From a1a5482a2c6e38a3ebed32e571625c56a8cc41a6 Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Fri, 17 Jun 2022 16:52:06 +0200 Subject: x86/extable: Fix ex_handler_msr() print condition On Fri, Jun 17, 2022 at 02:08:52PM +0300, Stephane Eranian wrote: > Some changes to the way invalid MSR accesses are reported by the > kernel is causing some problems with messages printed on the > console. > > We have seen several cases of ex_handler_msr() printing invalid MSR > accesses once but the callstack multiple times causing confusion on > the console. > The problem here is that another earlier commit (5.13): > > a358f40600b3 ("once: implement DO_ONCE_LITE for non-fast-path "do once" functionality") > > Modifies all the pr_*_once() calls to always return true claiming > that no caller is ever checking the return value of the functions. > > This is why we are seeing the callstack printed without the > associated printk() msg. Extract the ONCE_IF(cond) part into __ONCE_LTE_IF() and use that to implement DO_ONCE_LITE_IF() and fix the extable code. Fixes: a358f40600b3 ("once: implement DO_ONCE_LITE for non-fast-path "do once" functionality") Reported-by: Stephane Eranian Signed-off-by: Peter Zijlstra (Intel) Tested-by: Stephane Eranian Link: https://lkml.kernel.org/r/YqyVFsbviKjVGGZ9@worktop.programming.kicks-ass.net --- include/linux/once_lite.h | 20 ++++++++++++++++---- 1 file changed, 16 insertions(+), 4 deletions(-) (limited to 'include/linux/once_lite.h') diff --git a/include/linux/once_lite.h b/include/linux/once_lite.h index 861e606b820f..b7bce4983638 100644 --- a/include/linux/once_lite.h +++ b/include/linux/once_lite.h @@ -9,15 +9,27 @@ */ #define DO_ONCE_LITE(func, ...) \ DO_ONCE_LITE_IF(true, func, ##__VA_ARGS__) -#define DO_ONCE_LITE_IF(condition, func, ...) \ + +#define __ONCE_LITE_IF(condition) \ ({ \ static bool __section(".data.once") __already_done; \ - bool __ret_do_once = !!(condition); \ + bool __ret_cond = !!(condition); \ + bool __ret_once = false; \ \ - if (unlikely(__ret_do_once && !__already_done)) { \ + if (unlikely(__ret_cond && !__already_done)) { \ __already_done = true; \ - func(__VA_ARGS__); \ + __ret_once = true; \ } \ + unlikely(__ret_once); \ + }) + +#define DO_ONCE_LITE_IF(condition, func, ...) \ + ({ \ + bool __ret_do_once = !!(condition); \ + \ + if (__ONCE_LITE_IF(__ret_do_once)) \ + func(__VA_ARGS__); \ + \ unlikely(__ret_do_once); \ }) -- cgit v1.2.3-59-g8ed1b