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htl: Let Mach place thread stacks

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Instead of trying to allocate a thread stack at a specific address,
looping over the address space, just set the ANYWHERE flag in
vm_allocate (). The previous behavior:

- defeats ASLR (for Mach versions that support ASLR),
- is particularly slow if the lower 4 GB of the address space are mapped
  inaccessible, as we're planning to do on 64-bit Hurd,
- is just silly.

Signed-off-by: Sergey Bugaev <bugaevc@gmail.com>
Message-Id: <20230625231751.404120-1-bugaevc@gmail.com>
This commit is contained in:
Sergey Bugaev 2023-06-26 02:17:47 +03:00 committed by Samuel Thibault
parent efdb85183a
commit 019b0bbc84
1 changed files with 6 additions and 29 deletions
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35
sysdeps/mach/htl/pt-stack-alloc.c
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@ -19,14 +19,9 @@
#include <errno.h>
#include <mach.h>
#include <mach/machine/vm_param.h>
#include <pt-internal.h>
/* The next address to use for stack allocation. */
static vm_address_t next_stack_base = VM_MIN_ADDRESS;
/* Allocate a new stack of size STACKSIZE. If successful, store the
address of the newly allocated stack in *STACKADDR and return 0.
Otherwise return an error code (EINVAL for an invalid stack size,
@ -35,30 +30,12 @@ static vm_address_t next_stack_base = VM_MIN_ADDRESS;
int
__pthread_stack_alloc (void **stackaddr, size_t stacksize)
{
vm_offset_t base;
int i = 0;
error_t err;
get_stack:
i++;
for (base = next_stack_base;
base < VM_MAX_ADDRESS
&& __vm_allocate (__mach_task_self (), &base,
stacksize, FALSE) != KERN_SUCCESS; base += stacksize)
;
err = __vm_allocate (__mach_task_self (), (vm_offset_t *) stackaddr,
stacksize, TRUE);
if (base >= VM_MAX_ADDRESS)
{
if (i == 1)
{
next_stack_base = VM_MIN_ADDRESS;
goto get_stack;
}
else
return EAGAIN;
}
next_stack_base = base + stacksize;
(*stackaddr) = (void *) base;
return 0;
if (err == KERN_NO_SPACE)
err = EAGAIN;
return err;
}