Merge remote-tracking branch 'remotes/vivier2/tags/linux-user-for-2.12-pull-request' into staging

# gpg: Signature made Tue 23 Jan 2018 14:47:41 GMT
# gpg:                using RSA key 0xF30C38BD3F2FBE3C
# gpg: Good signature from "Laurent Vivier <lvivier@redhat.com>"
# gpg:                 aka "Laurent Vivier <laurent@vivier.eu>"
# gpg:                 aka "Laurent Vivier (Red Hat) <lvivier@redhat.com>"
# Primary key fingerprint: CD2F 75DD C8E3 A4DC 2E4F  5173 F30C 38BD 3F2F BE3C

* remotes/vivier2/tags/linux-user-for-2.12-pull-request:
  linux-user: implement renameat2
  page_unprotect(): handle calls to pages that are PAGE_WRITE
  linux-user: Propagate siginfo_t through to handle_cpu_signal()
  linux-user: remove nmi.c and fw-path-provider.c
  linux-user: Add getcpu() support
  linux-user: Add AT_SECURE auxval
  linux-user: Fix sched_get/setaffinity conversion
  linux-user/mmap.c: Avoid choosing NULL as start address
  linux-user: Translate flags argument to dup3 syscall
  linux-user: Don't use CMSG_ALIGN(sizeof struct cmsghdr)
  linux-user: Fix length calculations in host_to_target_cmsg()
  linux-user: wrap fork() in a start/end exclusive section
  linux-user: Fix locking order in fork_start()

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

1 files changed, 26 insertions, 26 deletions

diff --git a/accel/tcg/user-exec.c b/accel/tcg/user-exec.c
index f42285ea1c..c973752562 100644
--- a/accel/tcg/user-exec.c
+++ b/accel/tcg/user-exec.c
@@ -57,12 +57,13 @@ static void cpu_exit_tb_from_sighandler(CPUState *cpu, sigset_t *old_set)
    the effective address of the memory exception. 'is_write' is 1 if a
    write caused the exception and otherwise 0'. 'old_set' is the
    signal set which should be restored */
-static inline int handle_cpu_signal(uintptr_t pc, unsigned long address,
+static inline int handle_cpu_signal(uintptr_t pc, siginfo_t *info,
                                     int is_write, sigset_t *old_set)
 {
     CPUState *cpu = current_cpu;
     CPUClass *cc;
     int ret;
+    unsigned long address = (unsigned long)info->si_addr;
 
     /* We must handle PC addresses from two different sources:
      * a call return address and a signal frame address.
@@ -103,7 +104,18 @@ static inline int handle_cpu_signal(uintptr_t pc, unsigned long address,
            pc, address, is_write, *(unsigned long *)old_set);
 #endif
     /* XXX: locking issue */
-    if (is_write && h2g_valid(address)) {
+    /* Note that it is important that we don't call page_unprotect() unless
+     * this is really a "write to nonwriteable page" fault, because
+     * page_unprotect() assumes that if it is called for an access to
+     * a page that's writeable this means we had two threads racing and
+     * another thread got there first and already made the page writeable;
+     * so we will retry the access. If we were to call page_unprotect()
+     * for some other kind of fault that should really be passed to the
+     * guest, we'd end up in an infinite loop of retrying the faulting
+     * access.
+     */
+    if (is_write && info->si_signo == SIGSEGV && info->si_code == SEGV_ACCERR &&
+        h2g_valid(address)) {
         switch (page_unprotect(h2g(address), pc)) {
         case 0:
             /* Fault not caused by a page marked unwritable to protect
@@ -215,9 +227,8 @@ int cpu_signal_handler(int host_signum, void *pinfo,
 #endif
     pc = EIP_sig(uc);
     trapno = TRAP_sig(uc);
-    return handle_cpu_signal(pc, (unsigned long)info->si_addr,
-                             trapno == 0xe ?
-                             (ERROR_sig(uc) >> 1) & 1 : 0,
+    return handle_cpu_signal(pc, info,
+                             trapno == 0xe ? (ERROR_sig(uc) >> 1) & 1 : 0,
                              &MASK_sig(uc));
 }
 
@@ -261,9 +272,8 @@ int cpu_signal_handler(int host_signum, void *pinfo,
 #endif
 
     pc = PC_sig(uc);
-    return handle_cpu_signal(pc, (unsigned long)info->si_addr,
-                             TRAP_sig(uc) == 0xe ?
-                             (ERROR_sig(uc) >> 1) & 1 : 0,
+    return handle_cpu_signal(pc, info,
+                             TRAP_sig(uc) == 0xe ? (ERROR_sig(uc) >> 1) & 1 : 0,
                              &MASK_sig(uc));
 }
 
@@ -341,8 +351,7 @@ int cpu_signal_handler(int host_signum, void *pinfo,
         is_write = 1;
     }
 #endif
-    return handle_cpu_signal(pc, (unsigned long)info->si_addr,
-                             is_write, &uc->uc_sigmask);
+    return handle_cpu_signal(pc, info, is_write, &uc->uc_sigmask);
 }
 
 #elif defined(__alpha__)
@@ -372,8 +381,7 @@ int cpu_signal_handler(int host_signum, void *pinfo,
         is_write = 1;
     }
 
-    return handle_cpu_signal(pc, (unsigned long)info->si_addr,
-                             is_write, &uc->uc_sigmask);
+    return handle_cpu_signal(pc, info, is_write, &uc->uc_sigmask);
 }
 #elif defined(__sparc__)
 
@@ -432,8 +440,7 @@ int cpu_signal_handler(int host_signum, void *pinfo,
             break;
         }
     }
-    return handle_cpu_signal(pc, (unsigned long)info->si_addr,
-                             is_write, sigmask);
+    return handle_cpu_signal(pc, info, is_write, sigmask);
 }
 
 #elif defined(__arm__)
@@ -466,9 +473,7 @@ int cpu_signal_handler(int host_signum, void *pinfo,
      * later processor; on v5 we will always report this as a read).
      */
     is_write = extract32(uc->uc_mcontext.error_code, 11, 1);
-    return handle_cpu_signal(pc, (unsigned long)info->si_addr,
-                             is_write,
-                             &uc->uc_sigmask);
+    return handle_cpu_signal(pc, info, is_write, &uc->uc_sigmask);
 }
 
 #elif defined(__aarch64__)
@@ -495,8 +500,7 @@ int cpu_signal_handler(int host_signum, void *pinfo, void *puc)
                 /* Ignore bits 23 & 24, controlling indexing.  */
                 || (insn & 0x3a400000) == 0x28000000); /* C3.3.7,14-16 */
 
-    return handle_cpu_signal(pc, (uintptr_t)info->si_addr,
-                             is_write, &uc->uc_sigmask);
+    return handle_cpu_signal(pc, info, is_write, &uc->uc_sigmask);
 }
 
 #elif defined(__ia64)
@@ -529,9 +533,7 @@ int cpu_signal_handler(int host_signum, void *pinfo, void *puc)
     default:
         break;
     }
-    return handle_cpu_signal(ip, (unsigned long)info->si_addr,
-                             is_write,
-                             (sigset_t *)&uc->uc_sigmask);
+    return handle_cpu_signal(ip, info, is_write, (sigset_t *)&uc->uc_sigmask);
 }
 
 #elif defined(__s390__)
@@ -583,8 +585,7 @@ int cpu_signal_handler(int host_signum, void *pinfo,
         }
         break;
     }
-    return handle_cpu_signal(pc, (unsigned long)info->si_addr,
-                             is_write, &uc->uc_sigmask);
+    return handle_cpu_signal(pc, info, is_write, &uc->uc_sigmask);
 }
 
 #elif defined(__mips__)
@@ -599,8 +600,7 @@ int cpu_signal_handler(int host_signum, void *pinfo,
 
     /* XXX: compute is_write */
     is_write = 0;
-    return handle_cpu_signal(pc, (unsigned long)info->si_addr,
-                             is_write, &uc->uc_sigmask);
+    return handle_cpu_signal(pc, info, is_write, &uc->uc_sigmask);
 }
 
 #else