Author: mmel
Date: Tue Dec 12 11:25:30 2017
New Revision: 326794
URL: https://svnweb.freebsd.org/changeset/base/326794
Log:
Rework alignment handling in __libc_allocate_tls() for Variant I of TLS
layout.
There are two versions of variant I of TLS
- ARM and aarch64 uses original version of variant I here TP points to
start of TCB followed by aligned TLS segment. Both TCB and TLS must
be aligned to alignment of TLS section. The TCB[0] points to DTV vector
and DTV values are real addresses (without bias).
- MIPS, PowerPC and RISC-V use modified version of variant I,
where TP points (with bias) to TLS and TCB immediately precedes TLS
without any alignment gap. Only TLS should be aligned. The TCB[0]
points to DTV vector and DTV values are biased by constant value (0x8000)
from real addresses.
Take all this in account when allocating memory for TLS structures.
MFC after: 1 month
Reviewed by: kib, mizhka
Tested by: mizhka(on mips)
Differential Revision: https://reviews.freebsd.org/D13378
Modified:
head/lib/libc/gen/tls.c
Modified: head/lib/libc/gen/tls.c
==============================================================================
--- head/lib/libc/gen/tls.c Tue Dec 12 11:09:46 2017 (r326793)
+++ head/lib/libc/gen/tls.c Tue Dec 12 11:25:30 2017 (r326794)
@@ -89,6 +89,12 @@ void __libc_free_tls(void *tls, size_t tcbsize, size_t
#define TLS_VARIANT_II
#endif
+#if defined(__mips__) || defined(__powerpc__) || defined(__riscv)
+#define DTV_OFFSET 0x8000
+#else
+#define DTV_OFFSET 0
+#endif
+
#ifndef PIC
static size_t tls_static_space;
@@ -149,13 +155,70 @@ free_aligned(void *ptr)
#ifdef TLS_VARIANT_I
+/*
+ * There are two versions of variant I of TLS
+ *
+ * - ARM and aarch64 uses original variant I as is described in [1] and [2],
+ * where TP points to start of TCB followed by aligned TLS segment.
+ * Both TCB and TLS must be aligned to alignment of TLS section. The TCB[0]
+ * points to DTV vector and DTV values are real addresses (without bias).
+ * Note: for Local Exec TLS Model, the offsets from TP (TCB in this case) to
+ * TLS variables are computed by linker, so we cannot overalign TLS section.
+ *
+ * - MIPS, PowerPC and RISC-V use modified version of variant I,
+ * described in [3] where TP points (with bias) to TLS and TCB immediately
+ * precedes TLS without any alignment gap[4]. Only TLS should be aligned.
+ * The TCB[0] points to DTV vector and DTV values are biased by constant
+ * value (0x8000) from real addresses[5].
+ *
+ * [1] Ulrich Drepper: ELF Handling for Thread-Local Storage
+ * www.akkadia.org/drepper/tls.pdf
+ *
+ * [2] ARM IHI 0045E: Addenda to, and Errata in, the ABI for the ARM(r)
+ * Architecture
+ *
infocenter.arm.com/help/topic/com.arm.doc.ihi0045e/IHI0045E_ABI_addenda.pdf
+ *
+ * [3] OpenPOWER: Power Architecture 64-Bit ELF V2 ABI Specification
+ * https://members.openpowerfoundation.org/document/dl/576
+ *
+ * [4] Its unclear if "without any alignment gap" is hard ABI requirement,
+ * but we must follow this rule due to suboptimal _set_tp()
+ * (aka <ARCH>_SET_TP) implementation. This function doesn't expect TP but
+ * TCB as argument.
+ *
+ * [5] I'm not able to validate "values are biased" assertions.
+ */
+
#define TLS_TCB_SIZE (2 * sizeof(void *))
/*
- * Free Static TLS using the Variant I method.
+ * Return pointer to allocated TLS block
*/
+static void *
+get_tls_block_ptr(void *tcb, size_t tcbsize)
+{
+ size_t extra_size, post_size, pre_size, tls_block_size;
+
+ /* Compute fragments sizes. */
+ extra_size = tcbsize - TLS_TCB_SIZE;
+#if defined(__aarch64__) || defined(__arm__)
+ post_size = roundup2(TLS_TCB_SIZE, tls_init_align) - TLS_TCB_SIZE;
+#else
+ post_size = 0;
+#endif
+ tls_block_size = tcbsize + post_size;
+ pre_size = roundup2(tls_block_size, tls_init_align) - tls_block_size;
+
+ return ((char *)tcb - pre_size - extra_size);
+}
+
+/*
+ * Free Static TLS using the Variant I method. The tcbsize
+ * and tcbalign parameters must be the same as those used to allocate
+ * the block.
+ */
void
-__libc_free_tls(void *tcb, size_t tcbsize __unused, size_t tcbalign __unused)
+__libc_free_tls(void *tcb, size_t tcbsize, size_t tcbalign __unused)
{
Elf_Addr *dtv;
Elf_Addr **tls;
@@ -163,55 +226,88 @@ __libc_free_tls(void *tcb, size_t tcbsize __unused, si
tls = (Elf_Addr **)tcb;
dtv = tls[0];
__je_bootstrap_free(dtv);
- free_aligned(tls);
+ free_aligned(get_tls_block_ptr(tcb, tcbsize));
}
/*
* Allocate Static TLS using the Variant I method.
+ *
+ * To handle all above requirements, we setup the following layout for
+ * TLS block:
+ * (whole memory block is aligned with MAX(TLS_TCB_ALIGN, tls_init_align))
+ *
+ * +----------+--------------+--------------+-----------+------------------+
+ * | pre gap | extended TCB | TCB | post gap | TLS segment |
+ * | pre_size | extra_size | TLS_TCB_SIZE | post_size | tls_static_space |
+ * +----------+--------------+--------------+-----------+------------------+
+ *
+ * where:
+ * extra_size is tcbsize - TLS_TCB_SIZE
+ * post_size is used to adjust TCB to TLS aligment for first version of TLS
+ * layout and is always 0 for second version.
+ * pre_size is used to adjust TCB aligment for first version and to adjust
+ * TLS alignment for second version.
+ *
*/
void *
__libc_allocate_tls(void *oldtcb, size_t tcbsize, size_t tcbalign)
{
- Elf_Addr *dtv;
- Elf_Addr **tls;
+ Elf_Addr *dtv, **tcb;
+ char *tls_block, *tls;
+ size_t extra_size, maxalign, post_size, pre_size, tls_block_size;
if (oldtcb != NULL && tcbsize == TLS_TCB_SIZE)
return (oldtcb);
tls_assert(tcbalign >= TLS_TCB_ALIGN);
- tls_assert(tcbsize == TLS_TCB_SIZE);
+ maxalign = MAX(tcbalign, tls_init_align);
- tcbsize = roundup2(tcbsize, tcbalign);
- tls = malloc_aligned(tcbsize + tls_static_space, tcbalign);
- if (tls == NULL) {
+ /* Compute fragmets sizes. */
+ extra_size = tcbsize - TLS_TCB_SIZE;
+#if defined(__aarch64__) || defined(__arm__)
+ post_size = roundup2(TLS_TCB_SIZE, tls_init_align) - TLS_TCB_SIZE;
+#else
+ post_size = 0;
+#endif
+ tls_block_size = tcbsize + post_size;
+ pre_size = roundup2(tls_block_size, tls_init_align) - tls_block_size;
+ tls_block_size += pre_size + tls_static_space;
+
+ /* Allocate whole TLS block */
+ tls_block = malloc_aligned(tls_block_size, maxalign);
+ if (tls_block == NULL) {
tls_msg("__libc_allocate_tls: Out of memory.\n");
abort();
}
- memset(tls, 0, tcbsize + tls_static_space);
+ memset(tls_block, 0, tls_block_size);
+ tcb = (Elf_Addr **)(tls_block + pre_size + extra_size);
+ tls = (char *)tcb + TLS_TCB_SIZE + post_size;
if (oldtcb != NULL) {
- memcpy(tls, oldtcb, tcbsize + tls_static_space);
- __je_bootstrap_free(oldtcb);
+ memcpy(tls_block, get_tls_block_ptr(oldtcb, tcbsize),
+ tls_block_size);
+ free_aligned(oldtcb);
/* Adjust the DTV. */
- dtv = tls[0];
- dtv[2] = (Elf_Addr)tls + tcbsize;
+ dtv = tcb[0];
+ dtv[2] = (Elf_Addr)(tls + DTV_OFFSET);
} else {
dtv = __je_bootstrap_malloc(3 * sizeof(Elf_Addr));
if (dtv == NULL) {
tls_msg("__libc_allocate_tls: Out of memory.\n");
abort();
}
- tls[0] = dtv;
+ /* Build the DTV. */
+ tcb[0] = dtv;
dtv[0] = 1; /* Generation. */
dtv[1] = 1; /* Segments count. */
- dtv[2] = (Elf_Addr)tls + tcbsize;
+ dtv[2] = (Elf_Addr)(tls + DTV_OFFSET);
if (tls_init_size > 0)
- memcpy((void*)dtv[2], tls_init, tls_init_size);
+ memcpy(tls, tls_init, tls_init_size);
}
- return (tls);
+ return (tcb);
}
#endif
@@ -234,6 +330,7 @@ __libc_free_tls(void *tcb, size_t tcbsize __unused, si
* Figure out the size of the initial TLS block so that we can
* find stuff which ___tls_get_addr() allocated dynamically.
*/
+ tcbalign = MAX(tcbalign, tls_init_align);
size = roundup2(tls_static_space, tcbalign);
dtv = ((Elf_Addr**)tcb)[1];
@@ -254,6 +351,7 @@ __libc_allocate_tls(void *oldtls, size_t tcbsize, size
Elf_Addr *dtv;
Elf_Addr segbase, oldsegbase;
+ tcbalign = MAX(tcbalign, tls_init_align);
size = roundup2(tls_static_space, tcbalign);
if (tcbsize < 2 * sizeof(Elf_Addr))
@@ -368,9 +466,7 @@ _init_tls(void)
break;
}
}
-
- tls = _rtld_allocate_tls(NULL, TLS_TCB_SIZE,
- MAX(TLS_TCB_ALIGN, tls_init_align));
+ tls = _rtld_allocate_tls(NULL, TLS_TCB_SIZE, TLS_TCB_ALIGN);
_set_tp(tls);
#endif
_______________________________________________
svn-src-head@freebsd.org mailing list
https://lists.freebsd.org/mailman/listinfo/svn-src-head
To unsubscribe, send any mail to "svn-src-head-unsubscr...@freebsd.org"
