On Mon, Jun 7, 2021 at 2:27 PM lijiang <[email protected]> wrote:
>
> Hi, Pingfan
> Thank you for the update.
>
> On Fri, Jun 4, 2021 at 10:39 AM Pingfan Liu <[email protected]> wrote:
> >
> > At present, we have the following important changes for arm64 memory
> > layout:
> >
> > -1. redesigned ARM64 kernel virtual memory layout and associated KASLR
> > support that was introduced in Linux 4.6. And NEW_VMEMMAP is used to
> > flag it.
> > -2. memory layout flipped just right before introducing 52-bits kernel.
> > -3. introducing of vabits_actual and phyvirt_offset in kernel
> > -4. removing phyvirt_offset.
> >
> > These changes have effects on PTOV()/VTOP() formula. So introducing a
> > dedicate field mmlayout_flags to record it.
> >
> > Among above, 2 and 3 are introduced closely, and are not distinguished
> > in current implement. And this patch also keep this practice and use
> > vabits_actual as a hint to flag mem flipped.
> >
> > Signed-off-by: Pingfan Liu <[email protected]>
> > Cc: HAGIO KAZUHITO <[email protected]>
> > Cc: Lianbo Jiang <[email protected]>
> > Cc: Bhupesh Sharma <[email protected]>
> > To: [email protected]
> > ---
> > arm64.c | 11 +++++++++++
> > defs.h | 1 +
> > 2 files changed, 12 insertions(+)
> >
> > diff --git a/arm64.c b/arm64.c
> > index 8934961..eb88ced 100644
> > --- a/arm64.c
> > +++ b/arm64.c
> > @@ -88,6 +88,10 @@ static int arm64_is_uvaddr(ulong, struct task_context *);
> > static void arm64_calc_KERNELPACMASK(void);
> >
> >
>
> I tested this patchset with the old vmcore and the latest vmcore, and
> it passed. But I still have
Thanks for the quick response.
> some questions:
>
> > +/* arm64 kernel layout experiences changes, using these flags to
> > distinguish them */
> > +#define MMLAYOUT_FLAGS_FLIP 0x1
> [1] For this micro, is it possible to check the "vabits_actual" and
> "TCR_EL1_T1SZ" in order to
> achieve a similar purpose?
>
> if (kernel_symbol_exists("vabits_actual") || ...
> read_vmcoreinfo("NUMBER(TCR_EL1_T1SZ)"))
>
> > +#define MMLAYOUT_FLAGS_HAS_PHYSVIRT_OFFSET 0x2
> [2] For this one, can it be replaced with the following ways instead
> of adding a new micro definition?
>
> if (kernel_symbol_exists("physvirt_offset"))
>
Just like your understanding, these two macros derive from the
judgement of these conditions.
But there are two benefits of the usage of macro
-1. it only includes a bit-test, so quick.
-2. a concentrated place to organize all memory changes history. It
can serve as a hint for future code maintenance.
Thanks,
Pingfan
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