s390/kprobes: enable kretprobes framepointer verification

Vasily Gorbik · Vasily Gorbik · commit 09bc20c8fb35 · 2022-03-27T22:18:39.000+02:00
Use regs-&gt;gprs[15] for framepointer verification. This enables
additional sanity checks for nested kretprobes.

Reviewed-by: Tobias Huschle &lt;huschle@linux.ibm.com&gt;
Signed-off-by: Vasily Gorbik &lt;gor@linux.ibm.com&gt;
diff --git a/arch/s390/kernel/kprobes.c b/arch/s390/kernel/kprobes.c
@@ -284,11 +284,11 @@ NOKPROBE_SYMBOL(pop_kprobe);
 
 void arch_prepare_kretprobe(struct kretprobe_instance *ri, struct pt_regs *regs)
 {
-	ri->ret_addr = (kprobe_opcode_t *) regs->gprs[14];
-	ri->fp = NULL;
+	ri->ret_addr = (kprobe_opcode_t *)regs->gprs[14];
+	ri->fp = (void *)regs->gprs[15];
 
 	/* Replace the return addr with trampoline addr */
-	regs->gprs[14] = (unsigned long) &__kretprobe_trampoline;
+	regs->gprs[14] = (unsigned long)&__kretprobe_trampoline;
 }
 NOKPROBE_SYMBOL(arch_prepare_kretprobe);
 
@@ -385,7 +385,7 @@ NOKPROBE_SYMBOL(arch_kretprobe_fixup_return);
  */
 void trampoline_probe_handler(struct pt_regs *regs)
 {
-	kretprobe_trampoline_handler(regs, NULL);
+	kretprobe_trampoline_handler(regs, (void *)regs->gprs[15]);
 }
 NOKPROBE_SYMBOL(trampoline_probe_handler);
 

Original file line number	Diff line number	Diff line change
`@@ -284,11 +284,11 @@ NOKPROBE_SYMBOL(pop_kprobe);`
`284`	`284`
`285`	`285`	`void arch_prepare_kretprobe(struct kretprobe_instance ri, struct pt_regs regs)`
`286`	`286`	`{`
`287`		`- ri->ret_addr = (kprobe_opcode_t *) regs->gprs[14];`
`288`		`- ri->fp = NULL;`
	`287`	`+ ri->ret_addr = (kprobe_opcode_t *)regs->gprs[14];`
	`288`	`+ ri->fp = (void *)regs->gprs[15];`
`289`	`289`
`290`	`290`	`/* Replace the return addr with trampoline addr */`
`291`		`- regs->gprs[14] = (unsigned long) &__kretprobe_trampoline;`
	`291`	`+ regs->gprs[14] = (unsigned long)&__kretprobe_trampoline;`
`292`	`292`	`}`
`293`	`293`	`NOKPROBE_SYMBOL(arch_prepare_kretprobe);`
`294`	`294`
`@@ -385,7 +385,7 @@ NOKPROBE_SYMBOL(arch_kretprobe_fixup_return);`
`385`	`385`	`*/`
`386`	`386`	`void trampoline_probe_handler(struct pt_regs *regs)`
`387`	`387`	`{`
`388`		`- kretprobe_trampoline_handler(regs, NULL);`
	`388`	`+ kretprobe_trampoline_handler(regs, (void *)regs->gprs[15]);`
`389`	`389`	`}`
`390`	`390`	`NOKPROBE_SYMBOL(trampoline_probe_handler);`
`391`	`391`