Bug 215217
| Summary: | Kernel fails to boot at an early stage when built with GCC_PLUGIN_LATENT_ENTROPY=y (PowerMac G4 3,6) | ||
|---|---|---|---|
| Product: | Platform Specific/Hardware | Reporter: | Erhard F. (erhard_f) |
| Component: | PPC-32 | Assignee: | platform_ppc-32 |
| Status: | RESOLVED CODE_FIX | ||
| Severity: | normal | CC: | christophe.leroy, michael |
| Priority: | P1 | ||
| Hardware: | PPC-32 | ||
| OS: | Linux | ||
| Kernel Version: | 5.16-rc3 | Subsystem: | |
| Regression: | No | Bisected commit-id: | |
| Attachments: |
kernel .config (5.16-rc3, PowerMac G4 DP)
kernel .config (4.18.20, PowerMac G4 DP) kernel .config (5.16-rc4 + CFLAGS_setup_32.o +=... , PowerMac G4 DP) kernel zImage (5.16-rc5 + CFLAGS_setup_32.o/early_32.o +=... , PowerMac G4 DP) kernel vmlinux.xz (5.16-rc5 + CFLAGS_setup_32.o/early_32.o +=... , PowerMac G4 DP) |
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POWER9 doesn't have KASAN. Did you try G4 without KASAN ? Just rebuilt the kernel without KASAN but I still hit this bug. I tried your config under QEMU and it works. So I don't know how I could help. >> ============================================================= >> OpenBIOS 1.1 [Jul 22 2021 22:33] >> Configuration device id QEMU version 1 machine id 1 >> CPUs: 1 >> Memory: 2048M >> UUID: 00000000-0000-0000-0000-000000000000 >> CPU type PowerPC,G4 milliseconds isn't unique. Welcome to OpenBIOS v1.1 built on Jul 22 2021 22:33 >> [ppc] Kernel already loaded (0x01000000 + 0x00f39460) (initrd 0x0203a000 + >> 0x001d1a3b) >> [ppc] Kernel command line: noreboot >> switching to new context: OF stdout device is: /pci@f2000000/mac-io@c/escc@13000/ch-a@13020 Preparing to boot Linux version 5.16.0-rc3-PowerMacG4+ (chleroy@PO20335.IDSI0.si.c-s.fr) (powerpc64-linux-gcc (GCC) 11.1.0, GNU ld (GNU Binutils) 2.36.1) #669 SMP Sun Dec 5 18:41:30 CET 2021 Detected machine type: 00000400 command line: memory layout at init: memory_limit : 00000000 (16 MB aligned) alloc_bottom : 01f3e000 alloc_top : 30000000 alloc_top_hi : 80000000 rmo_top : 30000000 ram_top : 80000000 found display : /pci@f2000000/QEMU,VGA@e, opening... done copying OF device tree... Building dt strings... Building dt structure... Device tree strings 0x01f3f000 -> 0x01f3e0a4 Device tree struct 0x01f40000 -> 0x7fde7ef8 Quiescing Open Firmware ... Booting Linux via __start() @ 0x01000000 ... Hello World ! Total memory = 2048MB; using 4096kB for hash table Activating Kernel Userspace Execution Prevention Activating Kernel Userspace Access Protection Linux version 5.16.0-rc3-PowerMacG4+ (chleroy@PO20335.IDSI0.si.c-s.fr) (powerpc64-linux-gcc (GCC) 11.1.0, GNU ld (GNU Binutils) 2.36.1) #669 SMP Sun Dec 5 18:41:30 CET 2021 KASAN init done ioremap() called early from pmac_feature_init+0x248/0xfe4. Use early_ioremap() instead Found UniNorth memory controller & host bridge @ 0xf8000000 revision: 0x07 Mapped at 0xf53bf000 ioremap() called early from probe_one_macio+0x228/0x414. Use early_ioremap() instead Found a Keylargo mac-io controller, rev: 0, mapped at 0x(ptrval) PowerMac motherboard: PowerMac G4 AGP Graphics ioremap() called early from udbg_scc_init+0x1dc/0x380. Use early_ioremap() instead boot stdout isn't a display ! Using PowerMac machine description printk: bootconsole [udbg0] enabled CPU maps initialized for 1 thread per core Created attachment 299935 [details]
kernel .config (4.18.20, PowerMac G4 DP)
Hmm, strange...
I tried to bisect but found out that this issue goes back to kernel v4.18.20 at least. This one is the earliest I am able to build with GCC_PLUGIN_LATENT_ENTROPY=y, kernels before error out with:
make: ngcc: No such file or directory
Cannot use CONFIG_GCC_PLUGINS: plugin support on gcc <= 5.1 is buggy on powerpc, please upgrade to gcc 5.2 or newer
I used gcc 9.4.0 and reduced the kernel .config a lot but it's still the same. v4.18.20 with GCC_PLUGIN_LATENT_ENTROPY=y freezes at this early boot stage, without GCC_PLUGIN_LATENT_ENTROPY booting continues.
Also GCC_PLUGIN_LATENT_ENTROPY=y makes no problem on my G5 either. So it's only the G4 which is affected. Wildly guessing this may be a 32bit PowerPC gcc specific thing?
It's likely there's some 32-bit boot code that is being instrumented in a way that causes it to crash. We probably need to add some more uses of DISABLE_LATENT_ENTROPY_PLUGIN in arch/powerpc/kernel/Makefile. To start with you could try adding: CFLAGS_setup_32.o += $(DISABLE_LATENT_ENTROPY_PLUGIN) Ok I cheked that out. There are already some in the Makefile: CFLAGS_cputable.o += $(DISABLE_LATENT_ENTROPY_PLUGIN) CFLAGS_prom_init.o += $(DISABLE_LATENT_ENTROPY_PLUGIN) CFLAGS_btext.o += $(DISABLE_LATENT_ENTROPY_PLUGIN) CFLAGS_prom.o += $(DISABLE_LATENT_ENTROPY_PLUGIN) I added CFLAGS_setup_32.o += $(DISABLE_LATENT_ENTROPY_PLUGIN) on top of that, rebuilt the kernel after a make clean. No success so far, the kernel still does not boot. Created attachment 299967 [details]
kernel .config (5.16-rc4 + CFLAGS_setup_32.o +=... , PowerMac G4 DP)
early_32.o should likely also have DISABLE_LATENT_ENTROPY_PLUGIN, maybe even more important that for setup_32.o Erhard, were you able to redo the test with DISABLE_LATENT_ENTROPY_PLUGIN also disabled for early_32.o ? If you can try with it disabled for both early_32.o and setup_32.o Then if it works, retry with it disabled only for early_32.o Created attachment 300015 [details]
kernel zImage (5.16-rc5 + CFLAGS_setup_32.o/early_32.o +=... , PowerMac G4 DP)
Unfortunately still no success.
Relevant section in the Makefile now looks like this:
CFLAGS_early_32.o += $(DISABLE_LATENT_ENTROPY_PLUGIN)
CFLAGS_setup_32.o += $(DISABLE_LATENT_ENTROPY_PLUGIN)
CFLAGS_cputable.o += $(DISABLE_LATENT_ENTROPY_PLUGIN)
CFLAGS_prom_init.o += $(DISABLE_LATENT_ENTROPY_PLUGIN)
CFLAGS_btext.o += $(DISABLE_LATENT_ENTROPY_PLUGIN)
CFLAGS_prom.o += $(DISABLE_LATENT_ENTROPY_PLUGIN)
I'll attach the generated zImage, maybe you can make something out of it.
Ok, so that's not enough, must be something else. I guess you are right next step should be analysis of the image. zImage however can hardly be used for that. Could you provide vmlinux file ? Created attachment 300027 [details]
kernel vmlinux.xz (5.16-rc5 + CFLAGS_setup_32.o/early_32.o +=... , PowerMac G4 DP)
Ok. I .xz-compressed it afterwards as it would be too big otherwise.
arch/powerpc/lib/feature-fixups.o also need DISABLE_LATENT_ENTROPY_PLUGIN, see extract from you vmlinux below c0c0ad20 <apply_feature_fixups>: c0c0ad20: 94 21 ff e0 stwu r1,-32(r1) c0c0ad24: 3c 60 c0 db lis r3,-16165 c0c0ad28: 7c 08 02 a6 mflr r0 c0c0ad2c: 38 63 55 50 addi r3,r3,21840 c0c0ad30: bf 41 00 08 stmw r26,8(r1) c0c0ad34: 7c 3f 0b 78 mr r31,r1 c0c0ad38: 3f 60 c0 da lis r27,-16166 <== latent_entropy@h c0c0ad3c: 90 01 00 24 stw r0,36(r1) c0c0ad40: 3f 80 c0 d4 lis r28,-16172 c0c0ad44: 83 db 5b 50 lwz r30,23376(r27) <== latent_entropy@l c0c0ad48: 4b 40 60 35 bl c0010d7c <add_reloc_offset> (In reply to Christophe Leroy from comment #13) > arch/powerpc/lib/feature-fixups.o also need DISABLE_LATENT_ENTROPY_PLUGIN, > see extract from you vmlinux below I can confirm this works, thanks! I need arch/powerpc/kernel/Makefile: CFLAGS_early_32.o += $(DISABLE_LATENT_ENTROPY_PLUGIN) arch/powerpc/lib/Makefile: CFLAGS_feature-fixups.o += $(DISABLE_LATENT_ENTROPY_PLUGIN) to make it going on my G4 with GCC_PLUGIN_LATENT_ENTROPY=y. Modifying setup_32.o is not needed. Fix landed in kernel 5.16.5. Thanks! |
Created attachment 299871 [details] kernel .config (5.16-rc3, PowerMac G4 DP) Get this on my PowerMac G4 DP when I build a kernel with GCC_PLUGIN_LATENT_ENTROPY=y. The kernel gets decompressed but shortly afterwards the machine freezes, displaying in black letters on an entirely white screen: done found display : /pci@f0000000/ATY,AlteracParent@10/ATY,Alterac_B@1, opening... Same kernel config built without GCC_PLUGIN_LATENT_ENTROPY just boots fine. Happens on v5.15.5 and v5.16-rc3. I did not test other kernel versions yet. My Talos II (Power9) on the other hand just works fine with a GCC_PLUGIN_LATENT_ENTROPY=y built kernel.