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hurd: Fix mapping at address 0 with MAP_FIXED

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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>
This commit is contained in:
Sergey Bugaev 2023-06-26 02:17:50 +03:00 committed by Samuel Thibault
parent f84c3ceb04
commit 19c3b31812
1 changed files with 9 additions and 2 deletions
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11
sysdeps/mach/hurd/mmap.c
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@ -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,