git: c02aaba1b454 - main - rtld-elf: Fix dl_iterate_phdr's dlpi_tls_data for PowerPC and RISC-V

The branch main has been updated by jrtc27:

URL: https://cgit.FreeBSD.org/src/commit/?id=c02aaba1b4549c1c3b1481f7c935f6cc80b98e8d

commit c02aaba1b4549c1c3b1481f7c935f6cc80b98e8d
Author:     Jessica Clarke <jrtc27@FreeBSD.org>
AuthorDate: 2025-05-06 22:14:51 +0000
Commit:     Jessica Clarke <jrtc27@FreeBSD.org>
CommitDate: 2025-05-06 22:14:51 +0000

    rtld-elf: Fix dl_iterate_phdr's dlpi_tls_data for PowerPC and RISC-V
    
    The implementation of dl_iterate_phdr abuses tls_get_addr_slow to get to
    the start of the TLS block, inlining the implementation of
    __tls_get_addr as if the tls_index's ti_offset were 0 (historically it
    called __tls_get_addr itself but changed due to locking issues). For
    most architectures, tls_index's ti_offset (relocated by DTPOFF/DTPREL
    for GOT entries) is just the offset within that module's TLS block.
    However, for PowerPC and RISC-V, which have a non-zero TLS_DTV_OFFSET
    and thus are designed assuming DTV entries are biased by that value,
    ti_offset normally has TLS_DTV_OFFSET pre-subtracted, but it's
    __tls_get_addr's responsibility to compensate for that. By using an
    offset of zero here, tls_get_addr_slow will return a pointer to the
    start of the TLS block itself, so by adding TLS_DTV_OFFSET we will point
    TLS_DTV_OFFSET past the module's TLS block.
    
    Fix this by removing the extra bias (the alternative would be to pass
    -TLS_DTV_OFFSET and keep the addition, which would more closely follow
    what __tls_get_addr does, but this is more direct).
    
    (Note this also applies to MIPS on stable/13)
    
    Reviewed by:    kib
    Fixes:          d36d68161517 ("rtld dl_iterate_phdr(): dlpi_tls_data is wrong")
    MFC after:      1 week
    Differential Revision:  https://reviews.freebsd.org/D50184
---
 libexec/rtld-elf/rtld.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/libexec/rtld-elf/rtld.c b/libexec/rtld-elf/rtld.c
index 29d32e54e690..e4e14edbb5c8 100644
--- a/libexec/rtld-elf/rtld.c
+++ b/libexec/rtld-elf/rtld.c
@@ -4316,7 +4316,7 @@ rtld_fill_dl_phdr_info(const Obj_Entry *obj, struct dl_phdr_info *phdr_info)
 	phdr_info->dlpi_tls_modid = obj->tlsindex;
 	dtvp = &_tcb_get()->tcb_dtv;
 	phdr_info->dlpi_tls_data = (char *)tls_get_addr_slow(dtvp,
-	    obj->tlsindex, 0, true) + TLS_DTV_OFFSET;
+	    obj->tlsindex, 0, true);
 	phdr_info->dlpi_adds = obj_loads;
 	phdr_info->dlpi_subs = obj_loads - obj_count;
 }