[PATCH v3 1/5] dyxlat: building xlat dynamically
Dmitry V. Levin
ldv at altlinux.org
Tue Jun 13 21:55:03 UTC 2017
On Tue, Jun 13, 2017 at 05:26:41PM +0900, Masatake YAMATO wrote:
> xlat tables are generating in built-time of strace.
>
> printxval is suitable for printing `family' field of Netlink GENERIC
> protocol. However, contents of the xlat table cannot be defined in
> build-time because the values for the field are given by Linux kernel.
>
> dyxlat functions are for building xlat in run-time. Decoding the
> field is the primary use case of functions but they can be used
> another purpose.
>
> * defs.h (dyxlat_alloc, dyxlat_free, dyxlat_add_pair): New functions
> declarations.
> (struct dyxlat): New opaque data type.
>
> * dyxlat.c: New file.
>
> Changes in version 3 (suggested by ldv):
>
> * Rename dyxlat_new/dyxlat_delete to dyxlat_alloc/dyxlat_free.
> Rename dyxlat_may_add_pair to dyxlat_may_add_pair.
>
> * Move dyxlat declarations closer to other xlat related prototypes.
>
> * Change the field types of dyxlat structure from int to size_t.
>
> * Merge the file static functions in dyxlat.c to the exported functions
> in the file.
>
> Signed-off-by: Masatake YAMATO <yamato at redhat.com>
> ---
> Makefile.am | 1 +
> defs.h | 6 ++++
> dyxlat.c | 103 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
> 3 files changed, 110 insertions(+)
> create mode 100644 dyxlat.c
>
> diff --git a/Makefile.am b/Makefile.am
> index 80f8a34..d004ac6 100644
> --- a/Makefile.am
> +++ b/Makefile.am
> @@ -104,6 +104,7 @@ strace_SOURCES = \
> dirent.c \
> dirent64.c \
> dm.c \
> + dyxlat.c \
> empty.h \
> epoll.c \
> evdev.c \
> diff --git a/defs.h b/defs.h
> index 6449bce..52f40b3 100644
> --- a/defs.h
> +++ b/defs.h
> @@ -504,6 +504,12 @@ extern enum sock_proto getfdproto(struct tcb *, int);
> extern const char *xlookup(const struct xlat *, const uint64_t);
> extern const char *xlat_search(const struct xlat *, const size_t, const uint64_t);
>
> +struct dyxlat;
> +struct dyxlat *dyxlat_alloc(size_t allocation);
as "allocation" means number of elements (as nmemb argument of calloc),
let's call it "nmemb" or something like that.
> +void dyxlat_free(struct dyxlat *dyxlat);
Do you think "struct dyxlat *dyxlat" is more descriptive
than "struct dyxlat *"?
> +struct xlat *dyxlat_get(struct dyxlat *dyxlat);
This function doesn't change anything, let's change its prototype to
const struct xlat *dyxlat_get(const struct dyxlat *);
> +void dyxlat_add_pair(struct dyxlat *dyxlat, uint64_t val, const char *str);
It looks like in the primary use case (genl_parse_families_response)
it would be convenient to specify the string length as well.
I suggest changing this prototype to
void dyxlat_add_pair(struct dyxlat *, uint64_t val, const char *str, size_t len);
The implementation would invoke xstrndup instead of xstrdup
if len is not equal to zero.
> +
> extern unsigned long get_pagesize(void);
> extern int
> string_to_uint_ex(const char *str, char **endptr,
> diff --git a/dyxlat.c b/dyxlat.c
> new file mode 100644
> index 0000000..c0952ed
> --- /dev/null
> +++ b/dyxlat.c
> @@ -0,0 +1,103 @@
> +/*
> + * Copyright (c) 2017 The strace developers.
> + *
> + * Redistribution and use in source and binary forms, with or without
> + * modification, are permitted provided that the following conditions
> + * are met:
> + * 1. Redistributions of source code must retain the above copyright
> + * notice, this list of conditions and the following disclaimer.
> + * 2. Redistributions in binary form must reproduce the above copyright
> + * notice, this list of conditions and the following disclaimer in the
> + * documentation and/or other materials provided with the distribution.
> + * 3. The name of the author may not be used to endorse or promote products
> + * derived from this software without specific prior written permission.
> + *
> + * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
> + * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
> + * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
> + * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
> + * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
> + * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
> + * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
> + * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
> + * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
> + * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
> + */
> +
> +#include "defs.h"
> +
> +struct dyxlat {
> + size_t used;
> + size_t allocated;
> + struct xlat *xlat;
> +};
> +
> +#define MARK_END(xlat) \
> + do { \
> + (xlat).val = 0; \
> + (xlat).str = 0; \
> + } while (0)
> +
> +struct dyxlat *
> +dyxlat_alloc(size_t allocation)
> +{
> + struct dyxlat *dyxlat;
> +
> + dyxlat = xmalloc(sizeof(*dyxlat));
> +
> + dyxlat->used = 1;
> + dyxlat->allocated = allocation ? allocation : 10;
Why 10?
> + dyxlat->xlat = xcalloc(dyxlat->allocated, sizeof(struct xlat));
> + MARK_END(dyxlat->xlat[0]);
> +
> + return dyxlat;
> +}
> +
> +void
> +dyxlat_free(struct dyxlat *dyxlat)
> +{
> + size_t i;
> +
> + for (i = 0; i < dyxlat->used - 1; ++i) {
> + free((void *)(dyxlat->xlat[i].str));
> + dyxlat->xlat[i].str = NULL;
> + }
> +
> + free(dyxlat->xlat);
> + dyxlat->xlat = NULL;
> + free(dyxlat);
> +}
> +
> +struct xlat *
> +dyxlat_get(struct dyxlat *dyxlat)
> +{
> + return dyxlat->xlat;
> +}
> +
> +void
> +dyxlat_add_pair(struct dyxlat *dyxlat, uint64_t val, const char *str)
> +{
> + size_t i;
> +
> + for (i = 0; i < dyxlat->used - 1; i++) {
> + if (dyxlat->xlat[i].val == val) {
> + if (strcmp(dyxlat->xlat[i].str, str) == 0)
> + return;
> +
> + free((void *)(dyxlat->xlat[i].str));
> + dyxlat->xlat[i].str = xstrdup(str);
> + return;
> + }
> + }
> +
> + dyxlat->used++;
> + if (dyxlat->used == dyxlat->allocated) {
This won't work properly if dyxlat_alloc was called with the number
of elements equal to 1. Let's check for >= instead.
> + dyxlat->allocated *= 2;
> + dyxlat->xlat = xreallocarray(dyxlat->xlat, dyxlat->allocated,
> + sizeof(struct xlat));
> + }
> +
> + dyxlat->xlat[dyxlat->used - 2].val = val;
> + dyxlat->xlat[dyxlat->used - 2].str = xstrdup(str);
I think it would look a bit nicer if these two assignments were made
before dyxlat->used++.
> + MARK_END(dyxlat->xlat[dyxlat->used - 1]);
> +}
--
ldv
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