Commit 126f21f0 authored by Thomas Gleixner's avatar Thomas Gleixner

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: default avatarThomas Gleixner <tglx@linutronix.de>
Reviewed-by: default avatarAlexandre Chartre <alexandre.chartre@oracle.com>
Acked-by: default avatarPeter Zijlstra <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20200505134340.902709267@linutronix.de

parent 0372007f
...@@ -8,7 +8,7 @@ ...@@ -8,7 +8,7 @@
#include <linux/kprobes.h> #include <linux/kprobes.h>
#include <linux/sched.h> #include <linux/sched.h>
notrace static nokprobe_inline noinstr static
unsigned int check_preemption_disabled(const char *what1, const char *what2) unsigned int check_preemption_disabled(const char *what1, const char *what2)
{ {
int this_cpu = raw_smp_processor_id(); int this_cpu = raw_smp_processor_id();
...@@ -37,6 +37,7 @@ unsigned int check_preemption_disabled(const char *what1, const char *what2) ...@@ -37,6 +37,7 @@ unsigned int check_preemption_disabled(const char *what1, const char *what2)
*/ */
preempt_disable_notrace(); preempt_disable_notrace();
instrumentation_begin();
if (!printk_ratelimit()) if (!printk_ratelimit())
goto out_enable; goto out_enable;
...@@ -45,6 +46,7 @@ unsigned int check_preemption_disabled(const char *what1, const char *what2) ...@@ -45,6 +46,7 @@ unsigned int check_preemption_disabled(const char *what1, const char *what2)
printk("caller is %pS\n", __builtin_return_address(0)); printk("caller is %pS\n", __builtin_return_address(0));
dump_stack(); dump_stack();
instrumentation_end();
out_enable: out_enable:
preempt_enable_no_resched_notrace(); preempt_enable_no_resched_notrace();
...@@ -52,16 +54,14 @@ unsigned int check_preemption_disabled(const char *what1, const char *what2) ...@@ -52,16 +54,14 @@ unsigned int check_preemption_disabled(const char *what1, const char *what2)
return this_cpu; 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", ""); return check_preemption_disabled("smp_processor_id", "");
} }
EXPORT_SYMBOL(debug_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); check_preemption_disabled("__this_cpu_", op);
} }
EXPORT_SYMBOL(__this_cpu_preempt_check); EXPORT_SYMBOL(__this_cpu_preempt_check);
NOKPROBE_SYMBOL(__this_cpu_preempt_check);
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