From: Peter Zijlstra <pet...@infradead.org>
commit 4b33dadf37666c0860b88f9e52a16d07bf6d0b03 upstream.
In order to allow breakpoints to emulate call instructions, they need to push
the return address onto the stack. The x86_64 int3 handler adds a small gap
to allow the stack to grow some. Use this gap to add the return address to
be able to emulate a call instruction at the breakpoint location.
These helper functions are added:
int3_emulate_jmp(): changes the location of the regs->ip to return there.
(The next two are only for x86_64)
int3_emulate_push(): to push the address onto the gap in the stack
int3_emulate_call(): push the return address and change regs->ip
Cc: Andy Lutomirski <l...@kernel.org>
Cc: Nicolai Stange <nsta...@suse.de>
Cc: Thomas Gleixner <t...@linutronix.de>
Cc: Ingo Molnar <mi...@redhat.com>
Cc: Borislav Petkov <b...@alien8.de>
Cc: "H. Peter Anvin" <h...@zytor.com>
Cc: the arch/x86 maintainers <x...@kernel.org>
Cc: Josh Poimboeuf <jpoim...@redhat.com>
Cc: Jiri Kosina <ji...@kernel.org>
Cc: Miroslav Benes <mbe...@suse.cz>
Cc: Petr Mladek <pmla...@suse.com>
Cc: Joe Lawrence <joe.lawre...@redhat.com>
Cc: Shuah Khan <sh...@kernel.org>
Cc: Konrad Rzeszutek Wilk <konrad.w...@oracle.com>
Cc: Tim Chen <tim.c.c...@linux.intel.com>
Cc: Sebastian Andrzej Siewior <bige...@linutronix.de>
Cc: Mimi Zohar <zo...@linux.ibm.com>
Cc: Juergen Gross <jgr...@suse.com>
Cc: Nick Desaulniers <ndesaulni...@google.com>
Cc: Nayna Jain <na...@linux.ibm.com>
Cc: Masahiro Yamada <yamada.masah...@socionext.com>
Cc: Joerg Roedel <jroe...@suse.de>
Cc: "open list:KERNEL SELFTEST FRAMEWORK" <linux-kselft...@vger.kernel.org>
Cc: sta...@vger.kernel.org
Fixes: b700e7f03df5 ("livepatch: kernel: add support for live patching")
Tested-by: Nicolai Stange <nsta...@suse.de>
Reviewed-by: Nicolai Stange <nsta...@suse.de>
Reviewed-by: Masami Hiramatsu <mhira...@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <pet...@infradead.org>
[ Modified to only work for x86_64 and added comment to int3_emulate_push() ]
Signed-off-by: Steven Rostedt (VMware) <rost...@goodmis.org>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>
---
arch/x86/include/asm/text-patching.h | 28 ++++++++++++++++++++++++++++
1 file changed, 28 insertions(+)
--- a/arch/x86/include/asm/text-patching.h
+++ b/arch/x86/include/asm/text-patching.h
@@ -39,4 +39,32 @@ 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_jmp(struct pt_regs *regs, unsigned long ip)
+{
+ regs->ip = ip;
+}
+
+#define INT3_INSN_SIZE 1
+#define CALL_INSN_SIZE 5
+
+#ifdef CONFIG_X86_64
+static inline void int3_emulate_push(struct pt_regs *regs, unsigned long val)
+{
+ /*
+ * The int3 handler in entry_64.S adds a gap between the
+ * stack where the break point happened, and the saving of
+ * pt_regs. We can extend the original stack because of
+ * this gap. See the idtentry macro's create_gap option.
+ */
+ regs->sp -= sizeof(unsigned long);
+ *(unsigned long *)regs->sp = val;
+}
+
+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
+
#endif /* _ASM_X86_TEXT_PATCHING_H */
