Re: [PATCH] arm64: store phy_offset and memstart_addr separately

[piliu <piliu@xxxxxxxxxx>]

On 3/23/21 3:04 PM, lijiang wrote:
> 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@xxxxxxxxxx>
> > Cc: Lianbo Jiang <lijiang@xxxxxxxxxx>
> > To: crash-utility@xxxxxxxxxx
> > ---
> >   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?
Yes. I will update with V2.

Thanks,
Pingfan

> 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;

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