[Crash-utility] [PATCH] x86_64: Fix that Particular kvaddr is converted to wrong paddr (RHEL6 x86_64)
Dave Anderson
anderson at redhat.com
Mon Jan 4 16:44:33 UTC 2016
----- Original Message -----
> > But because it is such a fundamental change that you are proposing, it might
> > make sense to create a check/macro that is specific to the vsyscall region.
>
> What is check/macro? How do we check what?
> Certainly, these addresses are vsyscall region.
> After applying this patch, crash looks read vsyscall region correctly.
The vsyscall-region check fits more naturally in the x86_64_IS_VMALLOC_ADDR() function,
along with all of the other checks for non-unity-mapped addresses.
Queued for crash-7.1.5:
https://github.com/crash-utility/crash/commit/2e29d684a4583a45ae3c9b16014ab204eb6812fa
Thanks for the report,
Dave
>
>
>
> crash> sym vsyscall
> // abbreviation //
> ffffffffff600000 (t) .vsyscall_0
> ffffffffff600140 (t) .vsyscall_fn
> ffffffffff600180 (d) .vsyscall_gtod_data
> ffffffffff600180 (D) __vsyscall_gtod_data
> ffffffffff600400 (t) .vsyscall_1
> ffffffffff600800 (t) .vsyscall_2
> ffffffffff700680 (A) VDSO64_vsyscall_gtod_data
>
> crash> sym VDSO
> symbol not found: VDSO
> possible alternatives:
> ffffffffff700000 (A) VDSO64_PRELINK
> ffffffffff700670 (A) VDSO64_jiffies
> ffffffffff700678 (A) VDSO64_vgetcpu_mode
> ffffffffff700680 (A) VDSO64_vsyscall_gtod_data
>
>
> //////// not patched /////////
> crash> dis .vsyscall_0
> 0xffffffffff600000 <.vsyscall_0>: add %al,(%rax)
> 0xffffffffff600002 <vgettimeofday+2>: add %al,(%rax)
> 0xffffffffff600004 <vgettimeofday+4>: add %al,(%rax)
> 0xffffffffff600006 <vgettimeofday+6>: add %al,(%rax)
> 0xffffffffff600008 <vgettimeofday+8>: add %al,(%rax)
> 0xffffffffff60000a <vgettimeofday+10>: add %al,(%rax)
> // abbreviation //
>
>
> //////// after applying this patch /////////
> crash> dis .vsyscall_0
> 0xffffffffff600000 <.vsyscall_0>: push %rbp
> 0xffffffffff600001 <vgettimeofday+1>: mov %rsp,%rbp
> 0xffffffffff600004 <vgettimeofday+4>: push %r13
> 0xffffffffff600006 <vgettimeofday+6>: push %r12
> 0xffffffffff600008 <vgettimeofday+8>: mov %rdi,%r12
> 0xffffffffff60000b <vgettimeofday+11>: push %rbx
> 0xffffffffff60000c <vgettimeofday+12>: mov %rsi,%rbx
> 0xffffffffff60000f <vgettimeofday+15>: sub $0x8,%rsp
> 0xffffffffff600013 <vgettimeofday+19>: test %rdi,%rdi
> 0xffffffffff600016 <vgettimeofday+22>: je 0xffffffffff6000d5
> <vgettimeofday+213>
> // abbreviation //
>
>
> On 2015/12/22 22:42, Dave Anderson wrote:
> >
> >
> > ----- Original Message -----
> >> I didn't check XEN HYPER MODE, I don't have XEN.
> >> If we need similar statement "if (kvaddr < MODULES_END)"
> >> please add inside in "if (XEN_HYPER_MODE())" (1859 at x86_64_kvtop)
> >>
> >>
> >>
> >>
> >> >From ed300b74998e0923313e4fd14b9a41e305942b44 Mon Sep 17 00:00:00 2001
> >> From: Nakajima Akira <nakajima.akira at nttcom.co.jp>
> >> Date: Tue, 22 Dec 2015 15:46:42 +0900
> >> Subject: [PATCH] Fix that particular kvaddr is converted to wrong paddr
> >>
> >> BUG INFO
> >> Particular kvaddr is converted to wrong paddr.
> >> You can see this bug on RHEL6_x86_64. (at present only RHEL6)
> >> (I checked RHEL5, RHEL7, Fedora21, Fedora23)
> >
> >
> > I am out of the office until January 4th (only checking email until then),
> > and will not
> > be able to look into this until then. But because it is such a fundamental
> > change that
> > you are proposing, it might make sense to create a check/macro that is
> > specific to
> > the vsyscall region.
> >
> > Thanks,
> > Dave
> >
> >>
> >> from /proc/kallsyms
> >> ffffffffff6008c0 D __jiffies
> >>
> >> /////////// wrong ///////////
> >> crash> vtop ffffffffff6008c0
> >> VIRTUAL PHYSICAL
> >> ffffffffff6008c0 7f6008c0
> >>
> >> PAGE PHYSICAL MAPPING INDEX CNT FLAGS
> >> ffffea00000623b8 1c11000 0 0 1 20000000000400
> >> reserved
> >>
> >>
> >> crash> rd ffffffffff6008c0
> >> ffffffffff6008c0: 0000000000000000 ........
> >>
> >>
> >> /////////// correct ///////////
> >> crash> vtop ffffffffff6008c0
> >> VIRTUAL PHYSICAL
> >> ffffffffff6008c0 1c118c0
> >>
> >> PAGE PHYSICAL MAPPING INDEX CNT FLAGS
> >> ffffea00000623b8 1c11000 0 0 1 20000000000400
> >> reserved
> >>
> >>
> >> crash> rd ffffffffff6008c0
> >> ffffffffff6008c0: 00000000ffffe43a :.......
> >>
> >> Reported-by: Nakajima Akira <nakajima.akira at nttcom.co.jp>
> >> Signed-off-by: Nakajima Akira <nakajima.akira at nttcom.co.jp>
> >>
> >> ---
> >> x86_64.c | 28 +++++++++++++++-------------
> >> 1 files changed, 15 insertions(+), 13 deletions(-)
> >>
> >> diff --git a/x86_64.c b/x86_64.c
> >> index ff6fdd5..dab4d43 100644
> >> --- a/x86_64.c
> >> +++ b/x86_64.c
> >> @@ -1872,19 +1872,21 @@ x86_64_kvtop(struct task_context *tc, ulong
> >> kvaddr,
> >> physaddr_t *paddr, int verbo
> >> fprintf(fp, "PAGE DIRECTORY: %lx\n", *pml4);
> >> }
> >> } else {
> >> - if (!vt->vmalloc_start) {
> >> - *paddr = x86_64_VTOP(kvaddr);
> >> - return TRUE;
> >> - }
> >> -
> >> - if (!IS_VMALLOC_ADDR(kvaddr)) {
> >> - *paddr = x86_64_VTOP(kvaddr);
> >> - if (!verbose)
> >> - return TRUE;
> >> - }
> >> -
> >> - if (XEN() && (kt->xen_flags & WRITABLE_PAGE_TABLES))
> >> - return (x86_64_kvtop_xen_wpt(tc, kvaddr, paddr, verbose));
> >> + if (kvaddr < MODULES_END) {
> >> + if (!vt->vmalloc_start) {
> >> + *paddr = x86_64_VTOP(kvaddr);
> >> + return TRUE;
> >> + }
> >> +
> >> + if (!IS_VMALLOC_ADDR(kvaddr)) {
> >> + *paddr = x86_64_VTOP(kvaddr);
> >> + if (!verbose)
> >> + return TRUE;
> >> + }
> >> +
> >> + if (XEN() && (kt->xen_flags & WRITABLE_PAGE_TABLES))
> >> + return (x86_64_kvtop_xen_wpt(tc, kvaddr, paddr, verbose));
> >> + }
> >>
> >> /*
> >> * pgd = pgd_offset_k(addr);
> >> --
> >> 1.7.1
> >>
> >>
> >> --
> >> Crash-utility mailing list
> >> Crash-utility at redhat.com
> >> https://www.redhat.com/mailman/listinfo/crash-utility
> >
> > --
> > Crash-utility mailing list
> > Crash-utility at redhat.com
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> > .
> >
>
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