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Date: Wed, 1 May 2019 15:11:17 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Steven Rostedt <rostedt@...dmis.org>,
Andy Lutomirski <luto@...nel.org>,
Nicolai Stange <nstange@...e.de>,
Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
"H. Peter Anvin" <hpa@...or.com>,
the arch/x86 maintainers <x86@...nel.org>,
Josh Poimboeuf <jpoimboe@...hat.com>,
Jiri Kosina <jikos@...nel.org>,
Miroslav Benes <mbenes@...e.cz>,
Petr Mladek <pmladek@...e.com>,
Joe Lawrence <joe.lawrence@...hat.com>,
Shuah Khan <shuah@...nel.org>,
Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
Tim Chen <tim.c.chen@...ux.intel.com>,
Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
Mimi Zohar <zohar@...ux.ibm.com>,
Juergen Gross <jgross@...e.com>,
Nick Desaulniers <ndesaulniers@...gle.com>,
Nayna Jain <nayna@...ux.ibm.com>,
Masahiro Yamada <yamada.masahiro@...ionext.com>,
Joerg Roedel <jroedel@...e.de>,
Linux List Kernel Mailing <linux-kernel@...r.kernel.org>,
live-patching@...r.kernel.org,
"open list:KERNEL SELFTEST FRAMEWORK"
<linux-kselftest@...r.kernel.org>
Subject: Re: [RFC][PATCH] ftrace/x86: Emulate call function while updating in
breakpoint handler
On Tue, Apr 30, 2019 at 11:33:21AM -0700, Linus Torvalds wrote:
> Anyway, since Andy really likes the entry code change, can we have
> that patch in parallel and judge the difference that way? Iirc, that
> was x86-64 specific too.
Here goes, compile tested only...
It obviously needs a self-test, but that shoulnd't be too hard to
arrange.
---
arch/x86/entry/entry_32.S | 7 +++++++
arch/x86/entry/entry_64.S | 14 ++++++++++++--
arch/x86/include/asm/text-patching.h | 20 ++++++++++++++++++++
arch/x86/kernel/ftrace.c | 24 +++++++++++++++++++-----
4 files changed, 58 insertions(+), 7 deletions(-)
diff --git a/arch/x86/entry/entry_32.S b/arch/x86/entry/entry_32.S
index 7b23431be5cb..d246302085a3 100644
--- a/arch/x86/entry/entry_32.S
+++ b/arch/x86/entry/entry_32.S
@@ -1479,6 +1479,13 @@ ENTRY(int3)
ASM_CLAC
pushl $-1 # mark this as an int
+ testl $SEGMENT_RPL_MASK, PT_CS(%esp)
+ jnz .Lfrom_usermode_no_gap
+ .rept 6
+ pushl 5*4(%esp)
+ .endr
+.Lfrom_usermode_no_gap:
+
SAVE_ALL switch_stacks=1
ENCODE_FRAME_POINTER
TRACE_IRQS_OFF
diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
index 20e45d9b4e15..268cd9affe04 100644
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -878,7 +878,7 @@ apicinterrupt IRQ_WORK_VECTOR irq_work_interrupt smp_irq_work_interrupt
* @paranoid == 2 is special: the stub will never switch stacks. This is for
* #DF: if the thread stack is somehow unusable, we'll still get a useful OOPS.
*/
-.macro idtentry sym do_sym has_error_code:req paranoid=0 shift_ist=-1 ist_offset=0
+.macro idtentry sym do_sym has_error_code:req paranoid=0 shift_ist=-1 ist_offset=0 create_gap=0
ENTRY(\sym)
UNWIND_HINT_IRET_REGS offset=\has_error_code*8
@@ -898,6 +898,16 @@ ENTRY(\sym)
jnz .Lfrom_usermode_switch_stack_\@
.endif
+ .if \create_gap == 1
+ testb $3, CS-ORIG_RAX(%rsp)
+ jnz .Lfrom_usermode_no_gap_\@
+ .rept 6
+ pushq 5*8(%rsp)
+ .endr
+ UNWIND_HINT_IRET_REGS offset=8
+.Lfrom_usermode_no_gap_\@:
+ .endif
+
.if \paranoid
call paranoid_entry
.else
@@ -1129,7 +1139,7 @@ apicinterrupt3 HYPERV_STIMER0_VECTOR \
#endif /* CONFIG_HYPERV */
idtentry debug do_debug has_error_code=0 paranoid=1 shift_ist=IST_INDEX_DB ist_offset=DB_STACK_OFFSET
-idtentry int3 do_int3 has_error_code=0
+idtentry int3 do_int3 has_error_code=0 create_gap=1
idtentry stack_segment do_stack_segment has_error_code=1
#ifdef CONFIG_XEN_PV
diff --git a/arch/x86/include/asm/text-patching.h b/arch/x86/include/asm/text-patching.h
index e85ff65c43c3..ba275b6292db 100644
--- a/arch/x86/include/asm/text-patching.h
+++ b/arch/x86/include/asm/text-patching.h
@@ -39,4 +39,24 @@ extern int poke_int3_handler(struct pt_regs *regs);
extern void *text_poke_bp(void *addr, const void *opcode, size_t len, void *handler);
extern int after_bootmem;
+static inline void int3_emulate_push(struct pt_regs *regs, unsigned long val)
+{
+ regs->sp -= sizeof(unsigned long);
+ *(unsigned long *)regs->sp = val;
+}
+
+static inline void int3_emulate_jmp(struct pt_regs *regs, unsigned long ip)
+{
+ regs->ip = ip;
+}
+
+#define INT3_INSN_SIZE 1
+#define CALL_INSN_SIZE 5
+
+static inline void int3_emulate_call(struct pt_regs *regs, unsigned long func)
+{
+ int3_emulate_push(regs, regs->ip - INT3_INSN_SIZE + CALL_INSN_SIZE);
+ int3_emulate_jmp(regs, func);
+}
+
#endif /* _ASM_X86_TEXT_PATCHING_H */
diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c
index ef49517f6bb2..90d319687d7e 100644
--- a/arch/x86/kernel/ftrace.c
+++ b/arch/x86/kernel/ftrace.c
@@ -29,6 +29,7 @@
#include <asm/kprobes.h>
#include <asm/ftrace.h>
#include <asm/nops.h>
+#include <asm/text-patching.h>
#ifdef CONFIG_DYNAMIC_FTRACE
@@ -231,6 +232,7 @@ int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,
}
static unsigned long ftrace_update_func;
+static unsigned long ftrace_update_func_call;
static int update_ftrace_func(unsigned long ip, void *new)
{
@@ -259,6 +261,8 @@ int ftrace_update_ftrace_func(ftrace_func_t func)
unsigned char *new;
int ret;
+ ftrace_update_func_call = (unsigned long)func;
+
new = ftrace_call_replace(ip, (unsigned long)func);
ret = update_ftrace_func(ip, new);
@@ -295,12 +299,19 @@ int ftrace_int3_handler(struct pt_regs *regs)
return 0;
ip = regs->ip - 1;
- if (!ftrace_location(ip) && !is_ftrace_caller(ip))
- return 0;
-
- regs->ip += MCOUNT_INSN_SIZE - 1;
+ if (ftrace_location(ip)) {
+ int3_emulate_call(regs, ftrace_update_func_call);
+ return 1;
+ } else if (is_ftrace_caller(ip)) {
+ if (!ftrace_update_func_call) {
+ int3_emulate_jmp(regs, regs->ip - INT3_INSN_SIZE + CALL_INSN_SIZE);
+ return 1;
+ }
+ int3_emulate_call(regs, ftrace_update_func_call);
+ return 1;
+ }
- return 1;
+ return 0;
}
NOKPROBE_SYMBOL(ftrace_int3_handler);
@@ -859,6 +870,8 @@ void arch_ftrace_update_trampoline(struct ftrace_ops *ops)
func = ftrace_ops_get_func(ops);
+ ftrace_update_func_call = (unsigned long)func;
+
/* Do a safe modify in case the trampoline is executing */
new = ftrace_call_replace(ip, (unsigned long)func);
ret = update_ftrace_func(ip, new);
@@ -960,6 +973,7 @@ static int ftrace_mod_jmp(unsigned long ip, void *func)
{
unsigned char *new;
+ ftrace_update_func_call = 0UL;
new = ftrace_jmp_replace(ip, (unsigned long)func);
return update_ftrace_func(ip, new);
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