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d1d7f01f7c
Mark read-only data actually read-only (simple mprotect), and to be able to test it also implement _nofault accesses. This works by setting up a new "segv_continue" pointer in current, and then when we hit a segfault we change the signal return context so that we continue at that address. The code using this sets it up so that it jumps to a label and then aborts the access that way, returning -EFAULT. It's possible to optimize the ___backtrack_faulted() thing by using asm goto (compiler version dependent) and/or gcc's (not sure if clang has it) &&label extension, but at least in one attempt I made the && caused the compiler to not load -EFAULT into the register in case of jumping to the &&label from the fault handler. So leave it like this for now. Signed-off-by: Johannes Berg <johannes.berg@intel.com> Co-developed-by: Benjamin Berg <benjamin.berg@intel.com> Signed-off-by: Benjamin Berg <benjamin.berg@intel.com> Link: https://patch.msgid.link/20250210160926.420133-2-benjamin@sipsolutions.net Signed-off-by: Johannes Berg <johannes.berg@intel.com>
45 lines
1.3 KiB
C
45 lines
1.3 KiB
C
/*
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* Copyright (C) 2004 Fujitsu Siemens Computers GmbH
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* Author: Bodo Stroesser <bstroesser@fujitsu-siemens.com>
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* Licensed under the GPL
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*/
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#ifndef __FAULTINFO_I386_H
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#define __FAULTINFO_I386_H
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/* this structure contains the full arch-specific faultinfo
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* from the traps.
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* On i386, ptrace_faultinfo unfortunately doesn't provide
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* all the info, since trap_no is missing.
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* All common elements are defined at the same position in
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* both structures, thus making it easy to copy the
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* contents without knowledge about the structure elements.
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*/
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struct faultinfo {
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int error_code; /* in ptrace_faultinfo misleadingly called is_write */
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unsigned long cr2; /* in ptrace_faultinfo called addr */
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int trap_no; /* missing in ptrace_faultinfo */
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};
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#define FAULT_WRITE(fi) ((fi).error_code & 2)
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#define FAULT_ADDRESS(fi) ((fi).cr2)
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/* This is Page Fault */
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#define SEGV_IS_FIXABLE(fi) ((fi)->trap_no == 14)
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#define PTRACE_FULL_FAULTINFO 0
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#define ___backtrack_faulted(_faulted) \
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asm volatile ( \
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"mov $0, %0\n" \
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"movl $__get_kernel_nofault_faulted_%=,%1\n" \
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"jmp _end_%=\n" \
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"__get_kernel_nofault_faulted_%=:\n" \
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"mov $1, %0;" \
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"_end_%=:" \
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: "=r" (_faulted), \
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"=m" (current->thread.segv_continue) :: \
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)
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#endif
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