linux-user: fix mremap for 64bit targets on 32bit hosts

PATCH In review Felix Janda 3 participants 5 messages Sep 18, 2016 – Sep 29, 2016

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Felix Janda

author

2016-09-18 01:21 UTC #0 lore raw

PATCH 1/1 linux-user: fix mremap for 64bit targets on 32bit hosts

Signed-off-by Felix Janda <[email protected]>

---
 linux-user/mmap.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

linux-user/mmap.c +2 -2

index c4371d9..4882816 100644
@@ -682,7 +682,7 @@ abi_long target_mremap(abi_ulong old_addr, abi_ulong old_size,
 
     if (flags & MREMAP_FIXED) {
         host_addr = (void *) syscall(__NR_mremap, g2h(old_addr),
-                                     old_size, new_size,
+                                     (size_t) old_size, (size_t) new_size,
                                      flags,
                                      g2h(new_addr));

@@ -701,7 +701,7 @@ abi_long target_mremap(abi_ulong old_addr, abi_ulong old_size,
             host_addr = MAP_FAILED;
         } else {
             host_addr = (void *) syscall(__NR_mremap, g2h(old_addr),
-                                         old_size, new_size,
+                                         (size_t) old_size, (size_t) new_size,
                                          flags | MREMAP_FIXED,
                                          g2h(mmap_start));
             if (reserved_va) {

Signature · 1 line

2.7.3

Riku Voipio

2016-09-22 06:22 UTC #1 lore raw

Hi,

Quoted 1 line · Felix Janda

Signed-off-by Felix Janda <[email protected]>

Have you run the mremap tests of ltp with this on your host/guest combo?

Quoted 29 lines

---
 linux-user/mmap.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

linux-user/mmap.c +2 -2

index c4371d9..4882816 100644
@@ -682,7 +682,7 @@ abi_long target_mremap(abi_ulong old_addr, abi_ulong old_size,
 
     if (flags & MREMAP_FIXED) {
         host_addr = (void *) syscall(__NR_mremap, g2h(old_addr),
-                                     old_size, new_size,
+                                     (size_t) old_size, (size_t) new_size,
                                      flags,
                                      g2h(new_addr));

@@ -701,7 +701,7 @@ abi_long target_mremap(abi_ulong old_addr, abi_ulong old_size,
             host_addr = MAP_FAILED;
         } else {
             host_addr = (void *) syscall(__NR_mremap, g2h(old_addr),
-                                         old_size, new_size,
+                                         (size_t) old_size, (size_t) new_size,
                                          flags | MREMAP_FIXED,
                                          g2h(mmap_start));
             if (reserved_va) {

Signature · 1 line

2.7.3

Felix Janda

author

2016-09-23 00:38 UTC #2 lore raw

Quoted 7 lines · Riku Voipio

Hi,
Quoted 1 line · Felix Janda
Signed-off-by Felix Janda <[email protected]>
Have you run the mremap tests of ltp with this on your host/guest combo?

I have just run the tests. My host is arm and my guest is aarch64. Without the patch all but mremap02 fail. With the patch all but mremap04 pass. The mremap04 test indicates that shmat is broken.

Quoted 29 lines

---
 linux-user/mmap.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

linux-user/mmap.c +2 -2

index c4371d9..4882816 100644
@@ -682,7 +682,7 @@ abi_long target_mremap(abi_ulong old_addr, abi_ulong old_size,
 
     if (flags & MREMAP_FIXED) {
         host_addr = (void *) syscall(__NR_mremap, g2h(old_addr),
-                                     old_size, new_size,
+                                     (size_t) old_size, (size_t) new_size,
                                      flags,
                                      g2h(new_addr));

@@ -701,7 +701,7 @@ abi_long target_mremap(abi_ulong old_addr, abi_ulong old_size,
             host_addr = MAP_FAILED;
         } else {
             host_addr = (void *) syscall(__NR_mremap, g2h(old_addr),
-                                         old_size, new_size,
+                                         (size_t) old_size, (size_t) new_size,
                                          flags | MREMAP_FIXED,
                                          g2h(mmap_start));
             if (reserved_va) {

Signature · 1 line

2.7.3

Rather than this, I think it would be better to switch to using the mremap() library call rather than direct syscall here, which then matches the other mremap()s later in the function. (That will work right because mremap()'s prototype says it takes size_t arguments, whereas syscall() is a generic thing which doesn't, and so the C default promotions do the wrong thing with the abi_ulongs.)

The use of syscall(__NR_mremap, ...) originally dates back to 2008:
https://lists.gnu.org/archive/html/qemu-devel/2008-12/msg01087.html
https://lists.gnu.org/archive/html/qemu-devel/2008-12/msg00480.html

and was to permit compilation with glibc 2.4 which didn't support the 5-argument mremap() or define MREMAP_FIXED.

Since glibc 2.4 dates back to a decade ago now, we no longer need to carry this ugly (and buggy) workaround for it.

thanks
-- PMM

Felix Janda

author

2016-09-29 02:48 UTC #4 lore raw

Quoted 43 lines · Peter Maydell

Quoted 28 lines · Felix Janda

Signed-off-by Felix Janda <[email protected]>

---
 linux-user/mmap.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

linux-user/mmap.c +2 -3

index c4371d9..4882816 100644
@@ -682,7 +682,7 @@ abi_long target_mremap(abi_ulong old_addr, abi_ulong old_size,
 
     if (flags & MREMAP_FIXED) {
         host_addr = (void *) syscall(__NR_mremap, g2h(old_addr),
-                                     old_size, new_size,
+                                     (size_t) old_size, (size_t) new_size,
                                      flags,
                                      g2h(new_addr));

@@ -701,7 +701,7 @@ abi_long target_mremap(abi_ulong old_addr, abi_ulong old_size,
             host_addr = MAP_FAILED;
         } else {
             host_addr = (void *) syscall(__NR_mremap, g2h(old_addr),
-                                         old_size, new_size,
+                                         (size_t) old_size, (size_t) new_size,
                                          flags | MREMAP_FIXED,
                                          g2h(mmap_start));
             if (reserved_va) {
--

Quoted 1 line

2.7.3

Quoted 5 lines

and was to permit compilation with glibc 2.4 which didn't support the 5-argument mremap() or define MREMAP_FIXED.
Since glibc 2.4 dates back to a decade ago now, we no longer need to carry this ugly (and buggy) workaround for it.

This sounds like a good idea. Thanks also for digging up the history.

I will prepare a new patch.

Thanks,
Felix