[PATCH 5.14 333/849] parisc/unwind: fix unwinder when CONFIG_64BIT is enabled

Greg Kroah-Hartman
2021-11-15T22:51:14Z

From: Sven Schnelle <svens@stackframe.org>

[ Upstream commit 8e0ba125c2bf1030af3267058019ba86da96863f ]

With 64 bit kernels unwind_special() is not working because
it compares the pc to the address of the function descriptor.
Add a helper function that compares pc with the dereferenced
address. This fixes all of the backtraces on my c8000. Without
this changes, a lot of backtraces are missing in kdb or the
show-all-tasks command from /proc/sysrq-trigger.

Signed-off-by: Sven Schnelle <svens@stackframe.org>
Signed-off-by: Helge Deller <deller@gmx.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
arch/parisc/kernel/unwind.c | 21 ++++++++++++++-------
1 file changed, 14 insertions(+), 7 deletions(-)

diff --git a/arch/parisc/kernel/unwind.c b/arch/parisc/kernel/unwind.c
index 87ae476d1c4f5..86a57fb0e6fae 100644
--- a/arch/parisc/kernel/unwind.c
+++ b/arch/parisc/kernel/unwind.c
@@ -21,6 +21,8 @@
#include <asm/ptrace.h>

#include <asm/unwind.h>
+#include <asm/switch_to.h>
+#include <asm/sections.h>

/* #define DEBUG 1 */
#ifdef DEBUG
@@ -203,6 +205,11 @@ int __init unwind_init(void)
return 0;
}

+static bool pc_is_kernel_fn(unsigned long pc, void *fn)
+{
+ return (unsigned long)dereference_kernel_function_descriptor(fn) == pc;
+}
+
static int unwind_special(struct unwind_frame_info *info, unsigned long pc, int frame_size)
{
/*
@@ -221,7 +228,7 @@ static int unwind_special(struct unwind_frame_info *info, unsigned long pc, int
extern void * const _call_on_stack;
#endif /* CONFIG_IRQSTACKS */

- if (pc == (unsigned long) &handle_interruption) {
+ if (pc_is_kernel_fn(pc, handle_interruption)) {
struct pt_regs *regs = (struct pt_regs *)(info->sp - frame_size - PT_SZ_ALGN);
dbg("Unwinding through handle_interruption()\n");
info->prev_sp = regs->gr[30];
@@ -229,13 +236,13 @@ static int unwind_special(struct unwind_frame_info *info, unsigned long pc, int
return 1;
}

- if (pc == (unsigned long) &ret_from_kernel_thread ||
- pc == (unsigned long) &syscall_exit) {
+ if (pc_is_kernel_fn(pc, ret_from_kernel_thread) ||
+ pc_is_kernel_fn(pc, syscall_exit)) {
info->prev_sp = info->prev_ip = 0;
return 1;
}

- if (pc == (unsigned long) &intr_return) {
+ if (pc_is_kernel_fn(pc, intr_return)) {
struct pt_regs *regs;

dbg("Found intr_return()\n");
@@ -246,20 +253,20 @@ static int unwind_special(struct unwind_frame_info *info, unsigned long pc, int
return 1;
}

- if (pc == (unsigned long) &_switch_to_ret) {
+ if (pc_is_kernel_fn(pc, _switch_to) ||
+ pc_is_kernel_fn(pc, _switch_to_ret)) {
info->prev_sp = info->sp - CALLEE_SAVE_FRAME_SIZE;
info->prev_ip = *(unsigned long *)(info->prev_sp - RP_OFFSET);
return 1;
}

#ifdef CONFIG_IRQSTACKS
- if (pc == (unsigned long) &_call_on_stack) {
+ if (pc_is_kernel_fn(pc, _call_on_stack)) {
info->prev_sp = *(unsigned long *)(info->sp - FRAME_SIZE - REG_SZ);
info->prev_ip = *(unsigned long *)(info->sp - FRAME_SIZE - RP_OFFSET);
return 1;
}
#endif
-
return 0;
}

--
2.33.0