Re: [PATCH V3 1/2] RISC-V: Add arch_crash_save_vmcoreinfo support

From: Xianting Tian
Date: Wed Oct 19 2022 - 21:52:51 EST



在 2022/10/20 上午9:35, HAGIO KAZUHITO(萩尾 一仁) 写道:
On 2022/10/19 12:17, Xianting Tian wrote:

+    if (IS_ENABLED(CONFIG_64BIT)) {
+#ifdef CONFIG_KASAN
+        vmcoreinfo_append_str("NUMBER(KASAN_SHADOW_START)=0x%lx\n", KASAN_SHADOW_START);
+        vmcoreinfo_append_str("NUMBER(KASAN_SHADOW_END)=0x%lx\n", KASAN_SHADOW_END);
+#endif
+        vmcoreinfo_append_str("NUMBER(KERNEL_LINK_ADDR)=0x%lx\n", KERNEL_LINK_ADDR);
+        vmcoreinfo_append_str("NUMBER(ADDRESS_SPACE_END)=0x%lx\n", ADDRESS_SPACE_END);
Seems this is the firsr ARCH where kasan and kernel link/bpf space are
added to dump and analyze. Just curious, have you got code change to
make use of them to do dumping and analyze?
KASAN_SHADOW_START is not used, KERNEL_LINK_ADDR is used in the crash patch set:
https://patchwork.kernel.org/project/linux-riscv/cover/20220813031753.3097720-1-xianting.tian@xxxxxxxxxxxxxxxxx/
Oh, I would say please no. Sometime we got tons of objection when adding an
necessary one, we definitely should not add one for possible future
use.

For this kind of newly added one, we need get ack from
makedumpfile/crash utility maintainer so that we know they are necessary
to have. At least they don't oppose.
Hi Kazu, Li Jiang

Could you help comment whether we need KASAN_SHADOW_START and KERNEL_LINK_ADDR area export for vmcore from crash point of view?

In my crash patch set, I don't use KASAN_SHADOW_START,
And only get the value of KERNEL_LINK_ADDR, not realy use it.
https://patchwork.kernel.org/project/linux-riscv/cover/20220813031753.3097720-1-xianting.tian@xxxxxxxxxxxxxxxxx/
In your crash patch set, KERNEL_LINK_ADDR is used in VTOP() and looks
necessary to me.

The others (KASAN_SHADOW_START, KASAN_SHADOW_END and ADDRESS_SPACE_END)
are not currently used.  It may be better to add them when they are
really used.
I am very sorry, I missed it , KERNEL_LINK_ADDR is used indeed.

KASAN_SHADOW_START is not used, so I don't need to send crash patch set> again. only need to remove KASAN_SHADOW_END in kernel patch set.
I see that your v4 kernel patch set does not have ADDRESS_SPACE_END,
so it seems there would be need to change this part and related ones
at crash side.

if ((string = pc->read_vmcoreinfo("NUMBER(ADDRESS_SPACE_END)"))) {
ms->address_space_end = htol(string, QUIET, NULL);
free(string);
} else
goto error;
...
error:
error(FATAL, "cannot get vm layout\n");

thanks,

I just send V4 of crash patch set, the issue is also fixed in V4.


Thanks,
Kazu