Commit-ID: 11e86dc7f2746210f9c7dc10deaa7658f8dc8350 Gitweb: https://git.kernel.org/tip/11e86dc7f2746210f9c7dc10deaa7658f8dc8350 Author: Ingo Molnar <mi...@kernel.org> AuthorDate: Thu, 25 Apr 2019 11:50:39 +0200 Committer: Ingo Molnar <mi...@kernel.org> CommitDate: Thu, 25 Apr 2019 12:00:44 +0200
x86/paravirt: Detect over-sized patching bugs in paravirt_patch_call() paravirt_patch_call() currently handles patching failures inconsistently: we generate a warning in the retpoline case, but don't in other cases where we might end up with a non-working kernel as well. So just convert it all to a BUG_ON(), these patching calls are *not* supposed to fail, and if they do we want to know it immediately. This also makes the kernel smaller and removes an #ifdef ugly. I tried it with a richly paravirt-enabled kernel and no patching bugs were detected. Cc: Andy Lutomirski <l...@kernel.org> Cc: Borislav Petkov <b...@alien8.de> Cc: Brian Gerst <brge...@gmail.com> Cc: Denys Vlasenko <dvlas...@redhat.com> Cc: H. Peter Anvin <h...@zytor.com> Cc: Juergen Gross <jgr...@suse.com> Cc: Linus Torvalds <torva...@linux-foundation.org> Cc: Peter Zijlstra <pet...@infradead.org> Cc: Thomas Gleixner <t...@linutronix.de> Link: http://lkml.kernel.org/r/20190425095039.gc115...@gmail.com Signed-off-by: Ingo Molnar <mi...@kernel.org> --- arch/x86/kernel/paravirt.c | 16 ++++++++-------- 1 file changed, 8 insertions(+), 8 deletions(-) diff --git a/arch/x86/kernel/paravirt.c b/arch/x86/kernel/paravirt.c index 7f9121f2fdac..544d386ded45 100644 --- a/arch/x86/kernel/paravirt.c +++ b/arch/x86/kernel/paravirt.c @@ -73,21 +73,21 @@ struct branch { static unsigned paravirt_patch_call(void *insnbuf, const void *target, unsigned long addr, unsigned len) { + const int call_len = 5; struct branch *b = insnbuf; - unsigned long delta = (unsigned long)target - (addr+5); + unsigned long delta = (unsigned long)target - (addr+call_len); - if (len < 5) { -#ifdef CONFIG_RETPOLINE - WARN_ONCE(1, "Failing to patch indirect CALL in %ps\n", (void *)addr); -#endif - return len; /* call too long for patch site */ + if (len < call_len) { + pr_warn("paravirt: Failed to patch indirect CALL at %ps\n", (void *)addr); + /* Kernel might not be viable if patching fails, bail out: */ + BUG_ON(1); } b->opcode = 0xe8; /* call */ b->delta = delta; - BUILD_BUG_ON(sizeof(*b) != 5); + BUILD_BUG_ON(sizeof(*b) != call_len); - return 5; + return call_len; } #ifdef CONFIG_PARAVIRT_XXL
