[PATCH 13/13] x86/microcode/intel: Fix printing of microcode blobs in show_saved_mc()

Borislav Petkov
2015-02-24T10:38:23Z

From: Borislav Petkov <bp@suse.de>

When doing

echo 1 > /sys/devices/system/cpu/microcode/reload

in order to reload microcode, I get:

microcode: Total microcode saved: 1
BUG: using smp_processor_id() in preemptible [00000000] code: bash/2606
caller is debug_smp_processor_id+0x17/0x20
CPU: 1 PID: 2606 Comm: bash Not tainted 3.19.0-rc7+ #9
Hardware name: LENOVO 2320CTO/2320CTO, BIOS G2ET86WW (2.06 ) 11/13/2012
ffffffff81a4266d ffff8802131db808 ffffffff81666588 0000000000000007
0000000000000001 ffff8802131db838 ffffffff812e6eef ffff8802131db868
00000000000306a9 0000000000000010 0000000000000015 ffff8802131db848
Call Trace:
dump_stack
check_preemption_disabled
debug_smp_processor_id
show_saved_mc
? save_microcode.constprop.8
save_mc_for_early
? print_context_stack
? dump_trace
? __bfs
? mark_held_locks
? get_page_from_freelist
? trace_hardirqs_on_caller
? trace_hardirqs_on
? __alloc_pages_nodemask
? __get_vm_area_node
? map_vm_area
? __vmalloc_node_range
? generic_load_microcode
generic_load_microcode
? microcode_fini_cpu
request_microcode_fw
reload_store
dev_attr_store
sysfs_kf_write
kernfs_fop_write
vfs_write
? sysret_check
SyS_write
system_call_fastpath
microcode: CPU1: sig=0x306a9, pf=0x10, rev=0x15
microcode: mc_saved[0]: sig=0x306a9, pf=0x12, rev=0x1b, toal size=0x3000, date = 2014-05-29

because we're using smp_processor_id() in preemtible context. And we
don't really need to use it there because the microcode container we're
dumping is global and CPU-specific info is irrelevant.

While at it, make pr_* stuff use "microcode: " prefix for easier
grepping and document how to enable the DEBUG build.

Signed-off-by: Borislav Petkov <bp@suse.de>
---
arch/x86/kernel/cpu/microcode/intel_early.c | 14 ++++++++++++--
1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/cpu/microcode/intel_early.c b/arch/x86/kernel/cpu/microcode/intel_early.c
index 2fa9ad39e0e5..079d8d41fba3 100644
--- a/arch/x86/kernel/cpu/microcode/intel_early.c
+++ b/arch/x86/kernel/cpu/microcode/intel_early.c
@@ -16,6 +16,14 @@
* as published by the Free Software Foundation; either version
* 2 of the License, or (at your option) any later version.
*/
+
+/*
+ * This needs to be before all headers so that pr_debug in printk.h doesn't turn
+ * printk calls into no_printk().
+ *
+ *#define DEBUG
+ */
+
#include <linux/module.h>
#include <linux/mm.h>
#include <linux/slab.h>
@@ -28,6 +36,9 @@
#include <asm/tlbflush.h>
#include <asm/setup.h>

+#undef pr_fmt
+#define pr_fmt(fmt) "microcode: " fmt
+
static unsigned long mc_saved_in_initrd[MAX_UCODE_COUNT];
static struct mc_saved_data {
unsigned int mc_saved_count;
@@ -398,8 +409,7 @@ static void __ref show_saved_mc(void)
sig = uci.cpu_sig.sig;
pf = uci.cpu_sig.pf;
rev = uci.cpu_sig.rev;
- pr_debug("CPU%d: sig=0x%x, pf=0x%x, rev=0x%x\n",
- smp_processor_id(), sig, pf, rev);
+ pr_debug("CPU: sig=0x%x, pf=0x%x, rev=0x%x\n", sig, pf, rev);

for (i = 0; i < mc_saved_data.mc_saved_count; i++) {
struct microcode_header_intel *mc_saved_header;
--
2.2.0.33.gc18b867