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Date: Wed, 1 May 2019 14:52:00 -0400
From: Steven Rostedt <rostedt@...dmis.org>
To: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Andy Lutomirski <luto@...nel.org>,
Peter Zijlstra <peterz@...radead.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 v3] ftrace/x86_64: Emulate call function while
updating in breakpoint handler
On Wed, 1 May 2019 11:01:07 -0700
Linus Torvalds <torvalds@...ux-foundation.org> wrote:
> This looks sane to me, although I'm surprised that we didn't already
> have an annotation for the nonstandard stack frame for asm files. That
> probably would be cleaner in a separate commit, but I guess it doesn't
> matter.
It's still an RFC patch, and I was planning on breaking out the
non-standard stack change before the real patches.
>
> Anyway, I'm willing to consider the entry code version if it looks a
> _lot_ simpler than this (so I'd like to see them side-by-side), but
> it's not like this looks all that complicated to me either.
I got Peter's patch working. Here it is. What do you think?
What's nice about Peter's is that this will easily work for the static
call case too, without needing any more special trampolines.
The diffstat looks nice too:
Peter's patch:
entry/entry_32.S | 7 +++++++
entry/entry_64.S | 14 ++++++++++++--
include/asm/text-patching.h | 20 ++++++++++++++++++++
kernel/ftrace.c | 25 ++++++++++++++++++++-----
4 files changed, 59 insertions(+), 7 deletions(-)
My patch:
arch/x86/include/asm/frame.h | 15 ++++++
arch/x86/kernel/ftrace.c | 102 ++++++++++++++++++++++++++++++++++-
arch/x86/kernel/ftrace_64.S | 56 +++++++++++++++++++
3 files changed, 172 insertions(+), 1 deletion(-)
-- Steve
Index: linux-trace.git/arch/x86/entry/entry_32.S
===================================================================
--- linux-trace.git.orig/arch/x86/entry/entry_32.S
+++ linux-trace.git/arch/x86/entry/entry_32.S
@@ -1478,6 +1478,13 @@ 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
Index: linux-trace.git/arch/x86/entry/entry_64.S
===================================================================
--- linux-trace.git.orig/arch/x86/entry/entry_64.S
+++ linux-trace.git/arch/x86/entry/entry_64.S
@@ -879,7 +879,7 @@ apicinterrupt IRQ_WORK_VECTOR irq_work
* @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
+.macro idtentry sym do_sym has_error_code:req paranoid=0 shift_ist=-1 create_gap=0
ENTRY(\sym)
UNWIND_HINT_IRET_REGS offset=\has_error_code*8
@@ -899,6 +899,16 @@ 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
@@ -1130,7 +1140,7 @@ apicinterrupt3 HYPERV_STIMER0_VECTOR \
#endif /* CONFIG_HYPERV */
idtentry debug do_debug has_error_code=0 paranoid=1 shift_ist=DEBUG_STACK
-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
Index: linux-trace.git/arch/x86/include/asm/text-patching.h
===================================================================
--- linux-trace.git.orig/arch/x86/include/asm/text-patching.h
+++ linux-trace.git/arch/x86/include/asm/text-patching.h
@@ -39,4 +39,24 @@ extern int poke_int3_handler(struct pt_r
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 */
Index: linux-trace.git/arch/x86/kernel/ftrace.c
===================================================================
--- linux-trace.git.orig/arch/x86/kernel/ftrace.c
+++ linux-trace.git/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
}
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_fun
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);
@@ -294,13 +298,21 @@ int ftrace_int3_handler(struct pt_regs *
if (WARN_ON_ONCE(!regs))
return 0;
- ip = regs->ip - 1;
- if (!ftrace_location(ip) && !is_ftrace_caller(ip))
- return 0;
+ ip = regs->ip - INT3_INSN_SIZE;
- regs->ip += MCOUNT_INSN_SIZE - 1;
+ if (ftrace_location(ip)) {
+ int3_emulate_call(regs, (unsigned long)ftrace_regs_caller);
+ return 1;
+ } else if (is_ftrace_caller(ip)) {
+ if (!ftrace_update_func_call) {
+ int3_emulate_jmp(regs, ip + 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 +871,8 @@ void arch_ftrace_update_trampoline(struc
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 +974,7 @@ static int ftrace_mod_jmp(unsigned long
{
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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