x86/entry/vdso: Include GNU_PROPERTY and GNU_STACK PHDRs

Currently the vdso doesn't include .note.gnu.property or a GNU noexec
stack annotation (the -z noexecstack in the linker script is
ineffective because we specify PHDRs explicitly.)

The motivation is that the dynamic linker currently do not check
these.

However, this is a weak excuse: the vdso*.so are also supposed to be
usable at link libraries, and there is no reason why the dynamic
linker might not want or need to check these in the future, so add
them back in -- it is trivial enough.

Use symbolic constants for the PHDR permission flags.

[ v4: drop unrelated formatting changes ]

Signed-off-by: H. Peter Anvin (Intel) <hpa@zytor.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Link: https://patch.msgid.link/20251216212606.1325678-8-hpa@zytor.com

diff --git a/arch/x86/entry/vdso/common/vdso-layout.lds.S b/arch/x86/entry/vdso/common/vdso-layout.lds.S
index ec1ac191a0578e55dc72ceff7f5b5eb104042881..a1e30be3e83d41674f4b47a5045d796a0becc765 100644 (file)
--- a/arch/x86/entry/vdso/common/vdso-layout.lds.S
+++ b/arch/x86/entry/vdso/common/vdso-layout.lds.S
@@ -47,18 +47,18 @@ SECTIONS
                *(.gnu.linkonce.b.*)
        }                                               :text
 
-       /*
-        * Discard .note.gnu.property sections which are unused and have
-        * different alignment requirement from vDSO note sections.
-        */
-       /DISCARD/ : {
+       .note.gnu.property : {
                *(.note.gnu.property)
-       }
-       .note           : { *(.note.*) }                :text   :note
-
-       .eh_frame_hdr   : { *(.eh_frame_hdr) }          :text   :eh_frame_hdr
-       .eh_frame       : { KEEP (*(.eh_frame)) }       :text
+       }                                       :text :note :gnu_property
+       .note           : {
+               *(.note*)
+       }                                       :text :note
 
+       .eh_frame_hdr   : { *(.eh_frame_hdr) }  :text :eh_frame_hdr
+       .eh_frame       : {
+               KEEP (*(.eh_frame))
+               *(.eh_frame.*)
+       }                                       :text
 
        /*
         * Text is well-separated from actual data: there's plenty of
@@ -87,15 +87,23 @@ SECTIONS
  * Very old versions of ld do not recognize this name token; use the constant.
  */
 #define PT_GNU_EH_FRAME        0x6474e550
+#define PT_GNU_STACK   0x6474e551
+#define PT_GNU_PROPERTY        0x6474e553
 
 /*
  * We must supply the ELF program headers explicitly to get just one
  * PT_LOAD segment, and set the flags explicitly to make segments read-only.
- */
+*/
+#define PF_R   FLAGS(4)
+#define PF_RW  FLAGS(6)
+#define PF_RX  FLAGS(5)
+
 PHDRS
 {
-       text            PT_LOAD         FLAGS(5) FILEHDR PHDRS; /* PF_R|PF_X */
-       dynamic         PT_DYNAMIC      FLAGS(4);               /* PF_R */
-       note            PT_NOTE         FLAGS(4);               /* PF_R */
-       eh_frame_hdr    PT_GNU_EH_FRAME;
+       text            PT_LOAD         PF_RX FILEHDR PHDRS;
+       dynamic         PT_DYNAMIC      PF_R;
+       note            PT_NOTE         PF_R;
+       eh_frame_hdr    PT_GNU_EH_FRAME PF_R;
+       gnu_stack       PT_GNU_STACK    PF_RW;
+       gnu_property    PT_GNU_PROPERTY PF_R;
 }