From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-it0-f71.google.com (mail-it0-f71.google.com [209.85.214.71]) by kanga.kvack.org (Postfix) with ESMTP id F04476B40ED for ; Mon, 27 Aug 2018 10:28:57 -0400 (EDT) Received: by mail-it0-f71.google.com with SMTP id h5-v6so8687260itb.3 for ; Mon, 27 Aug 2018 07:28:57 -0700 (PDT) Received: from mail-sor-f65.google.com (mail-sor-f65.google.com. [209.85.220.65]) by mx.google.com with SMTPS id u10-v6sor5375730iob.204.2018.08.27.07.28.56 for (Google Transport Security); Mon, 27 Aug 2018 07:28:56 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: <20180827103353.GB13848@rapoport-lnx> References: <20180827082101.5036-1-brgl@bgdev.pl> <20180827103353.GB13848@rapoport-lnx> From: Bartosz Golaszewski Date: Mon, 27 Aug 2018 16:28:55 +0200 Message-ID: Subject: Re: [PATCH 1/2] devres: provide devm_kstrdup_const() Content-Type: text/plain; charset="UTF-8" Sender: owner-linux-mm@kvack.org List-ID: To: Mike Rapoport Cc: Michael Turquette , Stephen Boyd , Greg Kroah-Hartman , "Rafael J . Wysocki" , Arend van Spriel , Ulf Hansson , Bjorn Helgaas , Vivek Gautam , Robin Murphy , Joe Perches , Heikki Krogerus , Andrew Morton , Michal Hocko , Al Viro , Jonathan Corbet , Roman Gushchin , Huang Ying , Kees Cook , Bjorn Andersson , linux-clk , Linux Kernel Mailing List , linux-mm@kvack.org 2018-08-27 12:33 GMT+02:00 Mike Rapoport : > On Mon, Aug 27, 2018 at 10:21:00AM +0200, Bartosz Golaszewski wrote: >> Provide a resource managed version of kstrdup_const(). This variant >> internally calls devm_kstrdup() on pointers that are outside of >> .rodata section. Also provide a corresponding version of devm_kfree(). >> >> Signed-off-by: Bartosz Golaszewski >> --- >> include/linux/device.h | 2 ++ >> mm/util.c | 35 +++++++++++++++++++++++++++++++++++ >> 2 files changed, 37 insertions(+) >> >> diff --git a/include/linux/device.h b/include/linux/device.h >> index 8f882549edee..f8f5982d26b2 100644 >> --- a/include/linux/device.h >> +++ b/include/linux/device.h >> @@ -693,7 +693,9 @@ static inline void *devm_kcalloc(struct device *dev, >> return devm_kmalloc_array(dev, n, size, flags | __GFP_ZERO); >> } >> extern void devm_kfree(struct device *dev, void *p); >> +extern void devm_kfree_const(struct device *dev, void *p); >> extern char *devm_kstrdup(struct device *dev, const char *s, gfp_t gfp) __malloc; >> +extern char *devm_kstrdup_const(struct device *dev, const char *s, gfp_t gfp); >> extern void *devm_kmemdup(struct device *dev, const void *src, size_t len, >> gfp_t gfp); >> >> diff --git a/mm/util.c b/mm/util.c >> index d2890a407332..6d1f41b5775e 100644 >> --- a/mm/util.c >> +++ b/mm/util.c >> @@ -39,6 +39,20 @@ void kfree_const(const void *x) >> } >> EXPORT_SYMBOL(kfree_const); >> >> +/** >> + * devm_kfree_const - Resource managed conditional kfree >> + * @dev: device this memory belongs to >> + * @p: memory to free >> + * >> + * Function calls devm_kfree only if @p is not in .rodata section. >> + */ >> +void devm_kfree_const(struct device *dev, void *p) >> +{ >> + if (!is_kernel_rodata((unsigned long)p)) >> + devm_kfree(dev, p); >> +} >> +EXPORT_SYMBOL(devm_kfree_const); >> + >> /** >> * kstrdup - allocate space for and copy an existing string >> * @s: the string to duplicate >> @@ -78,6 +92,27 @@ const char *kstrdup_const(const char *s, gfp_t gfp) >> } >> EXPORT_SYMBOL(kstrdup_const); >> >> +/** >> + * devm_kstrdup_const - resource managed conditional string duplication >> + * @dev: device for which to duplicate the string >> + * @s: the string to duplicate >> + * @gfp: the GFP mask used in the kmalloc() call when allocating memory >> + * >> + * Function returns source string if it is in .rodata section otherwise it >> + * fallbacks to devm_kstrdup. > > Please make it proper "Returns:" description and move to the end of the > comment. See Documentation/doc-guide/kernel-doc.rst. > Sure. >> + * Strings allocated by devm_kstrdup_const will be automatically freed when >> + * the associated device is detached. >> + */ >> +char *devm_kstrdup_const(struct device *dev, const char *s, gfp_t gfp) >> +{ >> + if (is_kernel_rodata((unsigned long)s)) >> + return s; >> + >> + return devm_kstrdup(dev, s, gfp); >> +} >> +EXPORT_SYMBOL(devm_kstrdup_const); >> + > > The devm_ variants seem to belong to drivers/base/devres.c rather than > mm/util.c > Not all devm_ variants live in drivers/base/devres.c, many subsystems implement them locally. In this case we need to choose between exporting is_kernel_rodata() and putting devm_kstrdup_const() in mm/util.c. I chose the latter, since it's cleaner. Bart >> /** >> * kstrndup - allocate space for and copy an existing string >> * @s: the string to duplicate >> -- >> 2.18.0 >> > > -- > Sincerely yours, > Mike. >