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aarch64: Add GCS support to longjmp

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This implementations ensures that longjmp across different stacks
works: it scans for GCS cap token and switches GCS if necessary
then the target GCSPR is restored with a GCSPOPM loop once the
current GCSPR is on the same GCS.

This makes longjmp linear time in the number of jumped over stack
frames when GCS is enabled.

Reviewed-by: Carlos O'Donell <carlos@redhat.com>
Reviewed-by: Wilco Dijkstra <Wilco.Dijkstra@arm.com>
This commit is contained in:
Szabolcs Nagy 2023-02-23 08:54:04 +00:00 committed by Yury Khrustalev
parent 13cbbb0cb2
commit 5ff5e7836e
2 changed files with 40 additions and 0 deletions
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30
sysdeps/aarch64/__longjmp.S
View File

@ -91,6 +91,36 @@ ENTRY (__longjmp)
ldp d12, d13, [x0, #JB_D12<<3]
ldp d14, d15, [x0, #JB_D14<<3]
/* GCS support. */
mov x16, 1
CHKFEAT_X16
tbnz x16, 0, L(gcs_done)
MRS_GCSPR (x2)
ldr x3, [x0, #JB_GCSPR]
mov x4, x3
/* x2: GCSPR now. x3, x4: target GCSPR. x5, x6: tmp regs. */
L(gcs_scan):
cmp x2, 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 x2, x4, 8
GCSSS1 (x4)
GCSSS2 (xzr)
L(gcs_pop):
cmp x2, x3
b.eq L(gcs_done)
GCSPOPM (xzr)
add x2, x2, 8
b L(gcs_pop)
L(gcs_done):
/* Originally this was implemented with a series of
.cfi_restore() directives.

10
sysdeps/aarch64/setjmp.S
View File

@ -57,6 +57,16 @@ ENTRY (__sigsetjmp)
stp d10, d11, [x0, #JB_D10<<3]
stp d12, d13, [x0, #JB_D12<<3]
stp d14, d15, [x0, #JB_D14<<3]
/* GCS support. */
mov x16, 1
CHKFEAT_X16
tbnz x16, 0, L(gcs_done)
MRS_GCSPR (x2)
add x2, x2, 8 /* GCS state right after setjmp returns. */
str x2, [x0, #JB_GCSPR]
L(gcs_done):
#ifdef PTR_MANGLE
mov x4, sp
PTR_MANGLE (5, 4, 3, 2)