[Crash-utility] Re: [PATCH] get vmalloc start address from vmcoreinfo

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On 2024/03/01 16:02, Aditya Gupta wrote:
> Below error is noticed when running crash on vmcore collected from a linux-next
> kernel crash (linux-next tag next-20240121):
> 
>      # crash /boot/vmlinuz-6.8.0-rc5-next-20240221 ./vmcore
>      ……
>      ……
>      For help, type “help”.
>      Type "apropos word" to search for commands related to "word"...
> 
>      crash: page excluded: kernel virtual address: c00000000219a2c0  type: “vmlist"
> 
> This occured since getting the vmalloc area base address doesn't work in
> crash now, due to 'vmap_area_list' being removed in the linux kernel with
> below commit (in linux-next tree):
> 
>      commit 378eb24a0658dd922b29524e0ce35c6c43f56cba
>           mm/vmalloc: remove vmap_area_list
> 
> As an alternative, the commit introduced 'VMALLOC_START' in vmcoreinfo to
> get base address of vmalloc area, use it to return vmallow start address
> instead of depending on vmap_area_list and vmlist
> 
> Reported-by: Sachin Sant <sachinp@xxxxxxxxxxxxx>
> Signed-off-by: Aditya Gupta <adityag@xxxxxxxxxxxxx>
> ---
>   memory.c | 11 ++++++++++-
>   1 file changed, 10 insertions(+), 1 deletion(-)
> 
> diff --git a/memory.c b/memory.c
> index b84e974a3325..b3027bd101cd 100644
> --- a/memory.c
> +++ b/memory.c
> @@ -17220,11 +17220,20 @@ first_vmalloc_address(void)
>   {
>   	static ulong vmalloc_start = 0;
>           ulong vm_struct, vmap_area;
> +	char *vmalloc_start_string;
>   
>   	if (DUMPFILE() && vmalloc_start)
>   		return vmalloc_start;
>   
> -	if (vt->flags & USE_VMAP_AREA) {
> +	/*
> +	 * 'vmap_area_list' and 'vmlist' in newer kernels might be empty, prefer
> +	 * `VMALLOC_START` if exported in vmcoreinfo
> +	 */
> +	vmalloc_start_string = pc->read_vmcoreinfo("NUMBER(VMALLOC_START)");
> +	if (vmalloc_start_string) {
> +		vmalloc_start = stol(vmalloc_start_string, QUIET, NULL);

Thank you for the patch.  seems htol is better, changed and applied.
https://github.com/crash-utility/crash/commit/5b24e363a8980dd4f878b0494cf78d24559a7a67

Thanks,
Kazu


> +		free(vmalloc_start_string);
> +	} else if (vt->flags & USE_VMAP_AREA) {
>   		get_symbol_data("vmap_area_list", sizeof(void *), &vmap_area);
>   		if (!vmap_area)
>   			return 0;
--
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