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Peter Anvin" , the arch/x86 maintainers , Josh Poimboeuf , Jiri Kosina , Miroslav Benes , Petr Mladek , Joe Lawrence , Shuah Khan , Konrad Rzeszutek Wilk , Tim Chen , Sebastian Andrzej Siewior , Mimi Zohar , Juergen Gross , Nick Desaulniers , Nayna Jain , Masahiro Yamada , Joerg Roedel , "open list:KERNEL SELFTEST FRAMEWORK" , Masami Hiramatsu , "Peter Zijlstra (Intel)" , "Steven Rostedt (VMware)" Subject: [PATCH 4.14 33/77] x86_64: Allow breakpoints to emulate call instructions Date: Thu, 23 May 2019 21:05:51 +0200 Message-Id: <20190523181724.795243206@linuxfoundation.org> X-Mailer: git-send-email 2.21.0 In-Reply-To: <20190523181719.982121681@linuxfoundation.org> References: <20190523181719.982121681@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Peter Zijlstra 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 Cc: Nicolai Stange Cc: Thomas Gleixner Cc: Ingo Molnar Cc: Borislav Petkov Cc: "H. Peter Anvin" Cc: the arch/x86 maintainers Cc: Josh Poimboeuf Cc: Jiri Kosina Cc: Miroslav Benes Cc: Petr Mladek Cc: Joe Lawrence Cc: Shuah Khan Cc: Konrad Rzeszutek Wilk Cc: Tim Chen Cc: Sebastian Andrzej Siewior Cc: Mimi Zohar Cc: Juergen Gross Cc: Nick Desaulniers Cc: Nayna Jain Cc: Masahiro Yamada Cc: Joerg Roedel Cc: "open list:KERNEL SELFTEST FRAMEWORK" Cc: stable@vger.kernel.org Fixes: b700e7f03df5 ("livepatch: kernel: add support for live patching") Tested-by: Nicolai Stange Reviewed-by: Nicolai Stange Reviewed-by: Masami Hiramatsu Signed-off-by: Peter Zijlstra (Intel) [ Modified to only work for x86_64 and added comment to int3_emulate_push() ] Signed-off-by: Steven Rostedt (VMware) Signed-off-by: Greg Kroah-Hartman --- 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 @@ -38,4 +38,32 @@ extern void *text_poke(void *addr, const extern int poke_int3_handler(struct pt_regs *regs); extern void *text_poke_bp(void *addr, const void *opcode, size_t len, void *handler); +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 */