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Date: Sun, 31 May 2015 10:51:17 -0700
From: Joe Perches <joe@...ches.com>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: LKML <linux-kernel@...r.kernel.org>
Subject: Re: [RFC patch] vsprintf: Add %pav extension for print_vma_addr
On Wed, 2015-05-27 at 14:19 -0700, Andrew Morton wrote:
> On Wed, 27 May 2015 14:09:31 -0700 Joe Perches <joe@...ches.com> wrote:
>
> > > Problems when CONFIG_PREEMPT=n.
> > >
> > > > + down_read(&mm->mmap_sem);
> > > > + vma = find_vma(mm, ip);
> > > > + if (vma && vma->vm_file) {
> > > > + struct file *f = vma->vm_file;
> > > > + char *gfp_buf = (char *)__get_free_page(GFP_KERNEL);
> > >
> > > We shouldn't assume we can use GFP_KERNEL here. Even if the
> > > preempt_count() worked, we might be in a context which requires
> > > GFP_NOFS or GFP_NOIO.
> >
> > This code is basically a copy of the existing print_vma_addr()
> > so is that true for all the existing uses too?
>
> Yeah, the current code is pretty junky. But normally print_vma_addr()
> should never be called so nobody noticed...
>
> In e8bff74a Ingo did a fiddle to preempt_conditional_sti() which looks
> like it will address the CONFIG_PREEMPT=n issue, but only on x86.
Maybe this? (using GFP_ATOMIC and __GFP_NOWARN)
Documentation/printk-formats.txt | 5 +++
lib/vsprintf.c | 66 ++++++++++++++++++++++++++++++++++++----
2 files changed, 65 insertions(+), 6 deletions(-)
diff --git a/Documentation/printk-formats.txt b/Documentation/printk-formats.txt
index 2ec6d84..962f82c 100644
--- a/Documentation/printk-formats.txt
+++ b/Documentation/printk-formats.txt
@@ -86,6 +86,11 @@ DMA addresses types dma_addr_t:
For printing a dma_addr_t type which can vary based on build options,
regardless of the width of the CPU data path. Passed by reference.
+VMA addresses: where the content of an unsigned long * is used in find_vma()
+ %pav "%s[%lx+%lx]",
+ kbasename(d_path(vma->vm_file)),
+ vma->vm_start, vma->vm_end - vma->vm_start)
+
Raw buffer as an escaped string:
%*pE[achnops]
diff --git a/lib/vsprintf.c b/lib/vsprintf.c
index 8243e2f..bb4fa63 100644
--- a/lib/vsprintf.c
+++ b/lib/vsprintf.c
@@ -1313,23 +1313,74 @@ char *netdev_feature_string(char *buf, char *end, const u8 *addr,
}
static noinline_for_stack
+char *vma_addr(char *buf, char *end, const void *addr,
+ struct printf_spec spec, const char *fmt)
+{
+ struct mm_struct *mm = current->mm;
+ const char *errmsg;
+ struct vm_area_struct *vma;
+ char *page;
+ char *path;
+
+ /* if we are in atomic contexts (in exception stacks, etc.) */
+ if (preempt_count()) {
+ errmsg = "(atomic context)";
+ goto err_string;
+ }
+
+ down_read(&mm->mmap_sem);
+ vma = find_vma(mm, *(unsigned long *)addr);
+
+ if (!vma || !vma->vm_file) {
+ errmsg = "(find_vma failed)";
+ goto err_up_read;
+ }
+
+ page = (char *)__get_free_page(GFP_ATOMIC | __GFP_NOWARN);
+ if (!page) {
+ errmsg = "(__get_free_page failed)";
+ goto err_up_read;
+ }
+
+ path = d_path(&vma->vm_file->f_path, page, PAGE_SIZE);
+ if (IS_ERR(path))
+ path = "?";
+
+ buf += snprintf(buf, end > buf ? end - buf : 0, "%s[%lx+%lx]",
+ kbasename(path),
+ vma->vm_start, vma->vm_end - vma->vm_start);
+
+ free_page((unsigned long)page);
+ up_read(&mm->mmap_sem);
+ return buf;
+
+err_up_read:
+ up_read(&mm->mmap_sem);
+err_string:
+ return string(buf, end, errmsg, spec);
+}
+
+static noinline_for_stack
char *address_val(char *buf, char *end, const void *addr,
struct printf_spec spec, const char *fmt)
{
unsigned long long num;
- spec.flags |= SPECIAL | SMALL | ZEROPAD;
- spec.base = 16;
-
switch (fmt[1]) {
+ case 'v':
+ return vma_addr(buf, end, addr, spec, fmt);
case 'd':
- num = *(const dma_addr_t *)addr;
+ spec.flags |= SPECIAL | SMALL | ZEROPAD;
+ spec.base = 16;
spec.field_width = sizeof(dma_addr_t) * 2 + 2;
+ num = *(const dma_addr_t *)addr;
break;
case 'p':
default:
- num = *(const phys_addr_t *)addr;
+ spec.flags |= SPECIAL | SMALL | ZEROPAD;
+ spec.base = 16;
spec.field_width = sizeof(phys_addr_t) * 2 + 2;
+ num = *(const phys_addr_t *)addr;
break;
}
@@ -1453,7 +1504,10 @@ int kptr_restrict __read_mostly;
* N no separator
* The maximum supported length is 64 bytes of the input. Consider
* to use print_hex_dump() for the larger input.
- * - 'a[pd]' For address types [p] phys_addr_t, [d] dma_addr_t and derivatives
+ * - 'a[pdv]' For address types:
+ * [p] phys_addr_t and derivatives (resource_size_t)
+ * [d] dma_addr_t
+ * [v] vma_addr
* (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
--
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