[PATCH v4 18/27] x86/int3: Ensure that poke_int3_handler() is not traced

Peter Zijlstra
2020-02-21T13:34:34Z

From: Thomas Gleixner <tglx@linutronix.de>

In order to ensure poke_int3_handler() is completely self contained --
we call this while we're modifying other text, imagine the fun of
hitting another INT3 -- ensure that everything it uses is not traced.

The primary means here is to force inlining; bsearch() is notrace
because all of lib/ is.

Not-Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
---
arch/x86/include/asm/ptrace.h | 2 +-
arch/x86/include/asm/text-patching.h | 11 +++++++----
arch/x86/kernel/alternative.c | 11 +++++++----
3 files changed, 15 insertions(+), 9 deletions(-)

Index: linux-2.6/arch/x86/include/asm/ptrace.h
===================================================================
--- linux-2.6.orig/arch/x86/include/asm/ptrace.h
+++ linux-2.6/arch/x86/include/asm/ptrace.h
@@ -123,7 +123,7 @@ static inline void regs_set_return_value
* On x86_64, vm86 mode is mercifully nonexistent, and we don't need
* the extra check.
*/
-static inline int user_mode(struct pt_regs *regs)
+static __always_inline int user_mode(struct pt_regs *regs)
{
#ifdef CONFIG_X86_32
return ((regs->cs & SEGMENT_RPL_MASK) | (regs->flags & X86_VM_MASK)) >= USER_RPL;
Index: linux-2.6/arch/x86/include/asm/text-patching.h
===================================================================
--- linux-2.6.orig/arch/x86/include/asm/text-patching.h
+++ linux-2.6/arch/x86/include/asm/text-patching.h
@@ -64,7 +64,7 @@ extern void text_poke_finish(void);

#define DISP32_SIZE 4

-static inline int text_opcode_size(u8 opcode)
+static __always_inline int text_opcode_size(u8 opcode)
{
int size = 0;

@@ -118,12 +118,14 @@ extern __ro_after_init struct mm_struct
extern __ro_after_init unsigned long poking_addr;

#ifndef CONFIG_UML_X86
-static inline void int3_emulate_jmp(struct pt_regs *regs, unsigned long ip)
+static __always_inline
+void int3_emulate_jmp(struct pt_regs *regs, unsigned long ip)
{
regs->ip = ip;
}

-static inline void int3_emulate_push(struct pt_regs *regs, unsigned long val)
+static __always_inline
+void int3_emulate_push(struct pt_regs *regs, unsigned long val)
{
/*
* The int3 handler in entry_64.S adds a gap between the
@@ -138,7 +140,8 @@ static inline void int3_emulate_push(str
*(unsigned long *)regs->sp = val;
}

-static inline void int3_emulate_call(struct pt_regs *regs, unsigned long func)
+static __always_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);
Index: linux-2.6/arch/x86/kernel/alternative.c
===================================================================
--- linux-2.6.orig/arch/x86/kernel/alternative.c
+++ linux-2.6/arch/x86/kernel/alternative.c
@@ -956,7 +956,8 @@ struct bp_patching_desc {

static struct bp_patching_desc *bp_desc;

-static inline struct bp_patching_desc *try_get_desc(struct bp_patching_desc **descp)
+static __always_inline
+struct bp_patching_desc *try_get_desc(struct bp_patching_desc **descp)
{
struct bp_patching_desc *desc = READ_ONCE(*descp); /* rcu_dereference */

@@ -966,13 +967,13 @@ static inline struct bp_patching_desc *t
return desc;
}

-static inline void put_desc(struct bp_patching_desc *desc)
+static __always_inline void put_desc(struct bp_patching_desc *desc)
{
smp_mb__before_atomic();
atomic_dec(&desc->refs);
}

-static inline void *text_poke_addr(struct text_poke_loc *tp)
+static __always_inline void *text_poke_addr(struct text_poke_loc *tp)
{
return _stext + tp->rel_addr;
}