releases/4.19.46/x86_64-allow-breakpoints-to-emulate-call-instructions.patch

   1 From 4b33dadf37666c0860b88f9e52a16d07bf6d0b03 Mon Sep 17 00:00:00 2001
   2 From: Peter Zijlstra <peterz@infradead.org>
   3 Date: Wed, 1 May 2019 15:11:17 +0200
   4 Subject: x86_64: Allow breakpoints to emulate call instructions
   5
   6 From: Peter Zijlstra <peterz@infradead.org>
   7
   8 commit 4b33dadf37666c0860b88f9e52a16d07bf6d0b03 upstream.
   9
  10 In order to allow breakpoints to emulate call instructions, they need to push
  11 the return address onto the stack. The x86_64 int3 handler adds a small gap
  12 to allow the stack to grow some. Use this gap to add the return address to
  13 be able to emulate a call instruction at the breakpoint location.
  14
  15 These helper functions are added:
  16
  17   int3_emulate_jmp(): changes the location of the regs->ip to return there.
  18
  19  (The next two are only for x86_64)
  20   int3_emulate_push(): to push the address onto the gap in the stack
  21   int3_emulate_call(): push the return address and change regs->ip
  22
  23 Cc: Andy Lutomirski <luto@kernel.org>
  24 Cc: Nicolai Stange <nstange@suse.de>
  25 Cc: Thomas Gleixner <tglx@linutronix.de>
  26 Cc: Ingo Molnar <mingo@redhat.com>
  27 Cc: Borislav Petkov <bp@alien8.de>
  28 Cc: "H. Peter Anvin" <hpa@zytor.com>
  29 Cc: the arch/x86 maintainers <x86@kernel.org>
  30 Cc: Josh Poimboeuf <jpoimboe@redhat.com>
  31 Cc: Jiri Kosina <jikos@kernel.org>
  32 Cc: Miroslav Benes <mbenes@suse.cz>
  33 Cc: Petr Mladek <pmladek@suse.com>
  34 Cc: Joe Lawrence <joe.lawrence@redhat.com>
  35 Cc: Shuah Khan <shuah@kernel.org>
  36 Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
  37 Cc: Tim Chen <tim.c.chen@linux.intel.com>
  38 Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
  39 Cc: Mimi Zohar <zohar@linux.ibm.com>
  40 Cc: Juergen Gross <jgross@suse.com>
  41 Cc: Nick Desaulniers <ndesaulniers@google.com>
  42 Cc: Nayna Jain <nayna@linux.ibm.com>
  43 Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
  44 Cc: Joerg Roedel <jroedel@suse.de>
  45 Cc: "open list:KERNEL SELFTEST FRAMEWORK" <linux-kselftest@vger.kernel.org>
  46 Cc: stable@vger.kernel.org
  47 Fixes: b700e7f03df5 ("livepatch: kernel: add support for live patching")
  48 Tested-by: Nicolai Stange <nstange@suse.de>
  49 Reviewed-by: Nicolai Stange <nstange@suse.de>
  50 Reviewed-by: Masami Hiramatsu <mhiramat@kernel.org>
  51 Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
  52 [ Modified to only work for x86_64 and added comment to int3_emulate_push() ]
  53 Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
  54 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  55
  56 ---
  57  arch/x86/include/asm/text-patching.h |   28 ++++++++++++++++++++++++++++
  58  1 file changed, 28 insertions(+)
  59
  60 --- a/arch/x86/include/asm/text-patching.h
  61 +++ b/arch/x86/include/asm/text-patching.h
  62 @@ -39,4 +39,32 @@ extern int poke_int3_handler(struct pt_r
  63  extern void *text_poke_bp(void *addr, const void *opcode, size_t len, void *handler);
  64  extern int after_bootmem;
  65
  66 +static inline void int3_emulate_jmp(struct pt_regs *regs, unsigned long ip)
  67 +{
  68 +       regs->ip = ip;
  69 +}
  70 +
  71 +#define INT3_INSN_SIZE 1
  72 +#define CALL_INSN_SIZE 5
  73 +
  74 +#ifdef CONFIG_X86_64
  75 +static inline void int3_emulate_push(struct pt_regs *regs, unsigned long val)
  76 +{
  77 +       /*
  78 +        * The int3 handler in entry_64.S adds a gap between the
  79 +        * stack where the break point happened, and the saving of
  80 +        * pt_regs. We can extend the original stack because of
  81 +        * this gap. See the idtentry macro's create_gap option.
  82 +        */
  83 +       regs->sp -= sizeof(unsigned long);
  84 +       *(unsigned long *)regs->sp = val;
  85 +}
  86 +
  87 +static inline void int3_emulate_call(struct pt_regs *regs, unsigned long func)
  88 +{
  89 +       int3_emulate_push(regs, regs->ip - INT3_INSN_SIZE + CALL_INSN_SIZE);
  90 +       int3_emulate_jmp(regs, func);
  91 +}
  92 +#endif
  93 +
  94  #endif /* _ASM_X86_TEXT_PATCHING_H */