On Mon, Dec 19, 2016 at 01:02:37PM +0000, James Hogan <james.hogan@xxxxxxxxxx> wrote:
> Hi Matt,
>
> On Mon, Dec 19, 2016 at 12:04:54PM +0000, Matt Redfearn wrote:
> > On 19/12/16 02:07, Serge Semin wrote:
> > > It's useful to have some printed map of the kernel virtual memory,
> > > at least for debugging purpose.
> > >
> > > Signed-off-by: Serge Semin <fancer.lancer@xxxxxxxxx>
> > > ---
>
> > > @@ -106,6 +107,49 @@ static void __init zone_sizes_init(void)
> > > }
> > >
> > > /*
> > > + * Print out kernel memory layout
> > > + */
> > > +#define MLK(b, t) b, t, ((t) - (b)) >> 10
> > > +#define MLM(b, t) b, t, ((t) - (b)) >> 20
> > > +#define MLK_ROUNDUP(b, t) b, t, DIV_ROUND_UP(((t) - (b)), SZ_1K)
> > > +static void __init mem_print_kmap_info(void)
> > > +{
> > > + pr_notice("Virtual kernel memory layout:\n"
> > > + " lowmem : 0x%08lx - 0x%08lx (%4ld MB)\n"
> > > + " vmalloc : 0x%08lx - 0x%08lx (%4ld MB)\n"
> > > +#ifdef CONFIG_HIGHMEM
> > > + " pkmap : 0x%08lx - 0x%08lx (%4ld MB)\n"
> > > +#endif
> > > + " fixmap : 0x%08lx - 0x%08lx (%4ld kB)\n"
> > > + " .text : 0x%p" " - 0x%p" " (%4td kB)\n"
> > > + " .data : 0x%p" " - 0x%p" " (%4td kB)\n"
> > > + " .init : 0x%p" " - 0x%p" " (%4td kB)\n",
> > > + MLM(PAGE_OFFSET, (unsigned long)high_memory),
> > > + MLM(VMALLOC_START, VMALLOC_END),
> > > +#ifdef CONFIG_HIGHMEM
> > > + MLM(PKMAP_BASE, (PKMAP_BASE) + (LAST_PKMAP)*(PAGE_SIZE)),
> > > +#endif
> > > + MLK(FIXADDR_START, FIXADDR_TOP),
> > > + MLK_ROUNDUP(_text, _etext),
> > > + MLK_ROUNDUP(_sdata, _edata),
> > > + MLK_ROUNDUP(__init_begin, __init_end));
> >
> > Please drop printing the kernel addresses, or at least only do it if
> > KASLR is not turned on, otherwise you're removing the advantage of
> > KASLR, that critical kernel addresses cannot be determined easily from
> > userspace.
>
> According to Documentation/printk-formats.txt, this is what %pK is for.
> Better to use that instead?
>
> Cheers
> James
>
The function is called from the kernel directly, which is privileged
enough to do the printing. So I suppose Matt is right, to hide this
prints out unless debug is enabled.
Thanks,
-Sergey
> >
> > It may be better to merge the functionality of show_kernel_relocation
> > http://lxr.free-electrons.com/source/arch/mips/kernel/relocate.c#L354
> > into this function, but only print it under the same conditions as
> > currently, i.e.
> > #if defined(CONFIG_DEBUG_KERNEL) && defined(CONFIG_DEBUG_INFO)
> > http://lxr.free-electrons.com/source/arch/mips/kernel/setup.c#L530
> >
> > Thanks,
> > Matt
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