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| author | Gautham R. Shenoy <ego@linux.vnet.ibm.com> | 2017-11-07 13:39:29 +0530 |
|---|---|---|
| committer | Rafael J. Wysocki <rafael.j.wysocki@intel.com> | 2017-11-08 23:41:25 +0100 |
| commit | f7bc9b209e27c0b617378400136cc663a6314d0c (patch) | |
| tree | b54c5275965162f7df59cdf84c0c1ff82c7f87b4 | |
| parent | 0011c6da99ddc428a35456d5819d6e476005f6f2 (diff) | |
| download | linux-f7bc9b209e27c0b617378400136cc663a6314d0c.tar.bz2 | |
cpufreq: stats: Handle the case when trans_table goes beyond PAGE_SIZE
On platforms with large number of Pstates, the transition table, which
is a NxN matrix, can overflow beyond the PAGE_SIZE boundary.
This can be seen on POWER9 which has 100+ Pstates.
As a result, each time the trans_table is read for any of the CPUs, we
will get the following error.
---------------------------------------------------
fill_read_buffer: show+0x0/0xa0 returned bad count
---------------------------------------------------
This patch ensures that in case of an overflow, we print a warning
once in the dmesg and return FILE TOO LARGE error for this and all
subsequent accesses of trans_table.
Signed-off-by: Gautham R. Shenoy <ego@linux.vnet.ibm.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
| -rw-r--r-- | Documentation/cpu-freq/cpufreq-stats.txt | 3 | ||||
| -rw-r--r-- | drivers/cpufreq/cpufreq_stats.c | 7 |
2 files changed, 8 insertions, 2 deletions
diff --git a/Documentation/cpu-freq/cpufreq-stats.txt b/Documentation/cpu-freq/cpufreq-stats.txt index 2bbe207354ed..a873855c811d 100644 --- a/Documentation/cpu-freq/cpufreq-stats.txt +++ b/Documentation/cpu-freq/cpufreq-stats.txt @@ -90,6 +90,9 @@ Freq_i to Freq_j. Freq_i is in descending order with increasing rows and Freq_j is in descending order with increasing columns. The output here also contains the actual freq values for each row and column for better readability. +If the transition table is bigger than PAGE_SIZE, reading this will +return an -EFBIG error. + -------------------------------------------------------------------------------- <mysystem>:/sys/devices/system/cpu/cpu0/cpufreq/stats # cat trans_table From : To diff --git a/drivers/cpufreq/cpufreq_stats.c b/drivers/cpufreq/cpufreq_stats.c index e75880eb037d..1e55b5790853 100644 --- a/drivers/cpufreq/cpufreq_stats.c +++ b/drivers/cpufreq/cpufreq_stats.c @@ -118,8 +118,11 @@ static ssize_t show_trans_table(struct cpufreq_policy *policy, char *buf) break; len += snprintf(buf + len, PAGE_SIZE - len, "\n"); } - if (len >= PAGE_SIZE) - return PAGE_SIZE; + + if (len >= PAGE_SIZE) { + pr_warn_once("cpufreq transition table exceeds PAGE_SIZE. Disabling\n"); + return -EFBIG; + } return len; } cpufreq_freq_attr_ro(trans_table); |