The following commit has been merged into the ras/core branch of tip:
Commit-ID: 75581a203e63210aabb1336c8c9cb65a7858b596
Gitweb: https://git.kernel.org/tip/75581a203e63210aabb1336c8c9cb65a7858b596
Author: Borislav Petkov <bp@xxxxxxx>
AuthorDate: Tue, 02 Nov 2021 08:14:44 +01:00
Committer: Borislav Petkov <bp@xxxxxxx>
CommitterDate: Mon, 13 Dec 2021 14:13:35 +01:00
x86/mce: Move the tainting outside of the noinstr region
add_taint() is yet another external facility which the #MC handler
calls. Move that tainting call into the instrumentation-allowed part of
the handler.
Fixes
vmlinux.o: warning: objtool: do_machine_check()+0x617: call to add_taint() leaves .noinstr.text section
While at it, allow instrumentation around the mce_log() call.
Fixes
vmlinux.o: warning: objtool: do_machine_check()+0x690: call to mce_log() leaves .noinstr.text section
Signed-off-by: Borislav Petkov <bp@xxxxxxx>
Link: https://lore.kernel.org/r/20211208111343.8130-11-bp@xxxxxxxxx
---
arch/x86/kernel/cpu/mce/core.c | 41 ++++++++++++++++++++-------------
1 file changed, 26 insertions(+), 15 deletions(-)
diff --git a/arch/x86/kernel/cpu/mce/core.c b/arch/x86/kernel/cpu/mce/core.c
index 53b4cfc..044c94b 100644
--- a/arch/x86/kernel/cpu/mce/core.c
+++ b/arch/x86/kernel/cpu/mce/core.c
@@ -1180,13 +1180,14 @@ static noinstr bool mce_check_crashing_cpu(void)
return false;
}
-static void __mc_scan_banks(struct mce *m, struct pt_regs *regs, struct mce *final,
- unsigned long *toclear, unsigned long *valid_banks,
- int no_way_out, int *worst)
+static __always_inline int
+__mc_scan_banks(struct mce *m, struct pt_regs *regs, struct mce *final,
+ unsigned long *toclear, unsigned long *valid_banks, int no_way_out,
+ int *worst)
{
struct mce_bank *mce_banks = this_cpu_ptr(mce_banks_array);
struct mca_config *cfg = &mca_cfg;
- int severity, i;
+ int severity, i, taint = 0;
for (i = 0; i < this_cpu_read(mce_num_banks); i++) {
__clear_bit(i, toclear);
@@ -1213,7 +1214,7 @@ static void __mc_scan_banks(struct mce *m, struct pt_regs *regs, struct mce *fin
continue;
/* Set taint even when machine check was not enabled. */
- add_taint(TAINT_MACHINE_CHECK, LOCKDEP_NOW_UNRELIABLE);
+ taint++;
severity = mce_severity(m, regs, cfg->tolerant, NULL, true);
@@ -1236,7 +1237,13 @@ static void __mc_scan_banks(struct mce *m, struct pt_regs *regs, struct mce *fin
/* assuming valid severity level != 0 */
m->severity = severity;
+ /*
+ * Enable instrumentation around the mce_log() call which is
+ * done in #MC context, where instrumentation is disabled.
+ */
+ instrumentation_begin();
mce_log(m);
+ instrumentation_end();
if (severity > *worst) {
*final = *m;
@@ -1246,6 +1253,8 @@ static void __mc_scan_banks(struct mce *m, struct pt_regs *regs, struct mce *fin
/* mce_clear_state will clear *final, save locally for use later */
*m = *final;
+
+ return taint;
}
static void kill_me_now(struct callback_head *ch)
@@ -1362,7 +1371,7 @@ static noinstr void unexpected_machine_check(struct pt_regs *regs)
*/
noinstr void do_machine_check(struct pt_regs *regs)
{
- int worst = 0, order, no_way_out, kill_current_task, lmce;
+ int worst = 0, order, no_way_out, kill_current_task, lmce, taint = 0;
DECLARE_BITMAP(valid_banks, MAX_NR_BANKS) = { 0 };
DECLARE_BITMAP(toclear, MAX_NR_BANKS) = { 0 };
struct mca_config *cfg = &mca_cfg;
@@ -1441,7 +1450,7 @@ noinstr void do_machine_check(struct pt_regs *regs)
order = mce_start(&no_way_out);
}
- __mc_scan_banks(&m, regs, final, toclear, valid_banks, no_way_out, &worst);
+ taint = __mc_scan_banks(&m, regs, final, toclear, valid_banks, no_way_out, &worst);
if (!no_way_out)
mce_clear_state(toclear);
@@ -1473,17 +1482,19 @@ noinstr void do_machine_check(struct pt_regs *regs)
}
}
- if (worst != MCE_AR_SEVERITY && !kill_current_task)
- goto out;
-
/*
- * Enable instrumentation around the external facilities like
- * task_work_add() (via queue_task_work()), fixup_exception() etc.
- * For now, that is. Fixing this properly would need a lot more involved
- * reorganization.
+ * Enable instrumentation around the external facilities like task_work_add()
+ * (via queue_task_work()), fixup_exception() etc. For now, that is. Fixing this
+ * properly would need a lot more involved reorganization.
*/
instrumentation_begin();
+ if (taint)
+ add_taint(TAINT_MACHINE_CHECK, LOCKDEP_NOW_UNRELIABLE);
+
+ if (worst != MCE_AR_SEVERITY && !kill_current_task)
+ goto out;
+
/* Fault was in user mode and we need to take some action */
if ((m.cs & 3) == 3) {
/* If this triggers there is no way to recover. Die hard. */
@@ -1513,9 +1524,9 @@ noinstr void do_machine_check(struct pt_regs *regs)
queue_task_work(&m, msg, kill_me_never);
}
+out:
instrumentation_end();
-out:
mce_wrmsrl(MSR_IA32_MCG_STATUS, 0);
}
EXPORT_SYMBOL_GPL(do_machine_check);
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