- Rewrite register saving/restoring code

Based on patch from Masami Hiramatsu

Signed-off-by: Harvey Harrison
---
Sorry Ingo, I based my other 4/4 off the patch that had the one incorrect
ifdef around trampoline_probe_handler. This is based on your fixed one.

Masami, I think you want to check your register restoration code in
trampoline_probe_handler vs X86_32, it's obvious in this patch in the
section:

X86_32:
regs->cs = __KERNEL_CS | get_kernel_rpl();

yours:
regs->cs = __KERNEL_CS;

arch/x86/kernel/kprobes.c | 104 +++++++++++++++++++++++++--------------------
1 files changed, 58 insertions(+), 46 deletions(-)

diff --git a/arch/x86/kernel/kprobes.c b/arch/x86/kernel/kprobes.c
index 47bae2c..37a34a8 100644
--- a/arch/x86/kernel/kprobes.c
+++ b/arch/x86/kernel/kprobes.c
@@ -565,9 +565,8 @@ no_kprobe:
}

/*
- * For function-return probes, init_kprobes() establishes a probepoint
- * here. When a retprobed function returns, this probe is hit and
- * trampoline_probe_handler() runs, calling the kretprobe's handler.
+ * When a retprobed function returns,this code saves registers and
+ * calls trampoline_handler() runs, which calls the kretprobe's handler.
*/
void __kprobes kretprobe_trampoline_holder(void)
{
@@ -608,19 +607,59 @@ void __kprobes kretprobe_trampoline_holder(void)
#else
asm volatile ( ".global kretprobe_trampoline\n"
"kretprobe_trampoline: \n"
- "nop\n");
+ /* We don't bother saving the ss register */
+ " pushq %rsp\n"
+ " pushfq\n"
+ /*
+ * Skip cs, ip, orig_ax.
+ * trampoline_handler() will plug in these values
+ */
+ " subq $24, %rsp\n"
+ " pushq %rdi\n"
+ " pushq %rsi\n"
+ " pushq %rdx\n"
+ " pushq %rcx\n"
+ " pushq %rax\n"
+ " pushq %r8\n"
+ " pushq %r9\n"
+ " pushq %r10\n"
+ " pushq %r11\n"
+ " pushq %rbx\n"
+ " pushq %rbp\n"
+ " pushq %r12\n"
+ " pushq %r13\n"
+ " pushq %r14\n"
+ " pushq %r15\n"
+ " movq %rsp, %rdi\n"
+ " call trampoline_handler\n"
+ /* Replace saved sp with true return address. */
+ " movq %rax, 152(%rsp)\n"
+ " popq %r15\n"
+ " popq %r14\n"
+ " popq %r13\n"
+ " popq %r12\n"
+ " popq %rbp\n"
+ " popq %rbx\n"
+ " popq %r11\n"
+ " popq %r10\n"
+ " popq %r9\n"
+ " popq %r8\n"
+ " popq %rax\n"
+ " popq %rcx\n"
+ " popq %rdx\n"
+ " popq %rsi\n"
+ " popq %rdi\n"
+ /* Skip orig_ax, ip, cs */
+ " addq $24, %rsp\n"
+ " popfq\n"
+ " ret\n");
#endif
}

/*
- * X86_32 Called from kretprobe_trampoline
- * X86_64 Called when we hit the probe point at kretprobe_trampoline
+ * Called from kretprobe_trampoline
*/
-#ifdef CONFIG_X86_64
-int __kprobes trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs)
-#else
void *__kprobes trampoline_handler(struct pt_regs *regs)
-#endif
{
struct kretprobe_instance *ri = NULL;
struct hlist_head *head, empty_rp;
@@ -636,6 +675,11 @@ void *__kprobes trampoline_handler(struct pt_regs *regs)
regs->cs = __KERNEL_CS | get_kernel_rpl();
regs->ip = trampoline_address;
regs->orig_ax = 0xffffffff;
+#else
+ /* fixup rt regs */
+ regs->cs = __KERNEL_CS;
+ regs->ip = trampoline_address;
+ regs->orig_ax = 0xffffffffffffffff;
#endif
/*
* It is possible to have multiple instances associated with a given
@@ -654,17 +698,14 @@ void *__kprobes trampoline_handler(struct pt_regs *regs)
if (ri->task != current)
/* another task is sharing our hash bucket */
continue;
-#ifdef CONFIG_X86_32
+
if (ri->rp && ri->rp->handler) {
__get_cpu_var(current_kprobe) = &ri->rp->kp;
get_kprobe_ctlblk()->kprobe_status = KPROBE_HIT_ACTIVE;
ri->rp->handler(ri, regs);
__get_cpu_var(current_kprobe) = NULL;
}
-#else
- if (ri->rp && ri->rp->handler)
- ri->rp->handler(ri, regs);
-#endif
+
orig_ret_address = (unsigned long)ri->ret_addr;
recycle_rp_inst(ri, &empty_rp);

@@ -678,28 +719,14 @@ void *__kprobes trampoline_handler(struct pt_regs *regs)
}

kretprobe_assert(ri, orig_ret_address, trampoline_address);
-#ifdef CONFIG_X86_64
- regs->ip = orig_ret_address;
- reset_current_kprobe();
-#endif
spin_unlock_irqrestore(&kretprobe_lock, flags);
-#ifdef CONFIG_X86_64
- preempt_enable_no_resched();
-#endif
+
hlist_for_each_entry_safe(ri, node, tmp, &empty_rp, hlist) {
hlist_del(&ri->hlist);
kfree(ri);
}
-#ifdef CONFIG_X86_32
+
return (void*)orig_ret_address;
-#else
- /*
- * By returning a non-zero value, we are telling
- * kprobe_handler() that we don't want the post_handler
- * to run (and have re-enabled preemption)
- */
- return 1;
-#endif
}

/*
@@ -1042,27 +1069,12 @@ int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
return 0;
}

-#ifdef CONFIG_X86_64
-static struct kprobe trampoline_p = {
- .addr = (kprobe_opcode_t *) &kretprobe_trampoline,
- .pre_handler = trampoline_probe_handler
-};
-#endif
-
int __kprobes arch_trampoline_kprobe(struct kprobe *p)
{
-#ifdef CONFIG_X86_64
- if (p->addr == (kprobe_opcode_t *)&kretprobe_trampoline)
- return 1;
-#endif
return 0;
}

int __init arch_init_kprobes(void)
{
-#ifdef CONFIG_X86_64
- return register_kprobe(&trampoline_p);
-#else
return 0;
-#endif
}
--
1.5.4.rc0.1083.gf568

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