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x86: Rename __glibc_reserved2 to ssp_base in tcbhead_t

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This will be used to record the current shadow stack base for shadow
stack switching by getcontext, makecontext, setcontext and swapcontext.
If the target shadow stack base is the same as the current shadow stack
base, we unwind the shadow stack.  Otherwise it is a stack switch and
we look for a restore token to restore the target shadow stack.

	* sysdeps/i386/nptl/tcb-offsets.sym (SSP_BASE_OFFSET): New.
	* sysdeps/i386/nptl/tls.h (tcbhead_t): Replace __glibc_reserved2
	with ssp_base.
	* sysdeps/x86_64/nptl/tcb-offsets.sym (SSP_BASE_OFFSET): New.
	* sysdeps/x86_64/nptl/tls.h (tcbhead_t): Replace __glibc_reserved2
	with ssp_base.
This commit is contained in:
H.J. Lu 2018-07-25 04:39:26 -07:00
parent 9c79cec8cd
commit 9aa3113a42
5 changed files with 22 additions and 2 deletions
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9
ChangeLog
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@ -1,3 +1,12 @@
2018-07-25 H.J. Lu <hongjiu.lu@intel.com>
* sysdeps/i386/nptl/tcb-offsets.sym (SSP_BASE_OFFSET): New.
* sysdeps/i386/nptl/tls.h (tcbhead_t): Replace __glibc_reserved2
with ssp_base.
* sysdeps/x86_64/nptl/tcb-offsets.sym (SSP_BASE_OFFSET): New.
* sysdeps/x86_64/nptl/tls.h (tcbhead_t): Replace __glibc_reserved2
with ssp_base.
2018-07-25 Andreas Schwab <schwab@suse.de>
[BZ #23442]

1
sysdeps/i386/nptl/tcb-offsets.sym
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@ -13,3 +13,4 @@ CLEANUP_PREV offsetof (struct _pthread_cleanup_buffer, __prev)
MUTEX_FUTEX offsetof (pthread_mutex_t, __data.__lock)
POINTER_GUARD offsetof (tcbhead_t, pointer_guard)
FEATURE_1_OFFSET offsetof (tcbhead_t, feature_1)
SSP_BASE_OFFSET offsetof (tcbhead_t, ssp_base)

3
sysdeps/i386/nptl/tls.h
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@ -49,7 +49,8 @@ typedef struct
void *__private_tm[3];
/* GCC split stack support. */
void *__private_ss;
void *__glibc_reserved2;
/* The lowest address of shadow stack, */
unsigned long ssp_base;
} tcbhead_t;
/* morestack.S in libgcc uses offset 0x30 to access __private_ss, */

1
sysdeps/x86_64/nptl/tcb-offsets.sym
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@ -13,6 +13,7 @@ MULTIPLE_THREADS_OFFSET offsetof (tcbhead_t, multiple_threads)
POINTER_GUARD offsetof (tcbhead_t, pointer_guard)
VGETCPU_CACHE_OFFSET offsetof (tcbhead_t, vgetcpu_cache)
FEATURE_1_OFFSET offsetof (tcbhead_t, feature_1)
SSP_BASE_OFFSET offsetof (tcbhead_t, ssp_base)
-- Not strictly offsets, but these values are also used in the TCB.
TCB_CANCELSTATE_BITMASK CANCELSTATE_BITMASK

10
sysdeps/x86_64/nptl/tls.h
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@ -60,7 +60,8 @@ typedef struct
void *__private_tm[4];
/* GCC split stack support. */
void *__private_ss;
long int __glibc_reserved2;
/* The lowest address of shadow stack, */
unsigned long long int ssp_base;
/* Must be kept even if it is no longer used by glibc since programs,
like AddressSanitizer, depend on the size of tcbhead_t. */
__128bits __glibc_unused2[8][4] __attribute__ ((aligned (32)));
@ -72,10 +73,17 @@ typedef struct
/* morestack.S in libgcc uses offset 0x40 to access __private_ss, */
_Static_assert (offsetof (tcbhead_t, __private_ss) == 0x40,
"offset of __private_ss != 0x40");
/* NB: ssp_base used to be "long int __glibc_reserved2", which was
changed from 32 bits to 64 bits. Make sure that the offset of the
next field, __glibc_unused2, is unchanged. */
_Static_assert (offsetof (tcbhead_t, __glibc_unused2) == 0x60,
"offset of __glibc_unused2 != 0x60");
# else
/* morestack.S in libgcc uses offset 0x70 to access __private_ss, */
_Static_assert (offsetof (tcbhead_t, __private_ss) == 0x70,
"offset of __private_ss != 0x70");
_Static_assert (offsetof (tcbhead_t, __glibc_unused2) == 0x80,
"offset of __glibc_unused2 != 0x80");
# endif
#else /* __ASSEMBLER__ */