On Thu, 7 Jan 2021 10:32:45 +0200
"Tzvetomir Stoyanov (VMware)" <tz.stoyanov@xxxxxxxxx> wrote:
> These new APIs can be used to read integer from frtace file and to open
> ftrace file:
> tracefs_instance_file_read_int();
> tracefs_instance_file_open();
>
> Signed-off-by: Tzvetomir Stoyanov (VMware) <tz.stoyanov@xxxxxxxxx>
> ---
> include/tracefs.h | 6 ++++-
> src/tracefs-instance.c | 59 ++++++++++++++++++++++++++++++++++++++++--
> 2 files changed, 62 insertions(+), 3 deletions(-)
>
> diff --git a/include/tracefs.h b/include/tracefs.h
> index 3d70aca..460fa4c 100644
> --- a/include/tracefs.h
> +++ b/include/tracefs.h
> @@ -29,7 +29,11 @@ char *tracefs_instance_get_dir(struct tracefs_instance *instance);
> int tracefs_instance_file_write(struct tracefs_instance *instance,
> const char *file, const char *str);
> char *tracefs_instance_file_read(struct tracefs_instance *instance,
> - char *file, int *psize);
> + const char *file, int *psize);
> +int tracefs_instance_file_read_int(struct tracefs_instance *instance,
> + const char *file, long long *res);
> +int tracefs_instance_file_open(struct tracefs_instance *instance,
> + const char *file, int mode);
> int tracefs_instances_walk(int (*callback)(const char *, void *), void *context);
>
> bool tracefs_instance_exists(const char *name);
> diff --git a/src/tracefs-instance.c b/src/tracefs-instance.c
> index bf3de7c..27b9e99 100644
> --- a/src/tracefs-instance.c
> +++ b/src/tracefs-instance.c
> @@ -14,7 +14,7 @@
> #include <sys/stat.h>
> #include <fcntl.h>
> #include <dirent.h>
> -#include <linux/limits.h>
> +#include <limits.h>
> #include "tracefs.h"
> #include "tracefs-local.h"
>
> @@ -282,7 +282,7 @@ int tracefs_instance_file_write(struct tracefs_instance *instance,
> * The return string must be freed by free()
> */
> char *tracefs_instance_file_read(struct tracefs_instance *instance,
> - char *file, int *psize)
> + const char *file, int *psize)
The above is more of a clean up and should be a separate patch.
> {
> char *buf = NULL;
> int size = 0;
> @@ -301,6 +301,61 @@ char *tracefs_instance_file_read(struct tracefs_instance *instance,
> return buf;
> }
>
> +/**
> + * tracefs_instance_file_read_int - Read an integer from a trace file.
> + * @instance: ftrace instance, can be NULL for the top instance
> + * @file: name of the file
> + * @res: The integer from the file.
> + *
> + * Returns 0 if the reading is successful and the result is stored in res, -1
> + * in case of an error.
> + */
> +int tracefs_instance_file_read_int(struct tracefs_instance *instance,
> + const char *file, long long *res)
Let's call this "tracefs_instance_file_number()" as "int" may be confusing
as it really returns "long long".
> +{
> + long long ret = LLONG_MAX;
> + int size = 0;
> + char *str;
> +
> + str = tracefs_instance_file_read(instance, file, &size);
> + if (size && str)
> + ret = strtoll(str, NULL, 0);
> + free(str);
> +
> + if (LLONG_MIN == ret || LLONG_MAX == ret)
> + return -1;
As it is possible that the file could read LLONG_MIN or LLONG_MAX, we
should follow the man page and use errno to detect an error:
if (!size || !str)
return -1;
errno = 0;
ret = strtoll(str, NULL, 0);
if (errno)
return -1;
-- Steve
> + *res = ret;
> + return 0;
> +}
> +
> +/**
> + * tracefs_instance_file_open - Open a trace file for reading and writing
> + * @instance: ftrace instance, can be NULL for the top instance
> + * @file: name of the file
> + * @mode: file open flags, -1 for default O_RDWR
> + *
> + * Returns -1 in case of an error, or a valid file descriptor otherwise.
> + * The returned FD must be closed with close()
> + */
> +int tracefs_instance_file_open(struct tracefs_instance *instance,
> + const char *file, int mode)
> +{
> + int flags = O_RDWR;
> + int fd = -1;
> + char *path;
> +
> + path = tracefs_instance_get_file(instance, file);
> + if (!path)
> + return -1;
> +
> + if (mode >= 0)
> + flags = mode;
> + fd = open(path, flags);
> + tracefs_put_tracing_file(path);
> +
> + return fd;
> +}
> +
> static bool check_file_exists(struct tracefs_instance *instance,
> char *name, bool dir)
> {
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