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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: Tobias Huschle <huschle@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
This commit is contained in:
Vasily Gorbik 2022-03-05 13:16:07 +01:00
parent d81675b60d
commit 708b137639
2 changed files with 3 additions and 2 deletions
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1
arch/s390/Kconfig
View File

@ -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

4
arch/s390/kernel/unwind_bc.c
View File

@ -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);
}