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| author | Sergey Bugaev <bugaevc@gmail.com> | 2023-06-26 02:17:50 +0300 |
|---|---|---|
| committer | Samuel Thibault <samuel.thibault@ens-lyon.org> | 2023-07-03 01:38:12 +0200 |
| commit | 19c3b318127005444e55feb35e27d877a6af8461 (patch) | |
| tree | 065b4457c8a95c19fdcf378a5927f48dc8a5a6f8 | |
| parent | f84c3ceb0447477eb022cd5da6c8f27a705deae6 (diff) | |
| download | glibc-19c3b318127005444e55feb35e27d877a6af8461.tar.gz glibc-19c3b318127005444e55feb35e27d877a6af8461.tar.xz glibc-19c3b318127005444e55feb35e27d877a6af8461.zip | |
hurd: Fix mapping at address 0 with MAP_FIXED
Zero address passed to mmap () typically means the caller doesn't have any specific preferred address. Not so if MAP_FIXED is passed: in this case 0 means literal 0. Fix this case to pass anywhere = 0 into vm_map. Also add some documentation. Signed-off-by: Sergey Bugaev <bugaevc@gmail.com> Message-Id: <20230625231751.404120-4-bugaevc@gmail.com>
| -rw-r--r-- | sysdeps/mach/hurd/mmap.c | 11 |
1 files changed, 9 insertions, 2 deletions
diff --git a/sysdeps/mach/hurd/mmap.c b/sysdeps/mach/hurd/mmap.c index 5aa7008393..33672cf60a 100644 --- a/sysdeps/mach/hurd/mmap.c +++ b/sysdeps/mach/hurd/mmap.c @@ -38,7 +38,7 @@ __mmap (void *addr, size_t len, int prot, int flags, int fd, off_t offset) vm_prot_t vmprot, max_vmprot; memory_object_t memobj; vm_address_t mapaddr, mask; - boolean_t copy; + boolean_t copy, anywhere; mapaddr = (vm_address_t) addr; @@ -55,6 +55,7 @@ __mmap (void *addr, size_t len, int prot, int flags, int fd, off_t offset) vmprot |= VM_PROT_EXECUTE; copy = ! (flags & MAP_SHARED); + anywhere = ! (flags & MAP_FIXED); #ifdef __LP64__ if ((addr == NULL) && (prot & PROT_EXEC) @@ -141,9 +142,12 @@ __mmap (void *addr, size_t len, int prot, int flags, int fd, off_t offset) if (copy) max_vmprot = VM_PROT_ALL; + /* When ANYWHERE is true but the caller has provided a preferred address, + try mapping at that address with anywhere = 0 first. If this fails, + we'll retry with anywhere = 1 below. */ err = __vm_map (__mach_task_self (), &mapaddr, (vm_size_t) len, mask, - mapaddr == 0, + anywhere && (mapaddr == 0), memobj, (vm_offset_t) offset, copy, vmprot, max_vmprot, copy ? VM_INHERIT_COPY : VM_INHERIT_SHARE); @@ -165,7 +169,10 @@ __mmap (void *addr, size_t len, int prot, int flags, int fd, off_t offset) } else { + /* This mmap call is allowed to allocate anywhere, */ if (mapaddr != 0 && (err == KERN_NO_SPACE || err == KERN_INVALID_ADDRESS)) + /* ...but above, we tried allocating at the specific address, + and failed to. Now try again, with anywhere = 1 this time. */ err = __vm_map (__mach_task_self (), &mapaddr, (vm_size_t) len, mask, 1, memobj, (vm_offset_t) offset, |