diff options
| author | Johannes Berg <johannes.berg@intel.com> | 2025-02-10 17:09:25 +0100 |
|---|---|---|
| committer | Johannes Berg <johannes.berg@intel.com> | 2025-03-18 11:03:14 +0100 |
| commit | d1d7f01f7cd35e16c6bcef5a0e31988b5c9980f9 (patch) | |
| tree | ac2a7b2c4ccc6a9f1749c48eca519d615d125942 /arch/um/include/asm/uaccess.h | |
| parent | 5550187c4c21740942c32a9ae56f9f472a104cb4 (diff) | |
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>
Diffstat (limited to 'arch/um/include/asm/uaccess.h')
| -rw-r--r-- | arch/um/include/asm/uaccess.h | 20 |
1 files changed, 15 insertions, 5 deletions
diff --git a/arch/um/include/asm/uaccess.h b/arch/um/include/asm/uaccess.h index 1d4b6bbc1b65..3a08f9029a3f 100644 --- a/arch/um/include/asm/uaccess.h +++ b/arch/um/include/asm/uaccess.h @@ -9,6 +9,7 @@ #include <asm/elf.h> #include <linux/unaligned.h> +#include <sysdep/faultinfo.h> #define __under_task_size(addr, size) \ (((unsigned long) (addr) < TASK_SIZE) && \ @@ -44,19 +45,28 @@ static inline int __access_ok(const void __user *ptr, unsigned long size) __access_ok_vsyscall(addr, size)); } -/* no pagefaults for kernel addresses in um */ #define __get_kernel_nofault(dst, src, type, err_label) \ do { \ - *((type *)dst) = get_unaligned((type *)(src)); \ - if (0) /* make sure the label looks used to the compiler */ \ + int __faulted; \ + \ + ___backtrack_faulted(__faulted); \ + if (__faulted) { \ + *((type *)dst) = (type) 0; \ goto err_label; \ + } \ + *((type *)dst) = get_unaligned((type *)(src)); \ + current->thread.segv_continue = NULL; \ } while (0) #define __put_kernel_nofault(dst, src, type, err_label) \ do { \ - put_unaligned(*((type *)src), (type *)(dst)); \ - if (0) /* make sure the label looks used to the compiler */ \ + int __faulted; \ + \ + ___backtrack_faulted(__faulted); \ + if (__faulted) \ goto err_label; \ + put_unaligned(*((type *)src), (type *)(dst)); \ + current->thread.segv_continue = NULL; \ } while (0) #endif |