kernel/linux.git/arch/powerpc/include/asm/ppc_asm.h, branch v6.7

powerpc: merge 32-bit and 64-bit _switch implementation

2023-06-15T04:03:55+00:00

The _switch stack frame setup are substantially the same, so are the comments. The difference in how the stack and current are switched, and other hardware and software housekeeping is done is moved into macros. Generated code should be unchanged. Signed-off-by: Nicholas Piggin [mpe: Tweak include orer to fix compile errors on some configs] Signed-off-by: Michael Ellerman Link: https://msgid.link/20230606132447.315714-6-npiggin@gmail.com

powerpc/64: modules support building with PCREL addresing

2023-04-20T03:21:42+00:00

Build modules using PCREL addressing when CONFIG_PPC_KERNEL_PCREL=y. - The module loader must handle several new relocation types: * R_PPC64_REL24_NOTOC is a function call handled like R_PPC_REL24, but does not restore r2 upon return. The external function call stub is changed to use pcrel addressing to load the function pointer rather than based on the module TOC. * R_PPC64_GOT_PCREL34 is a reference to external data. A GOT table must be built by hand, because the linker adds this during the final link (which is not done for kernel modules). The GOT table is built similarly to the way the external function call stub table is. This section is called .mygot because .got has a special meaning for the linker and can become upset. * R_PPC64_PCREL34 is used for local data addressing, but there is a special case where the percpu section is moved at load-time to the percpu area which is out of range of this relocation. This requires the PCREL34 relocations are converted to use GOT_PCREL34 addressing. Signed-off-by: Nicholas Piggin [mpe: Some coding style & formatting fixups] Signed-off-by: Michael Ellerman Link: https://msgid.link/20230408021752.862660-7-npiggin@gmail.com

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: add CFUNC assembly label annotation

2023-04-20T02:54:24+00:00

This macro is to be used in assembly where C functions are called. pcrel addressing mode requires branches to functions with a localentry value of 1 to have either a trailing nop or @notoc. This macro permits the latter without changing callers. Signed-off-by: Nicholas Piggin [mpe: Add dummy definitions to fix selftests build] Signed-off-by: Michael Ellerman Link: https://msgid.link/20230408021752.862660-5-npiggin@gmail.com

powerpc: Implement arch_within_stack_frames

2023-04-04T12:11:03+00:00

Walks the stack when copy_{to,from}_user address is in the stack to ensure that the object being copied is entirely a single stack frame and does not contain stack metadata. Substantially similar to the x86 implementation. The back chain is used to traverse the stack and identify stack frame boundaries. Signed-off-by: Nicholas Miehlbradt Signed-off-by: Michael Ellerman Link: https://msgid.link/20230228054355.300628-1-nicholas@linux.ibm.com

powerpc/64: Add interrupt register sanitisation macros

2022-12-02T09:45:57+00:00

Include in asm/ppc_asm.h macros to be used in multiple successive patches to implement zeroising architected registers in interrupt handlers. Registers will be sanitised in this fashion in future patches to reduce the speculation influence of user-controlled register values. These mitigations will be configurable through the CONFIG_INTERRUPT_SANITIZE_REGISTERS Kconfig option. Included are macros for conditionally zeroising registers and restoring as required with the mitigation enabled. With the mitigation disabled, non-volatiles must be restored on demand at separate locations to those required by the mitigation. Reviewed-by: Nicholas Piggin Signed-off-by: Rohan McLure Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/20221201071019.1953023-2-rmclure@linux.ibm.com

powerpc/64e: provide an addressing macro for use with TOC in alternate register

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

The interrupt entry code carefully saves a minimal number of registers, so in some places the TOC is required, it is loaded into a different register, so provide a macro that can supply an alternate TOC register. This continues to use got addressing because TOC-relative results in "got/toc optimization is not supported" messages by the linker. Having r2 be one of the saved registers and using that for TOC addressing may be the best way to avoid that and switch this to TOC addressing. Signed-off-by: Nicholas Piggin Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/20220926034057.2360083-6-npiggin@gmail.com

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: switch asm helpers from GOT to TOC relative addressing

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

There is no need to use GOT addressing within the kernel. Signed-off-by: Nicholas Piggin Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/20220926034057.2360083-4-npiggin@gmail.com

powerpc: Add ZEROIZE_GPRS macros for register clears

2022-09-26T13:00:14+00:00

Provide register zeroing macros, following the same convention as existing register stack save/restore macros, to be used in later change to concisely zero a sequence of consecutive gprs. The resulting macros are called ZEROIZE_GPRS and ZEROIZE_NVGPRS, keeping with the naming of the accompanying restore and save macros, and usage of zeroize to describe this operation elsewhere in the kernel. Signed-off-by: Rohan McLure Reviewed-by: Nicholas Piggin Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/20220921065605.1051927-4-rmclure@linux.ibm.com