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SubjectRe: [PATCH] [RFC] arm64: enable HAVE_LD_DEAD_CODE_DATA_ELIMINATION
On Wed, Mar 17, 2021 at 02:37:57PM +0000, Catalin Marinas wrote:
> On Thu, Feb 25, 2021 at 12:20:56PM +0100, Arnd Bergmann wrote:
> > diff --git a/arch/arm64/kernel/vmlinux.lds.S b/arch/arm64/kernel/vmlinux.lds.S
> > index bad2b9eaab22..926cdb597a45 100644
> > --- a/arch/arm64/kernel/vmlinux.lds.S
> > +++ b/arch/arm64/kernel/vmlinux.lds.S
> > @@ -217,7 +217,7 @@ SECTIONS
> > INIT_CALLS
> > CON_INITCALL
> > INIT_RAM_FS
> > - *(.init.altinstructions .init.bss .init.bss.*) /* from the EFI stub */
> > + *(.init.altinstructions .init.data.* .init.bss .init.bss.*) /* from the EFI stub */
>
> INIT_DATA already covers .init.data and .init.data.*, so I don't think
> we need this change.

Ah, INIT_DATA only covers init.data.* (so no dot in front). The above
is needed for the EFI stub.

However, I gave this a quick try and under Qemu with -cpu max and -smp 2
(or more) it fails as below. I haven't debugged but the lr points to
just after the switch_to() call. Maybe some section got discarded and we
patched in the wrong instructions. It is fine with -cpu host or -smp 1.

-------------------8<------------------------
smp: Bringing up secondary CPUs ...
Detected PIPT I-cache on CPU1
CPU1: Booted secondary processor 0x0000000001 [0x000f0510]
Unable to handle kernel paging request at virtual address eb91d81ad2971160
Mem abort info:
ESR = 0x86000004
EC = 0x21: IABT (current EL), IL = 32 bits
SET = 0, FnV = 0
EA = 0, S1PTW = 0
[eb91d81ad2971160] address between user and kernel address ranges
Internal error: Oops: 86000004 [#1] PREEMPT SMP
Modules linked in:
CPU: 1 PID: 16 Comm: migration/1 Not tainted 5.12.0-rc3-00002-g128e977c1322 #1
Stopper: 0x0 <- 0x0
pstate: 60000085 (nZCv daIf -PAN -UAO -TCO BTYPE=--)
pc : 0xeb91d81ad2971160
lr : __schedule+0x230/0x6b8
sp : ffff80001009bd60
x29: ffff80001009bd60 x28: 0000000000000000
x27: ffff0000000a6760 x26: ffff0000000b7540
x25: 0080000000000000 x24: ffffd81ad3969000
x23: ffff0000000a6200 x22: 6ee0d81ad2971658
x21: ffff0000000a6200 x20: ffff000000080000
x19: ffff00007fbc6bc0 x18: 0000000000000030
x17: 0000000000000000 x16: 0000000000000000
x15: 00008952b30a9a9e x14: 0000000000000366
x13: 0000000000000192 x12: 0000000000000000
x11: 0000000000000003 x10: 00000000000009b0
x9 : ffff80001009bd30 x8 : ffff0000000a6c10
x7 : ffff00007fbc6cc0 x6 : 00000000fffedb30
x5 : 00000000ffffffff x4 : 0000000000000000
x3 : 0000000000000008 x2 : 0000000000000000
x1 : ffff0000000a6200 x0 : ffff0000000a3800
Call trace:
0xeb91d81ad2971160
schedule+0x70/0x108
schedule_preempt_disabled+0x24/0x40
__kthread_parkme+0x68/0xd0
kthread+0x138/0x170
ret_from_fork+0x10/0x30
Code: bad PC value
---[ end trace af3481062ecef3e7 ]---
--
Catalin

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