kernel.git/arch/powerpc/kernel/head_64.S, branch linux-5.9.y

powerpc/64: Don't initialise init_task->thread.regs

2020-05-15T01:58:54Z

Aneesh increased the size of struct pt_regs by 16 bytes and started seeing this WARN_ON: smp: Bringing up secondary CPUs ... ------------[ cut here ]------------ WARNING: CPU: 0 PID: 0 at arch/powerpc/kernel/process.c:455 giveup_all+0xb4/0x110 Modules linked in: CPU: 0 PID: 0 Comm: swapper/0 Not tainted 5.7.0-rc2-gcc-8.2.0-1.g8f6a41f-default+ #318 NIP: c00000000001a2b4 LR: c00000000001a29c CTR: c0000000031d0000 REGS: c0000000026d3980 TRAP: 0700 Not tainted (5.7.0-rc2-gcc-8.2.0-1.g8f6a41f-default+) MSR: 800000000282b033 CR: 48048224 XER: 00000000 CFAR: c000000000019cc8 IRQMASK: 1 GPR00: c00000000001a264 c0000000026d3c20 c0000000026d7200 800000000280b033 GPR04: 0000000000000001 0000000000000000 0000000000000077 30206d7372203164 GPR08: 0000000000002000 0000000002002000 800000000280b033 3230303030303030 GPR12: 0000000000008800 c0000000031d0000 0000000000800050 0000000002000066 GPR16: 000000000309a1a0 000000000309a4b0 000000000309a2d8 000000000309a890 GPR20: 00000000030d0098 c00000000264da40 00000000fd620000 c0000000ff798080 GPR24: c00000000264edf0 c0000001007469f0 00000000fd620000 c0000000020e5e90 GPR28: c00000000264edf0 c00000000264d200 000000001db60000 c00000000264d200 NIP [c00000000001a2b4] giveup_all+0xb4/0x110 LR [c00000000001a29c] giveup_all+0x9c/0x110 Call Trace: [c0000000026d3c20] [c00000000001a264] giveup_all+0x64/0x110 (unreliable) [c0000000026d3c90] [c00000000001ae34] __switch_to+0x104/0x480 [c0000000026d3cf0] [c000000000e0b8a0] __schedule+0x320/0x970 [c0000000026d3dd0] [c000000000e0c518] schedule_idle+0x38/0x70 [c0000000026d3df0] [c00000000019c7c8] do_idle+0x248/0x3f0 [c0000000026d3e70] [c00000000019cbb8] cpu_startup_entry+0x38/0x40 [c0000000026d3ea0] [c000000000011bb0] rest_init+0xe0/0xf8 [c0000000026d3ed0] [c000000002004820] start_kernel+0x990/0x9e0 [c0000000026d3f90] [c00000000000c49c] start_here_common+0x1c/0x400 Which was unexpected. The warning is checking the thread.regs->msr value of the task we are switching from: usermsr = tsk->thread.regs->msr; ... WARN_ON((usermsr & MSR_VSX) && !((usermsr & MSR_FP) && (usermsr & MSR_VEC))); ie. if MSR_VSX is set then both of MSR_FP and MSR_VEC are also set. Dumping tsk->thread.regs->msr we see that it's: 0x1db60000 Which is not a normal looking MSR, in fact the only valid bit is MSR_VSX, all the other bits are reserved in the current definition of the MSR. We can see from the oops that it was swapper/0 that we were switching from when we hit the warning, ie. init_task. So its thread.regs points to the base (high addresses) in init_stack. Dumping the content of init_task->thread.regs, with the members of pt_regs annotated (the 16 bytes larger version), we see: 0000000000000000 c000000002780080 gpr[0] gpr[1] 0000000000000000 c000000002666008 gpr[2] gpr[3] c0000000026d3ed0 0000000000000078 gpr[4] gpr[5] c000000000011b68 c000000002780080 gpr[6] gpr[7] 0000000000000000 0000000000000000 gpr[8] gpr[9] c0000000026d3f90 0000800000002200 gpr[10] gpr[11] c000000002004820 c0000000026d7200 gpr[12] gpr[13] 000000001db60000 c0000000010aabe8 gpr[14] gpr[15] c0000000010aabe8 c0000000010aabe8 gpr[16] gpr[17] c00000000294d598 0000000000000000 gpr[18] gpr[19] 0000000000000000 0000000000001ff8 gpr[20] gpr[21] 0000000000000000 c00000000206d608 gpr[22] gpr[23] c00000000278e0cc 0000000000000000 gpr[24] gpr[25] 000000002fff0000 c000000000000000 gpr[26] gpr[27] 0000000002000000 0000000000000028 gpr[28] gpr[29] 000000001db60000 0000000004750000 gpr[30] gpr[31] 0000000002000000 000000001db60000 nip msr 0000000000000000 0000000000000000 orig_r3 ctr c00000000000c49c 0000000000000000 link xer 0000000000000000 0000000000000000 ccr softe 0000000000000000 0000000000000000 trap dar 0000000000000000 0000000000000000 dsisr result 0000000000000000 0000000000000000 ppr kuap 0000000000000000 0000000000000000 pad[2] pad[3] This looks suspiciously like stack frames, not a pt_regs. If we look closely we can see return addresses from the stack trace above, c000000002004820 (start_kernel) and c00000000000c49c (start_here_common). init_task->thread.regs is setup at build time in processor.h: #define INIT_THREAD { \ .ksp = INIT_SP, \ .regs = (struct pt_regs *)INIT_SP - 1, /* XXX bogus, I think */ \ The early boot code where we setup the initial stack is: LOAD_REG_ADDR(r3,init_thread_union) /* set up a stack pointer */ LOAD_REG_IMMEDIATE(r1,THREAD_SIZE) add r1,r3,r1 li r0,0 stdu r0,-STACK_FRAME_OVERHEAD(r1) Which creates a stack frame of size 112 bytes (STACK_FRAME_OVERHEAD). Which is far too small to contain a pt_regs. So the result is init_task->thread.regs is pointing at some stack frames on the init stack, not at a pt_regs. We have gotten away with this for so long because with pt_regs at its current size the MSR happens to point into the first frame, at a location that is not written to by the early asm. With the 16 byte expansion the MSR falls into the second frame, which is used by the compiler, and collides with a saved register that tends to be non-zero. As far as I can see this has been wrong since the original merge of 64-bit ppc support, back in 2002. Conceptually swapper should have no regs, it never entered from userspace, and in fact that's what we do on 32-bit. It's also presumably what the "bogus" comment is referring to. So I think the right fix is to just not-initialise regs at all. I'm slightly worried this will break some code that isn't prepared for a NULL regs, but we'll have to see. Remove the comment in head_64.S which refers to us setting up the regs (even though we never did), and is otherwise not really accurate any more. Reported-by: Aneesh Kumar K.V Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/20200428123130.73078-1-mpe@ellerman.id.au

powerpc/64s: Fix section mismatch warnings from boot code

2020-03-25T01:07:59Z

We currently have two section mismatch warnings: The function __boot_from_prom() references the function __init prom_init(). The function start_here_common() references the function __init start_kernel(). The warnings are correct, we do have branches from non-init code into init code, which is freed after boot. But we don't expect to ever execute any of that early boot code after boot, if we did that would be a bug. In particular calling into OF after boot would be fatal because OF is no longer resident. So for now fix the warnings by marking the relevant functions as __REF, which puts them in the ".ref.text" section. This causes some reordering of the functions in the final link: @@ -217,10 +217,9 @@ c00000000000b088 t generic_secondary_common_init c00000000000b124 t __mmu_off c00000000000b14c t __start_initialization_multiplatform -c00000000000b1ac t __boot_from_prom -c00000000000b1ec t __after_prom_start -c00000000000b260 t p_end -c00000000000b27c T copy_and_flush +c00000000000b1ac t __after_prom_start +c00000000000b220 t p_end +c00000000000b23c T copy_and_flush c00000000000b300 T __secondary_start c00000000000b300 t copy_to_here c00000000000b344 t start_secondary_prolog @@ -228,8 +227,9 @@ c00000000000b36c t enable_64b_mode c00000000000b388 T relative_toc c00000000000b3a8 t p_toc -c00000000000b3b0 t start_here_common -c00000000000b3d0 t start_here_multiplatform +c00000000000b3b0 t __boot_from_prom +c00000000000b3f0 t start_here_multiplatform +c00000000000b480 t start_here_common c00000000000b880 T system_call_common c00000000000b974 t system_call c00000000000b9dc t system_call_exit In particular __boot_from_prom moves after copy_to_here, which means it's not copied to zero in the first stage of copy of the kernel to zero. But that's OK, because we only call __boot_from_prom before we do the copy, so it makes no difference when it's copied. The call sequence is: __start -> __start_initialization_multiplatform -> __boot_from_prom -> __start -> __start_initialization_multiplatform -> __after_prom_start -> copy_and_flush -> copy_and_flush (relocated to 0) -> start_here_multiplatform -> early_setup Reported-by: Mauricio Faria de Oliveira Reported-by: Roman Bolshakov Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/20200225031328.14676-1-mpe@ellerman.id.au

powerpc/prom: convert PROM_BUG() to standard trap

2019-08-28T01:31:18Z

Prior to commit 1bd98d7fbaf5 ("ppc64: Update BUG handling based on ppc32"), BUG() family was using BUG_ILLEGAL_INSTRUCTION which was an invalid instruction opcode to trap into program check exception. That commit converted them to using standard trap instructions, but prom/prom_init and their PROM_BUG() macro were left over. head_64.S and exception-64s.S were left aside as well. Convert them to using the standard BUG infrastructure. Signed-off-by: Christophe Leroy Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/cdaf4bbbb64c288a077845846f04b12683f8875a.1566817807.git.christophe.leroy@c-s.fr

powerpc/64: optimise LOAD_REG_IMMEDIATE_SYM()

2019-08-27T03:03:36Z

Optimise LOAD_REG_IMMEDIATE_SYM() using a temporary register to parallelise operations. It reduces the path from 5 to 3 instructions. Suggested-by: Segher Boessenkool Signed-off-by: Christophe Leroy Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/bad41ed02531bb0382420cbab50a0d7153b71767.1566311636.git.christophe.leroy@c-s.fr

powerpc: rewrite LOAD_REG_IMMEDIATE() as an intelligent macro

2019-08-27T03:03:36Z

Today LOAD_REG_IMMEDIATE() is a basic #define which loads all parts on a value into a register, including the parts that are NUL. This means always 2 instructions on PPC32 and always 5 instructions on PPC64. And those instructions cannot run in parallele as they are updating the same register. Ex: LOAD_REG_IMMEDIATE(r1,THREAD_SIZE) in head_64.S results in: 3c 20 00 00 lis r1,0 60 21 00 00 ori r1,r1,0 78 21 07 c6 rldicr r1,r1,32,31 64 21 00 00 oris r1,r1,0 60 21 40 00 ori r1,r1,16384 Rewrite LOAD_REG_IMMEDIATE() with GAS macro in order to skip the parts that are NUL. Rename existing LOAD_REG_IMMEDIATE() as LOAD_REG_IMMEDIATE_SYM() and use that one for loading value of symbols which are not known at compile time. Now LOAD_REG_IMMEDIATE(r1,THREAD_SIZE) in head_64.S results in: 38 20 40 00 li r1,16384 Signed-off-by: Christophe Leroy Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/d60ce8dd3a383c7adbfc322bf1d53d81724a6000.1566311636.git.christophe.leroy@c-s.fr

Merge tag 'powerpc-5.3-1' of git://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux

2019-07-13T23:08:36Z

Pull powerpc updates from Michael Ellerman: "Notable changes: - Removal of the NPU DMA code, used by the out-of-tree Nvidia driver, as well as some other functions only used by drivers that haven't (yet?) made it upstream. - A fix for a bug in our handling of hardware watchpoints (eg. perf record -e mem: ...) which could lead to register corruption and kernel crashes. - Enable HAVE_ARCH_HUGE_VMAP, which allows us to use large pages for vmalloc when using the Radix MMU. - A large but incremental rewrite of our exception handling code to use gas macros rather than multiple levels of nested CPP macros. And the usual small fixes, cleanups and improvements. Thanks to: Alastair D'Silva, Alexey Kardashevskiy, Andreas Schwab, Aneesh Kumar K.V, Anju T Sudhakar, Anton Blanchard, Arnd Bergmann, Athira Rajeev, Cédric Le Goater, Christian Lamparter, Christophe Leroy, Christophe Lombard, Christoph Hellwig, Daniel Axtens, Denis Efremov, Enrico Weigelt, Frederic Barrat, Gautham R. Shenoy, Geert Uytterhoeven, Geliang Tang, Gen Zhang, Greg Kroah-Hartman, Greg Kurz, Gustavo Romero, Krzysztof Kozlowski, Madhavan Srinivasan, Masahiro Yamada, Mathieu Malaterre, Michael Neuling, Nathan Lynch, Naveen N. Rao, Nicholas Piggin, Nishad Kamdar, Oliver O'Halloran, Qian Cai, Ravi Bangoria, Sachin Sant, Sam Bobroff, Satheesh Rajendran, Segher Boessenkool, Shaokun Zhang, Shawn Anastasio, Stewart Smith, Suraj Jitindar Singh, Thiago Jung Bauermann, YueHaibing" * tag 'powerpc-5.3-1' of git://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux: (163 commits) powerpc/powernv/idle: Fix restore of SPRN_LDBAR for POWER9 stop state. powerpc/eeh: Handle hugepages in ioremap space ocxl: Update for AFU descriptor template version 1.1 powerpc/boot: pass CONFIG options in a simpler and more robust way powerpc/boot: add {get, put}_unaligned_be32 to xz_config.h powerpc/irq: Don't WARN continuously in arch_local_irq_restore() powerpc/module64: Use symbolic instructions names. powerpc/module32: Use symbolic instructions names. powerpc: Move PPC_HA() PPC_HI() and PPC_LO() to ppc-opcode.h powerpc/module64: Fix comment in R_PPC64_ENTRY handling powerpc/boot: Add lzo support for uImage powerpc/boot: Add lzma support for uImage powerpc/boot: don't force gzipped uImage powerpc/8xx: Add microcode patch to move SMC parameter RAM. powerpc/8xx: Use IO accessors in microcode programming. powerpc/8xx: replace #ifdefs by IS_ENABLED() in microcode.c powerpc/8xx: refactor programming of microcode CPM params. powerpc/8xx: refactor printing of microcode patch name. powerpc/8xx: Refactor microcode write powerpc/8xx: refactor writing of CPM microcode arrays ...

powerpc/64: mark start_here_multiplatform as __ref

2019-06-15T14:00:30Z

Otherwise, the following warning is encountered: WARNING: vmlinux.o(.text+0x3dc6): Section mismatch in reference from the variable start_here_multiplatform to the function .init.text:.early_setup() The function start_here_multiplatform() references the function __init .early_setup(). This is often because start_here_multiplatform lacks a __init annotation or the annotation of .early_setup is wrong. Fixes: 56c46bba9bbf ("powerpc/64: Fix booting large kernels with STRICT_KERNEL_RWX") Cc: Russell Currey Signed-off-by: Christophe Leroy Signed-off-by: Michael Ellerman

treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152

2019-05-30T18:26:32Z

Based on 1 normalized pattern(s): this program is free software you can redistribute it and or modify it under the terms of the gnu general public license as published by the free software foundation either version 2 of the license or at your option any later version extracted by the scancode license scanner the SPDX license identifier GPL-2.0-or-later has been chosen to replace the boilerplate/reference in 3029 file(s). Signed-off-by: Thomas Gleixner Reviewed-by: Allison Randal Cc: linux-spdx@vger.kernel.org Link: https://lkml.kernel.org/r/20190527070032.746973796@linutronix.de Signed-off-by: Greg Kroah-Hartman

powerpc/64: Fix booting large kernels with STRICT_KERNEL_RWX

2019-04-20T12:02:12Z

With STRICT_KERNEL_RWX enabled anything marked __init is placed at a 16M boundary. This is necessary so that it can be repurposed later with different permissions. However, in kernels with text larger than 16M, this pushes early_setup past 32M, incapable of being reached by the branch instruction. Fix this by setting the CTR and branching there instead. Fixes: 1e0fc9d1eb2b ("powerpc/Kconfig: Enable STRICT_KERNEL_RWX for some configs") Signed-off-by: Russell Currey [mpe: Fix it to work on BE by using DOTSYM()] Signed-off-by: Michael Ellerman

powerpc/64: Simplify __secondary_start paca->kstack handling

2019-02-23T11:31:39Z

In __secondary_start() we load the thread_info of the idle task of the secondary CPU from current_set[cpu], and then convert it into a stack pointer before storing that back to paca->kstack. As pointed out in commit f761622e5943 ("powerpc: Initialise paca->kstack before early_setup_secondary") it's important that we initialise paca->kstack before calling the MMU setup code, in particular slb_initialize(), because it will bolt the SLB entry for the kstack into the SLB. However we have already setup paca->kstack in cpu_idle_thread_init(), since commit 3b5750644b2f ("[POWERPC] Bolt in SLB entry for kernel stack on secondary cpus") (May 2008). It's also in cpu_idle_thread_init() that we initialise current_set[cpu] with the thread_info pointer, so there is no issue of the timing being different between the two. Therefore the initialisation of paca->kstack in __setup_secondary() is completely redundant, so remove it. This has the added benefit of removing code that runs in real mode, and is therefore restricted by the RMO, and so opens the way for us to enable THREAD_INFO_IN_TASK. Signed-off-by: Michael Ellerman