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The s390 architecture defines two special per-CPU data pages called the "prefix area". In s390-linux terminology this is usually called "lowcore". This memory area contains system configuration data like old/new PSW's for system call/interrupt/machine check handlers and lots of other data. It is normally mapped to logical address 0. This area can only be accessed when in supervisor mode. This means that kernel code can dereference NULL pointers, because accesses to address 0 are allowed. Parts of lowcore can be write protected, but read accesses and write accesses outside of the write protected areas are not caught. To remove this limitation for debugging and testing, remap lowcore to another address and define a function get_lowcore() which simply returns the address where lowcore is mapped at. This would normally introduce a pointer dereference (=memory read). As lowcore is used for several very often used variables, add code to patch this function during runtime, so we avoid the memory reads. For C code get_lowcore() has to be used, for assembly code it is the GET_LC macro. When using this macro/function a reference is added to alternative patching. All these locations will be patched to the actual lowcore location when the kernel is booted or a module is loaded. To make debugging/bisecting problems easier, this patch adds all the infrastructure but the lowcore address is still hardwired to 0. This way the code can be converted on a per function basis, and the functionality is enabled in a patch after all the functions have been converted. Note that this requires at least z16 because the old lpsw instruction only allowed a 12 bit displacement. z16 introduced lpswey which allows 20 bits (signed), so the lowcore can effectively be mapped from address 0 - 0x7e000. To use 0x7e000 as address, a 6 byte lgfi instruction would have to be used in the alternative. To save two bytes, llilh can be used, but this only allows to set bits 16-31 of the address. In order to use the llilh instruction, use 0x70000 as alternative lowcore address. This is still large enough to catch NULL pointer dereferences into large arrays. Reviewed-by: Heiko Carstens <hca@linux.ibm.com> Signed-off-by: Sven Schnelle <svens@linux.ibm.com> Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
111 lines
4.0 KiB
C
111 lines
4.0 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef BOOT_BOOT_H
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#define BOOT_BOOT_H
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#include <linux/types.h>
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#define IPL_START 0x200
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#ifndef __ASSEMBLY__
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#include <asm/physmem_info.h>
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struct machine_info {
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unsigned char has_edat1 : 1;
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unsigned char has_edat2 : 1;
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unsigned char has_nx : 1;
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};
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struct vmlinux_info {
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unsigned long entry;
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unsigned long image_size; /* does not include .bss */
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unsigned long bss_size; /* uncompressed image .bss size */
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unsigned long bootdata_off;
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unsigned long bootdata_size;
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unsigned long bootdata_preserved_off;
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unsigned long bootdata_preserved_size;
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unsigned long got_start;
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unsigned long got_end;
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unsigned long amode31_size;
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unsigned long init_mm_off;
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unsigned long swapper_pg_dir_off;
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unsigned long invalid_pg_dir_off;
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unsigned long alt_instructions;
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unsigned long alt_instructions_end;
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#ifdef CONFIG_KASAN
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unsigned long kasan_early_shadow_page_off;
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unsigned long kasan_early_shadow_pte_off;
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unsigned long kasan_early_shadow_pmd_off;
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unsigned long kasan_early_shadow_pud_off;
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unsigned long kasan_early_shadow_p4d_off;
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#endif
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};
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void startup_kernel(void);
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unsigned long detect_max_physmem_end(void);
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void detect_physmem_online_ranges(unsigned long max_physmem_end);
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void physmem_set_usable_limit(unsigned long limit);
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void physmem_reserve(enum reserved_range_type type, unsigned long addr, unsigned long size);
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void physmem_free(enum reserved_range_type type);
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/* for continuous/multiple allocations per type */
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unsigned long physmem_alloc_top_down(enum reserved_range_type type, unsigned long size,
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unsigned long align);
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/* for single allocations, 1 per type */
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unsigned long physmem_alloc_range(enum reserved_range_type type, unsigned long size,
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unsigned long align, unsigned long min, unsigned long max,
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bool die_on_oom);
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unsigned long get_physmem_alloc_pos(void);
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bool ipl_report_certs_intersects(unsigned long addr, unsigned long size,
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unsigned long *intersection_start);
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bool is_ipl_block_dump(void);
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void store_ipl_parmblock(void);
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int read_ipl_report(void);
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void save_ipl_cert_comp_list(void);
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void setup_boot_command_line(void);
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void parse_boot_command_line(void);
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void verify_facilities(void);
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void print_missing_facilities(void);
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void sclp_early_setup_buffer(void);
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void print_pgm_check_info(void);
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unsigned long randomize_within_range(unsigned long size, unsigned long align,
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unsigned long min, unsigned long max);
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void setup_vmem(unsigned long kernel_start, unsigned long kernel_end, unsigned long asce_limit);
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void __printf(1, 2) decompressor_printk(const char *fmt, ...);
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void print_stacktrace(unsigned long sp);
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void error(char *m);
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int get_random(unsigned long limit, unsigned long *value);
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extern struct machine_info machine;
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/* Symbols defined by linker scripts */
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extern const char kernel_version[];
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extern unsigned long memory_limit;
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extern unsigned long vmalloc_size;
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extern int vmalloc_size_set;
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extern char __boot_data_start[], __boot_data_end[];
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extern char __boot_data_preserved_start[], __boot_data_preserved_end[];
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extern char __vmlinux_relocs_64_start[], __vmlinux_relocs_64_end[];
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extern char _decompressor_syms_start[], _decompressor_syms_end[];
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extern char _stack_start[], _stack_end[];
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extern char _end[], _decompressor_end[];
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extern unsigned char _compressed_start[];
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extern unsigned char _compressed_end[];
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extern struct vmlinux_info _vmlinux_info;
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#define vmlinux _vmlinux_info
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#define __lowcore_pa(x) ((unsigned long)(x) % sizeof(struct lowcore))
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#define __abs_lowcore_pa(x) (((unsigned long)(x) - __abs_lowcore) % sizeof(struct lowcore))
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#define __kernel_va(x) ((void *)((unsigned long)(x) - __kaslr_offset_phys + __kaslr_offset))
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#define __kernel_pa(x) ((unsigned long)(x) - __kaslr_offset + __kaslr_offset_phys)
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#define __identity_va(x) ((void *)((unsigned long)(x) + __identity_base))
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#define __identity_pa(x) ((unsigned long)(x) - __identity_base)
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static inline bool intersects(unsigned long addr0, unsigned long size0,
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unsigned long addr1, unsigned long size1)
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{
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return addr0 + size0 > addr1 && addr1 + size1 > addr0;
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}
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#endif /* __ASSEMBLY__ */
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#endif /* BOOT_BOOT_H */
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