The fchmodat2 syscall is new from Linux 6.6; it is like the
existing fchmodat syscall except that it takes a flags parameter.
If we have the host fchmodat2 syscall, we implement it as a
direct passthrough call; if we do not, then we can fall back
to using the libc fchmodat() function. The fallback can
handle the AT_SYMLINK_NOFOLLOW flag but won't be able to
do anything about AT_EMPTY_PATH.
Signed-off-by: Peter Maydell <peter.mayd...@linaro.org>
---
Tested very lightly (ran an fchmodat2 test from the
Linux Test Project test suite).
You could argue that the fallback-to-libc-fchmodat here isn't
worth bothering with, I guess.
linux-user/syscall.c | 20 ++++++++++++++++++++
1 file changed, 20 insertions(+)
diff --git a/linux-user/syscall.c b/linux-user/syscall.c
index fc37028597c..827b432bb31 100644
--- a/linux-user/syscall.c
+++ b/linux-user/syscall.c
@@ -790,6 +790,10 @@ safe_syscall6(ssize_t, copy_file_range, int, infd, loff_t
*, pinoff,
int, outfd, loff_t *, poutoff, size_t, length,
unsigned int, flags)
#endif
+#if defined(TARGET_NR_fchmodat2) && defined(__NR_fchmodat2)
+safe_syscall4(int, fchmodat2, int, dfd, const char *, filename,
+ unsigned short, mode, unsigned int, flags)
+#endif
/* We do ioctl like this rather than via safe_syscall3 to preserve the
* "third argument might be integer or pointer or not present" behaviour of
@@ -10713,6 +10717,22 @@ static abi_long do_syscall1(CPUArchState *cpu_env, int
num, abi_long arg1,
ret = get_errno(fchmodat(arg1, p, arg3, 0));
unlock_user(p, arg2, 0);
return ret;
+#endif
+#if defined(TARGET_NR_fchmodat2)
+ case TARGET_NR_fchmodat2:
+ if (!(p = lock_user_string(arg2)))
+ return -TARGET_EFAULT;
+#if defined(__NR_fchmodat2)
+ ret = get_errno(safe_fchmodat2(arg1, p, arg3, arg4));
+#else
+ /*
+ * fall back to using libc function: this will work for
+ * flag AT_SYMLINK_NOFOLLOW but not AT_EMPTY_PATH.
+ */
+ ret = get_errno(fchmodat(arg1, p, arg3, arg4));
+#endif
+ unlock_user(p, arg2, 0);
+ return ret;
#endif
case TARGET_NR_getpriority:
/* Note that negative values are valid for getpriority, so we must
--
2.43.0
