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* [PATCH] linux-user: Implement faccessat2
@ 2022-10-09  6:08 WANG Xuerui
  2022-10-10  8:53 ` Helge Deller
  2022-10-21 15:37 ` Laurent Vivier
  0 siblings, 2 replies; 7+ messages in thread
From: WANG Xuerui @ 2022-10-09  6:08 UTC (permalink / raw)
  To: qemu-devel
  Cc: Laurent Vivier, Philippe Mathieu-Daudé, WANG Xuerui,
	Andreas K . Hüttel

User space has been preferring this syscall for a while, due to its
closer match with C semantics, and newer platforms such as LoongArch
apparently have libc implementations that don't fallback to faccessat
so normal access checks are failing without the emulation in place.

Tested by successfully emerging several packages within a Gentoo loong
stage3 chroot, emulated on amd64 with help of static qemu-loongarch64.

Reported-by: Andreas K. Hüttel <dilfridge@gentoo.org>
Signed-off-by: WANG Xuerui <xen0n@gentoo.org>
---
 linux-user/strace.list | 3 +++
 linux-user/syscall.c   | 9 +++++++++
 2 files changed, 12 insertions(+)

diff --git a/linux-user/strace.list b/linux-user/strace.list
index a87415bf3d..3df2184580 100644
--- a/linux-user/strace.list
+++ b/linux-user/strace.list
@@ -178,6 +178,9 @@
 #ifdef TARGET_NR_faccessat
 { TARGET_NR_faccessat, "faccessat" , NULL, print_faccessat, NULL },
 #endif
+#ifdef TARGET_NR_faccessat2
+{ TARGET_NR_faccessat2, "faccessat2" , NULL, print_faccessat, NULL },
+#endif
 #ifdef TARGET_NR_fadvise64
 { TARGET_NR_fadvise64, "fadvise64" , NULL, NULL, NULL },
 #endif
diff --git a/linux-user/syscall.c b/linux-user/syscall.c
index 2e954d8dbd..a81f0b65b9 100644
--- a/linux-user/syscall.c
+++ b/linux-user/syscall.c
@@ -9110,6 +9110,15 @@ static abi_long do_syscall1(CPUArchState *cpu_env, int num, abi_long arg1,
         unlock_user(p, arg2, 0);
         return ret;
 #endif
+#if defined(TARGET_NR_faccessat2) && defined(__NR_faccessat2)
+    case TARGET_NR_faccessat2:
+        if (!(p = lock_user_string(arg2))) {
+            return -TARGET_EFAULT;
+        }
+        ret = get_errno(faccessat(arg1, p, arg3, arg4));
+        unlock_user(p, arg2, 0);
+        return ret;
+#endif
 #ifdef TARGET_NR_nice /* not on alpha */
     case TARGET_NR_nice:
         return get_errno(nice(arg1));
-- 
2.38.0



^ permalink raw reply related	[flat|nested] 7+ messages in thread
* [PATCH] linux-user: Implement faccessat2
@ 2022-07-29 20:14 Richard Henderson
  2022-07-31 15:38 ` Richard Henderson
  0 siblings, 1 reply; 7+ messages in thread
From: Richard Henderson @ 2022-07-29 20:14 UTC (permalink / raw)
  To: qemu-devel; +Cc: laurent

Split out do_faccessat2 helper, and use it for
accessat and faccessat as well.

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
Will we ever have a system libc for which __NR_faccessat2 is present,
but faccessat() does not try faccessat2 first?

r~
---
 linux-user/syscall.c | 44 +++++++++++++++++++++++++++++++-------------
 1 file changed, 31 insertions(+), 13 deletions(-)

diff --git a/linux-user/syscall.c b/linux-user/syscall.c
index b27a6552aa..acd8452048 100644
--- a/linux-user/syscall.c
+++ b/linux-user/syscall.c
@@ -8530,6 +8530,30 @@ static int do_getdents64(abi_long dirfd, abi_long arg2, abi_long count)
 _syscall2(int, pivot_root, const char *, new_root, const char *, put_old)
 #endif
 
+static int do_faccessat2(int dirfd, abi_ptr pathname, int mode, int flags)
+{
+    char *p = lock_user_string(pathname);
+    bool nosys = true;
+    int ret;
+
+    if (!p) {
+        return -TARGET_EFAULT;
+    }
+
+    /* Use the raw host syscall if possible, in case we have an old libc. */
+#ifdef __NR_faccessat2
+    ret = syscall(__NR_faccessat2, dirfd, p, mode, flags);
+    nosys = ret < 0 && errno == ENOSYS;
+#endif
+    /* If we don't have the syscall, defer to libc emulation. */
+    if (nosys) {
+        ret = faccessat(dirfd, p, mode, flags);
+    }
+
+    unlock_user(p, pathname, 0);
+    return get_errno(ret);
+}
+
 /* This is an internal helper for do_syscall so that it is easier
  * to have a single return point, so that actions, such as logging
  * of syscall results, can be performed.
@@ -9058,21 +9082,15 @@ static abi_long do_syscall1(CPUArchState *cpu_env, int num, abi_long arg1,
 #endif
 #ifdef TARGET_NR_access
     case TARGET_NR_access:
-        if (!(p = lock_user_string(arg1))) {
-            return -TARGET_EFAULT;
-        }
-        ret = get_errno(access(path(p), arg2));
-        unlock_user(p, arg1, 0);
-        return ret;
+        return do_faccessat2(AT_FDCWD, arg1, arg2, 0);
 #endif
-#if defined(TARGET_NR_faccessat) && defined(__NR_faccessat)
+#ifdef TARGET_NR_faccessat
     case TARGET_NR_faccessat:
-        if (!(p = lock_user_string(arg2))) {
-            return -TARGET_EFAULT;
-        }
-        ret = get_errno(faccessat(arg1, p, arg3, 0));
-        unlock_user(p, arg2, 0);
-        return ret;
+        return do_faccessat2(arg1, arg2, arg3, 0);
+#endif
+#ifdef TARGET_NR_faccessat2
+    case TARGET_NR_faccessat2:
+        return do_faccessat2(arg1, arg2, arg3, arg4);
 #endif
 #ifdef TARGET_NR_nice /* not on alpha */
     case TARGET_NR_nice:
-- 
2.34.1



^ permalink raw reply related	[flat|nested] 7+ messages in thread
end of thread, other threads:[~2022-10-21 15:39 UTC | newest]

Thread overview: 7+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2022-10-09  6:08 [PATCH] linux-user: Implement faccessat2 WANG Xuerui
2022-10-10  8:53 ` Helge Deller
2022-10-18  9:58   ` Michael Tokarev
2022-10-18 13:05     ` Luca Bonissi
2022-10-21 15:37 ` Laurent Vivier
  -- strict thread matches above, loose matches on Subject: below --
2022-07-29 20:14 Richard Henderson
2022-07-31 15:38 ` Richard Henderson

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