https://gcc.gnu.org/g:9f2fe2932ca35b736685753a85bd5c43459f24de
commit 9f2fe2932ca35b736685753a85bd5c43459f24de
Author: Szabolcs Nagy <szabolcs.n...@arm.com>
Date: Tue Apr 2 15:43:23 2024 +0100
aarch64: libitm: Add GCS support
Transaction begin and abort use setjmp/longjmp like operations that
need to be updated for GCS compatibility. We use similar logic to
libc setjmp/longjmp that support switching stack and thus switching
GCS (e.g. due to longjmp out of a makecontext stack), this is kept
even though it is likely not required for transaction aborts.
The gtm_jmpbuf is internal to libitm so we can change its layout
without breaking ABI.
libitm/ChangeLog:
* config/aarch64/sjlj.S: Add GCS support and mark GCS compatible.
* config/aarch64/target.h: Add gcs field to gtm_jmpbuf.
Diff:
---
libitm/config/aarch64/sjlj.S | 60 +++++++++++++++++++++++++++++++++++++++---
libitm/config/aarch64/target.h | 1 +
2 files changed, 58 insertions(+), 3 deletions(-)
diff --git a/libitm/config/aarch64/sjlj.S b/libitm/config/aarch64/sjlj.S
index 6b248f7c040..e21d751ef21 100644
--- a/libitm/config/aarch64/sjlj.S
+++ b/libitm/config/aarch64/sjlj.S
@@ -29,6 +29,13 @@
#define AUTIASP hint 29
#define PACIBSP hint 27
#define AUTIBSP hint 31
+#define CHKFEAT_X16 hint 40
+#define MRS_GCSPR(x) mrs x, s3_3_c2_c5_1
+#define GCSPOPM(x) sysl x, #3, c7, c7, #1
+#define GCSSS1(x) sys #3, c7, c7, #2, x
+#define GCSSS2(x) sysl x, #3, c7, c7, #3
+
+#define L(name) .L##name
#if defined(HAVE_AS_CFI_PSEUDO_OP) && defined(__GCC_HAVE_DWARF2_CFI_ASM)
# define cfi_window_save .cfi_window_save
@@ -80,7 +87,16 @@ _ITM_beginTransaction:
stp d10, d11, [sp, 7*16]
stp d12, d13, [sp, 8*16]
stp d14, d15, [sp, 9*16]
- str x1, [sp, 10*16]
+
+ /* GCS support. */
+ mov x2, 0
+ mov x16, 1
+ CHKFEAT_X16
+ tbnz x16, 0, L(gcs_done_sj)
+ MRS_GCSPR (x2)
+ add x2, x2, 8 /* GCS after _ITM_beginTransaction returns. */
+L(gcs_done_sj):
+ stp x2, x1, [sp, 10*16]
/* Invoke GTM_begin_transaction with the struct we just built. */
mov x1, sp
@@ -117,7 +133,38 @@ GTM_longjmp:
ldp d10, d11, [x1, 7*16]
ldp d12, d13, [x1, 8*16]
ldp d14, d15, [x1, 9*16]
+
+ /* GCS support. */
+ mov x16, 1
+ CHKFEAT_X16
+ tbnz x16, 0, L(gcs_done_lj)
+ MRS_GCSPR (x7)
ldr x3, [x1, 10*16]
+ mov x4, x3
+ /* x7: GCSPR now. x3, x4: target GCSPR. x5, x6: tmp regs. */
+L(gcs_scan):
+ cmp x7, x4
+ b.eq L(gcs_pop)
+ sub x4, x4, 8
+ /* Check for a cap token. */
+ ldr x5, [x4]
+ and x6, x4, 0xfffffffffffff000
+ orr x6, x6, 1
+ cmp x5, x6
+ b.ne L(gcs_scan)
+L(gcs_switch):
+ add x7, x4, 8
+ GCSSS1 (x4)
+ GCSSS2 (xzr)
+L(gcs_pop):
+ cmp x7, x3
+ b.eq L(gcs_done_lj)
+ GCSPOPM (xzr)
+ add x7, x7, 8
+ b L(gcs_pop)
+L(gcs_done_lj):
+
+ ldr x3, [x1, 10*16 + 8]
ldp x29, x30, [x1]
cfi_def_cfa(x1, 0)
CFI_PAC_TOGGLE
@@ -132,6 +179,7 @@ GTM_longjmp:
#define FEATURE_1_AND 0xc0000000
#define FEATURE_1_BTI 1
#define FEATURE_1_PAC 2
+#define FEATURE_1_GCS 4
/* Supported features based on the code generation options. */
#if defined(__ARM_FEATURE_BTI_DEFAULT)
@@ -146,6 +194,12 @@ GTM_longjmp:
# define PAC_FLAG 0
#endif
+#if __ARM_FEATURE_GCS_DEFAULT
+# define GCS_FLAG FEATURE_1_GCS
+#else
+# define GCS_FLAG 0
+#endif
+
/* Add a NT_GNU_PROPERTY_TYPE_0 note. */
#define GNU_PROPERTY(type, value) \
.section .note.gnu.property, "a"; \
@@ -163,7 +217,7 @@ GTM_longjmp:
.section .note.GNU-stack, "", %progbits
/* Add GNU property note if built with branch protection. */
-# if (BTI_FLAG|PAC_FLAG) != 0
-GNU_PROPERTY (FEATURE_1_AND, BTI_FLAG|PAC_FLAG)
+# if (BTI_FLAG|PAC_FLAG|GCS_FLAG) != 0
+GNU_PROPERTY (FEATURE_1_AND, BTI_FLAG|PAC_FLAG|GCS_FLAG)
# endif
#endif
diff --git a/libitm/config/aarch64/target.h b/libitm/config/aarch64/target.h
index 3d99197bfab..a1f39b4bf7a 100644
--- a/libitm/config/aarch64/target.h
+++ b/libitm/config/aarch64/target.h
@@ -30,6 +30,7 @@ typedef struct gtm_jmpbuf
unsigned long long pc; /* x30 */
unsigned long long gr[10]; /* x19-x28 */
unsigned long long vr[8]; /* d8-d15 */
+ void *gcs; /* GCSPR_EL0 */
void *cfa;
} gtm_jmpbuf;
