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lib/smp_processor_id: Move it into noinstr section 

That code is already not traceable. Move it into the noinstr section so the
objtool section validation does not trigger.

Annotate the warning code as "safe". While it might be not under all
circumstances, getting the information out is important enough.

Should this ever trigger from the sensitive code which is shielded against
instrumentation, e.g. low level entry, then the printk is the least of the
worries.

Addresses the objtool warnings:
 vmlinux.o: warning: objtool: context_tracking_recursion_enter()+0x7: call to __this_cpu_preempt_check() leaves .noinstr.text section
 vmlinux.o: warning: objtool: __context_tracking_exit()+0x17: call to __this_cpu_preempt_check() leaves .noinstr.text section
 vmlinux.o: warning: objtool: __context_tracking_enter()+0x2a: call to __this_cpu_preempt_check() leaves .noinstr.text section

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Alexandre Chartre <alexandre.chartre@oracle.com>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20200505134340.902709267@linutronix.de
This commit is contained in:
Thomas Gleixner 2020-03-10 23:47:39 +01:00
parent 0372007f5a
commit 126f21f0e8
1 changed files with 5 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

10
lib/smp_processor_id.c
View File

@ -8,7 +8,7 @@
#include <linux/kprobes.h>
#include <linux/sched.h>
notrace static nokprobe_inline
noinstr static
unsigned int check_preemption_disabled(const char *what1, const char *what2)
{
int this_cpu = raw_smp_processor_id();
@ -37,6 +37,7 @@ unsigned int check_preemption_disabled(const char *what1, const char *what2)
*/
preempt_disable_notrace();
instrumentation_begin();
if (!printk_ratelimit())
goto out_enable;
@ -45,6 +46,7 @@ unsigned int check_preemption_disabled(const char *what1, const char *what2)
printk("caller is %pS\n", __builtin_return_address(0));
dump_stack();
instrumentation_end();
out_enable:
preempt_enable_no_resched_notrace();
@ -52,16 +54,14 @@ out:
return this_cpu;
}
notrace unsigned int debug_smp_processor_id(void)
noinstr unsigned int debug_smp_processor_id(void)
{
return check_preemption_disabled("smp_processor_id", "");
}
EXPORT_SYMBOL(debug_smp_processor_id);
NOKPROBE_SYMBOL(debug_smp_processor_id);
notrace void __this_cpu_preempt_check(const char *op)
noinstr void __this_cpu_preempt_check(const char *op)
{
check_preemption_disabled("__this_cpu_", op);
}
EXPORT_SYMBOL(__this_cpu_preempt_check);
NOKPROBE_SYMBOL(__this_cpu_preempt_check);