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0138ba5783
linux/arch/powerpc/kernel
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Nicholas Piggin 0138ba5783 powerpc/64/signal: Balance return predictor stack in signal trampoline 
Returning from an interrupt or syscall to a signal handler currently
begins execution directly at the handler's entry point, with LR set to
the address of the sigreturn trampoline. When the signal handler
function returns, it runs the trampoline. It looks like this:

    # interrupt at user address xyz
    # kernel stuff... signal is raised
    rfid
    # void handler(int sig)
    addis 2,12,.TOC.-.LCF0@ha
    addi 2,2,.TOC.-.LCF0@l
    mflr 0
    std 0,16(1)
    stdu 1,-96(1)
    # handler stuff
    ld 0,16(1)
    mtlr 0
    blr
    # __kernel_sigtramp_rt64
    addi    r1,r1,__SIGNAL_FRAMESIZE
    li      r0,__NR_rt_sigreturn
    sc
    # kernel executes rt_sigreturn
    rfid
    # back to user address xyz

Note the blr with no matching bl. This can corrupt the return
predictor.

Solve this by instead resuming execution at the signal trampoline
which then calls the signal handler. qtrace-tools link_stack checker
confirms the entire user/kernel/vdso cycle is balanced after this
patch, whereas it's not upstream.

Alan confirms the dwarf unwind info still looks good. gdb still
recognises the signal frame and can step into parent frames if it
break inside a signal handler.

Performance is pretty noisy, not a very significant change on a POWER9
here, but branch misses are consistently a lot lower on a
microbenchmark:

 Performance counter stats for './signal':

       13,085.72 msec task-clock                #    1.000 CPUs utilized
  45,024,760,101      cycles                    #    3.441 GHz
  65,102,895,542      instructions              #    1.45  insn per cycle
  11,271,673,787      branches                  #  861.372 M/sec
      59,468,979      branch-misses             #    0.53% of all branches

       12,989.09 msec task-clock                #    1.000 CPUs utilized
  44,692,719,559      cycles                    #    3.441 GHz
  65,109,984,964      instructions              #    1.46  insn per cycle
  11,282,136,057      branches                  #  868.585 M/sec
      39,786,942      branch-misses             #    0.35% of all branches

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200511101952.1463138-1-npiggin@gmail.com
2020-07-15 11:08:27 +10:00
..
ptrace powerpc/watchpoint: Use builtin ALIGN*() macros 2020-05-19 00:11:05 +10:00
syscalls vfs: add faccessat2 syscall 2020-05-14 16:44:25 +02:00
trace maccess: rename probe_kernel_{read,write} to copy_{from,to}_kernel_nofault 2020-06-17 10:57:41 -07:00
vdso32 powerpc/vdso32: Fallback on getres syscall when clock is unknown 2020-05-11 19:24:29 +10:00
vdso64 powerpc/64/signal: Balance return predictor stack in signal trampoline 2020-07-15 11:08:27 +10:00
.gitignore .gitignore: add SPDX License Identifier 2020-03-25 11:50:48 +01:00
align.c powerpc: Define and use get_user_instr() et. al. 2020-05-19 00:10:37 +10:00
asm-offsets.c mm: don't include asm/pgtable.h if linux/mm.h is already included 2020-06-09 09:39:13 -07:00
audit.c
btext.c mm: reorder includes after introduction of linux/pgtable.h 2020-06-09 09:39:13 -07:00
cacheinfo.c powerpc/cacheinfo: Add per cpu per index shared_cpu_list 2020-07-15 11:07:20 +10:00
cacheinfo.h powerpc/cacheinfo: add cacheinfo_teardown, cacheinfo_rebuild 2019-06-15 16:52:06 +10:00
compat_audit.c
cpu_setup_6xx.S powerpc/32: Blacklist functions running with MMU disabled for kprobe 2020-06-02 20:59:11 +10:00
cpu_setup_44x.S treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
cpu_setup_fsl_booke.S powerpc/booke: Spelling s/date/data/ 2019-11-17 01:56:31 -06:00
cpu_setup_pa6t.S treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 333 2019-06-05 17:37:06 +02:00
cpu_setup_power.S powerpc: Add POWER10 architected mode 2020-06-02 20:59:20 +10:00
cpu_setup_ppc970.S treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
cputable.c powerpc: Add POWER10 architected mode 2020-06-02 20:59:20 +10:00
crash_dump.c powerpc: Add prefixed instructions to instruction data type 2020-05-19 00:10:39 +10:00
dawr.c powerpc/watchpoint: Disable all available watchpoints when !dawr_force_enable 2020-05-19 00:11:05 +10:00
dbell.c KVM: PPC: Book3S HV: use smp_mb() when setting/clearing host_ipi flag 2019-09-24 12:46:26 +10:00
dma-iommu.c powerpc updates for 5.4 2019-09-20 11:48:06 -07:00
dma-mask.c dma-mapping, powerpc: simplify the arch dma_set_mask override 2019-02-18 22:41:03 +11:00
dma-swiotlb.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
dt_cpu_ftrs.c powerpc/dt_cpu_ftrs: Make use of macro ISA_V3_1 2020-06-22 10:37:56 +10:00
early_32.c powerpc/fsl_booke/32: implement KASLR infrastructure 2019-11-13 19:27:40 +11:00
eeh_cache.c powerpc/eeh_cache: Don't use pci_dn when inserting new ranges 2020-01-23 21:31:18 +11:00
eeh_dev.c powerpc/eeh: Add bdfn field to eeh_dev 2019-08-22 23:12:46 +10:00
eeh_driver.c powerpc/eeh: Fix deadlock handling dead PHB 2020-02-17 12:47:05 +11:00
eeh_event.c powerpc/eeh: Fix build with STACKTRACE=n 2019-09-14 00:01:14 +10:00
eeh_pe.c powerpc/eeh: Clean up EEH PEs after recovery finishes 2019-09-05 14:22:37 +10:00
eeh_sysfs.c powerpc/eeh_sysfs: Make clearing EEH_DEV_SYSFS saner 2020-01-23 21:31:19 +11:00
eeh.c powerpc/eeh: Release EEH device state synchronously 2020-05-18 21:58:44 +10:00
entry_32.S powerpc/entry32: Blacklist exception exit points for kprobe. 2020-06-02 20:59:13 +10:00
entry_64.S powerpc/64: indirect function call use bctrl rather than blrl in ret_from_kernel_thread 2020-06-22 10:37:55 +10:00
epapr_hcalls.S treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
epapr_paravirt.c powerpc: Use a datatype for instructions 2020-05-19 00:10:37 +10:00
exceptions-64e.S powerpc/64s: Implement interrupt exit logic in C 2020-04-01 13:42:14 +11:00
exceptions-64s.S powerpc/64s: Fix KVM interrupt using wrong save area 2020-06-16 12:52:43 +10:00
fadump.c powerpc/fadump: Account for memory_limit while reserving memory 2020-06-02 20:59:05 +10:00
firmware.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
fpu.S mm: reorder includes after introduction of linux/pgtable.h 2020-06-09 09:39:13 -07:00
fsl_booke_entry_mapping.S powerpc/fsl_booke/32: implement KASLR infrastructure 2019-11-13 19:27:40 +11:00
head_8xx.S mm: reorder includes after introduction of linux/pgtable.h 2020-06-09 09:39:13 -07:00
head_32.h Merge branch 'fixes' into next 2020-03-10 15:16:42 +11:00
head_32.S mm: reorder includes after introduction of linux/pgtable.h 2020-06-09 09:39:13 -07:00
head_40x.S mm: reorder includes after introduction of linux/pgtable.h 2020-06-09 09:39:13 -07:00
head_44x.S mm: reorder includes after introduction of linux/pgtable.h 2020-06-09 09:39:13 -07:00
head_64.S powerpc/64: Don't initialise init_task->thread.regs 2020-05-15 11:58:54 +10:00
head_booke.h powerpc: Replace _ALIGN_UP() by ALIGN() 2020-05-11 23:15:15 +10:00
head_fsl_booke.S mm: reorder includes after introduction of linux/pgtable.h 2020-06-09 09:39:13 -07:00
hw_breakpoint.c powerpc/watchpoint: Don't allow concurrent perf and ptrace events 2020-05-19 00:14:45 +10:00
idle_6xx.S powerpc/32: Blacklist functions running with MMU disabled for kprobe 2020-06-02 20:59:11 +10:00
idle_book3e.S treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
idle_book3s.S powerpc/64s: Reimplement power4_idle code in C 2020-01-16 14:59:37 +10:00
idle_e500.S powerpc/32: Blacklist functions running with MMU disabled for kprobe 2020-06-02 20:59:11 +10:00
idle.c powerpc/64s: Reimplement power4_idle code in C 2020-01-16 14:59:37 +10:00
ima_arch.c powerpc/ima: Fix secure boot rules in ima arch policy 2020-05-07 17:25:54 +10:00
io-workarounds.c mm: reorder includes after introduction of linux/pgtable.h 2020-06-09 09:39:13 -07:00
io.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
iomap.c powerpc: iomap.c: introduce io{read|write}64_{lo_hi|hi_lo} 2018-04-05 14:59:26 +10:00
iommu.c Merge branch 'topic/ppc-kvm' into next 2019-08-30 09:52:57 +10:00
irq.c mm: reorder includes after introduction of linux/pgtable.h 2020-06-09 09:39:13 -07:00
isa-bridge.c powerpc: remove __ioremap_at and __iounmap_at 2020-06-02 10:59:10 -07:00
jump_label.c powerpc: Use a datatype for instructions 2020-05-19 00:10:37 +10:00
kgdb.c maccess: make get_kernel_nofault() check for minimal type compatibility 2020-06-18 12:10:37 -07:00
kprobes-ftrace.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 156 2019-05-30 11:26:35 -07:00
kprobes.c maccess: rename probe_kernel_address to get_kernel_nofault 2020-06-18 11:14:40 -07:00
kvm_emul.S powerpc/kvm: Add ifdefs around template code 2019-09-14 00:04:40 +10:00
kvm.c powerpc/kvm: Explicitly mark kvm guest code as __init 2019-09-14 00:04:40 +10:00
l2cr_6xx.S powerpc/32: Blacklist functions running with MMU disabled for kprobe 2020-06-02 20:59:11 +10:00
legacy_serial.c tty/serial: Migrate 8250_fsl to use has_sysrq 2019-12-18 15:04:42 +01:00
Makefile powerpc/64s: Disable sanitisers for C syscall/interrupt entry/exit code 2020-05-29 21:12:09 +10:00
mce_power.c mm: reorder includes after introduction of linux/pgtable.h 2020-06-09 09:39:13 -07:00
mce.c powerpc/64s: machine check do not trace real-mode handler 2020-05-19 00:10:34 +10:00
misc_32.S powerpc/32: Blacklist functions running with MMU disabled for kprobe 2020-06-02 20:59:11 +10:00
misc_64.S Merge branch 'topic/kaslr-book3e32' into next 2019-11-14 19:23:33 +11:00
misc.S powerpc/32: Blacklist functions running with MMU disabled for kprobe 2020-06-02 20:59:11 +10:00
module_32.c powerpc: module_[32|64].c: replace swap function with built-in one 2020-05-11 23:15:14 +10:00
module_64.c maccess: rename probe_kernel_{read,write} to copy_{from,to}_kernel_nofault 2020-06-17 10:57:41 -07:00
module.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 156 2019-05-30 11:26:35 -07:00
module.lds
msi.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
note.S powerpc: Add PowerPC Capabilities ELF note 2019-08-30 09:40:15 +10:00
nvram_64.c powerpc updates for 5.8 2020-06-05 12:39:30 -07:00
of_platform.c powerpc/eeh: Make early EEH init pseries specific 2020-03-25 12:09:39 +11:00
optprobes_head.S powerpc: Add prefixed instructions to instruction data type 2020-05-19 00:10:39 +10:00
optprobes.c powerpc: Add ppc_inst_as_u64() 2020-05-26 23:36:57 +10:00
paca.c powerpc/pseries/svm: Drop unused align argument in alloc_shared_lppaca() function 2020-06-22 10:37:59 +10:00
pci_32.c powerpc/64: Adjust order in pcibios_init() 2019-08-22 23:11:48 +10:00
pci_64.c powerpc updates for 5.8 2020-06-05 12:39:30 -07:00
pci_dn.c powerpc/pcidn: Warn when sriov pci_dn management is used incorrectly 2020-01-23 21:31:19 +11:00
pci_of_scan.c powerpc/pci: Remove pcibios_setup_bus_devices() 2020-01-06 16:25:29 +11:00
pci-common.c powerpc updates for 5.7 2020-04-05 11:12:59 -07:00
pci-hotplug.c powerpc/eeh: Release EEH device state synchronously 2020-05-18 21:58:44 +10:00
pmc.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
ppc32.h treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
ppc_save_regs.S powerpc: Improve ppc_save_regs() 2020-04-04 21:40:57 +11:00
proc_powerpc.c proc: convert everything to "struct proc_ops" 2020-02-04 03:05:26 +00:00
process.c powerpc fixes for 5.8 #3 2020-06-21 10:02:53 -07:00
prom_init_check.sh powerpc/prom_init: Undo relocation before entering secure mode 2019-10-29 15:12:17 +11:00
prom_init.c mm: reorder includes after introduction of linux/pgtable.h 2020-06-09 09:39:13 -07:00
prom_parse.c
prom.c mm: reorder includes after introduction of linux/pgtable.h 2020-06-09 09:39:13 -07:00
reloc_32.S treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
reloc_64.S treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
rtas_flash.c proc: convert everything to "struct proc_ops" 2020-02-04 03:05:26 +00:00
rtas_pci.c mm: reorder includes after introduction of linux/pgtable.h 2020-06-09 09:39:13 -07:00
rtas-proc.c proc: convert everything to "struct proc_ops" 2020-02-04 03:05:26 +00:00
rtas-rtc.c powerpc: use time64_t in read_persistent_clock 2018-06-03 20:43:33 +10:00
rtas.c powerpc/rtas: Implement reentrant rtas call 2020-06-02 20:59:08 +10:00
rtasd.c proc: convert everything to "struct proc_ops" 2020-02-04 03:05:26 +00:00
secure_boot.c powerpc: Detect the trusted boot state of the system 2019-11-12 12:25:49 +11:00
security.c powerpc: Use a macro for creating instructions from u32s 2020-05-19 00:10:36 +10:00
secvar-ops.c powerpc/powernv: Add OPAL API interface to access secure variable 2019-11-13 00:33:22 +11:00
secvar-sysfs.c powerpc: expose secure variables to userspace via sysfs 2019-11-13 00:33:22 +11:00
setup_32.c mm: reorder includes after introduction of linux/pgtable.h 2020-06-09 09:39:13 -07:00
setup_64.c mm: reorder includes after introduction of linux/pgtable.h 2020-06-09 09:39:13 -07:00
setup-common.c mm: reorder includes after introduction of linux/pgtable.h 2020-06-09 09:39:13 -07:00
setup.h powerpc/64: Prevent stack protection in early boot 2020-03-25 12:09:38 +11:00
signal_32.c mm: don't include asm/pgtable.h if linux/mm.h is already included 2020-06-09 09:39:13 -07:00
signal_64.c powerpc/64/signal: Balance return predictor stack in signal trampoline 2020-07-15 11:08:27 +10:00
signal.c powerpc/watchpoint: Convert thread_struct->hw_brk to an array 2020-05-19 00:11:05 +10:00
signal.h powerpc/64/sycall: Implement syscall entry/exit logic in C 2020-04-01 13:42:13 +11:00
smp-tbsync.c
smp.c mm: reorder includes after introduction of linux/pgtable.h 2020-06-09 09:39:13 -07:00
stacktrace.c kernel: rename show_stack_loglvl() => show_stack() 2020-06-09 09:39:13 -07:00
suspend.c PM: hibernate: powerpc: Expose pfn_is_nosave() prototype 2019-06-14 10:48:56 +02:00
swsusp_32.S powerpc/32: Blacklist functions running with MMU disabled for kprobe 2020-06-02 20:59:11 +10:00
swsusp_64.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 505 2019-06-19 17:11:22 +02:00
swsusp_asm64.S treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 505 2019-06-19 17:11:22 +02:00
swsusp_booke.S
swsusp.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
sys_ppc32.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
syscall_64.c powerpc/64/kuap: Conditionally restore AMR in interrupt exit 2020-05-28 23:24:37 +10:00
syscalls.c y2038: syscalls: change remaining timeval to __kernel_old_timeval 2019-11-15 14:38:29 +01:00
sysfs.c powerpc/sysfs: Show idle_purr and idle_spurr for every CPU 2020-04-30 12:35:26 +10:00
systbl_chk.sh treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
systbl.S powerpc/64/sycall: Implement syscall entry/exit logic in C 2020-04-01 13:42:13 +11:00
tau_6xx.c powerpc/tau: Make some function static 2018-05-25 12:04:44 +10:00
time.c Revert "powerpc/64: irq_work avoid interrupt when called with hardware irqs enabled" 2020-04-03 16:55:34 +11:00
tm.S powerpc/tm: update comment about interrupt re-entrancy 2019-07-02 21:39:49 +10:00
traps.c mm: don't include asm/pgtable.h if linux/mm.h is already included 2020-06-09 09:39:13 -07:00
ucall.S powerpc/kernel: Add ucall_norets() ultravisor call handler 2019-08-30 09:40:15 +10:00
udbg_16550.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
udbg.c powerpc/udbg: Make it safe to call udbg_printf() always 2019-10-11 19:33:25 +11:00
uprobes.c powerpc: Add ppc_inst_next() 2020-05-26 23:36:51 +10:00
vdso.c mmap locking API: use coccinelle to convert mmap_sem rwsem call sites 2020-06-09 09:39:14 -07:00
vecemu.c powerpc: Define and use get_user_instr() et. al. 2020-05-19 00:10:37 +10:00
vector.S powerpc/32: Blacklist functions running with MMU disabled for kprobe 2020-06-02 20:59:11 +10:00
vmlinux.lds.S powerpc updates for 5.8 2020-06-05 12:39:30 -07:00
watchdog.c powerpc/watchdog: Use hrtimers for per-CPU heartbeat 2019-04-30 11:31:02 +10:00