On Fri, 14 Aug 2020 10:53:03 -0700
Joe Perches <[email protected]> wrote:
> There is a print_vma_addr function used several places
> that requires KERN_CONT use.
>
> Add a %pv mechanism to avoid the need for KERN_CONT.
>
> An example conversion is arch/x86/kernel/signal.c
>
> from:
> if (show_unhandled_signals && printk_ratelimit()) {
> printk("%s"
> "%s[%d] bad frame in %s frame:%p ip:%lx sp:%lx orax:%lx",
> task_pid_nr(current) > 1 ? KERN_INFO : KERN_EMERG,
> me->comm, me->pid, where, frame,
> regs->ip, regs->sp, regs->orig_ax);
> print_vma_addr(KERN_CONT " in ", regs->ip);
> pr_cont("\n");
> to:
> printk("%s"
> "%s[%d] bad frame in %s frame:%p ip:%lx sp:%lx orax:%lx
> in %pv\n",
> task_pid_nr(current) > 1 ? KERN_INFO : KERN_EMERG,
> me->comm, me->pid, where, frame,
> regs->ip, regs->sp, regs->orig_ax, (void *)regs->ip);
> ---
> lib/vsprintf.c | 52 ++++++++++++++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 52 insertions(+)
>
> diff --git a/lib/vsprintf.c b/lib/vsprintf.c
> index c155769559ab..654402c43f8d 100644
> --- a/lib/vsprintf.c
> +++ b/lib/vsprintf.c
> @@ -995,6 +995,12 @@ static const struct printf_spec default_dec_spec = {
> .precision = -1,
> };
>
> +static const struct printf_spec default_hex_spec = {
> + .base = 16,
> + .precision = -1,
> + .flags = SMALL,
> +};
> +
> static const struct printf_spec default_dec02_spec = {
> .base = 10,
> .field_width = 2,
> @@ -2089,6 +2095,50 @@ char *fwnode_string(char *buf, char *end, struct
> fwnode_handle *fwnode,
> return widen_string(buf, buf - buf_start, end, spec);
> }
>
> +static noinline_for_stack
> +char *vma_addr(char *buf, char *end, void *ip,
> + struct printf_spec spec, const char *fmt)
> +{
> +#ifdef CONFIG_MMU
> + struct mm_struct *mm = current->mm;
> + struct vm_area_struct *vma;
> +
> + /*
> + * we might be running from an atomic context so we cannot sleep
> + */
> + if (!mmap_read_trylock(mm))
> + return buf;
> +
> + vma = find_vma(mm, (unsigned long)ip);
> + if (vma && vma->vm_file) {
> + char *p;
> + struct file *f = vma->vm_file;
> + char *page = (char *)__get_free_page(GFP_NOWAIT);
> +
> + if (page) {
> + p = file_path(f, page, PAGE_SIZE);
> + if (IS_ERR(p))
> + p = "?";
> + buf = string(buf, end, kbasename(p), default_str_spec);
> + buf = string_nocheck(buf, end, "[", default_str_spec);
> + buf = pointer_string(buf, end,
> + (void *)vma->vm_start,
> + default_hex_spec);
> + buf = string_nocheck(buf, end, "+", default_str_spec);
> + buf = pointer_string(buf, end,
> + (void *)(vma->vm_end -
> vma->vm_start),
> + default_hex_spec);
> + buf = string_nocheck(buf, end, "]", default_str_spec);
> + free_page((unsigned long)page);
> + }
> + }
> + mmap_read_unlock(mm);
> +#else
> + buf = string_nocheck(buf, end, "CONFIG_MMU=n", default_str_spec);
> +#endif
I'm fine with all his, but I feel more comfortable if this patch
created a single copy of the code. Perhaps add:
diff --git a/mm/memory.c b/mm/memory.c
index 87ec87cdc1ff..795a4db4d83d 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -4771,32 +4771,7 @@ EXPORT_SYMBOL_GPL(access_process_vm);
*/
void print_vma_addr(char *prefix, unsigned long ip)
{
- struct mm_struct *mm = current->mm;
- struct vm_area_struct *vma;
-
- /*
- * we might be running from an atomic context so we cannot sleep
- */
- if (!mmap_read_trylock(mm))
- return;
-
- vma = find_vma(mm, ip);
- if (vma && vma->vm_file) {
- struct file *f = vma->vm_file;
- char *buf = (char *)__get_free_page(GFP_NOWAIT);
- if (buf) {
- char *p;
-
- p = file_path(f, buf, PAGE_SIZE);
- if (IS_ERR(p))
- p = "?";
- printk("%s%s[%lx+%lx]", prefix, kbasename(p),
- vma->vm_start,
- vma->vm_end - vma->vm_start);
- free_page((unsigned long)buf);
- }
- }
- mmap_read_unlock(mm);
+ printk("%s%pv", prefix, ip);
}
#if defined(CONFIG_PROVE_LOCKING) || defined(CONFIG_DEBUG_ATOMIC_SLEEP)
And of course this would need for documentation.
-- Steve
> + return buf;
> +}
> +
> /*
> * Show a '%p' thing. A kernel extension is that the '%p' is followed
> * by an extra set of alphanumeric characters that are extended format
> @@ -2254,6 +2304,8 @@ char *pointer(const char *fmt, char *buf, char *end,
> void *ptr,
> return uuid_string(buf, end, ptr, spec, fmt);
> case 'V':
> return va_format(buf, end, ptr, spec, fmt);
> + case 'v':
> + return vma_addr(buf, end, ptr, spec, fmt);
> case 'K':
> return restricted_pointer(buf, end, ptr, spec);
> case 'N':
>
