[PATCH] regulator: Fix regulator_summary for deviceless consumers

From: Leonard Crestez
Date: Tue Feb 14 2017 - 10:32:49 EST

It is allowed to call regulator_get with a NULL dev argument
(_regulator_get explicitly checks for it) but this causes an error later
when printing /sys/kernel/debug/regulator_summary.

Fix this by explicitly handling "deviceless" consumers in the debugfs code.

This fixes errors like this:

root@leonard-imx6:~# cat /sys/kernel/debug/regulator/regulator_summary
Unable to handle kernel NULL pointer dereference at virtual address 0000015c
pgd = a8bd4000
[0000015c] *pgd=a8c15831, *pte=00000000, *ppte=00000000
Internal error: Oops: 17 [#2] PREEMPT SMP ARM
Modules linked in:
CPU: 0 PID: 673 Comm: cat Tainted: G D 4.9.5-01680-g3d4992e #18
Hardware name: Freescale i.MX6 SoloLite (Device Tree)
task: a8e07700 task.stack: a8c2a000
PC is at regulator_summary_show_subtree+0x1b4/0x274
LR is at seq_puts+0x48/0x58
pc : [<8044eb90>] lr : [<8021f82c>] psr: 800e0013
sp : a8c2bdf0 ip : 00000000 fp : 80c52720
r10: 80c21fc0 r9 : 00000004 r8 : 80f253a4
r7 : a821601c r6 : a874d400 r5 : a8216000 r4 : a8b1c000
r3 : 80c21fc0 r2 : 00000004 r1 : 80c52720 r0 : a8b1c000
Flags: Nzcv IRQs on FIQs on Mode SVC_32 ISA ARM Segment user
Control: 10c53c7d Table: a8bd404a DAC: 00000055
Process cat (pid: 673, stack limit = 0xa8c2a210)
Stack: (0xa8c2bdf0 to 0xa8c2c000)
bde0: 0000001e 80c167f0 00000001 00000002
be00: 00000000 00000000 00000004 0000001b 10624dd3 00000000 a80ca35c a8c2be64
be20: 8044ec50 a8190dac 00020000 a8216060 a8b1c000 8044ec50 a8c2bf80 00000001
be40: 00000000 a8c2be98 00020000 8044ec78 a8216060 804b942c 80c524f8 a8c2bf80
be60: 00000001 a80ca35c a82161ac 00000000 a8b1c000 a87cd240 a87cd240 8044dc6c
be80: a8b1c000 8021efc4 a8bd5db8 76e73000 a8b1c030 00000000 00000000 00000000
bea0: a8c2bf80 80177644 a60017f8 8021ee2c a87cd240 76e73000 00020000 a8c2bf80
bec0: 80a48d9c 00000000 00020000 80356080 a8bd3bc0 00000001 00000800 a87cd240
bee0: 80356034 00020000 a8c2bf80 00000000 00020000 801fbf4c 76e72004 a8c2bfb0
bf00: 00002710 76fca000 76faed14 801012b0 00000000 80114820 00022000 00022000
bf20: a8c2bf8c 00000003 00000000 a8b488c0 76e72000 00000022 00000073 801e44a4
bf40: 00076e72 a87cd240 76e73000 00020000 a8c2bf80 00000000 00020000 801fcd08
bf60: 00022000 00000003 a87cd240 a87cd240 00000000 00000000 76e73000 801fdb00
bf80: 00000000 00000000 00000000 00020000 00020000 76e73000 00000003 80107724
bfa0: a8c2a000 80107580 00020000 00020000 00000003 76e73000 00020000 0002a3fc
bfc0: 00020000 00020000 76e73000 00000003 7fffe000 00000000 76ffe000 00020000
bfe0: 00000000 7ea10b64 00014b14 76f52770 600e0010 00000003 00000000 00000000
[<8044eb90>] (regulator_summary_show_subtree) from [<8044ec78>] (regulator_summary_show_roots+0x28/0x30)
[<8044ec78>] (regulator_summary_show_roots) from [<804b942c>] (class_for_each_device+0x4c/0xb4)
[<804b942c>] (class_for_each_device) from [<8044dc6c>] (regulator_summary_show+0x3c/0x48)
[<8044dc6c>] (regulator_summary_show) from [<8021efc4>] (seq_read+0x198/0x4a0)
[<8021efc4>] (seq_read) from [<80356080>] (full_proxy_read+0x4c/0x6c)
[<80356080>] (full_proxy_read) from [<801fbf4c>] (__vfs_read+0x1c/0x10c)
[<801fbf4c>] (__vfs_read) from [<801fcd08>] (vfs_read+0x8c/0x118)
[<801fcd08>] (vfs_read) from [<801fdb00>] (SyS_read+0x3c/0x90)
[<801fdb00>] (SyS_read) from [<80107580>] (ret_fast_syscall+0x0/0x34)
Code: e59f80c4 e1a0100b e59d2018 e1a00004 (e59ce15c)
---[ end trace eca2c2e6d835da26 ]---

Signed-off-by: Leonard Crestez <leonard.crestez@xxxxxxx>
---
drivers/regulator/core.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)

Some quick grepping only finds a very small number of users for
regulator_get(NULL, ...), it might make more sense to simply require
always passing a device pointer. I found this because there was a patch
in the freescale imx tree which did this and in our case it was easier
to just fix the consumer.

Here are the current obvious upstream users:
$ git grep 'regulator_get(NULL'
arch/arm/mach-davinci/da850.c: cvdd = regulator_get(NULL, "cvdd");
arch/arm/mach-pxa/em-x270.c: em_x270_usb_ldo = regulator_get(NULL, "vcc usb");
drivers/cpufreq/pxa2xx-cpufreq.c: vcc_core = regulator_get(NULL, "vcc_core");
drivers/cpufreq/s3c2416-cpufreq.c: s3c_freq->vddarm = regulator_get(NULL, "vddarm");
drivers/cpufreq/s3c64xx-cpufreq.c: vddarm = regulator_get(NULL, "vddarm");
drivers/cpufreq/s5pv210-cpufreq.c: arm_regulator = regulator_get(NULL, "vddarm");
drivers/cpufreq/s5pv210-cpufreq.c: int_regulator = regulator_get(NULL, "vddint");

diff --git a/drivers/regulator/core.c b/drivers/regulator/core.c
index 04baac9..6631954 100644
--- a/drivers/regulator/core.c
+++ b/drivers/regulator/core.c
@@ -4391,12 +4391,13 @@ static void regulator_summary_show_subtree(struct seq_file *s,
seq_puts(s, "\n");

list_for_each_entry(consumer, &rdev->consumer_list, list) {
- if (consumer->dev->class == &regulator_class)
+ if (consumer->dev && consumer->dev->class == &regulator_class)
continue;

seq_printf(s, "%*s%-*s ",
(level + 1) * 3 + 1, "",
- 30 - (level + 1) * 3, dev_name(consumer->dev));
+ 30 - (level + 1) * 3,
+ consumer->dev ? dev_name(consumer->dev) : "deviceless");

switch (rdev->desc->type) {
case REGULATOR_VOLTAGE:
--
2.7.4