[1/1] linux-user: Preserve NULL hit in target_mmap subroutines

Commit Message

Richard Henderson Aug. 15, 2024, 1:05 a.m. UTC

Do not pass guest_base to the host mmap instead of zero hint.

Cc: [e-mail]
Resolves: https://gitlab.com/qemu-project/qemu/-/issues/2353
Signed-off-by: Richard Henderson <[e-mail]>
---
 linux-user/mmap.c | 18 +++++++++++++++---
 1 file changed, 15 insertions(+), 3 deletions(-)

Comments

Philippe Mathieu-Daudé Aug. 15, 2024, 9:14 a.m. UTC | #1

On 15/8/24 03:05, Richard Henderson wrote:
> Do not pass guest_base to the host mmap instead of zero hint.
> 
> Cc: [e-mail]
> Resolves: https://gitlab.com/qemu-project/qemu/-/issues/2353
> Signed-off-by: Richard Henderson <[e-mail]>

FTR per 
https://lore.kernel.org/qemu-devel/[e-mail]/:
Reviewed-by: Philippe Mathieu-Daudé <[e-mail]>

> ---
>   linux-user/mmap.c | 18 +++++++++++++++---
>   1 file changed, 15 insertions(+), 3 deletions(-)

Peter Maydell Aug. 15, 2024, 9:20 a.m. UTC | #2

On Thu, 15 Aug 2024 at 02:07, Richard Henderson
<[e-mail]> wrote:
>
> Do not pass guest_base to the host mmap instead of zero hint.
>
> Cc: [e-mail]
> Resolves: https://gitlab.com/qemu-project/qemu/-/issues/2353
> Signed-off-by: Richard Henderson <[e-mail]>

Typo in subject line: s/hit/hint/.

-- PMM

Patch

diff --git a/linux-user/mmap.c b/linux-user/mmap.c
index 4d09a72fad..6418e811f6 100644
--- a/linux-user/mmap.c
+++ b/linux-user/mmap.c
@@ -560,9 +560,13 @@  static abi_long mmap_h_eq_g(abi_ulong start, abi_ulong len,
                             int host_prot, int flags, int page_flags,
                             int fd, off_t offset)
 {
-    void *p, *want_p = g2h_untagged(start);
+    void *p, *want_p = NULL;
     abi_ulong last;
 
+    if (start || (flags & (MAP_FIXED | MAP_FIXED_NOREPLACE))) {
+        want_p = g2h_untagged(start);
+    }
+
     p = mmap(want_p, len, host_prot, flags, fd, offset);
     if (p == MAP_FAILED) {
         return -1;
@@ -610,11 +614,15 @@  static abi_long mmap_h_lt_g(abi_ulong start, abi_ulong len, int host_prot,
                             int mmap_flags, int page_flags, int fd,
                             off_t offset, int host_page_size)
 {
-    void *p, *want_p = g2h_untagged(start);
+    void *p, *want_p = NULL;
     off_t fileend_adj = 0;
     int flags = mmap_flags;
     abi_ulong last, pass_last;
 
+    if (start || (flags & (MAP_FIXED | MAP_FIXED_NOREPLACE))) {
+        want_p = g2h_untagged(start);
+    }
+
     if (!(flags & MAP_ANONYMOUS)) {
         struct stat sb;
 
@@ -740,12 +748,16 @@  static abi_long mmap_h_gt_g(abi_ulong start, abi_ulong len,
                             int flags, int page_flags, int fd,
                             off_t offset, int host_page_size)
 {
-    void *p, *want_p = g2h_untagged(start);
+    void *p, *want_p = NULL;
     off_t host_offset = offset & -host_page_size;
     abi_ulong last, real_start, real_last;
     bool misaligned_offset = false;
     size_t host_len;
 
+    if (start || (flags & (MAP_FIXED | MAP_FIXED_NOREPLACE))) {
+        want_p = g2h_untagged(start);
+    }
+
     if (!(flags & (MAP_FIXED | MAP_FIXED_NOREPLACE))) {
         /*
          * Adjust the offset to something representable on the host.