On 2023/08/04 18:15, Song Shuai wrote:
> Since RISC-V Linux v6.4, the commit 3335068f8721 ("riscv: Use
> PUD/P4D/PGD pages for the linear mapping") changes phys_ram_base from
> the physical start of the kernel to the actual start of the DRAM.
>
> The Crash's VTOP() still uses phys_ram_base and kernel_map.virt_addr
> to translate kernel virtual address, that made Crash boot failed with
> Linux v6.4 and later version.
>
> Let Linux export kernel_map.va_kernel_pa_offset in v6.5 and backported
> v6.4.0 stable, so Crash can use "va_kernel_pa_offset" to translate the
> kernel virtual address in VTOP() correctly.
>
> Signed-off-by: Song Shuai <suagrfillet@xxxxxxxxx>
> ---
> Changes since V1:
> - remove unnecessary first kernel version check as Kazu suggested
> - amend the commit-msg as Alex suggested
Thanks for the v2.
Acked-by: Kazuhito Hagio <k-hagio-ab@xxxxxxx>
Another way is that checking the vmcoreinfo entry before the kernel
version, but either is fine to me.
Thanks,
Kazu
> ---
> defs.h | 4 ++--
> riscv64.c | 23 +++++++++++++++++++++++
> 2 files changed, 25 insertions(+), 2 deletions(-)
>
> diff --git a/defs.h b/defs.h
> index 5ee60f1..c07e6d7 100644
> --- a/defs.h
> +++ b/defs.h
> @@ -3662,8 +3662,7 @@ typedef signed int s32;
> ulong _X = X; \
> (THIS_KERNEL_VERSION >= LINUX(5,13,0) && \
> (_X) >= machdep->machspec->kernel_link_addr) ? \
> - (((unsigned long)(_X)-(machdep->machspec->kernel_link_addr)) + \
> - machdep->machspec->phys_base): \
> + ((unsigned long)(_X)-(machdep->machspec->va_kernel_pa_offset)): \
> (((unsigned long)(_X)-(machdep->kvbase)) + \
> machdep->machspec->phys_base); \
> })
> @@ -7021,6 +7020,7 @@ struct machine_specific {
> ulong modules_vaddr;
> ulong modules_end;
> ulong kernel_link_addr;
> + ulong va_kernel_pa_offset;
>
> ulong _page_present;
> ulong _page_read;
> diff --git a/riscv64.c b/riscv64.c
> index 6b9a688..7b5dd3d 100644
> --- a/riscv64.c
> +++ b/riscv64.c
> @@ -418,6 +418,28 @@ error:
> error(FATAL, "cannot get vm layout\n");
> }
>
> +static void
> +riscv64_get_va_kernel_pa_offset(struct machine_specific *ms)
> +{
> + unsigned long kernel_version = riscv64_get_kernel_version();
> +
> + /*
> + * Since Linux v6.4 phys_base is not the physical start of the kernel,
> + * trying to use "va_kernel_pa_offset" to determine the offset between
> + * kernel virtual and physical addresses.
> + */
> + if (kernel_version >= LINUX(6,4,0)) {
> + char *string;
> + if ((string = pc->read_vmcoreinfo("NUMBER(va_kernel_pa_offset)"))) {
> + ms->va_kernel_pa_offset = htol(string, QUIET, NULL);
> + free(string);
> + } else
> + error(FATAL, "cannot read va_kernel_pa_offset\n");
> + }
> + else
> + ms->va_kernel_pa_offset = ms->kernel_link_addr - ms->phys_base;
> +}
> +
> static int
> riscv64_is_kvaddr(ulong vaddr)
> {
> @@ -1352,6 +1374,7 @@ riscv64_init(int when)
> riscv64_get_struct_page_size(machdep->machspec);
> riscv64_get_va_bits(machdep->machspec);
> riscv64_get_va_range(machdep->machspec);
> + riscv64_get_va_kernel_pa_offset(machdep->machspec);
>
> pt_level_alloc(&machdep->pgd, "cannot malloc pgd space.");
> pt_level_alloc(&machdep->machspec->p4d, "cannot malloc p4d space.");
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