git: fda0403eb083 - main - rtld: Support multiple PT_GNU_RELRO program headers

The branch main has been updated by jhb:

URL: https://cgit.FreeBSD.org/src/commit/?id=fda0403eb0839b29b0b271c69c5cb6bfc874a3b5

commit fda0403eb0839b29b0b271c69c5cb6bfc874a3b5
Author:     John Baldwin <jhb@FreeBSD.org>
AuthorDate: 2024-12-06 22:37:50 +0000
Commit:     John Baldwin <jhb@FreeBSD.org>
CommitDate: 2024-12-06 22:37:50 +0000

    rtld: Support multiple PT_GNU_RELRO program headers
    
    Iterate over all the program headers in obj_remap_relro and remove the
    relro fields from Obj_Entry.
    
    Skip the call to obj_enforce_relro() in relocate_object() for the rtld
    object as well as the main program object.  obj_enforce_relro() is
    called later when it safe to reference globals such as page_size.
    
    Reviewed by:    kib
    Obtained from:  CheriBSD
    Sponsored by:   AFRL, DARPA
    Differential Revision:  https://reviews.freebsd.org/D47884
---
 libexec/rtld-elf/map_object.c | 12 ------------
 libexec/rtld-elf/rtld.c       | 37 ++++++++++++++++++++-----------------
 libexec/rtld-elf/rtld.h       |  3 ---
 3 files changed, 20 insertions(+), 32 deletions(-)

diff --git a/libexec/rtld-elf/map_object.c b/libexec/rtld-elf/map_object.c
index 0b1500a15183..7dbab26f2c63 100644
--- a/libexec/rtld-elf/map_object.c
+++ b/libexec/rtld-elf/map_object.c
@@ -93,8 +93,6 @@ map_object(int fd, const char *path, const struct stat *sb)
     Elf_Addr bss_vlimit;
     caddr_t bss_addr;
     Elf_Word stack_flags;
-    Elf_Addr relro_page;
-    size_t relro_size;
     Elf_Addr note_start;
     Elf_Addr note_end;
     char *note_map;
@@ -114,8 +112,6 @@ map_object(int fd, const char *path, const struct stat *sb)
     nsegs = -1;
     phdyn = phinterp = phtls = NULL;
     phdr_vaddr = 0;
-    relro_page = 0;
-    relro_size = 0;
     note_start = 0;
     note_end = 0;
     note_map = NULL;
@@ -161,11 +157,6 @@ map_object(int fd, const char *path, const struct stat *sb)
 	    stack_flags = phdr->p_flags;
 	    break;
 
-	case PT_GNU_RELRO:
-	    relro_page = phdr->p_vaddr;
-	    relro_size = phdr->p_memsz;
-	    break;
-
 	case PT_NOTE:
 	    if (phdr->p_offset > page_size ||
 	      phdr->p_offset + phdr->p_filesz > page_size) {
@@ -323,9 +314,6 @@ map_object(int fd, const char *path, const struct stat *sb)
 	obj->tlsinit = mapbase + phtls->p_vaddr;
     }
     obj->stack_flags = stack_flags;
-    obj->relro_page = obj->relocbase + rtld_trunc_page(relro_page);
-    obj->relro_size = rtld_trunc_page(relro_page + relro_size) -
-      rtld_trunc_page(relro_page);
     if (note_start < note_end)
 	digest_notes(obj, note_start, note_end);
     if (note_map != NULL)
diff --git a/libexec/rtld-elf/rtld.c b/libexec/rtld-elf/rtld.c
index c585c47ce4da..7dc9d93dac26 100644
--- a/libexec/rtld-elf/rtld.c
+++ b/libexec/rtld-elf/rtld.c
@@ -1672,12 +1672,6 @@ digest_phdr(const Elf_Phdr *phdr, int phnum, caddr_t entry, const char *path)
 	    obj->stack_flags = ph->p_flags;
 	    break;
 
-	case PT_GNU_RELRO:
-	    obj->relro_page = obj->relocbase + rtld_trunc_page(ph->p_vaddr);
-	    obj->relro_size = rtld_trunc_page(ph->p_vaddr + ph->p_memsz) -
-	      rtld_trunc_page(ph->p_vaddr);
-	    break;
-
 	case PT_NOTE:
 	    note_start = (Elf_Addr)obj->relocbase + ph->p_vaddr;
 	    note_end = note_start + ph->p_filesz;
@@ -2369,11 +2363,6 @@ parse_rtld_phdr(Obj_Entry *obj)
 		case PT_GNU_STACK:
 			obj->stack_flags = ph->p_flags;
 			break;
-		case PT_GNU_RELRO:
-			obj->relro_page = obj->relocbase +
-			    rtld_trunc_page(ph->p_vaddr);
-			obj->relro_size = rtld_round_page(ph->p_memsz);
-			break;
 		case PT_NOTE:
 			note_start = (Elf_Addr)obj->relocbase + ph->p_vaddr;
 			note_end = note_start + ph->p_filesz;
@@ -3328,7 +3317,7 @@ relocate_object(Obj_Entry *obj, bool bind_now, Obj_Entry *rtldobj,
 	    lockstate) == -1)
 		return (-1);
 
-	if (!obj->mainprog && obj_enforce_relro(obj) == -1)
+	if (obj != rtldobj && !obj->mainprog && obj_enforce_relro(obj) == -1)
 		return (-1);
 
 	/*
@@ -5909,12 +5898,26 @@ _rtld_is_dlopened(void *arg)
 static int
 obj_remap_relro(Obj_Entry *obj, int prot)
 {
+	const Elf_Phdr *ph;
+	caddr_t relro_page;
+	size_t relro_size;
 
-	if (obj->relro_size > 0 && mprotect(obj->relro_page, obj->relro_size,
-	    prot) == -1) {
-		_rtld_error("%s: Cannot set relro protection to %#x: %s",
-		    obj->path, prot, rtld_strerror(errno));
-		return (-1);
+	for (ph = obj->phdr;  (const char *)ph < (const char *)obj->phdr +
+	    obj->phsize; ph++) {
+		switch (ph->p_type) {
+		case PT_GNU_RELRO:
+			relro_page = obj->relocbase +
+			    rtld_trunc_page(ph->p_vaddr);
+			relro_size =
+			    rtld_round_page(ph->p_vaddr + ph->p_memsz) -
+			    rtld_trunc_page(ph->p_vaddr);
+			if (mprotect(relro_page, relro_size, prot) == -1) {
+				_rtld_error("%s: Cannot set relro protection to %#x: %s",
+				    obj->path, prot, rtld_strerror(errno));
+				return (-1);
+			}
+			break;
+		}
 	}
 	return (0);
 }
diff --git a/libexec/rtld-elf/rtld.h b/libexec/rtld-elf/rtld.h
index 5527671d647e..383b8db2114c 100644
--- a/libexec/rtld-elf/rtld.h
+++ b/libexec/rtld-elf/rtld.h
@@ -165,9 +165,6 @@ typedef struct Struct_Obj_Entry {
     size_t tlsalign;		/* Alignment of static TLS block */
     size_t tlspoffset;		/* p_offset of the static TLS block */
 
-    caddr_t relro_page;
-    size_t relro_size;
-
     /* Items from the dynamic section. */
     Elf_Addr *pltgot;		/* PLT or GOT, depending on architecture */
     const Elf_Rel *rel;		/* Relocation entries */