[RFD 5/5] ld/aarch64elf: add support for DT_AARCH64_MEMTAG_STACK dynamic tag
Indu Bhagat
indu.bhagat@oracle.com
Thu Dec 5 22:58:32 GMT 2024
Add new command line option -z memtag-stack for aarch64 elf.
This option instructs the linker to generate the appropriate dynamic
tag, so the dynamic loader can 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
... ... ...
TBD:
1. Error/Warn if user says -z memtag-stack but does not select a
mode ?
2. Should ld check that all input ELF components were compiled with
-fsanitize=memtag-stack ? If yes, we likely need something like
GNU_PROPERTY_AARCH64_FEATURE_1_MEMTAG_STACK specified in the ABI.
Should we then allow the user to select the desirable action like we
do in other cases, via say memtag-report[=none|warning|error] ?
3. What about same constants in glibc ?
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.
---
bfd/elfnn-aarch64.c | 6 ++++++
bfd/elfxx-aarch64.h | 3 +++
binutils/readelf.c | 1 +
include/elf/aarch64.h | 1 +
ld/emultempl/aarch64elf.em | 5 +++++
ld/ld.texi | 5 +++++
ld/testsuite/ld-aarch64/aarch64-elf.exp | 1 +
ld/testsuite/ld-aarch64/dt-memtag-stack.d | 7 +++++++
8 files changed, 29 insertions(+)
create mode 100644 ld/testsuite/ld-aarch64/dt-memtag-stack.d
diff --git a/bfd/elfnn-aarch64.c b/bfd/elfnn-aarch64.c
index 339d4e7d22e..0c3233665fe 100644
--- a/bfd/elfnn-aarch64.c
+++ b/bfd/elfnn-aarch64.c
@@ -9870,6 +9870,12 @@ 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 a5180e839cf..1716efb306c 100644
--- a/bfd/elfxx-aarch64.h
+++ b/bfd/elfxx-aarch64.h
@@ -136,6 +136,9 @@ 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 63273214810..951ac433b7a 100644
--- a/binutils/readelf.c
+++ b/binutils/readelf.c
@@ -2566,6 +2566,7 @@ 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 1cbb76dc58a..14f74ade477 100644
--- a/include/elf/aarch64.h
+++ b/include/elf/aarch64.h
@@ -51,6 +51,7 @@
#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 44c5b1be9b0..d62e9002fca 100644
--- a/ld/emultempl/aarch64elf.em
+++ b/ld/emultempl/aarch64elf.em
@@ -42,6 +42,7 @@ 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) \
@@ -532,6 +533,8 @@ 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='
@@ -547,6 +550,8 @@ 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 5044cb0c322..4cf730a873c 100644
--- a/ld/ld.texi
+++ b/ld/ld.texi
@@ -8258,6 +8258,11 @@ dynamic tag. The @samp{sync} mode 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 61fdcf557d1..99238f68296 100644
--- 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
index 00000000000..242f61fa172
--- /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
+#...
--
2.43.0
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