git: 62dfddd083da - main - libc: Use variables more consistent with Variant I for Variant II TLS

The branch main has been updated by jrtc27:

URL: https://cgit.FreeBSD.org/src/commit/?id=62dfddd083dab8ed1b2d9dd390fa27d37d132416

commit 62dfddd083dab8ed1b2d9dd390fa27d37d132416
Author:     Jessica Clarke <jrtc27@FreeBSD.org>
AuthorDate: 2025-05-07 19:20:00 +0000
Commit:     Jessica Clarke <jrtc27@FreeBSD.org>
CommitDate: 2025-05-07 19:20:00 +0000

    libc: Use variables more consistent with Variant I for Variant II TLS
    
    Firstly, the first argument to __libc_allocate_tls is the old TCB
    (versus oldtls, which has less of a clear meaning), so rename it to
    oldtcb like Variant I.
    
    Secondly, segbase and oldsegbase are oriented towards what ends up in
    the segment registers, but that's not the main concern here, and those
    don't convey what they actually point to. Instead, rename segbase to tcb
    and change it to a uintptr_t **, and remove oldsegbase as it's always
    equal to oldtcb, again both matching Variant I.
    
    Finally, rename tls to tls_block, and add back a (different) tls
    variable rather than constantly recomputing tcb - libc_tls_static_space,
    again both matching Variant I.
    
    Whilst here, similarly fix the oldtls argument to be oldtcb in the PIC
    __libc_allocate_tls stub.
    
    Reviewed by:    kib
    Differential Revision:  https://reviews.freebsd.org/D50227
---
 lib/libc/gen/tls.c | 40 ++++++++++++++++++----------------------
 1 file changed, 18 insertions(+), 22 deletions(-)

diff --git a/lib/libc/gen/tls.c b/lib/libc/gen/tls.c
index ad6f43eb3534..9772c99833d5 100644
--- a/lib/libc/gen/tls.c
+++ b/lib/libc/gen/tls.c
@@ -323,62 +323,58 @@ __libc_free_tls(void *tcb, size_t tcbsize __unused, size_t tcbalign)
  * Allocate Static TLS using the Variant II method.
  */
 void *
-__libc_allocate_tls(void *oldtls, size_t tcbsize, size_t tcbalign)
+__libc_allocate_tls(void *oldtcb, size_t tcbsize, size_t tcbalign)
 {
 	size_t size;
-	char *tls;
-	uintptr_t *dtv;
-	uintptr_t segbase, oldsegbase;
+	char *tls_block, *tls;
+	uintptr_t *dtv, **tcb;
 
 	tcbalign = MAX(tcbalign, libc_tls_init_align);
 	size = roundup2(libc_tls_static_space, tcbalign);
 
 	if (tcbsize < 2 * sizeof(uintptr_t))
 		tcbsize = 2 * sizeof(uintptr_t);
-	tls = libc_malloc_aligned(size + tcbsize, tcbalign);
-	if (tls == NULL) {
+	tls_block = libc_malloc_aligned(size + tcbsize, tcbalign);
+	if (tls_block == NULL) {
 		tls_msg("__libc_allocate_tls: Out of memory.\n");
 		abort();
 	}
-	memset(tls, 0, size + tcbsize);
+	memset(tls_block, 0, size + tcbsize);
 	dtv = __je_bootstrap_malloc(3 * sizeof(uintptr_t));
 	if (dtv == NULL) {
 		tls_msg("__libc_allocate_tls: Out of memory.\n");
 		abort();
 	}
 
-	segbase = (uintptr_t)(tls + size);
-	((uintptr_t *)segbase)[0] = segbase;
-	((uintptr_t *)segbase)[1] = (uintptr_t)dtv;
+	tcb = (uintptr_t **)(tls_block + size);
+	tls = (char *)tcb - libc_tls_static_space;
+	tcb[0] = (uintptr_t *)tcb;
+	tcb[1] = dtv;
 
 	dtv[0] = 1;
 	dtv[1] = 1;
-	dtv[2] = segbase - libc_tls_static_space;
+	dtv[2] = (uintptr_t)tls;
 
-	if (oldtls) {
+	if (oldtcb != NULL) {
 		/*
 		 * Copy the static TLS block over whole.
 		 */
-		oldsegbase = (uintptr_t)oldtls;
-		memcpy((void *)(segbase - libc_tls_static_space),
-		    (const void *)(oldsegbase - libc_tls_static_space),
+		memcpy(tls, (const char *)oldtcb - libc_tls_static_space,
 		    libc_tls_static_space);
 
 		/*
 		 * We assume that this block was the one we created with
 		 * allocate_initial_tls().
 		 */
-		_rtld_free_tls(oldtls, 2 * sizeof(uintptr_t),
+		_rtld_free_tls(oldtcb, 2 * sizeof(uintptr_t),
 		    sizeof(uintptr_t));
 	} else {
-		memcpy((void *)(segbase - libc_tls_static_space),
-		    libc_tls_init, libc_tls_init_size);
-		memset((void *)(segbase - libc_tls_static_space +
-		    libc_tls_init_size), 0,
+		memcpy(tls, libc_tls_init, libc_tls_init_size);
+		memset(tls + libc_tls_init_size, 0,
 		    libc_tls_static_space - libc_tls_init_size);
 	}
 
-	return (void*) segbase;
+	return (tcb);
 }
 
 #endif /* TLS_VARIANT_II */
@@ -386,7 +382,7 @@ __libc_allocate_tls(void *oldtls, size_t tcbsize, size_t tcbalign)
 #else
 
 void *
-__libc_allocate_tls(void *oldtls __unused, size_t tcbsize __unused,
+__libc_allocate_tls(void *oldtcb __unused, size_t tcbsize __unused,
 	size_t tcbalign __unused)
 {
 	return (0);