On Fri, Mar 12, 2021 at 04:02:42PM +0100, Fabrice Gasnier wrote:

On 3/9/21 2:19 PM, William Breathitt Gray wrote:

quoted

+static ssize_t enums_available_show(const u32 *const enums,
+				    const size_t num_enums,
+				    const char *const strs[], char *buf)
+{
+	size_t len = 0;
+	size_t index;
+
+	for (index = 0; index < num_enums; index++)
+		len += sysfs_emit(buf + len, "%s\n", strs[enums[index]]);
+
+	return len;
+}
+
+static ssize_t strs_available_show(const struct counter_available *const avail,
+				   char *buf)
+{
+	size_t len = 0;
+	size_t index;
+
+	for (index = 0; index < avail->num_items; index++)
+		len += sysfs_emit(buf + len, "%s\n", avail->strs[index]);
+
+	return len;
+}

Hi William,

I was willing to do some testing on this series, on the stm32 counter
drivers, since we released few fixes around them.

I tried to apply this series against current testing branch, with few
patches applied (so it applies cleanly):
- dt-bindings: counter: add interrupt-counter binding
- counter: add IRQ or GPIO based counter
- counter: stm32-timer-cnt: fix ceiling miss-alignment with reload register
- counter: stm32-timer-cnt: fix ceiling write max value
 counter: stm32-timer-cnt: Report count function when SLAVE_MODE_DISABLED


For both the "stm32-lptimer-cnt" and "stm32-timer-cnt" drivers, I get a
warning message and stack dump in "sysfs_emit" when reading the
available functions from sysfs.
I started to do some testing on v8 of this series last week. I didn't
noticed that.

For both the "stm32-lptimer-cnt", there are 2 functions currently I get
1 stack dump. Only the "increase" function is printed correctly.

For the "stm32-timer-cnt", there are 4 functions currently, I get 3
stack dumps. Only the "increase" function is printed correctly

Sample log for "stm32-timer-cnt:

root@stm32mp1:/sys/devices/platform/soc/44000000.timer/44000000.timer:counter/counter0#
cat count0/function_available
[ 4689.195506] ------------[ cut here ]------------
[ 4689.198747] WARNING: CPU: 1 PID: 5841 at fs/sysfs/file.c:737
sysfs_emit+0x88/0x94
[ 4689.206233] invalid sysfs_emit: buf:f4a66208
[ 4689.210553] Modules linked in: sha256_generic libsha256 sha256_arm
cfg80211 panel_orisetech_otm8009a snd_soc_hdmi_codec
snd_soc_stm32_sai_sub stm32_lptimers
[ 4689.261444] CPU: 1 PID: 5841 Comm: cat Tainted: G        W
5.12.0-rc1 #534
[ 4689.268999] Hardware name: STM32 (Device Tree Support)
[ 4689.274166] [<c0310b38>] (unwind_backtrace) from [<c030b4ec>]
(show_stack+0x10/0x14)
[ 4689.281942] [<c030b4ec>] (show_stack) from [<c0fede70>]
(dump_stack+0xc0/0xd4)
[ 4689.289199] [<c0fede70>] (dump_stack) from [<c0345624>]
(__warn+0xec/0x148)
[ 4689.296194] [<c0345624>] (__warn) from [<c0fe9e90>]
(warn_slowpath_fmt+0x98/0xbc)
[ 4689.303714] [<c0fe9e90>] (warn_slowpath_fmt) from [<c0548ee0>]
(sysfs_emit+0x88/0x94)
[ 4689.311586] [<c0548ee0>] (sysfs_emit) from [<bf115de8>]
(counter_comp_available_show+0x11c/0x1a4 [counter])
[ 4689.321382] [<bf115de8>] (counter_comp_available_show [counter]) from
[<c0a21b70>] (dev_attr_show+0x18/0x48)
[ 4689.331263] [<c0a21b70>] (dev_attr_show) from [<c0549014>]
(sysfs_kf_seq_show+0x88/0xf0)
[ 4689.339394] [<c0549014>] (sysfs_kf_seq_show) from [<c04da6e8>]
(seq_read_iter+0x1a4/0x554)
[ 4689.347703] [<c04da6e8>] (seq_read_iter) from [<c04af6f0>]
(vfs_read+0x1ac/0x2c4)
[ 4689.355224] [<c04af6f0>] (vfs_read) from [<c04afc20>]
(ksys_read+0x64/0xdc)
[ 4689.362219] [<c04afc20>] (ksys_read) from [<c03000c0>]
(ret_fast_syscall+0x0/0x58)
[ 4689.369827] Exception stack(0xc7261fa8 to 0xc7261ff0)
[ 4689.374906] 1fa0:                   00000000 00020000 00000003
b6f35000 00020000 00000000
[ 4689.383126] 1fc0: 00000000 00020000 b6f56ce0 00000003 00000003
00000000 00020000 00000000
[ 4689.391344] 1fe0: 00000003 be8239a8 410bff27 4104c066
...
2 more stack dumps follow
...
[ 4689.810479] ---[ end trace 59ed79949efe984c ]---
increase

I get similar backtrace with other _available attributes:
$ cat signal0_action_available
$ cat signal1_action_available

Do you think I'm doing something wrong ?

I tested then "quadrature x4" on the timer driver... It seems all fine.

Best regards
Fabrice

quoted

+
+static ssize_t counter_comp_available_show(struct device *dev,
+					   struct device_attribute *attr,
+					   char *buf)
+{
+	const struct counter_attribute *const a = to_counter_attribute(attr);
+	const struct counter_count *const count = a->parent;
+	const struct counter_synapse *const synapse = a->comp.priv;
+	const struct counter_available *const avail = a->comp.priv;
+
+	switch (a->comp.type) {
+	case COUNTER_COMP_FUNCTION:
+		return enums_available_show(count->functions_list,
+					    count->num_functions,
+					    counter_function_str, buf);
+	case COUNTER_COMP_SYNAPSE_ACTION:
+		return enums_available_show(synapse->actions_list,
+					    synapse->num_actions,
+					    counter_synapse_action_str, buf);
+	case COUNTER_COMP_ENUM:
+		return strs_available_show(avail, buf);
+	case COUNTER_COMP_COUNT_MODE:
+		return enums_available_show(avail->enums, avail->num_items,
+					    counter_count_mode_str, buf);
+	default:
+		return -EINVAL;
+	}
+}

Hi Fabrice,

I can confirm that I'm hitting this regression as well with the
104-quad-8 driver. The warning seems to be caused by the
offset_in_page(buf) check in sysfs_emit(). It looks like the first loop
in enums_available_show() calls sysfs_emit() correctly, but subsequent
loops have an invalid buf offset.

The enums_available_show() callback is rather simple: call sysfs_emit()
for each enum string and increment buf by the length written each time.
I haven't modified this function since v8, so I am somewhat confused
about why the buf offset would be invalid here now. I wonder if there
has been a change somewhere else in the kernel that is causing
sysfs_emit() to now return an incorrect length.

William Breathitt Gray