linux/arch/um/include/shared/arch.h
Johannes Berg d1d7f01f7c um: mark rodata read-only and implement _nofault accesses
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>
2025-03-18 11:03:14 +01:00

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C

/* SPDX-License-Identifier: GPL-2.0 */
/*
* Copyright (C) 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
*/
#ifndef __ARCH_H__
#define __ARCH_H__
#include <sysdep/ptrace.h>
extern void arch_check_bugs(void);
extern int arch_fixup(unsigned long address, struct uml_pt_regs *regs);
extern void arch_examine_signal(int sig, struct uml_pt_regs *regs);
void mc_set_rip(void *_mc, void *target);
#endif