kernel.git/arch/powerpc/kernel/ppc_save_regs.S, branch linux-rolling-stable

powerpc: update ppc_save_regs to save current r1 in pt_regs

2023-07-19T14:36:16Z

[ Upstream commit b684c09f09e7a6af3794d4233ef785819e72db79 ] ppc_save_regs() skips one stack frame while saving the CPU register states. Instead of saving current R1, it pulls the previous stack frame pointer. When vmcores caused by direct panic call (such as `echo c > /proc/sysrq-trigger`), are debugged with gdb, gdb fails to show the backtrace correctly. On further analysis, it was found that it was because of mismatch between r1 and NIP. GDB uses NIP to get current function symbol and uses corresponding debug info of that function to unwind previous frames, but due to the mismatching r1 and NIP, the unwinding does not work, and it fails to unwind to the 2nd frame and hence does not show the backtrace. GDB backtrace with vmcore of kernel without this patch: --------- (gdb) bt #0 0xc0000000002a53e8 in crash_setup_regs (oldregs=, newregs=0xc000000004f8f8d8) at ./arch/powerpc/include/asm/kexec.h:69 #1 __crash_kexec (regs=) at kernel/kexec_core.c:974 #2 0x0000000000000063 in ?? () #3 0xc000000003579320 in ?? () --------- Further analysis revealed that the mismatch occurred because "ppc_save_regs" was saving the previous stack's SP instead of the current r1. This patch fixes this by storing current r1 in the saved pt_regs. GDB backtrace with vmcore of patched kernel: -------- (gdb) bt #0 0xc0000000002a53e8 in crash_setup_regs (oldregs=0x0, newregs=0xc00000000670b8d8) at ./arch/powerpc/include/asm/kexec.h:69 #1 __crash_kexec (regs=regs@entry=0x0) at kernel/kexec_core.c:974 #2 0xc000000000168918 in panic (fmt=fmt@entry=0xc000000001654a60 "sysrq triggered crash\n") at kernel/panic.c:358 #3 0xc000000000b735f8 in sysrq_handle_crash (key=) at drivers/tty/sysrq.c:155 #4 0xc000000000b742cc in __handle_sysrq (key=key@entry=99, check_mask=check_mask@entry=false) at drivers/tty/sysrq.c:602 #5 0xc000000000b7506c in write_sysrq_trigger (file=, buf=, count=2, ppos=) at drivers/tty/sysrq.c:1163 #6 0xc00000000069a7bc in pde_write (ppos=, count=, buf=, file=, pde=0xc00000000362cb40) at fs/proc/inode.c:340 #7 proc_reg_write (file=, buf=, count=, ppos=) at fs/proc/inode.c:352 #8 0xc0000000005b3bbc in vfs_write (file=file@entry=0xc000000006aa6b00, buf=buf@entry=0x61f498b4f60 , count=count@entry=2, pos=pos@entry=0xc00000000670bda0) at fs/read_write.c:582 #9 0xc0000000005b4264 in ksys_write (fd=, buf=0x61f498b4f60 , count=2) at fs/read_write.c:637 #10 0xc00000000002ea2c in system_call_exception (regs=0xc00000000670be80, r0=) at arch/powerpc/kernel/syscall.c:171 #11 0xc00000000000c270 in system_call_vectored_common () at arch/powerpc/kernel/interrupt_64.S:192 -------- Nick adds: So this now saves regs as though it was an interrupt taken in the caller, at the instruction after the call to ppc_save_regs, whereas previously the NIP was there, but R1 came from the caller's caller and that mismatch is what causes gdb's dwarf unwinder to go haywire. Signed-off-by: Aditya Gupta Fixes: d16a58f8854b1 ("powerpc: Improve ppc_save_regs()") Reivewed-by: Nicholas Piggin Signed-off-by: Michael Ellerman Link: https://msgid.link/20230615091047.90433-1-adityag@linux.ibm.com Signed-off-by: Sasha Levin

powerpc: add definition for pt_regs offset within an interrupt frame

2022-12-02T06:54:08Z

This is a common offset that currently uses the overloaded STACK_FRAME_OVERHEAD constant. It's easier to read and more flexible to use a specific regs offset for this. Signed-off-by: Nicholas Piggin Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/20221127124942.1665522-8-npiggin@gmail.com

powerpc: simplify ppc_save_regs

2022-12-02T06:54:08Z

Adjust the pt_regs pointer so the interrupt frame offsets can be used to save registers. Signed-off-by: Nicholas Piggin Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/20221127124942.1665522-7-npiggin@gmail.com

powerpc: Improve ppc_save_regs()

2020-04-04T10:40:57Z

Make ppc_save_regs() a bit more useful: - Set NIP to our caller rather rather than the caller's caller (which is what we save to LR in the stack frame). - Set SOFTE to the current irq soft-mask state rather than uninitialised. - Zero CFAR rather than leave it uninitialised. In qemu, injecting a nmi to an idle CPU gives a nicer stack trace (note NIP, IRQMASK, CFAR). Oops: System Reset, sig: 6 [#1] LE PAGE_SIZE=64K MMU=Hash PREEMPT SMP NR_CPUS=2048 NUMA PowerNV Modules linked in: CPU: 0 PID: 0 Comm: swapper/0 Not tainted 5.6.0-rc2-00429-ga76e38fd80bf #1277 NIP: c0000000000b6e5c LR: c0000000000b6e5c CTR: c000000000b06270 REGS: c00000000173fb08 TRAP: 0100 Not tainted MSR: 9000000000001033 CR: 28000224 XER: 00000000 CFAR: c0000000016a2128 IRQMASK: c00000000173fc80 GPR00: c0000000000b6e5c c00000000173fc80 c000000001743400 c00000000173fb08 GPR04: 0000000000000000 0000000000000000 0000000000000008 0000000000000001 GPR08: 00000001fea80000 0000000000000000 0000000000000000 ffffffffffffffff GPR12: c000000000b06270 c000000001930000 00000000300026c0 0000000000000000 GPR16: 0000000000000000 0000000000000000 0000000000000003 c0000000016a2128 GPR20: c0000001ffc97148 0000000000000001 c000000000f289a8 0000000000080000 GPR24: c0000000016e1480 000000011dc870ba 0000000000000000 0000000000000003 GPR28: c0000000016a2128 c0000001ffc97148 c0000000016a2260 0000000000000003 NIP [c0000000000b6e5c] power9_idle_type+0x5c/0x70 LR [c0000000000b6e5c] power9_idle_type+0x5c/0x70 Call Trace: [c00000000173fc80] [c0000000000b6e5c] power9_idle_type+0x5c/0x70 (unreliable) [c00000000173fcb0] [c000000000b062b0] stop_loop+0x40/0x60 [c00000000173fce0] [c000000000b022d8] cpuidle_enter_state+0xa8/0x660 [c00000000173fd60] [c000000000b0292c] cpuidle_enter+0x4c/0x70 [c00000000173fda0] [c00000000017624c] call_cpuidle+0x4c/0x90 [c00000000173fdc0] [c000000000176768] do_idle+0x338/0x460 [c00000000173fe60] [c000000000176b3c] cpu_startup_entry+0x3c/0x40 [c00000000173fe90] [c0000000000126b4] rest_init+0x124/0x140 [c00000000173fed0] [c0000000010948d4] start_kernel+0x938/0x988 [c00000000173ff90] [c00000000000cdcc] start_here_common+0x1c/0x20 Oops: System Reset, sig: 6 [#1] LE PAGE_SIZE=64K MMU=Hash PREEMPT SMP NR_CPUS=2048 NUMA PowerNV Modules linked in: CPU: 0 PID: 0 Comm: swapper/0 Not tainted 5.6.0-rc2-00430-gddce91b8712f #1278 NIP: c00000000001d150 LR: c0000000000b6e5c CTR: c000000000b06270 REGS: c00000000173fb08 TRAP: 0100 Not tainted MSR: 9000000000001033 CR: 28000224 XER: 00000000 CFAR: 0000000000000000 IRQMASK: 1 GPR00: c0000000000b6e5c c00000000173fc80 c000000001743400 c00000000173fb08 GPR04: 0000000000000000 0000000000000000 0000000000000008 0000000000000001 GPR08: 00000001fea80000 0000000000000000 0000000000000000 ffffffffffffffff GPR12: c000000000b06270 c000000001930000 00000000300026c0 0000000000000000 GPR16: 0000000000000000 0000000000000000 0000000000000003 c0000000016a2128 GPR20: c0000001ffc97148 0000000000000001 c000000000f289a8 0000000000080000 GPR24: c0000000016e1480 00000000b68db8ce 0000000000000000 0000000000000003 GPR28: c0000000016a2128 c0000001ffc97148 c0000000016a2260 0000000000000003 NIP [c00000000001d150] replay_system_reset+0x30/0xa0 LR [c0000000000b6e5c] power9_idle_type+0x5c/0x70 Call Trace: [c00000000173fc80] [c0000000000b6e5c] power9_idle_type+0x5c/0x70 (unreliable) [c00000000173fcb0] [c000000000b062b0] stop_loop+0x40/0x60 [c00000000173fce0] [c000000000b022d8] cpuidle_enter_state+0xa8/0x660 [c00000000173fd60] [c000000000b0292c] cpuidle_enter+0x4c/0x70 [c00000000173fda0] [c00000000017624c] call_cpuidle+0x4c/0x90 [c00000000173fdc0] [c000000000176768] do_idle+0x338/0x460 [c00000000173fe60] [c000000000176b38] cpu_startup_entry+0x38/0x40 [c00000000173fe90] [c0000000000126b4] rest_init+0x124/0x140 [c00000000173fed0] [c0000000010948d4] start_kernel+0x938/0x988 [c00000000173ff90] [c00000000000cdcc] start_here_common+0x1c/0x20 Signed-off-by: Nicholas Piggin Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/20200403131006.123243-1-npiggin@gmail.com

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: move ASM_CONST and stringify_in_c() into asm-const.h

2018-07-30T12:48:16Z

This patch moves ASM_CONST() and stringify_in_c() into dedicated asm-const.h, then cleans all related inclusions. Signed-off-by: Christophe Leroy [mpe: asm-compat.h should include asm-const.h] Signed-off-by: Michael Ellerman

powerpc/32: Use stmw/lmw for registers save/restore in asm

2018-05-17T14:09:06Z

arch/powerpc/Makefile activates -mmultiple on BE PPC32 configs in order to use multiple word instructions in functions entry/exit. The patch does the same for the asm parts, for consistency. On processors like the 8xx on which insn fetching is pretty slow, this speeds up registers save/restore. Signed-off-by: Christophe Leroy [mpe: PPC32 is BE only, so drop the endian checks] Signed-off-by: Michael Ellerman

Fix common misspellings

2011-03-31T14:26:23Z

Fixes generated by 'codespell' and manually reviewed. Signed-off-by: Lucas De Marchi

powerpc: Remove second definition of STACK_FRAME_OVERHEAD

2010-11-29T04:48:23Z

Since STACK_FRAME_OVERHEAD is defined in asm/ptrace.h and that is ASSEMBER safe, we can just include that instead of going via asm-offsets.h. Signed-off-by: Stephen Rothwell Signed-off-by: Benjamin Herrenschmidt

powerpc: Prepare xmon_save_regs for use with kdump

2008-12-23T04:13:28Z

Today the arch/powerpc/xmon/setjmp.S file contains only the xmon_save_regs function. We want to use it for kdump purposes, so let's move the file into arch/powerpc/kernel/ and give the function a more generic name (ppc_save_regs). Signed-off-by: Anton Vorontsov Signed-off-by: Paul Mackerras