On Wed, Mar 02, 2016 at 05:09:35PM -0800, Peter Feiner wrote:
> Functions to walk stack and print backtrace. The stack's unadorned as
>
> STACK: addr addr addr ...
>
> A follow-up patch post-processes the output to pretty-print the stack.
>
> Stack walker is just a stub on arm and ppc.
>
> Signed-off-by: Peter Feiner <pfeiner@xxxxxxxxxx>
> ---
> Makefile | 3 ++-
> arm/Makefile.common | 1 +
> lib/arm/dump_stack.c | 6 ++++++
> lib/libcflat.h | 4 ++++
> lib/powerpc/dump_stack.c | 6 ++++++
> lib/printf.c | 37 +++++++++++++++++++++++++++++++++++++
> lib/x86/dump_stack.c | 24 ++++++++++++++++++++++++
> powerpc/Makefile.common | 1 +
> x86/Makefile.common | 4 ++++
> 9 files changed, 85 insertions(+), 1 deletion(-)
> create mode 100644 lib/arm/dump_stack.c
> create mode 100644 lib/powerpc/dump_stack.c
> create mode 100644 lib/x86/dump_stack.c
>
> diff --git a/Makefile b/Makefile
> index ddba941..40ea4ec 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -42,7 +42,8 @@ cc-option = $(shell if $(CC) $(1) -S -o /dev/null -xc /dev/null \
>
> CFLAGS += -g
> CFLAGS += $(autodepend-flags) -Wall
> -CFLAGS += $(call cc-option, -fomit-frame-pointer, "")
> +frame-pointer-flag=-f$(if $(KEEP_FRAME_POINTER),no-,)omit-frame-pointer
> +CFLAGS += $(call cc-option, $(frame-pointer-flag), "")
> CFLAGS += $(call cc-option, -fno-stack-protector, "")
> CFLAGS += $(call cc-option, -fno-stack-protector-all, "")
>
> diff --git a/arm/Makefile.common b/arm/Makefile.common
> index dd3a0ca..054bdee 100644
> --- a/arm/Makefile.common
> +++ b/arm/Makefile.common
> @@ -39,6 +39,7 @@ cflatobjs += lib/arm/mmu.o
> cflatobjs += lib/arm/bitops.o
> cflatobjs += lib/arm/psci.o
> cflatobjs += lib/arm/smp.o
> +cflatobjs += lib/arm/dump_stack.o
>
> libeabi = lib/arm/libeabi.a
> eabiobjs = lib/arm/eabi_compat.o
> diff --git a/lib/arm/dump_stack.c b/lib/arm/dump_stack.c
> new file mode 100644
> index 0000000..528ba63
> --- /dev/null
> +++ b/lib/arm/dump_stack.c
> @@ -0,0 +1,6 @@
> +#include "libcflat.h"
> +
> +int walk_stack(unsigned long bp, unsigned long *stack, int max_depth)
> +{
> + return 0;
> +}
> diff --git a/lib/libcflat.h b/lib/libcflat.h
> index 1f0049c..42c94df 100644
> --- a/lib/libcflat.h
> +++ b/lib/libcflat.h
> @@ -65,6 +65,10 @@ extern void report_xfail(const char *msg_fmt, bool xfail, bool pass, ...);
> extern void report_abort(const char *msg_fmt, ...);
> extern int report_summary(void);
>
> +int walk_stack(unsigned long bp, unsigned long *stack, int max_depth);
> +void dump_stack(unsigned long ip, unsigned long bp);
> +void dump_current_stack(void);
The inputs are a bit x86ish. On ARM, for example, we call them pc and
fp. Acutally, how about we implement backtrace(3) instead? And then wrap
print_current_stack(void) around that.
Also, instead of building on a single arch function, walk_stack, how about
two
void *arch_frame_address(unsigned int level);
void *arch_return_address(void *frame, unsigned int level);
The architecture may be able to easily implement these with gcc builtins,
or not. I've added *frame to arch_return_address' parameters in case
__builtin_return_address(level) doesn't work.
And, let's just require the architectures to have the functions, not that
they have a dump_stack.c file. If we include lib/asm/<ARCH>/stack.h, or
whatever you want to call it, then the arch could just supply some inlines
there.
> +
> #define ARRAY_SIZE(_a) (sizeof(_a)/sizeof((_a)[0]))
>
> #define container_of(ptr, type, member) ({ \
> diff --git a/lib/powerpc/dump_stack.c b/lib/powerpc/dump_stack.c
> new file mode 100644
> index 0000000..528ba63
> --- /dev/null
> +++ b/lib/powerpc/dump_stack.c
> @@ -0,0 +1,6 @@
> +#include "libcflat.h"
> +
> +int walk_stack(unsigned long bp, unsigned long *stack, int max_depth)
> +{
> + return 0;
> +}
> diff --git a/lib/printf.c b/lib/printf.c
> index 2aec59a..e97fca9 100644
> --- a/lib/printf.c
> +++ b/lib/printf.c
> @@ -259,3 +259,40 @@ int printf(const char *fmt, ...)
> puts(buf);
> return r;
> }
> +
> +static void print_stack(unsigned long *stack, int depth,
> + bool top_is_return_address)
> +{
> + int i;
> +
> + printf("\tSTACK: " );
> + for (i = 0; i < depth; i++) {
> + int offset = -1;
> + if (i == 0 && !top_is_return_address)
> + offset = 0;
> + printf(" %lx", stack[i] + offset);
I'm afraid I don't understand the use of offset here. I fear it may
be x86-ness leaked into the arch-neutral print_stack().
> + }
> + printf("\n");
> +}
> +
> +#define MAX_DEPTH 10
> +
> +void dump_stack(unsigned long ip, unsigned long bp)
> +{
> + unsigned long stack[MAX_DEPTH];
> + int depth;
> +
> + stack[0] = ip;
> + depth = walk_stack(bp, &stack[1], MAX_DEPTH - 1);
> + print_stack(stack, depth + 1, false);
> +}
When would dump_stack() be useful, as opposed to dump_current_stack?
> +
> +void dump_current_stack(void)
> +{
> + unsigned long stack[MAX_DEPTH];
> + int depth;
> +
> + depth = walk_stack((unsigned long)__builtin_frame_address(1), stack,
> + MAX_DEPTH);
> + print_stack(stack, depth, true);
> +}
> diff --git a/lib/x86/dump_stack.c b/lib/x86/dump_stack.c
> new file mode 100644
> index 0000000..6e9d126
> --- /dev/null
> +++ b/lib/x86/dump_stack.c
> @@ -0,0 +1,24 @@
> +#include "libcflat.h"
> +
> +int walk_stack(unsigned long bp, unsigned long *stack, int max_depth)
> +{
> + static int walking;
> + int depth = 0;
> + unsigned long *frame = (unsigned long *) bp;
> +
> + if (walking) {
> + printf("RECURSIVE STACK WALK!!!\n");
> + return 0;
> + }
> + walking = 1;
> +
> + for (depth = 0; depth < max_depth; depth++) {
> + stack[depth] = frame[1];
> + if (stack[depth] == 0)
> + break;
> + frame = (unsigned long *) frame[0];
> + }
> +
> + walking = 0;
> + return depth;
> +}
> diff --git a/powerpc/Makefile.common b/powerpc/Makefile.common
> index 2ce6494..694dea0 100644
> --- a/powerpc/Makefile.common
> +++ b/powerpc/Makefile.common
> @@ -30,6 +30,7 @@ cflatobjs += lib/powerpc/io.o
> cflatobjs += lib/powerpc/hcall.o
> cflatobjs += lib/powerpc/setup.o
> cflatobjs += lib/powerpc/rtas.o
> +cflatobjs += lib/powerpc/dump_stack.o
>
> FLATLIBS = $(libcflat) $(LIBFDT_archive)
> %.elf: CFLAGS += $(arch_CFLAGS)
> diff --git a/x86/Makefile.common b/x86/Makefile.common
> index 3a14fea..d7c7eab 100644
> --- a/x86/Makefile.common
> +++ b/x86/Makefile.common
> @@ -12,6 +12,7 @@ cflatobjs += lib/x86/atomic.o
> cflatobjs += lib/x86/desc.o
> cflatobjs += lib/x86/isr.o
> cflatobjs += lib/x86/acpi.o
> +cflatobjs += lib/x86/dump_stack.o
>
> $(libcflat): LDFLAGS += -nostdlib
> $(libcflat): CFLAGS += -ffreestanding -I lib
> @@ -19,6 +20,9 @@ $(libcflat): CFLAGS += -ffreestanding -I lib
> CFLAGS += -m$(bits)
> CFLAGS += -O1
>
> +# dump_stack.o relies on frame pointers.
> +KEEP_FRAME_POINTER := y
> +
> libgcc := $(shell $(CC) -m$(bits) --print-libgcc-file-name)
>
> FLATLIBS = lib/libcflat.a $(libgcc)
> --
> 2.7.0.rc3.207.g0ac5344
Thanks,
drew
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