[PATCH 4/4] aarch64: Remove the bti link_map field [BZ #26831]

Szabolcs Nagy
2020-11-03T10:27:41Z

The bti link_map field is no longer necessary because PROT_BTI
is applied at note processing time immediately instead of in
_dl_open_check based on the bti field.

This is a separate patch that is not expected to be backported
to avoid changing the link_map layout that is libc internal ABI.
---
sysdeps/aarch64/dl-prop.h | 5 +----
sysdeps/aarch64/linkmap.h | 1 -
2 files changed, 1 insertion(+), 5 deletions(-)

diff --git a/sysdeps/aarch64/dl-prop.h b/sysdeps/aarch64/dl-prop.h
index 762bc93733..cf14381e4a 100644
--- a/sysdeps/aarch64/dl-prop.h
+++ b/sysdeps/aarch64/dl-prop.h
@@ -52,10 +52,7 @@ _dl_process_gnu_property (struct link_map *l, int fd, uint32_t type,

unsigned int feature_1 = *(unsigned int *) data;
if (feature_1 & GNU_PROPERTY_AARCH64_FEATURE_1_BTI)
- {
- l->l_mach.bti = true; /* No longer needed. */
- _dl_bti_protect (l, fd);
- }
+ _dl_bti_protect (l, fd);

/* Stop if we processed the property note. */
return 0;
diff --git a/sysdeps/aarch64/linkmap.h b/sysdeps/aarch64/linkmap.h
index 847a03ace2..e921e77495 100644
--- a/sysdeps/aarch64/linkmap.h
+++ b/sysdeps/aarch64/linkmap.h
@@ -22,5 +22,4 @@ struct link_map_machine
{
ElfW(Addr) plt; /* Address of .plt */
void *tlsdesc_table; /* Address of TLS descriptor hash table. */
- bool bti; /* Branch Target Identification is enabled. */
};
--
2.17.1