linux.git/arch/powerpc/kernel/trace, branch v6.1.168

powerpc/64: Add support to build with prefixed instructions

2024-10-17T13:21:24+00:00

[ Upstream commit dc5dac748af9087e9240bd2ae6ae7db48d5360ae ]

Add an option to build kernel and module with prefixed instructions if
the CPU and toolchain support it.

This is not related to kernel support for userspace execution of
prefixed instructions.

Building with prefixed instructions breaks some extended inline asm
memory addressing, for example it will provide immediates that exceed
the range of simple load/store displacement. Whether this is a
toolchain or a kernel asm problem remains to be seen. For now, these
are replaced with simpler and less efficient direct register addressing
when compiling with prefixed.

Signed-off-by: Nicholas Piggin 
Signed-off-by: Michael Ellerman 
Link: https://msgid.link/20230408021752.862660-4-npiggin@gmail.com
Stable-dep-of: 39190ac7cff1 ("powerpc/atomic: Use YZ constraints for DS-form instructions")
Signed-off-by: Sasha Levin

powerpc/ftrace: Fix stack teardown in ftrace_no_trace

2023-12-20T16:00:14+00:00

[ Upstream commit 4b3338aaa74d7d4ec5b6734dc298f0db94ec83d2 ]

Commit 41a506ef71eb ("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: 41a506ef71eb ("powerpc/ftrace: Create a dummy stackframe to fix stack unwind")
Cc: stable@vger.kernel.org # v6.5+
Signed-off-by: Naveen N Rao 
Signed-off-by: Michael Ellerman 
Link: https://msgid.link/20231130065947.2188860-1-naveen@kernel.org
Signed-off-by: Sasha Levin

powerpc/ftrace: Create a dummy stackframe to fix stack unwind

2023-08-11T10:08:21+00:00

commit 41a506ef71eb38d94fe133f565c87c3e06ccc072 upstream.

With ppc64 -mprofile-kernel and ppc32 -pg, profiling instructions to
call into ftrace are emitted right at function entry. The instruction
sequence used is minimal to reduce overhead. Crucially, a stackframe is
not created for the function being traced. This breaks stack unwinding
since the function being traced does not have a stackframe for itself.
As such, it never shows up in the backtrace:

/sys/kernel/debug/tracing # echo 1 > /proc/sys/kernel/stack_tracer_enabled
/sys/kernel/debug/tracing # cat stack_trace
        Depth    Size   Location    (17 entries)
        -----    ----   --------
  0)     4144      32   ftrace_call+0x4/0x44
  1)     4112     432   get_page_from_freelist+0x26c/0x1ad0
  2)     3680     496   __alloc_pages+0x290/0x1280
  3)     3184     336   __folio_alloc+0x34/0x90
  4)     2848     176   vma_alloc_folio+0xd8/0x540
  5)     2672     272   __handle_mm_fault+0x700/0x1cc0
  6)     2400     208   handle_mm_fault+0xf0/0x3f0
  7)     2192      80   ___do_page_fault+0x3e4/0xbe0
  8)     2112     160   do_page_fault+0x30/0xc0
  9)     1952     256   data_access_common_virt+0x210/0x220
 10)     1696     400   0xc00000000f16b100
 11)     1296     384   load_elf_binary+0x804/0x1b80
 12)      912     208   bprm_execve+0x2d8/0x7e0
 13)      704      64   do_execveat_common+0x1d0/0x2f0
 14)      640     160   sys_execve+0x54/0x70
 15)      480      64   system_call_exception+0x138/0x350
 16)      416     416   system_call_common+0x160/0x2c4

Fix this by having ftrace create a dummy stackframe for the function
being traced. With this, backtraces now capture the function being
traced:

/sys/kernel/debug/tracing # cat stack_trace
        Depth    Size   Location    (17 entries)
        -----    ----   --------
  0)     3888      32   _raw_spin_trylock+0x8/0x70
  1)     3856     576   get_page_from_freelist+0x26c/0x1ad0
  2)     3280      64   __alloc_pages+0x290/0x1280
  3)     3216     336   __folio_alloc+0x34/0x90
  4)     2880     176   vma_alloc_folio+0xd8/0x540
  5)     2704     416   __handle_mm_fault+0x700/0x1cc0
  6)     2288      96   handle_mm_fault+0xf0/0x3f0
  7)     2192      48   ___do_page_fault+0x3e4/0xbe0
  8)     2144     192   do_page_fault+0x30/0xc0
  9)     1952     608   data_access_common_virt+0x210/0x220
 10)     1344      16   0xc0000000334bbb50
 11)     1328     416   load_elf_binary+0x804/0x1b80
 12)      912      64   bprm_execve+0x2d8/0x7e0
 13)      848     176   do_execveat_common+0x1d0/0x2f0
 14)      672     192   sys_execve+0x54/0x70
 15)      480      64   system_call_exception+0x138/0x350
 16)      416     416   system_call_common+0x160/0x2c4

This results in two additional stores in the ftrace entry code, but
produces reliable backtraces.

Fixes: 153086644fd1 ("powerpc/ftrace: Add support for -mprofile-kernel ftrace ABI")
Cc: stable@vger.kernel.org
Signed-off-by: Naveen N Rao 
Signed-off-by: Michael Ellerman 
Link: https://msgid.link/20230621051349.759567-1-naveen@kernel.org
Signed-off-by: Greg Kroah-Hartman

powerpc/64: provide a helper macro to load r2 with the kernel TOC

2022-09-28T09:22:12+00:00

A later change stops the kernel using r2 and loads it with a poison
value.  Provide a PACATOC loading abstraction which can hide this
detail.

Signed-off-by: Nicholas Piggin 
Signed-off-by: Michael Ellerman 
Link: https://lore.kernel.org/r/20220926034057.2360083-5-npiggin@gmail.com

powerpc/64: asm use consistent global variable declaration and access

2022-09-28T09:22:12+00:00

Use helper macros to access global variables, and place them in .data
sections rather than in .toc. Putting addresses in TOC is not required
because the kernel is linked with a single TOC.

Signed-off-by: Nicholas Piggin 
Signed-off-by: Michael Ellerman 
Link: https://lore.kernel.org/r/20220926034057.2360083-3-npiggin@gmail.com

powerpc64/ftrace: Fix ftrace for clang builds

2022-08-10T05:38:16+00:00

Clang doesn't support -mprofile-kernel ABI, so guard the checks against
CONFIG_DYNAMIC_FTRACE_WITH_REGS, rather than the elf ABI version.

Fixes: 23b44fc248f4 ("powerpc/ftrace: Make __ftrace_make_{nop/call}() common to PPC32 and PPC64")
Cc: stable@vger.kernel.org # v5.19+
Reported-by: Nick Desaulniers 
Reported-by: Ondrej Mosnacek 
Signed-off-by: Naveen N. Rao 
Tested-by: Ondrej Mosnacek 
Acked-by: Nick Desaulniers 
Signed-off-by: Michael Ellerman 
Link: https://github.com/llvm/llvm-project/issues/57031
Link: https://github.com/ClangBuiltLinux/linux/issues/1682
Link: https://lore.kernel.org/r/20220809095907.418764-1-naveen.n.rao@linux.vnet.ibm.com

powerpc: Fix all occurences of duplicate words

2022-07-25T02:05:15+00:00

Since commit 87c78b612f4f ("powerpc: Fix all occurences of "the the"")
fixed "the the", there's now a steady stream of patches fixing other
duplicate words.

Just fix them all at once, to save the overhead of dealing with
individual patches for each case.

This leaves a few cases of "that that", which in some contexts is
correct.

Signed-off-by: Michael Ellerman 
Link: https://lore.kernel.org/r/20220718095158.326606-1-mpe@ellerman.id.au

powerpc/64: Drop ppc_inst_as_str()

2022-06-29T09:37:07+00:00

The ppc_inst_as_str() macro tries to make printing variable length,
aka "prefixed", instructions convenient. It mostly succeeds, but it does
hide an on-stack buffer, which triggers stack protector.

More problematically it doesn't compile at all with GCC 12,
with -Wdangling-pointer, due to the fact that it returns the char buffer
declared inside the macro:

  arch/powerpc/kernel/trace/ftrace.c: In function '__ftrace_modify_call':
  ./include/linux/printk.h:475:44: error: using a dangling pointer to '__str' [-Werror=dangling-pointer=]
    475 | #define printk(fmt, ...) printk_index_wrap(_printk, fmt, ##__VA_ARGS__)
    ...
  arch/powerpc/kernel/trace/ftrace.c:567:17: note: in expansion of macro 'pr_err'
    567 |                 pr_err("Not expected bl: opcode is %s\n", ppc_inst_as_str(op));
        |                 ^~~~~~
  ./arch/powerpc/include/asm/inst.h:156:14: note: '__str' declared here
    156 |         char __str[PPC_INST_STR_LEN];   \
        |              ^~~~~

This could be fixed by having the caller declare the buffer, but in some
places there'd need to be two buffers. In all cases where
ppc_inst_as_str() is used the output is not really meant for user
consumption, it's almost always indicative of a kernel bug.

A simpler solution is to just print the value as an unsigned long. For
normal instructions the output is identical. For prefixed instructions
the value is printed as a single 64-bit quantity, whereas previously the
low half was printed first. But that is good enough for debug output,
especially as prefixed instructions will be rare in kernel code in
practice.

Old:
  c000000000111170  60420000      ori     r2,r2,0
  c000000000111174  04100001 e580fb00     .long 0xe580fb0004100001

New:
  c00000000010f90c  60420000      ori     r2,r2,0
  c00000000010f910  e580fb0004100001      .long 0xe580fb0004100001

Reported-by: Bagas Sanjaya 
Reported-by: Petr Mladek 
Signed-off-by: Michael Ellerman 
Tested-by: Bagas Sanjaya 
Link: https://lore.kernel.org/r/20220531065936.3674348-1-mpe@ellerman.id.au

powerpc/ftrace: Remove ftrace init tramp once kernel init is complete

2022-05-22T05:58:29+00:00

Stop using the ftrace trampoline for init section once kernel init is
complete.

Fixes: 67361cf8071286 ("powerpc/ftrace: Handle large kernel configs")
Cc: stable@vger.kernel.org # v4.20+
Signed-off-by: Naveen N. Rao 
Signed-off-by: Michael Ellerman 
Link: https://lore.kernel.org/r/20220516071422.463738-1-naveen.n.rao@linux.vnet.ibm.com

powerpc/ftrace: Minimise number of #ifdefs

2022-05-22T05:58:26+00:00

A lot of #ifdefs can be replaced by IS_ENABLED()

Do so.

Signed-off-by: Christophe Leroy 
[mpe: Fold in changes suggested by Naveen and Christophe on list]
Signed-off-by: Michael Ellerman 
Link: https://lore.kernel.org/r/18ce6708d6f8c71d87436f9c6019f04df4125128.1652074503.git.christophe.leroy@csgroup.eu