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6bda667037
This change simplifies the task of making the decompressor relocatable.
The decompressor's image contains special DMA sections between _sdma and
_edma. This DMA segment is loaded at boot as part of the decompressor and
then simply handed over to the decompressed kernel. The decompressor itself
never uses it in any way. The primary reason for this is the need to keep
the aforementioned DMA segment below 2GB which is required by architecture,
and because the decompressor is always loaded at a fixed low physical
address, it is guaranteed that the DMA region will not cross the 2GB
memory limit. If the DMA region had been placed in the decompressed kernel,
then KASLR would make this guarantee impossible to fulfill or it would
be restricted to the first 2GB of memory address space.
This commit moves all DMA sections between _sdma and _edma from
the decompressor's image to the decompressed kernel's image. The complete
DMA region is placed in the init section of the decompressed kernel and
immediately relocated below 2GB at start-up before it is needed by other
parts of the decompressed kernel. The relocation of the DMA region happens
even if the decompressed kernel is already located below 2GB in order
to keep the first implementation simple. The relocation should not have
any noticeable impact on boot time because the DMA segment is only a couple
of pages.
After relocating the DMA sections, the kernel has to fix all references
which point into it. In order to automate this, place all variables
pointing into the DMA sections in a special .dma.refs section. All such
variables must be defined using the new __dma_ref macro. Only variables
containing addresses within the DMA sections must be placed in the new
.dma.refs section.
Furthermore, move the initialization of control registers from
the decompressor to the decompressed kernel because some control registers
reference tables that must be placed in the DMA data section to
guarantee that their addresses are below 2G. Because the decompressed
kernel relocates the DMA sections at startup, the content of control
registers CR2, CR5 and CR15 must be updated with new addresses after
the relocation. The decompressed kernel initializes all control registers
early at boot and then updates the content of CR2, CR5 and CR15
as soon as the DMA relocation has occurred. This practically reverts
the commit a80313ff91ab ("s390/kernel: introduce .dma sections").
Signed-off-by: Alexander Egorenkov <egorenar@linux.ibm.com>
Acked-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
77 lines
2.5 KiB
C
77 lines
2.5 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef _ENTRY_H
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#define _ENTRY_H
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#include <linux/percpu.h>
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#include <linux/types.h>
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#include <linux/signal.h>
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#include <asm/ptrace.h>
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#include <asm/idle.h>
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extern void *restart_stack;
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void system_call(void);
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void pgm_check_handler(void);
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void ext_int_handler(void);
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void io_int_handler(void);
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void mcck_int_handler(void);
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void restart_int_handler(void);
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void __ret_from_fork(struct task_struct *prev, struct pt_regs *regs);
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void __do_pgm_check(struct pt_regs *regs);
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void __do_syscall(struct pt_regs *regs, int per_trap);
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void do_protection_exception(struct pt_regs *regs);
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void do_dat_exception(struct pt_regs *regs);
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void do_secure_storage_access(struct pt_regs *regs);
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void do_non_secure_storage_access(struct pt_regs *regs);
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void do_secure_storage_violation(struct pt_regs *regs);
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void do_report_trap(struct pt_regs *regs, int si_signo, int si_code, char *str);
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void kernel_stack_overflow(struct pt_regs * regs);
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void do_signal(struct pt_regs *regs);
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void handle_signal32(struct ksignal *ksig, sigset_t *oldset,
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struct pt_regs *regs);
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void do_notify_resume(struct pt_regs *regs);
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void __init init_IRQ(void);
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void do_io_irq(struct pt_regs *regs);
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void do_ext_irq(struct pt_regs *regs);
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void do_restart(void *arg);
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void __init startup_init(void);
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void die(struct pt_regs *regs, const char *str);
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int setup_profiling_timer(unsigned int multiplier);
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void __init time_init(void);
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unsigned long prepare_ftrace_return(unsigned long parent, unsigned long sp, unsigned long ip);
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struct s390_mmap_arg_struct;
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struct fadvise64_64_args;
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struct old_sigaction;
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long sys_rt_sigreturn(void);
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long sys_sigreturn(void);
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long sys_s390_personality(unsigned int personality);
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long sys_s390_runtime_instr(int command, int signum);
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long sys_s390_guarded_storage(int command, struct gs_cb __user *);
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long sys_s390_pci_mmio_write(unsigned long, const void __user *, size_t);
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long sys_s390_pci_mmio_read(unsigned long, void __user *, size_t);
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long sys_s390_sthyi(unsigned long function_code, void __user *buffer, u64 __user *return_code, unsigned long flags);
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DECLARE_PER_CPU(u64, mt_cycles[8]);
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unsigned long stack_alloc(void);
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void stack_free(unsigned long stack);
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extern char kprobes_insn_page[];
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extern char _sdma[], _edma[];
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extern char _stext_dma[], _etext_dma[];
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extern struct exception_table_entry _start_dma_ex_table[];
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extern struct exception_table_entry _stop_dma_ex_table[];
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#define __dma_data __section(".dma.data")
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#define __dma_ref __section(".dma.refs")
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extern long _start_dma_refs[], _end_dma_refs[];
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#endif /* _ENTRY_H */
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