Re: [PATCH V3 02/10] ras: acpi/apei: cper: generic error data entry v3 per ACPI 6.1

From: Russell King - ARM Linux
Date: Tue Oct 11 2016 - 15:03:19 EST


On Fri, Oct 07, 2016 at 03:31:14PM -0600, Tyler Baicar wrote:
> +static void cper_estatus_print_section_v300(const char *pfx,
> + const struct acpi_hest_generic_data_v300 *gdata)
> +{
> + __u8 hour, min, sec, day, mon, year, century, *timestamp;
> +
> + if (gdata->validation_bits & ACPI_HEST_GEN_VALID_TIMESTAMP) {
> + timestamp = (__u8 *)&(gdata->time_stamp);
> + memcpy(&sec, timestamp, 1);
> + memcpy(&min, timestamp + 1, 1);
> + memcpy(&hour, timestamp + 2, 1);
> + memcpy(&day, timestamp + 4, 1);
> + memcpy(&mon, timestamp + 5, 1);
> + memcpy(&year, timestamp + 6, 1);
> + memcpy(&century, timestamp + 7, 1);

This is utterly silly. Why are you using memcpy() to access individual
bytes of a u8 pointer? What's wrong with:

sec = timestamp[0];
min = timestamp[1];
hour = timestamp[2];
day = timestamp[4];
mon = timestamp[5];
year = timestamp[6];
century = timestamp[7];

or even do the conversion here:

sec = bcd2bin(timestamp[0]);
... etc ...

> + printk("%stime: ", pfx);
> + printk("%7s", 0x01 & *(timestamp + 3) ? "precise" : "");
> + printk(" %02d:%02d:%02d %02d%02d-%02d-%02d\n",
> + bcd2bin(hour), bcd2bin(min), bcd2bin(sec),
> + bcd2bin(century), bcd2bin(year), bcd2bin(mon),
> + bcd2bin(day));
> + }

It's also a good idea to (as much as possible) keep to single printk()
statements - which makes the emission of the string more atomic wrt
other CPUs and contexts. So, this should probably become (with the
conversion being done at the assignment of sec etc):

printk("%stime: %7s %02d:%02d:%02d %02d%02d-%02d-%02d\n",
pfx, 0x01 & timestamp[3] ? "precise" : "",
hour, min, sec, century, year, mon, day);

which, IMHO, looks a lot nicer and doesn't risk some other printk()
getting between each individual part of the line.

> +}
> +
> static void cper_estatus_print_section(
> - const char *pfx, const struct acpi_hest_generic_data *gdata, int sec_no)
> + const char *pfx, struct acpi_hest_generic_data *gdata, int sec_no)
> {
> uuid_le *sec_type = (uuid_le *)gdata->section_type;
> __u16 severity;
> char newpfx[64];
>
> + if ((gdata->revision >> 8) >= 0x03)
> + cper_estatus_print_section_v300(pfx,
> + (const struct acpi_hest_generic_data_v300 *)gdata);
> +
> severity = gdata->error_severity;
> printk("%s""Error %d, type: %s\n", pfx, sec_no,
> cper_severity_str(severity));

Not sure why you have the "" here - %sError works just as well and the
"" is just obfuscation - the compiler will eliminate the double-double
quote and merge the strings anyway.

--
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