[Crash-utility] [PATCH] arm64: store phy_offset and memstart_addr separately

[lijiang]

Hi, Pingfan
Thanks for the fix.
在 2021年03月18日 09:36, Pingfan Liu 写道:
> With kernel commit 7bc1a0f9e176 ("arm64: mm: use single quantity to
> represent the PA to VA translation"), memstart_addr can be negative,
> which makes it different from real phy_offset.
> 
> In crash utility, PTOV() needs memstart_addr, while getting PFN offset
> in a dumpfile, phy_offset is required. So storing them separately for
> different purpose.
> 
> Signed-off-by: Pingfan Liu <piliu at redhat.com>
> Cc: Lianbo Jiang <lijiang at redhat.com>
> To: crash-utility at redhat.com
> ---
>  arm64.c | 22 +++++++++++++++++++---
>  defs.h  |  1 +
>  2 files changed, 20 insertions(+), 3 deletions(-)
> 
> diff --git a/arm64.c b/arm64.c
> index 37aed07..e560d07 100644
> --- a/arm64.c
> +++ b/arm64.c
> @@ -687,6 +687,7 @@ arm64_dump_machdep_table(ulong arg)
>  		fprintf(fp, "        kimage_voffset: %016lx\n", ms->kimage_voffset);
>  	}
>  	fprintf(fp, "           phys_offset: %lx\n", ms->phys_offset);
> +	fprintf(fp, "         memstart_addr: %lx\n", ms->memstart_addr);
>  	fprintf(fp, "__exception_text_start: %lx\n", ms->__exception_text_start);
>  	fprintf(fp, "  __exception_text_end: %lx\n", ms->__exception_text_end);
>  	fprintf(fp, " __irqentry_text_start: %lx\n", ms->__irqentry_text_start);
> @@ -987,7 +988,7 @@ arm64_calc_physvirt_offset(void)
>  	ulong physvirt_offset;
>  	struct syment *sp;
>  
> -	ms->physvirt_offset = ms->phys_offset - ms->page_offset;
> +	ms->physvirt_offset = ms->memstart_addr - ms->page_offset;
>  
>  	if ((sp = kernel_symbol_search("physvirt_offset")) &&
>  			machdep->machspec->kimage_voffset) {
> @@ -1028,7 +1029,11 @@ arm64_calc_phys_offset(void)
>  		    ms->kimage_voffset && (sp = kernel_symbol_search("memstart_addr"))) {
>  			if (pc->flags & PROC_KCORE) {
>  				if ((string = pc->read_vmcoreinfo("NUMBER(PHYS_OFFSET)"))) {
> -					ms->phys_offset = htol(string, QUIET, NULL);
> +					ms->memstart_addr = htol(string, QUIET, NULL);
> +					if (ms->memstart_addr < 0)
> +						ms->phys_offset = ms->memstart_addr + 0xffff000000000000 - 0xfff0000000000000;

Is that possible to explicitly use the following ways instead of the magic number? For example:

((UL(1) << (52))) - ((UL(1) << (48))) or ((UL(1) << (VA_BITS))) something?

Thanks.
Lianbo

> +					else
> +						ms->phys_offset = ms->memstart_addr;
>  					free(string);
>  					return;
>  				}
> @@ -1080,7 +1085,18 @@ arm64_calc_phys_offset(void)
>  	} else if (DISKDUMP_DUMPFILE() && diskdump_phys_base(&phys_offset)) {
>  		ms->phys_offset = phys_offset;
>  	} else if (KDUMP_DUMPFILE() && arm64_kdump_phys_base(&phys_offset)) {
> -		ms->phys_offset = phys_offset;
> +		/*
> +		 * When running a 52bits kernel on 48bits hardware. Kernel plays a trick:
> +		 * if (IS_ENABLED(CONFIG_ARM64_VA_BITS_52) && (vabits_actual != 52))
> +                 *       memstart_addr -= _PAGE_OFFSET(48) - _PAGE_OFFSET(52);
> +		 *
> +		 * In crash, this should be detected to get a real physical start address.
> +		 */
> +		ms->memstart_addr = phys_offset;
> +		if ((long)phys_offset < 0)
> +			ms->phys_offset = phys_offset + 0xffff000000000000 - 0xfff0000000000000;
> +		else
> +			ms->phys_offset = phys_offset;
>  	} else {
>  		error(WARNING,
>  			"phys_offset cannot be determined from the dumpfile.\n");
> diff --git a/defs.h b/defs.h
> index 35b983a..64f2bcb 100644
> --- a/defs.h
> +++ b/defs.h
> @@ -3290,6 +3290,7 @@ struct machine_specific {
>  	ulong modules_vaddr;
>  	ulong modules_end;
>  	ulong phys_offset;
> +	long memstart_addr;
>  	ulong __exception_text_start;
>  	ulong __exception_text_end;
>  	struct arm64_pt_regs *panic_task_regs;
>