ld/aarch64elf: add support for DT_AARCH64_MEMTAG_STACK dynamic tag

Add new command line option -z memtag-stack for aarch64 elf.  This
option instructs the linker to generate the necessary dynamic tag
DT_AARCH64_MEMTAG_STACK, which the dynamic loader can then use to
protect the stack memory with PROT_MTE.  Linker issues an
'unrecognized option' error when -z memtag-stack is specified for
non-aarch64 based emulations.

readelf displays the dynamic tag when present:

$ readelf -d <exectutable>
Dynamic section at offset 0xfdd8 contains XX entries:
Tag        Type                         Name/Value
0x0000000000000001 (NEEDED)             Shared library: [libc.so.6]
0x000000000000000c (INIT)               0x400520
0x000000000000000d (FINI)               0x400b64
0x0000000000000019 (INIT_ARRAY)         0x41fdc8
...                 ...                 ...
0x000000007000000c (AARCH64_MEMTAG_STACK) 0x1
...                 ...                 ...

ChangeLog:

        * bfd/elfnn-aarch64.c (elfNN_aarch64_late_size_sections): Emit
	DT_AARCH64_MEMTAG_STACK dynamic tag.
        * bfd/elfxx-aarch64.h (struct aarch64_memtag_opts): Add new
	member for tracking whether stack access uses MTE insns.
        * binutils/readelf.c (get_aarch64_dynamic_type): Handle
	DT_AARCH64_MEMTAG_STACK.
        * ld/emultempl/aarch64elf.em: Add new command line option.
        * ld/ld.texi: Add documentation for -z memtag-stack.
        * ld/testsuite/ld-aarch64/aarch64-elf.exp: Add new test.
        * ld/testsuite/ld-aarch64/dt-memtag-stack.d: New test.

include/ChangeLog:

        * elf/aarch64.h (DT_AARCH64_MEMTAG_STACK): New definition.

diff --git a/bfd/elfnn-aarch64.c b/bfd/elfnn-aarch64.c
index 0e9e22e210be14a6b031bc0b9865f519b140e83b..9e98215d638be837be9f1f6c8bfe9a3816b6faeb 100644 (file)
--- a/bfd/elfnn-aarch64.c
+++ b/bfd/elfnn-aarch64.c
@@ -9786,6 +9786,12 @@ elfNN_aarch64_late_size_sections (bfd *output_bfd ATTRIBUTE_UNUSED,
          && !add_dynamic_entry (DT_AARCH64_MEMTAG_MODE,
                                 htab->memtag_opts.memtag_mode == AARCH64_MEMTAG_MODE_ASYNC))
        return false;
+
+      if (is_aarch64_elf (output_bfd)
+         && htab->memtag_opts.memtag_stack == 1
+         && !add_dynamic_entry (DT_AARCH64_MEMTAG_STACK,
+                                htab->memtag_opts.memtag_stack == 1))
+       return false;
     }
 
 #undef add_dynamic_entry

diff --git a/bfd/elfxx-aarch64.h b/bfd/elfxx-aarch64.h
index 66c1f48d4500674f6da233cb46eb9e7c0af03ccb..bd3642cbefe539bc15c3e8794ac03250aa26cddb 100644 (file)
--- a/bfd/elfxx-aarch64.h
+++ b/bfd/elfxx-aarch64.h
@@ -147,6 +147,9 @@ struct aarch64_memtag_opts
 {
   /* Mode of MTE operation.  */
   aarch64_memtag_mode_type memtag_mode;
+
+  /* Whether stack accesses use MTE insns.  */
+  unsigned int memtag_stack;
 };
 
 typedef struct aarch64_memtag_opts aarch64_memtag_opts;

diff --git a/binutils/readelf.c b/binutils/readelf.c
index 0d8daf3626f6691d6a8c0a1d934b3a80874abcaf..cfccdd2ba657d4961ef1e2e6143f50afc3b86279 100644 (file)
--- a/binutils/readelf.c
+++ b/binutils/readelf.c
@@ -2588,6 +2588,7 @@ get_aarch64_dynamic_type (unsigned long type)
     case DT_AARCH64_PAC_PLT:      return "AARCH64_PAC_PLT";
     case DT_AARCH64_VARIANT_PCS:  return "AARCH64_VARIANT_PCS";
     case DT_AARCH64_MEMTAG_MODE:  return "AARCH64_MEMTAG_MODE";
+    case DT_AARCH64_MEMTAG_STACK: return "AARCH64_MEMTAG_STACK";
 
     default:
       return NULL;

diff --git a/include/elf/aarch64.h b/include/elf/aarch64.h
index 747d8dc022fa5aedb009b35e2b28e5c41a7597e3..74bd7b402e0cb2cba0dd3ba6112dab7cf7299ca7 100644 (file)
--- a/include/elf/aarch64.h
+++ b/include/elf/aarch64.h
@@ -53,6 +53,7 @@
 #define DT_AARCH64_PAC_PLT     (DT_LOPROC + 3)
 #define DT_AARCH64_VARIANT_PCS (DT_LOPROC + 5)
 #define DT_AARCH64_MEMTAG_MODE (DT_LOPROC + 9)
+#define DT_AARCH64_MEMTAG_STACK (DT_LOPROC + 12)
 
 /* AArch64-specific values for st_other.  */
 #define STO_AARCH64_VARIANT_PCS        0x80  /* Symbol may follow different call

diff --git a/ld/emultempl/aarch64elf.em b/ld/emultempl/aarch64elf.em
index d7e4eb78059c0567433f0cf93caba10cceb3444e..66eaf1cd861842cb7ce56f3220aab41033c9f366 100644 (file)
--- a/ld/emultempl/aarch64elf.em
+++ b/ld/emultempl/aarch64elf.em
@@ -44,6 +44,7 @@ static aarch64_protection_opts sw_protections = {
 
 static aarch64_memtag_opts memtag_opts = {
   .memtag_mode = AARCH64_MEMTAG_MODE_NONE,
+  .memtag_stack = 0,
 };
 
 #define COMPILE_TIME_STRLEN(s) \
@@ -557,6 +558,8 @@ PARSE_AND_LIST_OPTIONS='
                                          sync: Enable precise exceptions when mismatched address and\n\
                                                allocation tags detected on load/store operations.\n\
                                          async: Enable imprecise exceptions.\n"));
+  fprintf (file, _("\
+  -z memtag-stack               Mark program stack with MTE protection.\n"));
 '
 
 PARSE_AND_LIST_ARGS_CASE_Z_AARCH64='
@@ -574,6 +577,8 @@ PARSE_AND_LIST_ARGS_CASE_Z_AARCH64='
        {}
      else if (aarch64_parse_memtag_mode_option (optarg))
        {}
+     else if (strcmp (optarg, "memtag-stack") == 0)
+       memtag_opts.memtag_stack = 1;
 '
 PARSE_AND_LIST_ARGS_CASE_Z="$PARSE_AND_LIST_ARGS_CASE_Z $PARSE_AND_LIST_ARGS_CASE_Z_AARCH64"
 

diff --git a/ld/ld.texi b/ld/ld.texi
index f5350e799bb1e221e670bffae6fbf06ec814fe2a..413335ad765c169719dfc1fa0187e54d08322350 100644 (file)
--- a/ld/ld.texi
+++ b/ld/ld.texi
@@ -8384,6 +8384,11 @@ implies precise exceptions, with the runtime providing the exact
 instruction where the fault occurred, and the exact faulting address.
 The @samp{async} mode implies imprecise exceptions.
 
+@kindex -z memtag-stack
+@cindex Mark program stack for MTE protection
+The @samp{-z memtag-stack} specifies that output object uses MTE
+instructions for stack memory usage.
+
 @ifclear GENERIC
 @lowersections
 @end ifclear

diff --git a/ld/testsuite/ld-aarch64/aarch64-elf.exp b/ld/testsuite/ld-aarch64/aarch64-elf.exp
index 56e68c584fb28fbcfc8c8461870be1f263d031df..8d56beb64c7b26095b43fe39f69754eb9b6a2f11 100644 (file)
--- a/ld/testsuite/ld-aarch64/aarch64-elf.exp
+++ b/ld/testsuite/ld-aarch64/aarch64-elf.exp
@@ -378,6 +378,7 @@ run_dump_test_lp64 "variant_pcs-now"
 
 run_dump_test_lp64 "mte-tagged-frame"
 run_dump_test_lp64 "dt-memtag-mode"
+run_dump_test_lp64 "dt-memtag-stack"
 
 set aarch64elflinktests {
   {"ld-aarch64/so with global symbol" "-shared" "" "" {copy-reloc-so.s}

diff --git a/ld/testsuite/ld-aarch64/dt-memtag-stack.d b/ld/testsuite/ld-aarch64/dt-memtag-stack.d
new file mode 100644 (file)
index 0000000..242f61f
--- /dev/null
+++ b/ld/testsuite/ld-aarch64/dt-memtag-stack.d
@@ -0,0 +1,7 @@
+#source: dt-memtag.s
+#ld: -shared -z memtag-stack
+#readelf: -d
+
+#...
+ 0x000000007000000c \(AARCH64_MEMTAG_STACK\) 0x1
+#...