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7e3a68be42
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 <npiggin@gmail.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://msgid.link/20230408021752.862660-6-npiggin@gmail.com
80 lines
1.9 KiB
C
80 lines
1.9 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef _ASM_POWERPC_SECTIONS_H
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#define _ASM_POWERPC_SECTIONS_H
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#ifdef __KERNEL__
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#include <linux/elf.h>
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#include <linux/uaccess.h>
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#ifdef CONFIG_HAVE_FUNCTION_DESCRIPTORS
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typedef struct func_desc func_desc_t;
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#endif
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#include <asm-generic/sections.h>
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extern char __head_end[];
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extern char __srwx_boundary[];
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/* Patch sites */
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extern s32 patch__call_flush_branch_caches1;
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extern s32 patch__call_flush_branch_caches2;
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extern s32 patch__call_flush_branch_caches3;
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extern s32 patch__flush_count_cache_return;
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extern s32 patch__flush_link_stack_return;
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extern s32 patch__call_kvm_flush_link_stack;
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extern s32 patch__call_kvm_flush_link_stack_p9;
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extern s32 patch__memset_nocache, patch__memcpy_nocache;
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extern long flush_branch_caches;
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extern long kvm_flush_link_stack;
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#ifdef __powerpc64__
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extern char __start_interrupts[];
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extern char __end_interrupts[];
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#ifdef CONFIG_PPC_POWERNV
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extern char start_real_trampolines[];
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extern char end_real_trampolines[];
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extern char start_virt_trampolines[];
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extern char end_virt_trampolines[];
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#endif
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/*
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* This assumes the kernel is never compiled -mcmodel=small or
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* the total .toc is always less than 64k.
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*/
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static inline unsigned long kernel_toc_addr(void)
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{
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#ifdef CONFIG_PPC_KERNEL_PCREL
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BUILD_BUG();
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return -1UL;
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#else
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unsigned long toc_ptr;
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asm volatile("mr %0, 2" : "=r" (toc_ptr));
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return toc_ptr;
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#endif
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}
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static inline int overlaps_interrupt_vector_text(unsigned long start,
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unsigned long end)
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{
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unsigned long real_start, real_end;
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real_start = __start_interrupts - _stext;
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real_end = __end_interrupts - _stext;
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return start < (unsigned long)__va(real_end) &&
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(unsigned long)__va(real_start) < end;
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}
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static inline int overlaps_kernel_text(unsigned long start, unsigned long end)
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{
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return start < (unsigned long)__init_end &&
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(unsigned long)_stext < end;
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}
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#endif
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#endif /* __KERNEL__ */
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#endif /* _ASM_POWERPC_SECTIONS_H */
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