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e95c3f7a09
As of commitfea82210("m68k: switch to saner kernel_execve() semantics") the non-mmu m68k targets have trapped on booting. The execing of /bin/init causes the exec path to try and return through a 0x0 return address - thus trapping or otherwise hanging or crashing. The problem isn't in the exec path as such though, but rather in the m68knommu start_thread() macro. It is trying to clear the a6 register that it assumes is part of a struct switch_stack below the thread registers on our stack. But that is not what the stack frames look like when this is run. So it ends up corrupting our call stack and zeroing out a function return address that is sitting there. The clearing of a6 was introduced many years ago in commit7bf9a37d8d("m68knommu: force stack alignment on ColdFire"). It used to work because the kernel init exec code path had a short cut back to the exception return code, and it didn't need to return through the calls on the stack. Signed-off-by: Greg Ungerer <gerg@uclinux.org>
181 lines
4.3 KiB
C
181 lines
4.3 KiB
C
/*
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* include/asm-m68k/processor.h
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*
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* Copyright (C) 1995 Hamish Macdonald
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*/
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#ifndef __ASM_M68K_PROCESSOR_H
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#define __ASM_M68K_PROCESSOR_H
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/*
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* Default implementation of macro that returns current
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* instruction pointer ("program counter").
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*/
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#define current_text_addr() ({ __label__ _l; _l: &&_l;})
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#include <linux/thread_info.h>
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#include <asm/segment.h>
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#include <asm/fpu.h>
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#include <asm/ptrace.h>
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static inline unsigned long rdusp(void)
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{
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#ifdef CONFIG_COLDFIRE_SW_A7
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extern unsigned int sw_usp;
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return sw_usp;
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#else
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register unsigned long usp __asm__("a0");
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/* move %usp,%a0 */
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__asm__ __volatile__(".word 0x4e68" : "=a" (usp));
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return usp;
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#endif
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}
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static inline void wrusp(unsigned long usp)
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{
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#ifdef CONFIG_COLDFIRE_SW_A7
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extern unsigned int sw_usp;
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sw_usp = usp;
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#else
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register unsigned long a0 __asm__("a0") = usp;
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/* move %a0,%usp */
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__asm__ __volatile__(".word 0x4e60" : : "a" (a0) );
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#endif
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}
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/*
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* User space process size: 3.75GB. This is hardcoded into a few places,
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* so don't change it unless you know what you are doing.
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*/
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#ifdef CONFIG_MMU
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#if defined(CONFIG_COLDFIRE)
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#define TASK_SIZE (0xC0000000UL)
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#elif defined(CONFIG_SUN3)
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#define TASK_SIZE (0x0E000000UL)
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#else
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#define TASK_SIZE (0xF0000000UL)
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#endif
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#else
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#define TASK_SIZE (0xFFFFFFFFUL)
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#endif
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#ifdef __KERNEL__
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#define STACK_TOP TASK_SIZE
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#define STACK_TOP_MAX STACK_TOP
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#endif
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/* This decides where the kernel will search for a free chunk of vm
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* space during mmap's.
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*/
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#ifdef CONFIG_MMU
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#if defined(CONFIG_COLDFIRE)
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#define TASK_UNMAPPED_BASE 0x60000000UL
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#elif defined(CONFIG_SUN3)
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#define TASK_UNMAPPED_BASE 0x0A000000UL
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#else
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#define TASK_UNMAPPED_BASE 0xC0000000UL
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#endif
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#define TASK_UNMAPPED_ALIGN(addr, off) PAGE_ALIGN(addr)
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#else
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#define TASK_UNMAPPED_BASE 0
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#endif
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struct thread_struct {
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unsigned long ksp; /* kernel stack pointer */
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unsigned long usp; /* user stack pointer */
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unsigned short sr; /* saved status register */
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unsigned short fs; /* saved fs (sfc, dfc) */
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unsigned long crp[2]; /* cpu root pointer */
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unsigned long esp0; /* points to SR of stack frame */
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unsigned long faddr; /* info about last fault */
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int signo, code;
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unsigned long fp[8*3];
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unsigned long fpcntl[3]; /* fp control regs */
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unsigned char fpstate[FPSTATESIZE]; /* floating point state */
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};
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#define INIT_THREAD { \
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.ksp = sizeof(init_stack) + (unsigned long) init_stack, \
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.sr = PS_S, \
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.fs = __KERNEL_DS, \
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}
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/*
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* ColdFire stack format sbould be 0x4 for an aligned usp (will always be
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* true on thread creation). We need to set this explicitly.
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*/
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#ifdef CONFIG_COLDFIRE
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#define setframeformat(_regs) do { (_regs)->format = 0x4; } while(0)
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#else
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#define setframeformat(_regs) do { } while (0)
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#endif
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#ifdef CONFIG_MMU
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/*
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* Do necessary setup to start up a newly executed thread.
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*/
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static inline void start_thread(struct pt_regs * regs, unsigned long pc,
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unsigned long usp)
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{
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regs->pc = pc;
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regs->sr &= ~0x2000;
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setframeformat(regs);
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wrusp(usp);
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}
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extern int handle_kernel_fault(struct pt_regs *regs);
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#else
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#define start_thread(_regs, _pc, _usp) \
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do { \
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(_regs)->pc = (_pc); \
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setframeformat(_regs); \
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if (current->mm) \
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(_regs)->d5 = current->mm->start_data; \
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(_regs)->sr &= ~0x2000; \
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wrusp(_usp); \
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} while(0)
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static inline int handle_kernel_fault(struct pt_regs *regs)
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{
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/* Any fault in kernel is fatal on non-mmu */
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return 0;
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}
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#endif
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/* Forward declaration, a strange C thing */
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struct task_struct;
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/* Free all resources held by a thread. */
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static inline void release_thread(struct task_struct *dead_task)
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{
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}
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/*
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* Free current thread data structures etc..
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*/
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static inline void exit_thread(void)
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{
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}
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extern unsigned long thread_saved_pc(struct task_struct *tsk);
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unsigned long get_wchan(struct task_struct *p);
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#define KSTK_EIP(tsk) \
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({ \
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unsigned long eip = 0; \
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if ((tsk)->thread.esp0 > PAGE_SIZE && \
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(virt_addr_valid((tsk)->thread.esp0))) \
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eip = ((struct pt_regs *) (tsk)->thread.esp0)->pc; \
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eip; })
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#define KSTK_ESP(tsk) ((tsk) == current ? rdusp() : (tsk)->thread.usp)
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#define task_pt_regs(tsk) ((struct pt_regs *) ((tsk)->thread.esp0))
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#define cpu_relax() barrier()
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#endif
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