[glibc] htl: Respect GL(dl_stack_flags) when allocating stacks

[glibc] htl: Respect GL(dl_stack_flags) when allocating stacks

[Samuel Thibault]

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=a4273efa219480a7f2c9c8fa7bc8bb71c48c3604

commit a4273efa219480a7f2c9c8fa7bc8bb71c48c3604
Author: Sergey Bugaev <bugaevc@gmail.com>
Date:   Sat Mar 23 20:32:47 2024 +0300

    htl: Respect GL(dl_stack_flags) when allocating stacks
    
    Previously, HTL would always allocate non-executable stacks.  This has
    never been noticed, since GNU Mach on x86 ignores VM_PROT_EXECUTE and
    makes all pages implicitly executable.  Since GNU Mach on AArch64
    supports non-executable pages, HTL forgetting to pass VM_PROT_EXECUTE
    immediately breaks any code that (unfortunately, still) relies on
    executable stacks.
    
    Signed-off-by: Sergey Bugaev <bugaevc@gmail.com>
    Message-ID: <20240323173301.151066-7-bugaevc@gmail.com>

Diff:
---
 sysdeps/htl/Versions              | 4 ++++
 sysdeps/mach/htl/pt-stack-alloc.c | 9 +++++++--
 2 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/sysdeps/htl/Versions b/sysdeps/htl/Versions
index 3a3b1e8b3d..7b5450d20e 100644
--- a/sysdeps/htl/Versions
+++ b/sysdeps/htl/Versions
@@ -12,4 +12,8 @@ libc {
     pthread_spin_destroy; pthread_spin_init; pthread_spin_lock;
     pthread_spin_trylock; pthread_spin_unlock;
   }
+
+  GLIBC_PRIVATE {
+    __vm_map;
+  }
 }
diff --git a/sysdeps/mach/htl/pt-stack-alloc.c b/sysdeps/mach/htl/pt-stack-alloc.c
index 61974bd571..0597770bab 100644
--- a/sysdeps/mach/htl/pt-stack-alloc.c
+++ b/sysdeps/mach/htl/pt-stack-alloc.c
@@ -31,9 +31,14 @@ int
 __pthread_stack_alloc (void **stackaddr, size_t stacksize)
 {
   error_t err;
+  vm_prot_t prot = VM_PROT_READ | VM_PROT_WRITE;
 
-  err = __vm_allocate (__mach_task_self (), (vm_offset_t *) stackaddr,
-		       stacksize, TRUE);
+  if (GL(dl_stack_flags) & PF_X)
+    prot |= VM_PROT_EXECUTE;
+
+  err = __vm_map (__mach_task_self (), (vm_offset_t *) stackaddr,
+		  stacksize, 0, TRUE, MEMORY_OBJECT_NULL, 0, FALSE,
+		  prot, VM_PROT_ALL, VM_INHERIT_COPY);
 
   if (err == KERN_NO_SPACE)
     err = EAGAIN;