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Author SHA1 Message Date
Hari Bathini
cb5b691f82 powerpc64/ftrace: fix clobbered r15 during livepatching 
While r15 is clobbered always with PPC_FTRACE_OUT_OF_LINE, it is
not restored in livepatch sequence leading to not so obvious fails
like below:

  BUG: Unable to handle kernel data access on write at 0xc0000000000f9078
  Faulting instruction address: 0xc0000000018ff958
  Oops: Kernel access of bad area, sig: 11 [#1]
  ...
  NIP:  c0000000018ff958 LR: c0000000018ff930 CTR: c0000000009c0790
  REGS: c00000005f2e7790 TRAP: 0300   Tainted: G              K      (6.14.0+)
  MSR:  8000000000009033 <SF,EE,ME,IR,DR,RI,LE>  CR: 2822880b  XER: 20040000
  CFAR: c0000000008addc0 DAR: c0000000000f9078 DSISR: 0a000000 IRQMASK: 1
  GPR00: c0000000018f2584 c00000005f2e7a30 c00000000280a900 c000000017ffa488
  GPR04: 0000000000000008 0000000000000000 c0000000018f24fc 000000000000000d
  GPR08: fffffffffffe0000 000000000000000d 0000000000000000 0000000000008000
  GPR12: c0000000009c0790 c000000017ffa480 c00000005f2e7c78 c0000000000f9070
  GPR16: c00000005f2e7c90 0000000000000000 0000000000000000 0000000000000000
  GPR20: 0000000000000000 c00000005f3efa80 c00000005f2e7c60 c00000005f2e7c88
  GPR24: c00000005f2e7c60 0000000000000001 c0000000000f9078 0000000000000000
  GPR28: 00007fff97960000 c000000017ffa480 0000000000000000 c0000000000f9078
  ...
  Call Trace:
    check_heap_object+0x34/0x390 (unreliable)
  __mutex_unlock_slowpath.isra.0+0xe4/0x230
  seq_read_iter+0x430/0xa90
  proc_reg_read_iter+0xa4/0x200
  vfs_read+0x41c/0x510
  ksys_read+0xa4/0x190
  system_call_exception+0x1d0/0x440
  system_call_vectored_common+0x15c/0x2ec

Fix it by restoring r15 always.

Fixes: eec37961a5 ("powerpc64/ftrace: Move ftrace sequence out of line")
Reported-by: Viktor Malik <vmalik@redhat.com>
Closes: https://lore.kernel.org/lkml/1aec4a9a-a30b-43fd-b303-7a351caeccb7@redhat.com
Cc: stable@vger.kernel.org # v6.13+
Signed-off-by: Hari Bathini <hbathini@linux.ibm.com>
Tested-by: Viktor Malik <vmalik@redhat.com>
Acked-by: Naveen N Rao (AMD) <naveen@kernel.org>
Signed-off-by: Madhavan Srinivasan <maddy@linux.ibm.com>
Link: https://patch.msgid.link/20250416191227.201146-1-hbathini@linux.ibm.com
 2025-04-29 11:03:07 +05:30
Naveen N Rao
a52f6043a2 powerpc/ftrace: Add support for DYNAMIC_FTRACE_WITH_DIRECT_CALLS 
Add support for DYNAMIC_FTRACE_WITH_DIRECT_CALLS similar to the arm64
implementation.

ftrace direct calls allow custom trampolines to be called into directly
from function ftrace call sites, bypassing the ftrace trampoline
completely. This functionality is currently utilized by BPF trampolines
to hook into kernel function entries.

Since we have limited relative branch range, we support ftrace direct
calls through support for DYNAMIC_FTRACE_WITH_CALL_OPS. In this
approach, ftrace trampoline is not entirely bypassed. Rather, it is
re-purposed into a stub that reads direct_call field from the associated
ftrace_ops structure and branches into that, if it is not NULL. For
this, it is sufficient if we can ensure that the ftrace trampoline is
reachable from all traceable functions.

When multiple ftrace_ops are associated with a call site, we utilize a
call back to set pt_regs->orig_gpr3 that can then be tested on the
return path from the ftrace trampoline to branch into the direct caller.

Signed-off-by: Naveen N Rao <naveen@kernel.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://patch.msgid.link/20241030070850.1361304-16-hbathini@linux.ibm.com
 2024-10-31 11:00:55 +11:00
Naveen N Rao
e717754f0b powerpc/ftrace: Add support for DYNAMIC_FTRACE_WITH_CALL_OPS 
Implement support for DYNAMIC_FTRACE_WITH_CALL_OPS similar to the
arm64 implementation.

This works by patching-in a pointer to an associated ftrace_ops
structure before each traceable function. If multiple ftrace_ops are
associated with a call site, then a special ftrace_list_ops is used to
enable iterating over all the registered ftrace_ops. If no ftrace_ops
are associated with a call site, then a special ftrace_nop_ops structure
is used to render the ftrace call as a no-op. ftrace trampoline can then
read the associated ftrace_ops for a call site by loading from an offset
from the LR, and branch directly to the associated function.

The primary advantage with this approach is that we don't have to
iterate over all the registered ftrace_ops for call sites that have a
single ftrace_ops registered. This is the equivalent of implementing
support for dynamic ftrace trampolines, which set up a special ftrace
trampoline for each registered ftrace_ops and have individual call sites
branch into those directly.

A secondary advantage is that this gives us a way to add support for
direct ftrace callers without having to resort to using stubs. The
address of the direct call trampoline can be loaded from the ftrace_ops
structure.

To support this, we reserve a nop before each function on 32-bit
powerpc. For 64-bit powerpc, two nops are reserved before each
out-of-line stub. During ftrace activation, we update this location with
the associated ftrace_ops pointer. Then, on ftrace entry, we load from
this location and call into ftrace_ops->func().

For 64-bit powerpc, we ensure that the out-of-line stub area is
doubleword aligned so that ftrace_ops address can be updated atomically.

Signed-off-by: Naveen N Rao <naveen@kernel.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://patch.msgid.link/20241030070850.1361304-15-hbathini@linux.ibm.com
 2024-10-31 11:00:55 +11:00
Naveen N Rao
cf9bc0efcc powerpc64/ftrace: Support .text larger than 32MB with out-of-line stubs 
We are restricted to a .text size of ~32MB when using out-of-line
function profile sequence. Allow this to be extended up to the previous
limit of ~64MB by reserving space in the middle of .text.

A new config option CONFIG_PPC_FTRACE_OUT_OF_LINE_NUM_RESERVE is
introduced to specify the number of function stubs that are reserved in
.text. On boot, ftrace utilizes stubs from this area first before using
the stub area at the end of .text.

A ppc64le defconfig has ~44k functions that can be traced. A more
conservative value of 32k functions is chosen as the default value of
PPC_FTRACE_OUT_OF_LINE_NUM_RESERVE so that we do not allot more space
than necessary by default. If building a kernel that only has 32k
trace-able functions, we won't allot any more space at the end of .text
during the pass on vmlinux.o. Otherwise, only the remaining functions
get space for stubs at the end of .text. This default value should help
cover a .text size of ~48MB in total (including space reserved at the
end of .text which can cover up to 32MB), which should be sufficient for
most common builds. For a very small kernel build, this can be set to 0.
Or, this can be bumped up to a larger value to support vmlinux .text
size up to ~64MB.

Signed-off-by: Naveen N Rao <naveen@kernel.org>
Signed-off-by: Hari Bathini <hbathini@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://patch.msgid.link/20241030070850.1361304-14-hbathini@linux.ibm.com
 2024-10-31 11:00:55 +11:00
Naveen N Rao
eec37961a5 powerpc64/ftrace: Move ftrace sequence out of line 
Function profile sequence on powerpc includes two instructions at the
beginning of each function:
	mflr	r0
	bl	ftrace_caller

The call to ftrace_caller() gets nop'ed out during kernel boot and is
patched in when ftrace is enabled.

Given the sequence, we cannot return from ftrace_caller with 'blr' as we
need to keep LR and r0 intact. This results in link stack (return
address predictor) imbalance when ftrace is enabled. To address that, we
would like to use a three instruction sequence:
	mflr	r0
	bl	ftrace_caller
	mtlr	r0

Further more, to support DYNAMIC_FTRACE_WITH_CALL_OPS, we need to
reserve two instruction slots before the function. This results in a
total of five instruction slots to be reserved for ftrace use on each
function that is traced.

Move the function profile sequence out-of-line to minimize its impact.
To do this, we reserve a single nop at function entry using
-fpatchable-function-entry=1 and add a pass on vmlinux.o to determine
the total number of functions that can be traced. This is then used to
generate a .S file reserving the appropriate amount of space for use as
ftrace stubs, which is built and linked into vmlinux.

On bootup, the stub space is split into separate stubs per function and
populated with the proper instruction sequence. A pointer to the
associated stub is maintained in dyn_arch_ftrace.

For modules, space for ftrace stubs is reserved from the generic module
stub space.

This is restricted to and enabled by default only on 64-bit powerpc,
though there are some changes to accommodate 32-bit powerpc. This is
done so that 32-bit powerpc could choose to opt into this based on
further tests and benchmarks.

As an example, after this patch, kernel functions will have a single nop
at function entry:
<kernel_clone>:
	addis	r2,r12,467
	addi	r2,r2,-16028
	nop
	mfocrf	r11,8
	...

When ftrace is enabled, the nop is converted to an unconditional branch
to the stub associated with that function:
<kernel_clone>:
	addis	r2,r12,467
	addi	r2,r2,-16028
	b	ftrace_ool_stub_text_end+0x11b28
	mfocrf	r11,8
	...

The associated stub:
<ftrace_ool_stub_text_end+0x11b28>:
	mflr	r0
	bl	ftrace_caller
	mtlr	r0
	b	kernel_clone+0xc
	...

This change showed an improvement of ~10% in null_syscall benchmark on a
Power 10 system with ftrace enabled.

Signed-off-by: Naveen N Rao <naveen@kernel.org>
Signed-off-by: Hari Bathini <hbathini@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://patch.msgid.link/20241030070850.1361304-13-hbathini@linux.ibm.com
 2024-10-31 11:00:54 +11:00
Naveen N Rao
654b3fa61b powerpc32/ftrace: Unify 32-bit and 64-bit ftrace entry code 
On 32-bit powerpc, gcc generates a three instruction sequence for
function profiling:
	mflr	r0
	stw	r0, 4(r1)
	bl	_mcount

On kernel boot, the call to _mcount() is nop-ed out, to be patched back
in when ftrace is actually enabled. The 'stw' instruction therefore is
not necessary unless ftrace is enabled. Nop it out during ftrace init.

When ftrace is enabled, we want the 'stw' so that stack unwinding works
properly. Perform the same within the ftrace handler, similar to 64-bit
powerpc.

Reviewed-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Naveen N Rao <naveen@kernel.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://patch.msgid.link/20241030070850.1361304-5-hbathini@linux.ibm.com
 2024-10-31 11:00:53 +11:00
Linus Torvalds
968b803324 powerpc updates for 6.8 
- Add initial support to recognise the HeXin C2000 processor.
 
  - Add papr-vpd and papr-sysparm character device drivers for VPD & sysparm
    retrieval, so userspace tools can be adapted to avoid doing raw firmware
    calls from userspace.
 
  - Sched domains optimisations for shared processor partitions on P9/P10.
 
  - A series of optimisations for KVM running as a nested HV under PowerVM.
 
  - Other small features and fixes.
 
 Thanks to: Aditya Gupta, Aneesh Kumar K.V, Arnd Bergmann, Christophe Leroy,
 Colin Ian King, Dario Binacchi, David Heidelberg, Geoff Levand, Gustavo A.
 R. Silva, Haoran Liu, Jordan Niethe, Kajol Jain, Kevin Hao, Kunwu Chan, Li
 kunyu, Li zeming, Masahiro Yamada, Michal Suchánek, Nathan Lynch, Naveen N Rao,
 Nicholas Piggin, Randy Dunlap, Sathvika Vasireddy, Srikar Dronamraju, Stephen
 Rothwell, Vaibhav Jain, Zhao Ke.
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Merge tag 'powerpc-6.8-1' of git://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux

Pull powerpc updates from Michael Ellerman:

 - Add initial support to recognise the HeXin C2000 processor.

 - Add papr-vpd and papr-sysparm character device drivers for VPD &
   sysparm retrieval, so userspace tools can be adapted to avoid doing
   raw firmware calls from userspace.

 - Sched domains optimisations for shared processor partitions on
   P9/P10.

 - A series of optimisations for KVM running as a nested HV under
   PowerVM.

 - Other small features and fixes.

Thanks to Aditya Gupta, Aneesh Kumar K.V, Arnd Bergmann, Christophe
Leroy, Colin Ian King, Dario Binacchi, David Heidelberg, Geoff Levand,
Gustavo A. R. Silva, Haoran Liu, Jordan Niethe, Kajol Jain, Kevin Hao,
Kunwu Chan, Li kunyu, Li zeming, Masahiro Yamada, Michal Suchánek,
Nathan Lynch, Naveen N Rao, Nicholas Piggin, Randy Dunlap, Sathvika
Vasireddy, Srikar Dronamraju, Stephen Rothwell, Vaibhav Jain, and
Zhao Ke.

* tag 'powerpc-6.8-1' of git://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux: (96 commits)
  powerpc/ps3_defconfig: Disable PPC64_BIG_ENDIAN_ELF_ABI_V2
  powerpc/86xx: Drop unused CONFIG_MPC8610
  powerpc/powernv: Add error handling to opal_prd_range_is_valid
  selftests/powerpc: Fix spelling mistake "EACCESS" -> "EACCES"
  powerpc/hvcall: Reorder Nestedv2 hcall opcodes
  powerpc/ps3: Add missing set_freezable() for ps3_probe_thread()
  powerpc/mpc83xx: Use wait_event_freezable() for freezable kthread
  powerpc/mpc83xx: Add the missing set_freezable() for agent_thread_fn()
  powerpc/fsl: Fix fsl,tmu-calibration to match the schema
  powerpc/smp: Dynamically build Powerpc topology
  powerpc/smp: Avoid asym packing within thread_group of a core
  powerpc/smp: Add __ro_after_init attribute
  powerpc/smp: Disable MC domain for shared processor
  powerpc/smp: Enable Asym packing for cores on shared processor
  powerpc/sched: Cleanup vcpu_is_preempted()
  powerpc: add cpu_spec.cpu_features to vmcoreinfo
  powerpc/imc-pmu: Add a null pointer check in update_events_in_group()
  powerpc/powernv: Add a null pointer check in opal_powercap_init()
  powerpc/powernv: Add a null pointer check in opal_event_init()
  powerpc/powernv: Add a null pointer check to scom_debug_init_one()
  ...
 2024-01-08 16:22:47 -08:00
Naveen N Rao
ae24db43b3 powerpc/ftrace: Remove nops after the call to ftrace_stub 
ftrace_stub is within the same CU, so there is no need for a subsequent
nop instruction.

Signed-off-by: Naveen N Rao <naveen@kernel.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/8ee5ec520e37d5523654bb2cd65a17512fb774e2.1702045299.git.naveen@kernel.org
 2023-12-13 21:49:22 +11:00
Naveen N Rao
4b3338aaa7 powerpc/ftrace: Fix stack teardown in ftrace_no_trace 
Commit 41a506ef71 ("powerpc/ftrace: Create a dummy stackframe to fix
stack unwind") added use of a new stack frame on ftrace entry to fix
stack unwind. However, the commit missed updating the offset used while
tearing down the ftrace stack when ftrace is disabled. Fix the same.

In addition, the commit missed saving the correct stack pointer in
pt_regs. Update the same.

Fixes: 41a506ef71 ("powerpc/ftrace: Create a dummy stackframe to fix stack unwind")
Cc: stable@vger.kernel.org # v6.5+
Signed-off-by: Naveen N Rao <naveen@kernel.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20231130065947.2188860-1-naveen@kernel.org
 2023-12-05 14:14:12 +11:00
Linus Torvalds
4ad0a4c234 powerpc updates for 6.6 
- Add HOTPLUG_SMT support (/sys/devices/system/cpu/smt) and honour the
    configured SMT state when hotplugging CPUs into the system.
 
  - Combine final TLB flush and lazy TLB mm shootdown IPIs when using the Radix
    MMU to avoid a broadcast TLBIE flush on exit.
 
  - Drop the exclusion between ptrace/perf watchpoints, and drop the now unused
    associated arch hooks.
 
  - Add support for the "nohlt" command line option to disable CPU idle.
 
  - Add support for -fpatchable-function-entry for ftrace, with GCC >= 13.1.
 
  - Rework memory block size determination, and support 256MB size on systems
    with GPUs that have hotpluggable memory.
 
  - Various other small features and fixes.
 
 Thanks to: Andrew Donnellan, Aneesh Kumar K.V, Arnd Bergmann, Athira Rajeev,
 Benjamin Gray, Christophe Leroy, Frederic Barrat, Gautam Menghani, Geoff Levand,
 Hari Bathini, Immad Mir, Jialin Zhang, Joel Stanley, Jordan Niethe, Justin
 Stitt, Kajol Jain, Kees Cook, Krzysztof Kozlowski, Laurent Dufour, Liang He,
 Linus Walleij, Mahesh Salgaonkar, Masahiro Yamada, Michal Suchanek, Nageswara
 R Sastry, Nathan Chancellor, Nathan Lynch, Naveen N Rao, Nicholas Piggin, Nick
 Desaulniers, Omar Sandoval, Randy Dunlap, Reza Arbab, Rob Herring, Russell
 Currey, Sourabh Jain, Thomas Gleixner, Trevor Woerner, Uwe Kleine-König, Vaibhav
 Jain, Xiongfeng Wang, Yuan Tan, Zhang Rui, Zheng Zengkai.
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Merge tag 'powerpc-6.6-1' of git://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux

Pull powerpc updates from Michael Ellerman:

 - Add HOTPLUG_SMT support (/sys/devices/system/cpu/smt) and honour the
   configured SMT state when hotplugging CPUs into the system

 - Combine final TLB flush and lazy TLB mm shootdown IPIs when using the
   Radix MMU to avoid a broadcast TLBIE flush on exit

 - Drop the exclusion between ptrace/perf watchpoints, and drop the now
   unused associated arch hooks

 - Add support for the "nohlt" command line option to disable CPU idle

 - Add support for -fpatchable-function-entry for ftrace, with GCC >=
   13.1

 - Rework memory block size determination, and support 256MB size on
   systems with GPUs that have hotpluggable memory

 - Various other small features and fixes

Thanks to Andrew Donnellan, Aneesh Kumar K.V, Arnd Bergmann, Athira
Rajeev, Benjamin Gray, Christophe Leroy, Frederic Barrat, Gautam
Menghani, Geoff Levand, Hari Bathini, Immad Mir, Jialin Zhang, Joel
Stanley, Jordan Niethe, Justin Stitt, Kajol Jain, Kees Cook, Krzysztof
Kozlowski, Laurent Dufour, Liang He, Linus Walleij, Mahesh Salgaonkar,
Masahiro Yamada, Michal Suchanek, Nageswara R Sastry, Nathan Chancellor,
Nathan Lynch, Naveen N Rao, Nicholas Piggin, Nick Desaulniers, Omar
Sandoval, Randy Dunlap, Reza Arbab, Rob Herring, Russell Currey, Sourabh
Jain, Thomas Gleixner, Trevor Woerner, Uwe Kleine-König, Vaibhav Jain,
Xiongfeng Wang, Yuan Tan, Zhang Rui, and Zheng Zengkai.

* tag 'powerpc-6.6-1' of git://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux: (135 commits)
  macintosh/ams: linux/platform_device.h is needed
  powerpc/xmon: Reapply "Relax frame size for clang"
  powerpc/mm/book3s64: Use 256M as the upper limit with coherent device memory attached
  powerpc/mm/book3s64: Fix build error with SPARSEMEM disabled
  powerpc/iommu: Fix notifiers being shared by PCI and VIO buses
  powerpc/mpc5xxx: Add missing fwnode_handle_put()
  powerpc/config: Disable SLAB_DEBUG_ON in skiroot
  powerpc/pseries: Remove unused hcall tracing instruction
  powerpc/pseries: Fix hcall tracepoints with JUMP_LABEL=n
  powerpc: dts: add missing space before {
  powerpc/eeh: Use pci_dev_id() to simplify the code
  powerpc/64s: Move CPU -mtune options into Kconfig
  powerpc/powermac: Fix unused function warning
  powerpc/pseries: Rework lppaca_shared_proc() to avoid DEBUG_PREEMPT
  powerpc: Don't include lppaca.h in paca.h
  powerpc/pseries: Move hcall_vphn() prototype into vphn.h
  powerpc/pseries: Move VPHN constants into vphn.h
  cxl: Drop unused detach_spa()
  powerpc: Drop zalloc_maybe_bootmem()
  powerpc/powernv: Use struct opal_prd_msg in more places
  ...
 2023-08-31 12:43:10 -07:00
Naveen N Rao
0f71dcfb4a powerpc/ftrace: Add support for -fpatchable-function-entry 
GCC v13.1 updated support for -fpatchable-function-entry on ppc64le to
emit nops after the local entry point, rather than before it. This
allows us to use this in the kernel for ftrace purposes. A new script is
added under arch/powerpc/tools/ to help detect if nops are emitted after
the function local entry point, or before the global entry point.

With -fpatchable-function-entry, we no longer have the profiling
instructions generated at function entry, so we only need to validate
the presence of two nops at the ftrace location in ftrace_init_nop(). We
patch the preceding instruction with 'mflr r0' to match the
-mprofile-kernel ABI for subsequent ftrace use.

This changes the profiling instructions used on ppc32. The default -pg
option emits an additional 'stw' instruction after 'mflr r0' and before
the branch to _mcount 'bl _mcount'. This is very similar to the original
-mprofile-kernel implementation on ppc64le, where an additional 'std'
instruction was used to save LR to its save location in the caller's
stackframe. Subsequently, this additional store was removed in later
compiler versions for performance reasons. The same reasons apply for
ppc32 so we only patch in a 'mflr r0'.

Signed-off-by: Naveen N Rao <naveen@kernel.org>
Reviewed-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/68586d22981a2c3bb45f27a2b621173d10a7d092.1687166935.git.naveen@kernel.org
 2023-08-22 00:09:06 +10:00
Naveen N Rao
bad90aa52d powerpc/ftrace: Consolidate ftrace support into fewer files 
ftrace_low.S has just the _mcount stub and return_to_handler(). Merge
this back into ftrace_mprofile.S and ftrace_64_pg.S to keep all ftrace
code together, and to allow those to evolve independently.

ftrace_mprofile.S is also not an entirely accurate name since this also
holds ppc32 code. This will be all the more incorrect once support for
-fpatchable-function-entry is added. Rename files here to more
accurately describe the code:
- ftrace_mprofile.S is renamed to ftrace_entry.S
- ftrace_pg.c is renamed to ftrace_64_pg.c
- ftrace_64_pg.S is rename to ftrace_64_pg_entry.S

Signed-off-by: Naveen N Rao <naveen@kernel.org>
Reviewed-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/b900c9a8bba9d6c3c295e0f99886acf3e5bf6f7b.1687166935.git.naveen@kernel.org
 2023-08-22 00:09:05 +10:00