Commit 708b1376 authored by Vasily Gorbik's avatar Vasily Gorbik
Browse files

s390/unwind: avoid duplicated unwinding entries for kretprobes 



Currently when unwinding starts from pt_regs or encounters pt_regs along
the way unwinder tries to yield 2 unwinding entries:
1. (reliable)     ip1: pt_regs->psw.addr,  sp1: regs->gprs[15]
2. (non-reliable) ip2: sp1->gprs[8] (r14), sp2: regs->gprs[15]

In case of kretprobes those are identical and serves no other purpose
than causing confusion over duplicated entries and cause kprobes tests
to fail. So, skip a duplicate non-reliable entry in this case.

With that kretprobes and unwinder implementation now comply with
ARCH_CORRECT_STACKTRACE_ON_KRETPROBE.

Reviewed-by: default avatarTobias Huschle <huschle@linux.ibm.com>
Signed-off-by: default avatarVasily Gorbik <gor@linux.ibm.com>
parent d81675b6

arch/s390/Kconfig

+1 −0
Original line number Diff line number Diff line
@@ -58,6 +58,7 @@ config S390 
	select ALTERNATE_USER_ADDRESS_SPACE

	select ARCH_32BIT_USTAT_F_TINODE

	select ARCH_BINFMT_ELF_STATE

	select ARCH_CORRECT_STACKTRACE_ON_KRETPROBE

	select ARCH_ENABLE_MEMORY_HOTPLUG if SPARSEMEM

	select ARCH_ENABLE_MEMORY_HOTREMOVE

	select ARCH_ENABLE_SPLIT_PMD_PTLOCK if PGTABLE_LEVELS > 2

arch/s390/kernel/unwind_bc.c

+2 −2
Original line number Diff line number Diff line
@@ -64,8 +64,8 @@ bool unwind_next_frame(struct unwind_state *state) 
		ip = READ_ONCE_NOCHECK(sf->gprs[8]);

		reliable = false;

		regs = NULL;

		if (!__kernel_text_address(ip)) {

			/* skip bogus %r14 */

		/* skip bogus %r14 or if is the same as regs->psw.addr */

		if (!__kernel_text_address(ip) || state->ip == unwind_recover_ret_addr(state, ip)) {

			state->regs = NULL;

			return unwind_next_frame(state);

		}