On Tue, Apr 19, 2016 at 7:28 AM, Andrew Jones <drjones@xxxxxxxxxx> wrote:
> This actually fixes the arm build too, as arm's __builtin_return_address
> doesn't allow any input other than zero, and thus the common backtrace()
> wasn't compiling.
>
> Signed-off-by: Andrew Jones <drjones@xxxxxxxxxx>
> ---
> arm/Makefile.arm | 4 ++++
> lib/arm/asm/stack.h | 3 +++
> lib/arm/processor.c | 1 +
> lib/arm/stack.c | 41 +++++++++++++++++++++++++++++++++++++++++
> 4 files changed, 49 insertions(+)
> create mode 100644 lib/arm/stack.c
>
> diff --git a/arm/Makefile.arm b/arm/Makefile.arm
> index 946422872532d..92f375700c45e 100644
> --- a/arm/Makefile.arm
> +++ b/arm/Makefile.arm
> @@ -8,12 +8,16 @@ ldarch = elf32-littlearm
> kernel_offset = 0x10000
> machine = -marm
>
> +# stack.o relies on frame pointers.
> +KEEP_FRAME_POINTER := y
> +
> CFLAGS += $(machine)
> CFLAGS += -mcpu=$(PROCESSOR)
>
> cstart.o = $(TEST_DIR)/cstart.o
> cflatobjs += lib/arm/spinlock.o
> cflatobjs += lib/arm/processor.o
> +cflatobjs += lib/arm/stack.o
>
> # arm specific tests
> tests =
> diff --git a/lib/arm/asm/stack.h b/lib/arm/asm/stack.h
> index fe97ac5d4b7d9..ebcedc2ef938c 100644
> --- a/lib/arm/asm/stack.h
> +++ b/lib/arm/asm/stack.h
> @@ -5,4 +5,7 @@
> #error Do not directly include <asm/stack.h>. Just use <stack.h>.
> #endif
>
> +#define HAVE_ARCH_BACKTRACE_FRAME
> +#define HAVE_ARCH_BACKTRACE
> +
> #endif
> diff --git a/lib/arm/processor.c b/lib/arm/processor.c
> index 1cef46ab28647..54fdb87ef0196 100644
> --- a/lib/arm/processor.c
> +++ b/lib/arm/processor.c
> @@ -108,6 +108,7 @@ void do_handle_exception(enum vector v, struct pt_regs *regs)
> asm volatile("mrc p15, 0, %0, c5, c0, 1": "=r" (fsr));
> printf("IFAR: %08lx IFSR: %08lx\n", far, fsr);
> }
> + dump_frame_stack((void *)regs->ARM_pc, (void *)regs->ARM_fp);
> abort();
> }
>
> diff --git a/lib/arm/stack.c b/lib/arm/stack.c
> new file mode 100644
> index 0000000000000..f58b731f277bf
> --- /dev/null
> +++ b/lib/arm/stack.c
> @@ -0,0 +1,41 @@
> +/*
> + * backtrace support (this is a modified lib/x86/stack.c)
> + *
> + * Copyright (C) 2016, Red Hat Inc, Andrew Jones <drjones@xxxxxxxxxx>
> + *
> + * This work is licensed under the terms of the GNU LGPL, version 2.
> + */
> +#include <libcflat.h>
> +#include <stack.h>
> +
> +int backtrace_frame(const void *frame, const void **return_addrs,
> + int max_depth)
> +{
> + static int walking;
> + int depth = 0;
Nit: unnecessary initialization.
> + const unsigned long *fp = (unsigned long *)frame;
> +
> + if (walking) {
> + printf("RECURSIVE STACK WALK!!!\n");
> + return 0;
> + }
> + walking = 1;
> +
> + for (depth = 0; depth < max_depth; depth++) {
> + if (!fp)
Interesting difference in termination case here from x86. Instead of
checking for a null return address, you check for a null frame
address. Any particular reason why?
> + break;
> + return_addrs[depth] = (void *)fp[0];
> + if (return_addrs[depth] == 0)
> + break;
> + fp = (unsigned long *)fp[-1];
> + }
> +
> + walking = 0;
> + return depth;
> +}
> +
> +int backtrace(const void **return_addrs, int max_depth)
> +{
> + return backtrace_frame(__builtin_frame_address(0),
> + return_addrs, max_depth);
> +}
> --
> 2.4.11
>
Nice fix!
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