linux-stable.git/arch/powerpc/include/asm/code-patching.h, branch v4.14.331

powerpc/lib: Add helper to check if offset is within conditional branch range

2021-11-26T10:40:36+00:00

upstream commit 4549c3ea3160fa8b3f37dfe2f957657bb265eda9

Add a helper to check if a given offset is within the branch range for a
powerpc conditional branch instruction, and update some sites to use the
new helper.

Signed-off-by: Naveen N. Rao 
Reviewed-by: Christophe Leroy 
Acked-by: Song Liu 
Signed-off-by: Michael Ellerman 
Link: https://lore.kernel.org/r/442b69a34ced32ca346a0d9a855f3f6cfdbbbd41.1633464148.git.naveen.n.rao@linux.vnet.ibm.com
Signed-off-by: Naveen N. Rao 
Signed-off-by: Greg Kroah-Hartman

powerpc/64s: Fix instruction encoding for lis in ppc_function_entry()

2021-03-17T15:34:35+00:00

commit cea15316ceee2d4a51dfdecd79e08a438135416c upstream.

'lis r2,N' is 'addis r2,0,N' and the instruction encoding in the macro
LIS_R2 is incorrect (it currently maps to 'addis r0,r2,N'). Fix the
same.

Fixes: c71b7eff426f ("powerpc: Add ABIv2 support to ppc_function_entry")
Cc: stable@vger.kernel.org # v3.16+
Reported-by: Jiri Olsa 
Signed-off-by: Naveen N. Rao 
Acked-by: Segher Boessenkool 
Signed-off-by: Michael Ellerman 
Link: https://lore.kernel.org/r/20210304020411.16796-1-naveen.n.rao@linux.vnet.ibm.com
Signed-off-by: Greg Kroah-Hartman

powerpc/asm: Add a patch_site macro & helpers for patching instructions

2019-04-03T04:25:13+00:00

commit 06d0bbc6d0f56dacac3a79900e9a9a0d5972d818 upstream.

Add a macro and some helper C functions for patching single asm
instructions.

The gas macro means we can do something like:

  1:	nop
  	patch_site 1b, patch__foo

Which is less visually distracting than defining a GLOBAL symbol at 1,
and also doesn't pollute the symbol table which can confuse eg. perf.

These are obviously similar to our existing feature sections, but are
not automatically patched based on CPU/MMU features, rather they are
designed to be manually patched by C code at some arbitrary point.

Signed-off-by: Michael Ellerman 
Signed-off-by: Greg Kroah-Hartman

powerpc/lib/feature-fixups: use raw_patch_instruction()

2018-10-20T07:48:52+00:00

commit 8183d99f4a22c2abbc543847a588df3666ef0c0c upstream.

feature fixups need to use patch_instruction() early in the boot,
even before the code is relocated to its final address, requiring
patch_instruction() to use PTRRELOC() in order to address data.

But feature fixups applies on code before it is set to read only,
even for modules. Therefore, feature fixups can use
raw_patch_instruction() instead.

Signed-off-by: Christophe Leroy 
Signed-off-by: Michael Ellerman 
Reported-by: David Gounaris 
Tested-by: David Gounaris 
Signed-off-by: Greg Kroah-Hartman

powerpc/modules: Don't try to restore r2 after a sibling call

2018-03-19T07:42:54+00:00

[ Upstream commit b9eab08d012fa093947b230f9a87257c27fb829b ]

When attempting to load a livepatch module, I got the following error:

  module_64: patch_module: Expect noop after relocate, got 3c820000

The error was triggered by the following code in
unregister_netdevice_queue():

  14c:   00 00 00 48     b       14c 
                         14c: R_PPC64_REL24      net_set_todo
  150:   00 00 82 3c     addis   r4,r2,0

GCC didn't insert a nop after the branch to net_set_todo() because it's
a sibling call, so it never returns.  The nop isn't needed after the
branch in that case.

Signed-off-by: Josh Poimboeuf 
Acked-by: Naveen N. Rao 
Reviewed-and-tested-by: Kamalesh Babulal 
Signed-off-by: Michael Ellerman 
Signed-off-by: Sasha Levin 
Signed-off-by: Greg Kroah-Hartman

Revert "powerpc64/elfv1: Only dereference function descriptor for non-text symbols"

2017-11-01T04:50:12+00:00

This reverts commit 83e840c770f2c5 ("powerpc64/elfv1: Only dereference
function descriptor for non-text symbols").

Chandan reported that on newer kernels, trying to enable function_graph
tracer on ppc64 (BE) locks up the system with the following trace:

  Unable to handle kernel paging request for data at address 0x600000002fa30010
  Faulting instruction address: 0xc0000000001f1300
  Thread overran stack, or stack corrupted
  Oops: Kernel access of bad area, sig: 11 [#1]
  BE SMP NR_CPUS=2048 DEBUG_PAGEALLOC NUMA pSeries
  Modules linked in:
  CPU: 1 PID: 6586 Comm: bash Not tainted 4.14.0-rc3-00162-g6e51f1f-dirty #20
  task: c000000625c07200 task.stack: c000000625c07310
  NIP:  c0000000001f1300 LR: c000000000121cac CTR: c000000000061af8
  REGS: c000000625c088c0 TRAP: 0380   Not tainted  (4.14.0-rc3-00162-g6e51f1f-dirty)
  MSR:  8000000000001032   CR: 28002848  XER: 00000000
  CFAR: c0000000001f1320 SOFTE: 0
  ...
  NIP [c0000000001f1300] .__is_insn_slot_addr+0x30/0x90
  LR [c000000000121cac] .kernel_text_address+0x18c/0x1c0
  Call Trace:
  [c000000625c08b40] [c0000000001bd040] .is_module_text_address+0x20/0x40 (unreliable)
  [c000000625c08bc0] [c000000000121cac] .kernel_text_address+0x18c/0x1c0
  [c000000625c08c50] [c000000000061960] .prepare_ftrace_return+0x50/0x130
  [c000000625c08cf0] [c000000000061b10] .ftrace_graph_caller+0x14/0x34
  [c000000625c08d60] [c000000000121b40] .kernel_text_address+0x20/0x1c0
  [c000000625c08df0] [c000000000061960] .prepare_ftrace_return+0x50/0x130
  ...
  [c000000625c0ab30] [c000000000061960] .prepare_ftrace_return+0x50/0x130
  [c000000625c0abd0] [c000000000061b10] .ftrace_graph_caller+0x14/0x34
  [c000000625c0ac40] [c000000000121b40] .kernel_text_address+0x20/0x1c0
  [c000000625c0acd0] [c000000000061960] .prepare_ftrace_return+0x50/0x130
  [c000000625c0ad70] [c000000000061b10] .ftrace_graph_caller+0x14/0x34
  [c000000625c0ade0] [c000000000121b40] .kernel_text_address+0x20/0x1c0

This is because ftrace is using ppc_function_entry() for obtaining the
address of return_to_handler() in prepare_ftrace_return(). The call to
kernel_text_address() itself gets traced and we end up in a recursive
loop.

Fixes: 83e840c770f2 ("powerpc64/elfv1: Only dereference function descriptor for non-text symbols")
Cc: stable@vger.kernel.org # v4.13+
Reported-by: Chandan Rajendra 
Signed-off-by: Naveen N. Rao 
Signed-off-by: Michael Ellerman

powerpc64/elfv1: Only dereference function descriptor for non-text symbols

2017-07-03T13:08:50+00:00

Currently, we assume that the function pointer we receive in
ppc_function_entry() points to a function descriptor. However, this is
not always the case. In particular, assembly symbols without the right
annotation do not have an associated function descriptor. Some of these
symbols are added to the kprobe blacklist using _ASM_NOKPROBE_SYMBOL().

When such addresses are subsequently processed through
arch_deref_entry_point() in populate_kprobe_blacklist(), we see the
below errors during bootup:
    [    0.663963] Failed to find blacklist at 7d9b02a648029b6c
    [    0.663970] Failed to find blacklist at a14d03d0394a0001
    [    0.663972] Failed to find blacklist at 7d5302a6f94d0388
    [    0.663973] Failed to find blacklist at 48027d11e8610178
    [    0.663974] Failed to find blacklist at f8010070f8410080
    [    0.663976] Failed to find blacklist at 386100704801f89d
    [    0.663977] Failed to find blacklist at 7d5302a6f94d00b0

Fix this by checking if the function pointer we receive in
ppc_function_entry() already points to kernel text. If so, we just
return it as is. If not, we assume that this is a function descriptor
and proceed to dereference it.

Suggested-by: Nicholas Piggin 
Reviewed-by: Nicholas Piggin 
Signed-off-by: Naveen N. Rao 
Signed-off-by: Michael Ellerman

powerpc: Introduce a new helper to obtain function entry points

2017-04-24T09:07:58+00:00

kprobe_lookup_name() is specific to the kprobe subsystem and may not always
return the function entry point (in a subsequent patch for KPROBES_ON_FTRACE).
For looking up function entry points, introduce a separate helper and use it
in optprobes.c

Signed-off-by: Naveen N. Rao 
Signed-off-by: Michael Ellerman

powerpc/kprobes: Implement Optprobes

2017-02-10T02:28:04+00:00

Current infrastructure of kprobe uses the unconditional trap instruction
to probe a running kernel. Optprobe allows kprobe to replace the trap
with a branch instruction to a detour buffer. Detour buffer contains
instructions to create an in memory pt_regs. Detour buffer also has a
call to optimized_callback() which in turn call the pre_handler(). After
the execution of the pre-handler, a call is made for instruction
emulation. The NIP is determined in advanced through dummy instruction
emulation and a branch instruction is created to the NIP at the end of
the trampoline.

To address the limitation of branch instruction in POWER architecture,
detour buffer slot is allocated from a reserved area. For the time
being, 64KB is reserved in memory for this purpose.

Instructions which can be emulated using analyse_instr() are the
candidates for optimization. Before optimization ensure that the address
range between the detour buffer allocated and the instruction being
probed is within +/- 32MB.

Signed-off-by: Anju T Sudhakar 
Signed-off-by: Naveen N. Rao 
Acked-by: Masami Hiramatsu 
Signed-off-by: Michael Ellerman

powerpc: Add helper to check if offset is within relative branch range

2017-02-10T02:28:03+00:00

To permit the use of relative branch instruction in powerpc, the target
address has to be relatively nearby, since the address is specified in an
immediate field (24 bit filed) in the instruction opcode itself. Here
nearby refers to 32MB on either side of the current instruction.

This patch verifies whether the target address is within +/- 32MB
range or not.

Signed-off-by: Naveen N. Rao 
Signed-off-by: Anju T Sudhakar 
Signed-off-by: Michael Ellerman