kernel/linux.git/arch/powerpc/include/asm/sections.h, branch v6.12.80

powerpc/ftrace: Ignore ftrace locations in exit text sections

2024-02-14T03:24:06+00:00

Michael reported that we are seeing an ftrace bug on bootup when KASAN is enabled and we are using -fpatchable-function-entry: ftrace: allocating 47780 entries in 18 pages ftrace-powerpc: 0xc0000000020b3d5c: No module provided for non-kernel address ------------[ ftrace bug ]------------ ftrace faulted on modifying [] 0xc0000000020b3d5c Initializing ftrace call sites ftrace record flags: 0 (0) expected tramp: c00000000008cef4 ------------[ cut here ]------------ WARNING: CPU: 0 PID: 0 at kernel/trace/ftrace.c:2180 ftrace_bug+0x3c0/0x424 Modules linked in: CPU: 0 PID: 0 Comm: swapper Not tainted 6.5.0-rc3-00120-g0f71dcfb4aef #860 Hardware name: IBM pSeries (emulated by qemu) POWER9 (raw) 0x4e1202 0xf000005 of:SLOF,HEAD hv:linux,kvm pSeries NIP: c0000000003aa81c LR: c0000000003aa818 CTR: 0000000000000000 REGS: c0000000033cfab0 TRAP: 0700 Not tainted (6.5.0-rc3-00120-g0f71dcfb4aef) MSR: 8000000002021033 CR: 28028240 XER: 00000000 CFAR: c0000000002781a8 IRQMASK: 3 ... NIP [c0000000003aa81c] ftrace_bug+0x3c0/0x424 LR [c0000000003aa818] ftrace_bug+0x3bc/0x424 Call Trace: ftrace_bug+0x3bc/0x424 (unreliable) ftrace_process_locs+0x5f4/0x8a0 ftrace_init+0xc0/0x1d0 start_kernel+0x1d8/0x484 With CONFIG_FTRACE_MCOUNT_USE_PATCHABLE_FUNCTION_ENTRY=y and CONFIG_KASAN=y, compiler emits nops in functions that it generates for registering and unregistering global variables (unlike with -pg and -mprofile-kernel where calls to _mcount() are not generated in those functions). Those functions then end up in INIT_TEXT and EXIT_TEXT respectively. We don't expect to see any profiled functions in EXIT_TEXT, so ftrace_init_nop() assumes that all addresses that aren't in the core kernel text belongs to a module. Since these functions do not match that criteria, we see the above bug. Address this by having ftrace ignore all locations in the text exit sections of vmlinux. Fixes: 0f71dcfb4aef ("powerpc/ftrace: Add support for -fpatchable-function-entry") Cc: stable@vger.kernel.org # v6.6+ Reported-by: Michael Ellerman Signed-off-by: Naveen N Rao Reviewed-by: Benjamin Gray Signed-off-by: Michael Ellerman Link: https://msgid.link/20240213175410.1091313-1-naveen@kernel.org

powerpc/ftrace: Extend ftrace support for large kernels to ppc32

2023-08-21T14:09:05+00:00

Commit 67361cf8071286 ("powerpc/ftrace: Handle large kernel configs") added ftrace support for ppc64 kernel images with a text section larger than 32MB. The approach itself isn't specific to ppc64, so extend the same to also work on ppc32. While at it, reduce the space reserved for the stub from 64 bytes to 32 bytes since the different stub variants are all less than 8 instructions. To reduce use of #ifdef, a stub implementation is provided for kernel_toc_address() and -SZ_2G is cast to 'long long' to prevent errors on ppc32. Signed-off-by: Naveen N Rao Reviewed-by: Christophe Leroy Signed-off-by: Michael Ellerman Link: https://msgid.link/9fa3258cbb9105cf8a0a8135214d44ffbc75fe84.1687166935.git.naveen@kernel.org

powerpc/64: vmlinux support building with PCREL addresing

2023-04-20T02:59:21+00:00

PC-Relative or PCREL addressing is an extension to the ELF ABI which uses Power ISA v3.1 PC-relative instructions to calculate addresses, rather than the traditional TOC scheme. Add an option to build vmlinux using pcrel addressing. Modules continue to use TOC addressing. - TOC address helpers and r2 are poisoned with -1 when running vmlinux. r2 could be used for something useful once things are ironed out. - Assembly must call C functions with @notoc annotation, or the linker complains aobut a missing nop after the call. This is done with the CFUNC macro introduced earlier. - Boot: with the exception of prom_init, the execution branches to the kernel virtual address early in boot, before any addresses are generated, which ensures 34-bit pcrel addressing does not miss the high PAGE_OFFSET bits. TOC relative addressing has a similar requirement. prom_init does not go to the virtual address and its addresses should not carry over to the post-prom kernel. - Ftrace trampolines are converted from TOC addressing to pcrel addressing, including module ftrace trampolines that currently use the kernel TOC to find ftrace target functions. - BPF function prologue and function calling generation are converted from TOC to pcrel. - copypage_64.S has an interesting problem, prefixed instructions have alignment restrictions so the linker can add padding, which makes the assembler treat the difference between two local labels as non-constant even if alignment is arranged so padding is not required. This may need toolchain help to solve nicely, for now move the prefix instruction out of the alternate patch section to work around it. This reduces kernel text size by about 6%. Signed-off-by: Nicholas Piggin Signed-off-by: Michael Ellerman Link: https://msgid.link/20230408021752.862660-6-npiggin@gmail.com

powerpc/vmlinux.lds: Add an explicit symbol for the SRWX boundary

2022-09-26T10:58:16+00:00

Currently __init_begin is used as the boundary for strict RWX between executable/read-only text and data, and non-executable (after boot) code and data. But that's a little subtle, so add an explicit symbol to document that the SRWX boundary lies there, and add a comment making it clear that __init_begin must also begin there. Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/20220916131422.318752-2-mpe@ellerman.id.au

powerpc/64: Remove unused prom_init_toc symbols

2022-09-26T10:58:16+00:00

Commit 24d33ac5b8ff ("powerpc/64s: Make prom_init require RELOCATABLE") made prom_init depend on CONFIG_RELOCATABLE. But it missed cleaning up a case in the linker script for RELOCATABLE=n, and associated symbols. Remove them now. Fixes: 24d33ac5b8ff ("powerpc/64s: Make prom_init require RELOCATABLE") Reported-by: Christophe Leroy Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/20220920131157.1032707-1-mpe@ellerman.id.au

powerpc: Move patch sites out of asm-prototypes.h

2022-08-26T01:02:20+00:00

The definitions for the patch sites etc. don't belong in asm-prototypes.h, they are not EXPORT'ed asm symbols. Move them into sections.h which is traditionally used for asm symbols. Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/20220818050659.187181-1-mpe@ellerman.id.au

asm-generic: Refactor dereference_[kernel]_function_descriptor()

2022-02-16T12:25:11+00:00

dereference_function_descriptor() and dereference_kernel_function_descriptor() are identical on the three architectures implementing them. Make them common and put them out-of-line in kernel/extable.c which is one of the users and has similar type of functions. Signed-off-by: Christophe Leroy Reviewed-by: Kees Cook Reviewed-by: Arnd Bergmann Acked-by: Helge Deller Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/449db09b2eba57f4ab05f80102a67d8675bc8bcd.1644928018.git.christophe.leroy@csgroup.eu

asm-generic: Define 'func_desc_t' to commonly describe function descriptors

2022-02-16T12:25:11+00:00

We have three architectures using function descriptors, each with its own type and name. Add a common typedef that can be used in generic code. Also add a stub typedef for architecture without function descriptors, to avoid a forest of #ifdefs. It replaces the similar 'func_desc_t' previously defined in arch/powerpc/kernel/module_64.c Signed-off-by: Christophe Leroy Reviewed-by: Kees Cook Acked-by: Arnd Bergmann Acked-by: Helge Deller Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/f1f91b142b3c1082bdc1586ce71c9bac1e75213c.1644928018.git.christophe.leroy@csgroup.eu

asm-generic: Define CONFIG_HAVE_FUNCTION_DESCRIPTORS

2022-02-16T12:25:11+00:00

Replace HAVE_DEREFERENCE_FUNCTION_DESCRIPTOR by a config option named CONFIG_HAVE_FUNCTION_DESCRIPTORS and use it instead of 'dereference_function_descriptor' macro to know whether an arch has function descriptors. To limit churn in one of the following patches, use an #ifdef/#else construct with empty first part instead of an #ifndef in asm-generic/sections.h On powerpc, make sure the config option matches the ABI used by the compiler with a BUILD_BUG_ON() and add missing _CALL_ELF=2 when calling 'sparse' so that sparse sees the same piece of code as GCC. And include a helper to check whether an arch has function descriptors or not : have_function_descriptors() Signed-off-by: Christophe Leroy Reviewed-by: Kees Cook Reviewed-by: Nicholas Piggin Acked-by: Helge Deller Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/4a0f11fb0ea74a3197bc44dd7ba25e53a24fd03d.1644928018.git.christophe.leroy@csgroup.eu

powerpc: Use 'struct func_desc' instead of 'struct ppc64_opd_entry'

2022-02-16T12:25:10+00:00

'struct ppc64_opd_entry' is somehow redundant with 'struct func_desc', the later is more correct/complete as it includes the third field which is unused. So use 'struct func_desc' instead of 'struct ppc64_opd_entry' Signed-off-by: Christophe Leroy Reviewed-by: Kees Cook Reviewed-by: Daniel Axtens Reviewed-by: Nicholas Piggin Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/34e76bac6cbe95a63ecd37df69fb7feb93b0ea7c.1644928018.git.christophe.leroy@csgroup.eu