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dtrace/amd64: Implement emulation of call instructions

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Here, the provider is responsible for updating the trapframe to redirect
control flow and for computing the return address.  Once software-saved
registers are restored, the emulation shifts the remaining context down
on the stack to make space for the return address, then copies the
address provided by the invop handler.  dtrace_invop() is modified to
allocate temporary storage space on the stack for use by the provider to
return the return address.

This is to support a new provider for amd64 which can instrument
arbitrary instructions, not just function entry and exit instructions as
FBT does.

In collaboration with:	christos
Sponsored by:	Google, Inc. (GSoC 2022)
Sponsored by:	The FreeBSD Foundation
MFC after:	2 weeks
This commit is contained in:
Mark Johnston 2022-08-09 16:08:13 -04:00
parent a7aa3d4d75
commit 3ba8e9dc4a
3 changed files with 59 additions and 7 deletions
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4
sys/cddl/contrib/opensolaris/uts/common/sys/dtrace.h
View file

@ -2440,6 +2440,10 @@ extern void dtrace_helpers_destroy(proc_t *);
#define DTRACE_INVOP_NOP 4
#define DTRACE_INVOP_RET 5
#if defined(__amd64)
#define DTRACE_INVOP_CALL 6
#endif
#elif defined(__powerpc__)
#define DTRACE_INVOP_BCTR 1

51
sys/cddl/dev/dtrace/amd64/dtrace_asm.S
View file

@ -58,6 +58,8 @@
swapgs; \
1: addq $TF_RIP,%rsp;
.globl dtrace_invop_callsite
.type dtrace_invop_callsite,@function
ENTRY(dtrace_invop_start)
@ -69,11 +71,22 @@
movq TF_RIP(%rsp), %rdi
decq %rdi
movq %rsp, %rsi
movq TF_RAX(%rsp), %rdx
/*
* Allocate some scratch space to let the invop handler return a value.
* This is needed when emulating "call" instructions.
*/
subq $16, %rsp
movq %rsp, %rdx
call dtrace_invop
ENTRY(dtrace_invop_callsite)
dtrace_invop_callsite:
addq $16, %rsp
cmpl $DTRACE_INVOP_PUSHL_EBP, %eax
je bp_push
cmpl $DTRACE_INVOP_CALL, %eax
je bp_call
cmpl $DTRACE_INVOP_LEAVE, %eax
je bp_leave
cmpl $DTRACE_INVOP_NOP, %eax
@ -109,6 +122,40 @@ bp_push:
iretq /* return from interrupt */
/*NOTREACHED*/
bp_call:
/*
* Emulate a "call" instruction. The invop handler must have already
* updated the saved copy of %rip in the register set. It's our job to
* pull the hardware-saved registers down to make space for the return
* address, which is provided by the invop handler in our scratch
* space.
*/
INTR_POP
subq $16, %rsp /* make room for %rbp */
pushq %rax /* push temp */
pushq %rbx /* push temp */
movq 32(%rsp), %rax /* load calling RIP */
movq %rax, 16(%rsp) /* store calling RIP */
movq 40(%rsp), %rax /* load calling CS */
movq %rax, 24(%rsp) /* store calling CS */
movq 48(%rsp), %rax /* load calling RFLAGS */
movq %rax, 32(%rsp) /* store calling RFLAGS */
movq 56(%rsp), %rax /* load calling RSP */
subq $8, %rax /* make room for return address */
movq %rax, 40(%rsp) /* store calling RSP */
movq 64(%rsp), %rax /* load calling SS */
movq %rax, 48(%rsp) /* store calling SS */
movq -(TF_RIP - 16)(%rsp), %rax /* load return address */
movq 40(%rsp), %rbx /* reload calling RSP */
movq %rax, (%rbx) /* store return address */
popq %rbx /* pop temp */
popq %rax /* pop temp */
iretq /* return from interrupt */
/*NOTREACHED*/
bp_leave:
/*
* We must emulate a "leave", which is the same as a "movq %rbp, %rsp"

11
sys/cddl/dev/dtrace/amd64/dtrace_subr.c
View file

@ -50,7 +50,7 @@
extern void dtrace_getnanotime(struct timespec *tsp);
extern int (*dtrace_invop_jump_addr)(struct trapframe *);
int dtrace_invop(uintptr_t, struct trapframe *, uintptr_t);
int dtrace_invop(uintptr_t, struct trapframe *, void **);
int dtrace_invop_start(struct trapframe *frame);
void dtrace_invop_init(void);
void dtrace_invop_uninit(void);
@ -63,15 +63,16 @@ typedef struct dtrace_invop_hdlr {
dtrace_invop_hdlr_t *dtrace_invop_hdlr;
int
dtrace_invop(uintptr_t addr, struct trapframe *frame, uintptr_t eax)
dtrace_invop(uintptr_t addr, struct trapframe *frame, void **scratch)
{
dtrace_invop_hdlr_t *hdlr;
int rval;
for (hdlr = dtrace_invop_hdlr; hdlr != NULL; hdlr = hdlr->dtih_next)
if ((rval = hdlr->dtih_func(addr, frame, eax)) != 0)
for (hdlr = dtrace_invop_hdlr; hdlr != NULL; hdlr = hdlr->dtih_next) {
rval = hdlr->dtih_func(addr, frame, (uintptr_t)scratch);
if (rval != 0)
return (rval);
}
return (0);
}