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Merge branch 'perf/kprobes' into perf/core, to pick up finished branch

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Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Ingo Molnar 2021-02-17 11:50:11 +01:00
commit 8bcfdd7cad
2 changed files with 81 additions and 98 deletions
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11
arch/x86/include/asm/kprobes.h
View File

@ -58,14 +58,17 @@ struct arch_specific_insn {
/* copy of the original instruction */
kprobe_opcode_t *insn;
/*
* boostable = false: This instruction type is not boostable.
* boostable = true: This instruction has been boosted: we have
* boostable = 0: This instruction type is not boostable.
* boostable = 1: This instruction has been boosted: we have
* added a relative jump after the instruction copy in insn,
* so no single-step and fixup are needed (unless there's
* a post_handler).
*/
bool boostable;
bool if_modifier;
unsigned boostable:1;
unsigned if_modifier:1;
unsigned is_call:1;
unsigned is_pushf:1;
unsigned is_abs_ip:1;
/* Number of bytes of text poked */
int tp_len;
};

168
arch/x86/kernel/kprobes/core.c
View File

@ -132,26 +132,6 @@ void synthesize_relcall(void *dest, void *from, void *to)
}
NOKPROBE_SYMBOL(synthesize_relcall);
/*
* Skip the prefixes of the instruction.
*/
static kprobe_opcode_t *skip_prefixes(kprobe_opcode_t *insn)
{
insn_attr_t attr;
attr = inat_get_opcode_attribute((insn_byte_t)*insn);
while (inat_is_legacy_prefix(attr)) {
insn++;
attr = inat_get_opcode_attribute((insn_byte_t)*insn);
}
#ifdef CONFIG_X86_64
if (inat_is_rex_prefix(attr))
insn++;
#endif
return insn;
}
NOKPROBE_SYMBOL(skip_prefixes);
/*
* Returns non-zero if INSN is boostable.
* RIP relative instructions are adjusted at copying time in 64 bits mode
@ -311,25 +291,6 @@ static int can_probe(unsigned long paddr)
return (addr == paddr);
}
/*
* Returns non-zero if opcode modifies the interrupt flag.
*/
static int is_IF_modifier(kprobe_opcode_t *insn)
{
/* Skip prefixes */
insn = skip_prefixes(insn);
switch (*insn) {
case 0xfa: /* cli */
case 0xfb: /* sti */
case 0xcf: /* iret/iretd */
case 0x9d: /* popf/popfd */
return 1;
}
return 0;
}
/*
* Copy an instruction with recovering modified instruction by kprobes
* and adjust the displacement if the instruction uses the %rip-relative
@ -411,9 +372,9 @@ static int prepare_boost(kprobe_opcode_t *buf, struct kprobe *p,
synthesize_reljump(buf + len, p->ainsn.insn + len,
p->addr + insn->length);
len += JMP32_INSN_SIZE;
p->ainsn.boostable = true;
p->ainsn.boostable = 1;
} else {
p->ainsn.boostable = false;
p->ainsn.boostable = 0;
}
return len;
@ -450,6 +411,67 @@ void free_insn_page(void *page)
module_memfree(page);
}
static void set_resume_flags(struct kprobe *p, struct insn *insn)
{
insn_byte_t opcode = insn->opcode.bytes[0];
switch (opcode) {
case 0xfa: /* cli */
case 0xfb: /* sti */
case 0x9d: /* popf/popfd */
/* Check whether the instruction modifies Interrupt Flag or not */
p->ainsn.if_modifier = 1;
break;
case 0x9c: /* pushfl */
p->ainsn.is_pushf = 1;
break;
case 0xcf: /* iret */
p->ainsn.if_modifier = 1;
fallthrough;
case 0xc2: /* ret/lret */
case 0xc3:
case 0xca:
case 0xcb:
case 0xea: /* jmp absolute -- ip is correct */
/* ip is already adjusted, no more changes required */
p->ainsn.is_abs_ip = 1;
/* Without resume jump, this is boostable */
p->ainsn.boostable = 1;
break;
case 0xe8: /* call relative - Fix return addr */
p->ainsn.is_call = 1;
break;
#ifdef CONFIG_X86_32
case 0x9a: /* call absolute -- same as call absolute, indirect */
p->ainsn.is_call = 1;
p->ainsn.is_abs_ip = 1;
break;
#endif
case 0xff:
opcode = insn->opcode.bytes[1];
if ((opcode & 0x30) == 0x10) {
/*
* call absolute, indirect
* Fix return addr; ip is correct.
* But this is not boostable
*/
p->ainsn.is_call = 1;
p->ainsn.is_abs_ip = 1;
break;
} else if (((opcode & 0x31) == 0x20) ||
((opcode & 0x31) == 0x21)) {
/*
* jmp near and far, absolute indirect
* ip is correct.
*/
p->ainsn.is_abs_ip = 1;
/* Without resume jump, this is boostable */
p->ainsn.boostable = 1;
}
break;
}
}
static int arch_copy_kprobe(struct kprobe *p)
{
struct insn insn;
@ -467,8 +489,8 @@ static int arch_copy_kprobe(struct kprobe *p)
*/
len = prepare_boost(buf, p, &insn);
/* Check whether the instruction modifies Interrupt Flag or not */
p->ainsn.if_modifier = is_IF_modifier(buf);
/* Analyze the opcode and set resume flags */
set_resume_flags(p, &insn);
/* Also, displacement change doesn't affect the first byte */
p->opcode = buf[0];
@ -491,6 +513,9 @@ int arch_prepare_kprobe(struct kprobe *p)
if (!can_probe((unsigned long)p->addr))
return -EILSEQ;
memset(&p->ainsn, 0, sizeof(p->ainsn));
/* insn: must be on special executable page on x86. */
p->ainsn.insn = get_insn_slot();
if (!p->ainsn.insn)
@ -806,11 +831,6 @@ NOKPROBE_SYMBOL(trampoline_handler);
* 2) If the single-stepped instruction was a call, the return address
* that is atop the stack is the address following the copied instruction.
* We need to make it the address following the original instruction.
*
* If this is the first time we've single-stepped the instruction at
* this probepoint, and the instruction is boostable, boost it: add a
* jump instruction after the copied instruction, that jumps to the next
* instruction after the probepoint.
*/
static void resume_execution(struct kprobe *p, struct pt_regs *regs,
struct kprobe_ctlblk *kcb)
@ -818,60 +838,20 @@ static void resume_execution(struct kprobe *p, struct pt_regs *regs,
unsigned long *tos = stack_addr(regs);
unsigned long copy_ip = (unsigned long)p->ainsn.insn;
unsigned long orig_ip = (unsigned long)p->addr;
kprobe_opcode_t *insn = p->ainsn.insn;
/* Skip prefixes */
insn = skip_prefixes(insn);
regs->flags &= ~X86_EFLAGS_TF;
switch (*insn) {
case 0x9c: /* pushfl */
/* Fixup the contents of top of stack */
if (p->ainsn.is_pushf) {
*tos &= ~(X86_EFLAGS_TF | X86_EFLAGS_IF);
*tos |= kcb->kprobe_old_flags;
break;
case 0xc2: /* iret/ret/lret */
case 0xc3:
case 0xca:
case 0xcb:
case 0xcf:
case 0xea: /* jmp absolute -- ip is correct */
/* ip is already adjusted, no more changes required */
p->ainsn.boostable = true;
goto no_change;
case 0xe8: /* call relative - Fix return addr */
} else if (p->ainsn.is_call) {
*tos = orig_ip + (*tos - copy_ip);
break;
#ifdef CONFIG_X86_32
case 0x9a: /* call absolute -- same as call absolute, indirect */
*tos = orig_ip + (*tos - copy_ip);
goto no_change;
#endif
case 0xff:
if ((insn[1] & 0x30) == 0x10) {
/*
* call absolute, indirect
* Fix return addr; ip is correct.
* But this is not boostable
*/
*tos = orig_ip + (*tos - copy_ip);
goto no_change;
} else if (((insn[1] & 0x31) == 0x20) ||
((insn[1] & 0x31) == 0x21)) {
/*
* jmp near and far, absolute indirect
* ip is correct. And this is boostable
*/
p->ainsn.boostable = true;
goto no_change;
}
break;
default:
break;
}
regs->ip += orig_ip - copy_ip;
if (!p->ainsn.is_abs_ip)
regs->ip += orig_ip - copy_ip;
no_change:
restore_btf();
}
NOKPROBE_SYMBOL(resume_execution);