| Message ID | 20210623055011.22916-3-justin.he@arm.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | make '%pD' print the full path of file | expand |
On Wed, Jun 23, 2021 at 01:50:09PM +0800, Jia He wrote: > Previously, the specifier '%pD' is for printing dentry name of struct > file. It may not be perfect (by default it only prints one component.) > > As suggested by Linus [1]: > > A dentry has a parent, but at the same time, a dentry really does > > inherently have "one name" (and given just the dentry pointers, you > > can't show mount-related parenthood, so in many ways the "show just > > one name" makes sense for "%pd" in ways it doesn't necessarily for > > "%pD"). But while a dentry arguably has that "one primary component", > > a _file_ is certainly not exclusively about that last component. > > Hence change the behavior of '%pD' to print the full path of that file. > > If someone invokes snprintf() with small but positive space, > prepend_name_with_len() moves or truncates the string partially. More > than that, kasprintf() will pass NULL @buf and @end as the parameters, > and @end - @buf can be negative in some case. Hence make it return at > the very beginning with false in these cases. > > Precision is never going to be used with %p (or any of its kernel > extensions) if -Wformat is turned on. ... > + char *p; > + const struct path *path; > + int prepend_len, widen_len, dpath_len; Reversed xmas tree order?
On Wed 2021-06-23 13:50:09, Jia He wrote: > Previously, the specifier '%pD' is for printing dentry name of struct > file. It may not be perfect (by default it only prints one component.) > > As suggested by Linus [1]: > > A dentry has a parent, but at the same time, a dentry really does > > inherently have "one name" (and given just the dentry pointers, you > > can't show mount-related parenthood, so in many ways the "show just > > one name" makes sense for "%pd" in ways it doesn't necessarily for > > "%pD"). But while a dentry arguably has that "one primary component", > > a _file_ is certainly not exclusively about that last component. > > Hence change the behavior of '%pD' to print the full path of that file. > > If someone invokes snprintf() with small but positive space, > prepend_name_with_len() moves or truncates the string partially. Does this comment belong to the 1st patch? prepend_name_with_len() is not called in this patch. > More > than that, kasprintf() will pass NULL @buf and @end as the parameters, > and @end - @buf can be negative in some case. Hence make it return at > the very beginning with false in these cases. Same here. file_d_path_name() does not return bool. Well, please mention in the commit message that %pD uses the entire given buffer as a scratch space. It might write something behind the trailing '\0'. It would make sense to warn about this also in Documentation/core-api/printk-formats.rst. It is a bit non-standard behavior. > diff --git a/lib/vsprintf.c b/lib/vsprintf.c > index f0c35d9b65bf..f4494129081f 100644 > --- a/lib/vsprintf.c > +++ b/lib/vsprintf.c > @@ -920,13 +921,44 @@ char *dentry_name(char *buf, char *end, const struct dentry *d, struct printf_sp > } > > static noinline_for_stack > -char *file_dentry_name(char *buf, char *end, const struct file *f, > +char *file_d_path_name(char *buf, char *end, const struct file *f, > struct printf_spec spec, const char *fmt) > { > + char *p; > + const struct path *path; > + int prepend_len, widen_len, dpath_len; > + > if (check_pointer(&buf, end, f, spec)) > return buf; > > - return dentry_name(buf, end, f->f_path.dentry, spec, fmt); > + path = &f->f_path; > + if (check_pointer(&buf, end, path, spec)) > + return buf; > + > + p = d_path_unsafe(path, buf, end - buf, &prepend_len); > + > + /* Calculate the full d_path length, ignoring the tail '\0' */ > + dpath_len = end - buf - prepend_len - 1; > + > + widen_len = max_t(int, dpath_len, spec.field_width); > + > + /* Case 1: Already started past the buffer. Just forward @buf. */ > + if (buf >= end) > + return buf + widen_len; > + > + /* > + * Case 2: The entire remaining space of the buffer filled by > + * the truncated path. Still need to get moved right when > + * the filled width is greather than the full path length. s/filled/field/ ? > + */ > + if (prepend_len < 0) > + return widen_string(buf + dpath_len, dpath_len, end, spec); Otherwise, it looks good to me. Best Regards, Petr
On Thu, Jun 24, 2021 at 11:01:31AM +0200, Petr Mladek wrote: > On Wed 2021-06-23 13:50:09, Jia He wrote: ... > > If someone invokes snprintf() with small but positive space, > > prepend_name_with_len() moves or truncates the string partially. > > Does this comment belong to the 1st patch? > prepend_name_with_len() is not called in this patch. > > > More > > than that, kasprintf() will pass NULL @buf and @end as the parameters, > > and @end - @buf can be negative in some case. Hence make it return at > > the very beginning with false in these cases. > > Same here. file_d_path_name() does not return bool. It was my (apparently unclear) suggestion either to move it here, or be rewritten in generic way as you suggested in the other thread.
Hi Petr > -----Original Message----- > From: Petr Mladek <pmladek@suse.com> > Sent: Thursday, June 24, 2021 5:02 PM > To: Justin He <Justin.He@arm.com> > Cc: Steven Rostedt <rostedt@goodmis.org>; Sergey Senozhatsky > <senozhatsky@chromium.org>; Andy Shevchenko > <andriy.shevchenko@linux.intel.com>; Rasmus Villemoes > <linux@rasmusvillemoes.dk>; Jonathan Corbet <corbet@lwn.net>; Alexander > Viro <viro@zeniv.linux.org.uk>; Linus Torvalds <torvalds@linux- > foundation.org>; Peter Zijlstra (Intel) <peterz@infradead.org>; Eric > Biggers <ebiggers@google.com>; Ahmed S. Darwish <a.darwish@linutronix.de>; > linux-doc@vger.kernel.org; linux-kernel@vger.kernel.org; linux- > fsdevel@vger.kernel.org; Matthew Wilcox <willy@infradead.org>; Christoph > Hellwig <hch@infradead.org>; nd <nd@arm.com> > Subject: Re: [PATCH v2 2/4] lib/vsprintf.c: make '%pD' print the full path > of file > > On Wed 2021-06-23 13:50:09, Jia He wrote: > > Previously, the specifier '%pD' is for printing dentry name of struct > > file. It may not be perfect (by default it only prints one component.) > > > > As suggested by Linus [1]: > > > A dentry has a parent, but at the same time, a dentry really does > > > inherently have "one name" (and given just the dentry pointers, you > > > can't show mount-related parenthood, so in many ways the "show just > > > one name" makes sense for "%pd" in ways it doesn't necessarily for > > > "%pD"). But while a dentry arguably has that "one primary component", > > > a _file_ is certainly not exclusively about that last component. > > > > Hence change the behavior of '%pD' to print the full path of that file. > > > > If someone invokes snprintf() with small but positive space, > > prepend_name_with_len() moves or truncates the string partially. > > Does this comment belong to the 1st patch? > prepend_name_with_len() is not called in this patch. > Tend to remove this paragraph since the comments in do_path_unsafe (patch1/4) was clear enough. > > More > > than that, kasprintf() will pass NULL @buf and @end as the parameters, > > and @end - @buf can be negative in some case. Hence make it return at > > the very beginning with false in these cases. > > Same here. file_d_path_name() does not return bool. > > Well, please mention in the commit message that %pD uses the entire > given buffer as a scratch space. It might write something behind > the trailing '\0'. > > It would make sense to warn about this also in > Documentation/core-api/printk-formats.rst. It is a bit non-standard > behavior. > Okay > > diff --git a/lib/vsprintf.c b/lib/vsprintf.c > > index f0c35d9b65bf..f4494129081f 100644 > > --- a/lib/vsprintf.c > > +++ b/lib/vsprintf.c > > @@ -920,13 +921,44 @@ char *dentry_name(char *buf, char *end, const > struct dentry *d, struct printf_sp > > } > > > > static noinline_for_stack > > -char *file_dentry_name(char *buf, char *end, const struct file *f, > > +char *file_d_path_name(char *buf, char *end, const struct file *f, > > struct printf_spec spec, const char *fmt) > > { > > + char *p; > > + const struct path *path; > > + int prepend_len, widen_len, dpath_len; > > + > > if (check_pointer(&buf, end, f, spec)) > > return buf; > > > > - return dentry_name(buf, end, f->f_path.dentry, spec, fmt); > > + path = &f->f_path; > > + if (check_pointer(&buf, end, path, spec)) > > + return buf; > > + > > + p = d_path_unsafe(path, buf, end - buf, &prepend_len); > > + > > + /* Calculate the full d_path length, ignoring the tail '\0' */ > > + dpath_len = end - buf - prepend_len - 1; > > + > > + widen_len = max_t(int, dpath_len, spec.field_width); > > + > > + /* Case 1: Already started past the buffer. Just forward @buf. */ > > + if (buf >= end) > > + return buf + widen_len; > > + > > + /* > > + * Case 2: The entire remaining space of the buffer filled by > > + * the truncated path. Still need to get moved right when > > + * the filled width is greather than the full path length. > > s/filled/field/ ? > Ah, sorry, I changed it. I would have thought it as a typo
> -----Original Message----- > From: Justin He > Sent: Friday, June 25, 2021 10:30 AM > To: Petr Mladek <pmladek@suse.com> > Cc: Steven Rostedt <rostedt@goodmis.org>; Sergey Senozhatsky > <senozhatsky@chromium.org>; Andy Shevchenko > <andriy.shevchenko@linux.intel.com>; Rasmus Villemoes > <linux@rasmusvillemoes.dk>; Jonathan Corbet <corbet@lwn.net>; Alexander > Viro <viro@zeniv.linux.org.uk>; Linus Torvalds <torvalds@linux- > foundation.org>; Peter Zijlstra (Intel) <peterz@infradead.org>; Eric > Biggers <ebiggers@google.com>; Ahmed S. Darwish <a.darwish@linutronix.de>; > linux-doc@vger.kernel.org; linux-kernel@vger.kernel.org; linux- > fsdevel@vger.kernel.org; Matthew Wilcox <willy@infradead.org>; Christoph > Hellwig <hch@infradead.org>; nd <nd@arm.com> > Subject: RE: [PATCH v2 2/4] lib/vsprintf.c: make '%pD' print the full path > of file > > Hi Petr > > > -----Original Message----- > > From: Petr Mladek <pmladek@suse.com> > > Sent: Thursday, June 24, 2021 5:02 PM > > To: Justin He <Justin.He@arm.com> > > Cc: Steven Rostedt <rostedt@goodmis.org>; Sergey Senozhatsky > > <senozhatsky@chromium.org>; Andy Shevchenko > > <andriy.shevchenko@linux.intel.com>; Rasmus Villemoes > > <linux@rasmusvillemoes.dk>; Jonathan Corbet <corbet@lwn.net>; Alexander > > Viro <viro@zeniv.linux.org.uk>; Linus Torvalds <torvalds@linux- > > foundation.org>; Peter Zijlstra (Intel) <peterz@infradead.org>; Eric > > Biggers <ebiggers@google.com>; Ahmed S. Darwish <a.darwish@linutronix.de>; > > linux-doc@vger.kernel.org; linux-kernel@vger.kernel.org; linux- > > fsdevel@vger.kernel.org; Matthew Wilcox <willy@infradead.org>; Christoph > > Hellwig <hch@infradead.org>; nd <nd@arm.com> > > Subject: Re: [PATCH v2 2/4] lib/vsprintf.c: make '%pD' print the full > path > > of file > > > > On Wed 2021-06-23 13:50:09, Jia He wrote: > > > Previously, the specifier '%pD' is for printing dentry name of struct > > > file. It may not be perfect (by default it only prints one component.) > > > > > > As suggested by Linus [1]: > > > > A dentry has a parent, but at the same time, a dentry really does > > > > inherently have "one name" (and given just the dentry pointers, you > > > > can't show mount-related parenthood, so in many ways the "show just > > > > one name" makes sense for "%pd" in ways it doesn't necessarily for > > > > "%pD"). But while a dentry arguably has that "one primary component", > > > > a _file_ is certainly not exclusively about that last component. > > > > > > Hence change the behavior of '%pD' to print the full path of that file. > > > > > > If someone invokes snprintf() with small but positive space, > > > prepend_name_with_len() moves or truncates the string partially. > > > > Does this comment belong to the 1st patch? > > prepend_name_with_len() is not called in this patch. > > > Tend to remove this paragraph since the comments in do_path_unsafe > (patch1/4) > was clear enough. Hi, I noticed your suggested commit msg in another thread. Please ignore above my words. -- Cheers, Justin (Jia He)
diff --git a/Documentation/core-api/printk-formats.rst b/Documentation/core-api/printk-formats.rst index f063a384c7c8..3c0d0f90b171 100644 --- a/Documentation/core-api/printk-formats.rst +++ b/Documentation/core-api/printk-formats.rst @@ -408,12 +408,13 @@ dentry names :: %pd{,2,3,4} - %pD{,2,3,4} + %pD For printing dentry name; if we race with :c:func:`d_move`, the name might be a mix of old and new ones, but it won't oops. %pd dentry is a safer equivalent of %s dentry->d_name.name we used to use, %pd<n> prints ``n`` -last components. %pD does the same thing for struct file. +last components. %pD prints full file path together with mount-related +parenthood. Passed by reference. diff --git a/lib/vsprintf.c b/lib/vsprintf.c index f0c35d9b65bf..f4494129081f 100644 --- a/lib/vsprintf.c +++ b/lib/vsprintf.c @@ -26,6 +26,7 @@ #include <linux/types.h> #include <linux/string.h> #include <linux/ctype.h> +#include <linux/dcache.h> #include <linux/kernel.h> #include <linux/kallsyms.h> #include <linux/math64.h> @@ -920,13 +921,44 @@ char *dentry_name(char *buf, char *end, const struct dentry *d, struct printf_sp } static noinline_for_stack -char *file_dentry_name(char *buf, char *end, const struct file *f, +char *file_d_path_name(char *buf, char *end, const struct file *f, struct printf_spec spec, const char *fmt) { + char *p; + const struct path *path; + int prepend_len, widen_len, dpath_len; + if (check_pointer(&buf, end, f, spec)) return buf; - return dentry_name(buf, end, f->f_path.dentry, spec, fmt); + path = &f->f_path; + if (check_pointer(&buf, end, path, spec)) + return buf; + + p = d_path_unsafe(path, buf, end - buf, &prepend_len); + + /* Calculate the full d_path length, ignoring the tail '\0' */ + dpath_len = end - buf - prepend_len - 1; + + widen_len = max_t(int, dpath_len, spec.field_width); + + /* Case 1: Already started past the buffer. Just forward @buf. */ + if (buf >= end) + return buf + widen_len; + + /* + * Case 2: The entire remaining space of the buffer filled by + * the truncated path. Still need to get moved right when + * the filled width is greather than the full path length. + */ + if (prepend_len < 0) + return widen_string(buf + dpath_len, dpath_len, end, spec); + + /* + * Case 3: The full path is printed at the end of the buffer. + * Print it at the right location in the same buffer. + */ + return string_nocheck(buf, end, p, spec); } #ifdef CONFIG_BLOCK static noinline_for_stack @@ -2296,7 +2328,7 @@ early_param("no_hash_pointers", no_hash_pointers_enable); * - 'a[pd]' For address types [p] phys_addr_t, [d] dma_addr_t and derivatives * (default assumed to be phys_addr_t, passed by reference) * - 'd[234]' For a dentry name (optionally 2-4 last components) - * - 'D[234]' Same as 'd' but for a struct file + * - 'D' For full path name of a struct file * - 'g' For block_device name (gendisk + partition number) * - 't[RT][dt][r]' For time and date as represented by: * R struct rtc_time @@ -2395,7 +2427,7 @@ char *pointer(const char *fmt, char *buf, char *end, void *ptr, case 'C': return clock(buf, end, ptr, spec, fmt); case 'D': - return file_dentry_name(buf, end, ptr, spec, fmt); + return file_d_path_name(buf, end, ptr, spec, fmt); #ifdef CONFIG_BLOCK case 'g': return bdev_name(buf, end, ptr, spec, fmt);