On Fri, Sep 13, 2024 at 10:30:56AM +0200, Christophe Leroy wrote:

Le 13/09/2024 à 09:38, Luming Yu a écrit :

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On Fri, Sep 13, 2024 at 08:54:12AM +0200, Christophe Leroy wrote:

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Le 13/09/2024 à 03:40, Luming Yu a écrit :

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On Thu, Sep 12, 2024 at 12:23:29PM +0200, Christophe Leroy wrote:

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Le 12/09/2024 à 10:24, Luming Yu a écrit :

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From: Yu Luming <redacted>

convert powerpc entry code in syscall and fault to use syscall_work
and irqentry_state as well as common calls from generic entry infrastructure.

Signed-off-by: Luming Yu <redacted>
---
    arch/powerpc/Kconfig                   | 1 +
    arch/powerpc/include/asm/hw_irq.h      | 5 +++++
    arch/powerpc/include/asm/processor.h   | 6 ++++++
    arch/powerpc/include/asm/syscall.h     | 5 +++++
    arch/powerpc/include/asm/thread_info.h | 1 +
    arch/powerpc/kernel/syscall.c          | 6 +++++-
    arch/powerpc/mm/fault.c                | 5 +++++
    7 files changed, 28 insertions(+), 1 deletion(-)

There is another build problem:

    CC      kernel/entry/common.o
kernel/entry/common.c: In function 'irqentry_exit':
kernel/entry/common.c:335:21: error: implicit declaration of function
'regs_irqs_disabled'; did you mean 'raw_irqs_disabled'?
[-Werror=implicit-function-declaration]
    335 |         } else if (!regs_irqs_disabled(regs)) {
        |                     ^~~~~~~~~~~~~~~~~~
        |                     raw_irqs_disabled


You have put regs_irqs_disabled() in a section dedicated to PPC64, so it
fails on PPC32.


After fixing this problem and providing an empty asm/entry-common.h it is
now possible to build the kernel. But that's not enough, the board is stuck
after:

...
[    2.871391] Freeing unused kernel image (initmem) memory: 1228K
[    2.877990] Run /init as init process

Thanks for these questions. :-)
I haven't gotten chance to run it in ppc32 qemu.
the common syscall trace enter lost this hunk
-       if (!is_32bit_task())
-               audit_syscall_entry(regs->gpr[0], regs->gpr[3], regs->gpr[4],
-                                   regs->gpr[5], regs->gpr[6]);
-       else
-               audit_syscall_entry(regs->gpr[0],
-                                   regs->gpr[3] & 0xffffffff,
-                                   regs->gpr[4] & 0xffffffff,
-                                   regs->gpr[5] & 0xffffffff,
-                                   regs->gpr[6] & 0xffffffff);
which I don't understand whether we need a arch callbacks for it.

I don't thing so.

As far as I can see, audit_syscall_entry() is called by
syscall_enter_audit() in kernel/entry/common.c

And the masking of arguments based on is_32bit_task() is done in
syscall_get_arguments() with is called by
syscall_enter_audit() just before calling audit_syscall_entry() and which is
an arch callback that does the same as the removed hunk.

so, syscall_get_arguments is the ppc arch callback. thanks. :-)

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Before I sent out the RFC patch set, the very limited compile and boot test goes well with a ppc64 qemu VM. Surely, there will be a lot of test, debug and following up patch set update that is necessary to make it a complete convert.

Even on ppc64 it doesn't build, at the first place because
arch/powerpc/include/asm/entry-common.h is missing in your patch. Did you
forget to 'git add' it ?

oh, I forget that I was testing this patch on top of the early user notifier patch:
https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub.com%2Flinuxppc%2Fissues%2Fissues%2F477&data=05%7C02%7Cchristophe.leroy%40csgroup.eu%7C35a08ca9a81f4c6ff8ce08dcd3c73555%7C8b87af7d86474dc78df45f69a2011bb5%7C0%7C0%7C638618099770810941%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C0%7C%7C%7C&sdata=yCQWLIAXL%2BNHnzrh0e91WIBvF0c5WfF6pY6ZMHstocA%3D&reserved=0, https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fpatchwork.ozlabs.org%2Fproject%2Flinuxppc-dev%2Fpatch%2F1FD36D52828D2506%2B20231218031309.2063-1-luming.yu%40shingroup.cn%2F&data=05%7C02%7Cchristophe.leroy%40csgroup.eu%7C35a08ca9a81f4c6ff8ce08dcd3c73555%7C8b87af7d86474dc78df45f69a2011bb5%7C0%7C0%7C638618099770819779%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C0%7C%7C%7C&sdata=0WBSUlpAbL6EMdPEAtJv1HUHkbeUjjUcP98wYf9IxM4%3D&reserved=0
and the entry-common.h is as follows:
[root@localhost linux]# cat arch/powerpc/include/asm/entry-common.h
/* SPDX-License-Identifier: GPL-2.0 */
#ifndef ARCH_POWERPC_ENTRY_COMMON_H
#define ARCH_POWERPC_ENTRY_COMMON_H

#include <linux/user-return-notifier.h>

static inline void arch_exit_to_user_mode_prepare(struct pt_regs *regs,
                                                   unsigned long ti_work)
{
         if (ti_work & _TIF_USER_RETURN_NOTIFY)
                 fire_user_return_notifiers();
}

#define arch_exit_to_user_mode_prepare arch_exit_to_user_mode_prepare

#endif

As you could see , it looks irrelevant.

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And same as with PPC32, when I build PPC64 with an empty asm/entry-common.h,
it doesn't work. So, I guess you had some needed code in that file and you
have to send it.

please send me your kernel config and let me reproduce and double check
if there could be another bit of code make the difference. My test p8 64bit VM boots
an unmodified fedora 38 user space just fine with the patch.
After boot, the only difference is make install of kernel could hang for a while, that
I'm not sure how that could happen yet. and I plan to do some unit test for many common
features like : lockdep, ptrace, rcu, audit...

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I tested with both ppc64_defconfig and ppc64le_defconfig. With those two
configs QEMU remains stuck after the following lines. I use QEMU with
machine pseries:

[    2.701874][    T1] Running code patching self-tests ...
[    2.734007][    T1] registered taskstats version 1
[    2.735891][    T1] Loading compiled-in X.509 certificates
[    2.756472][    T1] Loaded X.509 cert 'Build time autogenerated kernel
key: 003f25410c2285abf44b4685b6d63682a2dc9f11'
[    2.784474][    T1] Demotion targets for Node 0: null
[    2.784748][    T1] page_owner is disabled
[    2.786795][    T1] Secure boot mode disabled
[    2.787436][    T1] ima: No TPM chip found, activating TPM-bypass!
[    2.787568][    T1] Loading compiled-in module X.509 certificates
[    2.790854][    T1] Loaded X.509 cert 'Build time autogenerated kernel
key: 003f25410c2285abf44b4685b6d63682a2dc9f11'
[    2.791289][    T1] ima: Allocated hash algorithm: sha256
[    2.796260][    T1] Secure boot mode disabled
[    2.796448][    T1] Trusted boot mode disabled
[    2.796560][    T1] ima: No architecture policies found
[    2.799580][    T1] printk: legacy console [netcon0] enabled
[    2.799696][    T1] netconsole: network logging started
[    2.880282][    T1] Freeing unused kernel image (initmem) memory: 6528K
[    2.884618][    T1] Checked W+X mappings: passed, no W+X pages found
[    2.885366][    T1] rodata_test: all tests were successful
[    2.885749][    T1] Run /init as init process
[    3.214730][   T58] mount (58) used greatest stack depth: 28672 bytes
left
...
nothing happens after that.

reproduced with ppc64_defconfig
[    0.818972][    T1] Run /init as init process
[    5.851684][  T240] request_module: modprobe binfmt-4c46 cannot be processed, kmod busy with 50 threads for more than 5 seconds now
[    5.851742][  T240] kworker/u33:18 (240) used greatest stack depth: 13584 bytes left
[    5.860081][  T232] kworker/u33:16 (232) used greatest stack depth: 13072 bytes left
[    5.863145][  T210] kworker/u35:13 (210) used greatest stack depth: 12928 bytes left
[    5.865000][    T1] Failed to execute /init (error -8)
[    5.868897][    T1] Run /sbin/init as init process
[   10.891673][  T315] request_module: modprobe binfmt-4c46 cannot be processed, kmod busy with 50 threads for more than 5 seconds now
[   10.894036][    T1] Starting init: /sbin/init exists but couldn't execute it (error -8)
[   10.901455][    T1] Run /etc/init as init process
[   10.903154][    T1] Run /bin/init as init process
[   10.904747][    T1] Run /bin/sh as init process
[   15.931679][  T367] request_module: modprobe binfmt-4c46 cannot be processed, kmod busy with 50 threads for more than 5 seconds now
[   15.934689][    T1] Starting init: /bin/sh exists but couldn't execute it (error -8)
[   15.940766][    T1] Kernel panic - not syncing: No working init found.  Try passing init= option to kernel. See Linux Documentation/admin-guide/init.rst for guidance.
[   15.946981][    T1] CPU: 13 PID: 1 Comm: swapper/0 Not tainted 6.7.0-rc1 #24
[   15.950050][    T1] Hardware name: IBM pSeries (emulated by qemu) POWER8 (raw) 0x4d0200 0xf000004 of:SLOF,git-3a259d hv:linux,kvm pSeries
[   15.955633][    T1] Call Trace:
[   15.956714][    T1] [c0000000080fbd20] [c0000000011811e8] dump_stack_lvl+0x6c/0x9c (unreliable)
[   15.959302][    T1] [c0000000080fbd50] [c00000000016b654] panic+0x178/0x424
[   15.961929][    T1] [c0000000080fbdf0] [c00000000001048c] kernel_init+0x19c/0x1a0
[   15.965310][    T1] [c0000000080fbe50] [c00000000000d394] ret_from_kernel_user_thread+0x14/0x1c
[   15.968494][    T1] --- interrupt: 0 at 0x0
[   15.989760][    T1] pstore: backend (nvram) writing error (-1)
qemu-system-ppc64: OS terminated: `
[root@localhost home]#
It would take some time to debug out from the issue. Stay tuned.
Thanks very much!

For PPC32 I use pmac32_defconfig and QEMU machine mac99

Christophe