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arm64: Make KMSAN aware of exceptions

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- Call kmsan_intr_enter() when an exception occurs.  This ensures that
  code running in the exception context does not clobber thread-local
  KMSAN state.
- Ensure that stack memory containing trap frames is treated as
  initialized.

Co-authored-by: Alexander Stetsenko <alex.stetsenko@klarasystems.com>
Reviewed by:	imp
MFC after:	2 weeks
Sponsored by:	Klara, Inc.
Sponsored by:	Juniper Networks, Inc.
Differential Revision:	https://reviews.freebsd.org/D43155
This commit is contained in:
Mark Johnston 2024-02-08 10:57:36 -05:00
parent 52bf6257c2
commit c05d7bdaf6
3 changed files with 45 additions and 0 deletions
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34
sys/arm64/arm64/exception.S
View File

@ -193,55 +193,89 @@
2:
.endm
#ifdef KMSAN
/*
* The KMSAN runtime relies on a TLS block to track initialization and origin
* state for function parameters and return values. To keep this state
* consistent in the face of asynchronous kernel-mode traps, the runtime
* maintains a stack of blocks: when handling an exception or interrupt,
* kmsan_intr_enter() pushes the new block to be used until the handler is
* complete, at which point kmsan_intr_leave() restores the previous block.
*
* Thus, KMSAN_ENTER/LEAVE hooks are required only in handlers for events that
* may have happened while in kernel-mode. In particular, they are not required
* around amd64_syscall() or ast() calls. Otherwise, kmsan_intr_enter() can be
* called unconditionally, without distinguishing between entry from user-mode
* or kernel-mode.
*/
#define KMSAN_ENTER bl kmsan_intr_enter
#define KMSAN_LEAVE bl kmsan_intr_leave
#else
#define KMSAN_ENTER
#define KMSAN_LEAVE
#endif
ENTRY(handle_el1h_sync)
save_registers 1
KMSAN_ENTER
ldr x0, [x18, #PC_CURTHREAD]
mov x1, sp
bl do_el1h_sync
KMSAN_LEAVE
restore_registers 1
ERET
END(handle_el1h_sync)
ENTRY(handle_el1h_irq)
save_registers 1
KMSAN_ENTER
mov x0, sp
bl intr_irq_handler
KMSAN_LEAVE
restore_registers 1
ERET
END(handle_el1h_irq)
ENTRY(handle_el0_sync)
save_registers 0
KMSAN_ENTER
ldr x0, [x18, #PC_CURTHREAD]
mov x1, sp
str x1, [x0, #TD_FRAME]
bl do_el0_sync
do_ast
KMSAN_LEAVE
restore_registers 0
ERET
END(handle_el0_sync)
ENTRY(handle_el0_irq)
save_registers 0
KMSAN_ENTER
mov x0, sp
bl intr_irq_handler
do_ast
KMSAN_LEAVE
restore_registers 0
ERET
END(handle_el0_irq)
ENTRY(handle_serror)
save_registers 0
KMSAN_ENTER
mov x0, sp
1: bl do_serror
b 1b
KMSAN_LEAVE
END(handle_serror)
ENTRY(handle_empty_exception)
save_registers 0
KMSAN_ENTER
mov x0, sp
1: bl unhandled_exception
b 1b
KMSAN_LEAVE
END(handle_empty_exception)
.macro vector name, el

9
sys/arm64/arm64/trap.c
View File

@ -33,6 +33,7 @@
#include <sys/kernel.h>
#include <sys/ktr.h>
#include <sys/lock.h>
#include <sys/msan.h>
#include <sys/mutex.h>
#include <sys/proc.h>
#include <sys/ptrace.h>
@ -478,6 +479,8 @@ do_el1h_sync(struct thread *td, struct trapframe *frame)
int dfsc;
kasan_mark(frame, sizeof(*frame), sizeof(*frame), 0);
kmsan_mark(frame, sizeof(*frame), KMSAN_STATE_INITED);
far = frame->tf_far;
/* Read the esr register to get the exception details */
esr = frame->tf_esr;
@ -591,6 +594,8 @@ do_el0_sync(struct thread *td, struct trapframe *frame)
get_pcpu(), READ_SPECIALREG(tpidr_el1)));
kasan_mark(frame, sizeof(*frame), sizeof(*frame), 0);
kmsan_mark(frame, sizeof(*frame), KMSAN_STATE_INITED);
far = frame->tf_far;
esr = frame->tf_esr;
exception = ESR_ELx_EXCEPTION(esr);
@ -737,6 +742,8 @@ do_serror(struct trapframe *frame)
uint64_t esr, far;
kasan_mark(frame, sizeof(*frame), sizeof(*frame), 0);
kmsan_mark(frame, sizeof(*frame), KMSAN_STATE_INITED);
far = frame->tf_far;
esr = frame->tf_esr;
@ -752,6 +759,8 @@ unhandled_exception(struct trapframe *frame)
uint64_t esr, far;
kasan_mark(frame, sizeof(*frame), sizeof(*frame), 0);
kmsan_mark(frame, sizeof(*frame), KMSAN_STATE_INITED);
far = frame->tf_far;
esr = frame->tf_esr;

2
sys/kern/subr_intr.c
View File

@ -54,6 +54,7 @@
#include <sys/kernel.h>
#include <sys/lock.h>
#include <sys/malloc.h>
#include <sys/msan.h>
#include <sys/mutex.h>
#include <sys/proc.h>
#include <sys/queue.h>
@ -334,6 +335,7 @@ intr_irq_handler(struct trapframe *tf)
KASSERT(irq_root_filter != NULL, ("%s: no filter", __func__));
kasan_mark(tf, sizeof(*tf), sizeof(*tf), 0);
kmsan_mark(tf, sizeof(*tf), KMSAN_STATE_INITED);
VM_CNT_INC(v_intr);
critical_enter();