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FAILED: patch "[PATCH] x86_64: Allow breakpoints to emulate call instructions" failed to apply to 4.9-stable tree

PATCH gregkh at linuxfoundation.org (gregkh at linuxfoundation.org) 1 participant 1 message May 23, 2019

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gregkh at linuxfoundation.org (gregkh at linuxfoundation.org)

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The patch below does not apply to the 4.9-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <stable at vger.kernel.org>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

Quoted 1 line

From 4b33dadf37666c0860b88f9e52a16d07bf6d0b03 Mon Sep 17 00:00:00 2001

From: Peter Zijlstra <[email protected]>
Date: Wed, 1 May 2019 15:11:17 +0200
Subject: [PATCH] x86_64: Allow breakpoints to emulate call instructions

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 <luto at kernel.org>
Cc Nicolai Stange <nstange at suse.de>
Cc Thomas Gleixner <tglx at linutronix.de>
Cc Ingo Molnar <mingo at redhat.com>
Cc Borislav Petkov <bp at alien8.de>
Cc "H. Peter Anvin" <hpa at zytor.com>
Cc the arch/x86 maintainers <x86 at kernel.org>
Cc Josh Poimboeuf <jpoimboe at redhat.com>
Cc Jiri Kosina <jikos at kernel.org>
Cc Miroslav Benes <mbenes at suse.cz>
Cc Petr Mladek <pmladek at suse.com>
Cc Joe Lawrence <joe.lawrence at redhat.com>
Cc Shuah Khan <shuah at kernel.org>
Cc Konrad Rzeszutek Wilk <konrad.wilk at oracle.com>
Cc Tim Chen <tim.c.chen at linux.intel.com>
Cc Sebastian Andrzej Siewior <bigeasy at linutronix.de>
Cc Mimi Zohar <zohar at linux.ibm.com>
Cc Juergen Gross <jgross at suse.com>
Cc Nick Desaulniers <ndesaulniers at google.com>
Cc Nayna Jain <nayna at linux.ibm.com>
Cc Masahiro Yamada <yamada.masahiro at socionext.com>
Cc Joerg Roedel <jroedel at suse.de>
Cc "open list:KERNEL SELFTEST FRAMEWORK" <linux-kselftest at vger.kernel.org>
Cc stable at vger.kernel.org
Fixes b700e7f03df5 ("livepatch: kernel: add support for live patching")
Tested-by Nicolai Stange <nstange at suse.de>
Reviewed-by Nicolai Stange <nstange at suse.de>
Reviewed-by Masami Hiramatsu <mhiramat at kernel.org>
Signed-off-by Peter Zijlstra (Intel) <peterz at infradead.org>
[ Modified to only work for x86_64 and added comment to int3_emulate_push() ]
Signed-off-by Steven Rostedt (VMware) <rostedt at goodmis.org>
arch/x86/include/asm/text-patching.h +28 -0
index e85ff65c43c3..05861cc08787 100644
@@ -39,4 +39,32 @@ extern int poke_int3_handler(struct pt_regs *regs);
 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 */