On Mon, Feb 26, 2024 at 08:11:50PM +1000, Nicholas Piggin wrote:
> Add support for backtracing across interrupt stacks, and
> add interrupt frame backtrace for unhandled interrupts.
>
> Signed-off-by: Nicholas Piggin <npiggin@xxxxxxxxx>
> ---
> lib/powerpc/processor.c | 4 ++-
> lib/ppc64/asm/stack.h | 3 +++
> lib/ppc64/stack.c | 55 +++++++++++++++++++++++++++++++++++++++++
> powerpc/Makefile.ppc64 | 1 +
> powerpc/cstart64.S | 7 ++++--
> 5 files changed, 67 insertions(+), 3 deletions(-)
> create mode 100644 lib/ppc64/stack.c
>
> diff --git a/lib/powerpc/processor.c b/lib/powerpc/processor.c
> index ad0d95666..114584024 100644
> --- a/lib/powerpc/processor.c
> +++ b/lib/powerpc/processor.c
> @@ -51,7 +51,9 @@ void do_handle_exception(struct pt_regs *regs)
> return;
> }
>
> - printf("unhandled cpu exception %#lx at NIA:0x%016lx MSR:0x%016lx\n", regs->trap, regs->nip, regs->msr);
> + printf("Unhandled cpu exception %#lx at NIA:0x%016lx MSR:0x%016lx\n",
> + regs->trap, regs->nip, regs->msr);
> + dump_frame_stack((void *)regs->nip, (void *)regs->gpr[1]);
> abort();
> }
>
> diff --git a/lib/ppc64/asm/stack.h b/lib/ppc64/asm/stack.h
> index 9734bbb8f..94fd1021c 100644
> --- a/lib/ppc64/asm/stack.h
> +++ b/lib/ppc64/asm/stack.h
> @@ -5,4 +5,7 @@
> #error Do not directly include <asm/stack.h>. Just use <stack.h>.
> #endif
>
> +#define HAVE_ARCH_BACKTRACE
> +#define HAVE_ARCH_BACKTRACE_FRAME
> +
> #endif
> diff --git a/lib/ppc64/stack.c b/lib/ppc64/stack.c
> new file mode 100644
> index 000000000..fcb7fa860
> --- /dev/null
> +++ b/lib/ppc64/stack.c
> @@ -0,0 +1,55 @@
> +#include <libcflat.h>
> +#include <asm/ptrace.h>
> +#include <stack.h>
> +
> +extern char exception_stack_marker[];
> +
> +int backtrace_frame(const void *frame, const void **return_addrs, int max_depth)
> +{
> + static int walking;
> + int depth = 0;
> + const unsigned long *bp = (unsigned long *)frame;
> + void *return_addr;
> +
> + asm volatile("" ::: "lr"); /* Force it to save LR */
> +
> + if (walking) {
> + printf("RECURSIVE STACK WALK!!!\n");
> + return 0;
> + }
> + walking = 1;
> +
> + bp = (unsigned long *)bp[0];
> + return_addr = (void *)bp[2];
> +
> + for (depth = 0; bp && depth < max_depth; depth++) {
> + return_addrs[depth] = return_addr;
> + if (return_addrs[depth] == 0)
> + break;
> + if (return_addrs[depth] == exception_stack_marker) {
> + struct pt_regs *regs;
> +
> + regs = (void *)bp + STACK_FRAME_OVERHEAD;
> + bp = (unsigned long *)bp[0];
> + /* Represent interrupt frame with vector number */
> + return_addr = (void *)regs->trap;
> + if (depth + 1 < max_depth) {
> + depth++;
> + return_addrs[depth] = return_addr;
> + return_addr = (void *)regs->nip;
> + }
> + } else {
> + bp = (unsigned long *)bp[0];
> + return_addr = (void *)bp[2];
> + }
> + }
> +
> + walking = 0;
> + return depth;
> +}
> +
> +int backtrace(const void **return_addrs, int max_depth)
> +{
> + return backtrace_frame(__builtin_frame_address(0), return_addrs,
> + max_depth);
> +}
I'm about to post a series which has a couple treewide tracing changes
in them. Depending on which series goes first the other will need to
accommodate.
Thanks,
drew
