On Mon, Mar 07, 2016 at 09:46:53AM -0800, Peter Feiner wrote:
> Functions to walk stack and print backtrace. The stack's unadorned as
>
> STACK: [@]addr addr addr ...
>
> where the optional @ indicates that addr isn't a return address.
>
> A follow-up patch post-processes the output to pretty-print the stack.
>
> Frame stack walker is just a stub on arm and ppc.
>
> Signed-off-by: Peter Feiner <pfeiner@xxxxxxxxxx>
> ---
> Makefile | 6 ++--
> lib/arm/asm/stack.h | 0
> lib/arm64/asm/stack.h | 0
> lib/asm-generic/stack.c | 3 ++
> lib/libcflat.h | 3 ++
> lib/powerpc/asm/stack.h | 0
> lib/ppc64/asm/stack.h | 0
> lib/stack.c | 96 +++++++++++++++++++++++++++++++++++++++++++++++++
> lib/stack.h | 20 +++++++++++
> lib/x86/asm/stack.h | 18 ++++++++++
> lib/x86/stack.c | 25 +++++++++++++
> x86/Makefile.common | 4 +++
> 12 files changed, 173 insertions(+), 2 deletions(-)
> create mode 100644 lib/arm/asm/stack.h
> create mode 100644 lib/arm64/asm/stack.h
> create mode 100644 lib/asm-generic/stack.c
> create mode 100644 lib/powerpc/asm/stack.h
> create mode 100644 lib/ppc64/asm/stack.h
> create mode 100644 lib/stack.c
> create mode 100644 lib/stack.h
> create mode 100644 lib/x86/asm/stack.h
> create mode 100644 lib/x86/stack.c
>
> diff --git a/Makefile b/Makefile
> index 72e6711..c53aff6 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -22,7 +22,8 @@ cflatobjs := \
> lib/printf.o \
> lib/string.o \
> lib/abort.o \
> - lib/report.o
> + lib/report.o \
> + lib/stack.o
>
> # libfdt paths
> LIBFDT_objdir = lib/libfdt
> @@ -42,7 +43,8 @@ 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/lib/arm/asm/stack.h b/lib/arm/asm/stack.h
> new file mode 100644
> index 0000000..e69de29
> diff --git a/lib/arm64/asm/stack.h b/lib/arm64/asm/stack.h
> new file mode 100644
> index 0000000..e69de29
> diff --git a/lib/asm-generic/stack.c b/lib/asm-generic/stack.c
> new file mode 100644
> index 0000000..40c67c2
> --- /dev/null
> +++ b/lib/asm-generic/stack.c
> @@ -0,0 +1,3 @@
> +#include <libcflat.h>
> +#include <asm-generic/stack.h>
> +
Looks like you forgot to remove this file.
> diff --git a/lib/libcflat.h b/lib/libcflat.h
> index b58a8a1..55bddca 100644
> --- a/lib/libcflat.h
> +++ b/lib/libcflat.h
> @@ -81,6 +81,9 @@ 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);
>
> +extern void dump_stack(void);
> +extern void dump_frame_stack(const void *instruction, const void *frame);
> +
> #define ARRAY_SIZE(_a) (sizeof(_a)/sizeof((_a)[0]))
>
> #define container_of(ptr, type, member) ({ \
> diff --git a/lib/powerpc/asm/stack.h b/lib/powerpc/asm/stack.h
> new file mode 100644
> index 0000000..e69de29
> diff --git a/lib/ppc64/asm/stack.h b/lib/ppc64/asm/stack.h
> new file mode 100644
> index 0000000..e69de29
> diff --git a/lib/stack.c b/lib/stack.c
> new file mode 100644
> index 0000000..035fe27
> --- /dev/null
> +++ b/lib/stack.c
> @@ -0,0 +1,96 @@
> +#include <libcflat.h>
> +#include <stack.h>
> +
> +#define MAX_DEPTH 20
> +
> +static void print_stack(const void **return_addrs, int depth,
> + bool top_is_return_address)
> +{
> + int i = 0;
> +
> + printf("\tSTACK:");
> +
> + /* @addr indicates a non-return address, as expected by the stack
> + * pretty printer script. */
> + if (depth > 0 && !top_is_return_address) {
> + printf(" @%lx", (unsigned long) return_addrs[0]);
> + i++;
> + }
> +
> + for (; i < depth; i++) {
> + printf(" %lx", (unsigned long) return_addrs[i]);
> + }
> + printf("\n");
> +}
> +
> +void dump_stack(void)
> +{
> + const void *return_addrs[MAX_DEPTH];
> + int depth;
> +
> + depth = backtrace(return_addrs, MAX_DEPTH);
> + print_stack(return_addrs, depth, true);
> +}
> +
> +void dump_frame_stack(const void *instruction, const void *frame)
> +{
> + const void *return_addrs[MAX_DEPTH];
> + int depth;
> +
> + return_addrs[0] = instruction;
> + depth = backtrace_frame(frame, &return_addrs[1], MAX_DEPTH - 1);
> + print_stack(return_addrs, depth + 1, false);
> +}
> +
> +#ifndef HAVE_ARCH_BACKTRACE
> +int backtrace(const void **return_addrs, int max_depth)
> +{
> + static int walking;
> + int depth = 0;
> + void *addr;
> +
> + if (walking) {
> + printf("RECURSIVE STACK WALK!!!\n");
> + return 0;
> + }
> + walking = 1;
> +
> + /* __builtin_return_address requires a compile-time constant argument */
> +#define GET_RETURN_ADDRESS(i) \
> + if (max_depth == i) \
> + goto done; \
> + addr = __builtin_return_address(i + 1); \
Is the +1 to skip a level, which means addr is an address two levels up?
If we do that, then won't we skip the callers of backtrace, which may or
may not be dump_stack?
> + if (!addr) \
> + goto done; \
> + return_addrs[i] = __builtin_extract_return_addr(addr); \
So here we put the i+1th return address into return_addrs[i]. I find
that a bit confusing. Maybe we should leave it to the callers of
backtrace to do any level skipping they want, i.e. here we shouldn't
skip anything, but dump_stack could start printing at i=1.
> + depth = i + 1; \
> +
> + GET_RETURN_ADDRESS(0)
> + GET_RETURN_ADDRESS(1)
> + GET_RETURN_ADDRESS(2)
> + GET_RETURN_ADDRESS(3)
> + GET_RETURN_ADDRESS(4)
> + GET_RETURN_ADDRESS(5)
> + GET_RETURN_ADDRESS(6)
> + GET_RETURN_ADDRESS(7)
> + GET_RETURN_ADDRESS(8)
> + GET_RETURN_ADDRESS(9)
> + GET_RETURN_ADDRESS(10)
> + GET_RETURN_ADDRESS(11)
> + GET_RETURN_ADDRESS(12)
> + GET_RETURN_ADDRESS(13)
> + GET_RETURN_ADDRESS(14)
> + GET_RETURN_ADDRESS(15)
> + GET_RETURN_ADDRESS(16)
> + GET_RETURN_ADDRESS(17)
> + GET_RETURN_ADDRESS(18)
> + GET_RETURN_ADDRESS(19)
> + GET_RETURN_ADDRESS(20)
> +
> +#undef GET_RETURN_ADDRESS
> +
> +done:
> + walking = 0;
> + return depth;
> +}
> +#endif /* HAVE_ARCH_BACKTRACE */
> diff --git a/lib/stack.h b/lib/stack.h
> new file mode 100644
> index 0000000..bb6b9aa
> --- /dev/null
> +++ b/lib/stack.h
> @@ -0,0 +1,20 @@
> +#ifndef _STACK_H_
> +#define _STACK_H_
> +
> +#include <libcflat.h>
> +#include <asm/stack.h>
> +
> +#ifndef HAVE_ARCH_BACKTRACE_FRAME
> +static inline int
> +backtrace_frame(const void *frame __unused, const void **return_addrs __unused,
> + int max_depth __unused)
> +{
> + return 0;
> +}
> +#endif
> +
> +#ifndef HAVE_ARCH_BACKTRACE
> +int backtrace(const void **return_addrs, int max_depth);
> +#endif
> +
> +#endif
> diff --git a/lib/x86/asm/stack.h b/lib/x86/asm/stack.h
> new file mode 100644
> index 0000000..bb1c2c0
> --- /dev/null
> +++ b/lib/x86/asm/stack.h
> @@ -0,0 +1,18 @@
> +#ifndef _X86ASM_STACK_H_
> +#define _X86ASM_STACK_H_
> +
> +#ifndef _STACK_H_
> +#error Do not directly include <asm/stack.h>. Just use <stack.h>.
> +#endif
> +
> +#define HAVE_ARCH_BACKTRACE_FRAME
> +int backtrace_frame(const void *frame, const void **return_addrs, int max_depth);
> +
> +#define HAVE_ARCH_BACKTRACE
> +static inline int backtrace(const void **return_addrs, int max_depth)
> +{
> + return backtrace_frame(__builtin_frame_address(0), return_addrs,
> + max_depth);
> +}
> +
> +#endif
> diff --git a/lib/x86/stack.c b/lib/x86/stack.c
> new file mode 100644
> index 0000000..3227800
> --- /dev/null
> +++ b/lib/x86/stack.c
> @@ -0,0 +1,25 @@
> +#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;
> + const unsigned long *bp = (unsigned long *) frame;
> +
> + if (walking) {
> + printf("RECURSIVE STACK WALK!!!\n");
> + return 0;
> + }
> + walking = 1;
> +
> + for (depth = 0; depth < max_depth; depth++) {
> + return_addrs[depth] = (void *) bp[1];
> + if (return_addrs[depth] == 0)
> + break;
> + bp = (unsigned long *) bp[0];
> + }
> +
> + walking = 0;
> + return depth;
> +}
> diff --git a/x86/Makefile.common b/x86/Makefile.common
> index 3a14fea..ca80367 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/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
>
> --
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Thanks,
drew
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