic
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);
void hv_vtom_init(void);
#else
static inline void hv_ghcb_msr_write(u64 msr, u64 value) {}
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -190,6 +190,7 @@ static bool __dead_end_function(struct o
"do_exit",
"do_task_dead",
"fortify_panic",
+ "hv_ghcb_terminate",
"kunit_try_catch_throw",
"lbug_with_loc",
"machine_real_restart",