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SubjectRe: ARM64: Regression with commit e3067861ba66 ("arm64: add basic VMAP_STACK support")
On Tue, Oct 17, 2017 at 05:36:58PM +0800, Leo Yan wrote:
> On Tue, Oct 17, 2017 at 10:32:21AM +0100, Ard Biesheuvel wrote:
>
> [...]
>
> > > AFAICT, erratum 836870 results in livelock rather than memory
> > > corruption, so I think we can ignore that.
> > >
> > > I'm a little worried by erratum 843419. The VMAP_STACK patches changed
> > > {adr,ldr}_this_cpu (and some users thereof), and it's possible we're
> > > managing to tickle that issue.
> > >
> > > If you still have an affected kernel, could you dump the output of:
> > >
> > > $ aarch64-linux-gnu-objdump -d vmlinux | grep -A 3 'ff[8c]:\s\+[a-f0-9]\+\s\+adrp'
> > >
> > > ... that would show us if there are any affected sequences.
> > >
> > > From a quick scan of my own vmlinux build from commit e3067861ba66, I
> > > didn't see any, but it's possible this depends on the config used.
> > >
> >
> > The linker should take care of that: it scans the entire executable,
> > and inserts a veneer if an adrp happens to end up at a vulnerable
> > offset in the page.
>
> Is this dependent on any GCC version?

It is, but we should warn if CONFIG_ARM64_ERRATUM_843419 is selected and
the linked doesn't support the --fix-cortex-a53-843419 option:

ld does not support --fix-cortex-a53-843419; kernel may be susceptible to erratum)

... do you see this when building the kernel?

> I am using GCC 6.2.1, so I get many affected sequences with Mark's command:

I beleive these are all beningn. AFAICT, none of these meet the conditions for
sequence 1 or sequence 2 affected by the erratum. e.g. many don't have
loads/stores using the adrp result.

Thanks,
Mark.

> leoy@leoy-linaro:~/Work/reference/opensource/linux$ aarch64-linux-gnu-objdump -d vmlinux | grep -A 3 'ff[8c]:\s\+[a-f0-9]\+\s\+adrp'
> ffff0000080a1ffc: 90007340 adrp x0, ffff000008f09000 <page_wait_table+0x1280>
> ffff0000080a2000: a900fedf stp xzr, xzr, [x22,#8]
> ffff0000080a2004: 91374000 add x0, x0, #0xdd0
> ffff0000080a2008: f9000ec0 str x0, [x22,#24]
> --
> ffff0000080b6ff8: b0007ce0 adrp x0, ffff000009053000 <chunk_hash_heads+0x680>
> ffff0000080b6ffc: 52901801 mov w1, #0x80c0 // #32960
> ffff0000080b7000: 72a02801 movk w1, #0x140, lsl #16
> ffff0000080b7004: 9102e273 add x19, x19, #0xb8
> --
> ffff0000080f1ff8: d00070a1 adrp x1, ffff000008f07000 <bit_wait_table+0xd80>
> ffff0000080f1ffc: f9406402 ldr x2, [x0,#200]
> ffff0000080f2000: f9405c03 ldr x3, [x0,#184]
> ffff0000080f2004: 14002915 b ffff0000080fc458 <e843419@00ce_00000e94_3c4>
> --
> ffff0000080feff8: 90000002 adrp x2, ffff0000080fe000 <prio_changed_rt+0x88>
> ffff0000080feffc: 9136e042 add x2, x2, #0xdb8
> ffff0000080ff000: f9000462 str x2, [x3,#8]
> ffff0000080ff004: f9448e62 ldr x2, [x19,#2328]
> --
> ffff00000810affc: f0006fe1 adrp x1, ffff000008f09000 <page_wait_table+0x1280>
> ffff00000810b000: f94017a2 ldr x2, [x29,#40]
> ffff00000810b004: aa1303e0 mov x0, x19
> ffff00000810b008: 1400013d b ffff00000810b4fc <e843419@00e7_000010c5_338>
> --
> ffff00000811dff8: d0005c80 adrp x0, ffff000008caf000 <kallsyms_token_index+0xaf00>
> ffff00000811dffc: 912be021 add x1, x1, #0xaf8
> ffff00000811e000: 912ae000 add x0, x0, #0xab8
> ffff00000811e004: 97ffe6ab bl ffff000008117ab0 <printk>
> --
> ffff000008137ff8: f0004443 adrp x3, ffff0000089c2000 <clock_monotonic+0x50>
> ffff000008137ffc: 910ac042 add x2, x2, #0x2b0
> ffff000008138000: 9113c063 add x3, x3, #0x4f0
> ffff000008138004: 71000c9f cmp w4, #0x3
> --
> ffff00000815eff8: b0005aa1 adrp x1, ffff000008cb3000 <kallsyms_token_index+0xef00>
> ffff00000815effc: 91362021 add x1, x1, #0xd88
> ffff00000815f000: 97ffffc8 bl ffff00000815ef20 <audit_log_format>
> ffff00000815f004: b94023a1 ldr w1, [x29,#32]

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