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x86/extable: Fix ex_handler_msr() print condition

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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):
>
> a358f40600 ("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: a358f40600 ("once: implement DO_ONCE_LITE for non-fast-path "do once" functionality")
Reported-by: Stephane Eranian <eranian@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: Stephane Eranian <eranian@google.com>
Link: https://lkml.kernel.org/r/YqyVFsbviKjVGGZ9@worktop.programming.kicks-ass.net
This commit is contained in:
Peter Zijlstra 2022-06-17 16:52:06 +02:00
parent 09d09531a5
commit a1a5482a2c
2 changed files with 25 additions and 11 deletions
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16
arch/x86/mm/extable.c
View File

@ -94,16 +94,18 @@ static bool ex_handler_copy(const struct exception_table_entry *fixup,
static bool ex_handler_msr(const struct exception_table_entry *fixup,
struct pt_regs *regs, bool wrmsr, bool safe, int reg)
{
if (!safe && wrmsr &&
pr_warn_once("unchecked MSR access error: WRMSR to 0x%x (tried to write 0x%08x%08x) at rIP: 0x%lx (%pS)\n",
(unsigned int)regs->cx, (unsigned int)regs->dx,
(unsigned int)regs->ax, regs->ip, (void *)regs->ip))
if (__ONCE_LITE_IF(!safe && wrmsr)) {
pr_warn("unchecked MSR access error: WRMSR to 0x%x (tried to write 0x%08x%08x) at rIP: 0x%lx (%pS)\n",
(unsigned int)regs->cx, (unsigned int)regs->dx,
(unsigned int)regs->ax, regs->ip, (void *)regs->ip);
show_stack_regs(regs);
}
if (!safe && !wrmsr &&
pr_warn_once("unchecked MSR access error: RDMSR from 0x%x at rIP: 0x%lx (%pS)\n",
(unsigned int)regs->cx, regs->ip, (void *)regs->ip))
if (__ONCE_LITE_IF(!safe && !wrmsr)) {
pr_warn("unchecked MSR access error: RDMSR from 0x%x at rIP: 0x%lx (%pS)\n",
(unsigned int)regs->cx, regs->ip, (void *)regs->ip);
show_stack_regs(regs);
}
if (!wrmsr) {
/* Pretend that the read succeeded and returned 0. */

20
include/linux/once_lite.h
View File

@ -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_cond = !!(condition); \
bool __ret_once = false; \
\
if (unlikely(__ret_cond && !__already_done)) { \
__already_done = true; \
__ret_once = true; \
} \
unlikely(__ret_once); \
})
#define DO_ONCE_LITE_IF(condition, func, ...) \
({ \
bool __ret_do_once = !!(condition); \
\
if (unlikely(__ret_do_once && !__already_done)) { \
__already_done = true; \
if (__ONCE_LITE_IF(__ret_do_once)) \
func(__VA_ARGS__); \
} \
\
unlikely(__ret_do_once); \
})