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Re: [PATCH] x86/CET: Renumber ARCH_CET_LEGACY_BITMAP to 0x3006
On Wed, Nov 21, 2018 at 3:02 PM Florian Weimer <fweimer@redhat.com> wrote:
>
> * H. J. Lu:
>
> >> Maybe you can log the size of the mapping attempt? That could be useful
> >> to diagnose failures.
> >
> > It isn't easy since _dl_signal_error only takes strings.
>
> Ah. We have _dl_exception_create_format and _dl_signal_exception for
> that; this functionality is split across two function.
>
Here is the updated patch, which depends on
https://sourceware.org/ml/libc-alpha/2018-11/msg00596.html
to add support for %x, %lx and %Zx to _dl_exception_create_format.
--
H.J.
From d7f6e11594bd094ea719a6c452600748561a56c3 Mon Sep 17 00:00:00 2001
From: "H.J. Lu" <hjl.tools@gmail.com>
Date: Wed, 31 Oct 2018 13:59:29 -0700
Subject: [PATCH] x86/CET: Renumber ARCH_CET_LEGACY_BITMAP to 0x3006
The current CET kernel:
https://github.com/yyu168/linux_cet
changed legacy region bitmap allocation from kernel to user space and
renumbered the prctl number from 0x3005 to 0x3006. This patch updates
glibc with:
/* Enable legacy region bitmap with unsigned long long *addr:
address: addr[0].
size: addr[1].
*/
# define ARCH_CET_LEGACY_BITMAP 0x3006
* sysdeps/unix/sysv/linux/x86/dl-cet.h
(dl_cet_allocate_legacy_bitmap ): Removed.
(dl_cet_enable_legacy_bitmap): New.
* sysdeps/unix/sysv/linux/x86/include/asm/prctl.h
(ARCH_CET_LEGACY_BITMAP): Renumbered to 0x3006.
* sysdeps/x86/dl-cet.c (dl_cet_check): Mmap legacy bitmap.
Call dl_cet_enable_legacy_bitmap instead of
dl_cet_allocate_legacy_bitmap.
---
sysdeps/unix/sysv/linux/x86/dl-cet.h | 17 ++++-------
.../unix/sysv/linux/x86/include/asm/prctl.h | 4 +--
sysdeps/x86/dl-cet.c | 29 +++++++++++++++++--
3 files changed, 34 insertions(+), 16 deletions(-)
diff --git a/sysdeps/unix/sysv/linux/x86/dl-cet.h b/sysdeps/unix/sysv/linux/x86/dl-cet.h
index 3fbcfebed5..4da8d165dc 100644
--- a/sysdeps/unix/sysv/linux/x86/dl-cet.h
+++ b/sysdeps/unix/sysv/linux/x86/dl-cet.h
@@ -19,24 +19,19 @@
#include <asm/prctl.h>
static inline int __attribute__ ((always_inline))
-dl_cet_allocate_legacy_bitmap (unsigned long *legacy_bitmap)
+dl_cet_enable_legacy_bitmap (unsigned long *legacy_bitmap)
{
/* Allocate legacy bitmap. */
INTERNAL_SYSCALL_DECL (err);
#ifdef __LP64__
- return (int) INTERNAL_SYSCALL (arch_prctl, err, 2,
- ARCH_CET_LEGACY_BITMAP, legacy_bitmap);
+ unsigned long *legacy_bitmap_u64 = legacy_bitmap;
#else
unsigned long long legacy_bitmap_u64[2];
- int res = INTERNAL_SYSCALL (arch_prctl, err, 2,
- ARCH_CET_LEGACY_BITMAP, legacy_bitmap_u64);
- if (res == 0)
- {
- legacy_bitmap[0] = legacy_bitmap_u64[0];
- legacy_bitmap[1] = legacy_bitmap_u64[1];
- }
- return res;
+ legacy_bitmap_u64[0] = legacy_bitmap[0];
+ legacy_bitmap_u64[1] = legacy_bitmap[1];
#endif
+ return (int) INTERNAL_SYSCALL (arch_prctl, err, 2,
+ ARCH_CET_LEGACY_BITMAP, legacy_bitmap_u64);
}
static inline int __attribute__ ((always_inline))
diff --git a/sysdeps/unix/sysv/linux/x86/include/asm/prctl.h b/sysdeps/unix/sysv/linux/x86/include/asm/prctl.h
index f67f3299b9..94196aa768 100644
--- a/sysdeps/unix/sysv/linux/x86/include/asm/prctl.h
+++ b/sysdeps/unix/sysv/linux/x86/include/asm/prctl.h
@@ -24,9 +24,9 @@
OUT: allocated shadow stack address: *addr.
*/
# define ARCH_CET_ALLOC_SHSTK 0x3004
-/* Return legacy region bitmap info in unsigned long long *addr:
+/* Enable legacy region bitmap with unsigned long long *addr:
address: addr[0].
size: addr[1].
*/
-# define ARCH_CET_LEGACY_BITMAP 0x3005
+# define ARCH_CET_LEGACY_BITMAP 0x3006
#endif /* ARCH_CET_STATUS */
diff --git a/sysdeps/x86/dl-cet.c b/sysdeps/x86/dl-cet.c
index 78f36bcf53..b43387f6b4 100644
--- a/sysdeps/x86/dl-cet.c
+++ b/sysdeps/x86/dl-cet.c
@@ -202,13 +202,36 @@ mprotect_failure:
N_("mprotect legacy bitmap failed"));
}
}
- else
+ else if (!GL(dl_x86_legacy_bitmap)[0])
{
- /* Allocate legacy bitmap. */
- int res = dl_cet_allocate_legacy_bitmap
+ /* Allocate and enable legacy bitmap. */
+ size_t legacy_bitmap_size
+ = ((uintptr_t) __libc_stack_end
+ / GLRO(dl_pagesize) / 8);
+ void *legacy_bitmap_addr
+ = __mmap (NULL, legacy_bitmap_size,
+ PROT_READ | PROT_WRITE,
+ MAP_ANON | MAP_PRIVATE | MAP_NORESERVE,
+ -1, 0);
+ if (legacy_bitmap_addr == MAP_FAILED)
+ {
+ struct dl_exception exception;
+ /* NB: We cannot translate the message. */
+ _dl_exception_create_format
+ (&exception, DSO_FILENAME (l->l_name),
+ "mmap size 0x%Zx failed", legacy_bitmap_size);
+ _dl_signal_cexception
+ (errno, &exception, N_("legacy bitmap error"));
+ _dl_exception_free (&exception);
+ }
+ GL(dl_x86_legacy_bitmap)[0]
+ = (uintptr_t) legacy_bitmap_addr;
+ GL(dl_x86_legacy_bitmap)[1] = legacy_bitmap_size;
+ int res = dl_cet_enable_legacy_bitmap
(GL(dl_x86_legacy_bitmap));
if (res != 0)
{
+ __munmap (legacy_bitmap_addr, legacy_bitmap_size);
if (program)
_dl_fatal_printf ("%s: legacy bitmap isn't available\n",
l->l_name);
--
2.19.1