On 4 August 2016 at 17:22, Josh Poimboeuf <jpoim...@redhat.com> wrote:
> diff --git a/arch/x86/kernel/unwind_frame.c b/arch/x86/kernel/unwind_frame.c
> new file mode 100644
> index 0000000..f28f1b5
> --- /dev/null
> +++ b/arch/x86/kernel/unwind_frame.c
> @@ -0,0 +1,84 @@
> +#include <linux/sched.h>
> +#include <asm/ptrace.h>
> +#include <asm/bitops.h>
> +#include <asm/stacktrace.h>
> +#include <asm/unwind.h>
> +
> +#define FRAME_HEADER_SIZE (sizeof(long) * 2)
> +
> +unsigned long unwind_get_return_address(struct unwind_state *state)
> +{
> + unsigned long *addr_p = unwind_get_return_address_ptr(state);
> + unsigned long addr;
> +
> + if (state->stack_info.type == STACK_TYPE_UNKNOWN)
> + return 0;
> +
> + addr = ftrace_graph_ret_addr(state->task, &state->graph_idx, *addr_p,
> + addr_p);
> +
> + return __kernel_text_address(addr) ? addr : 0;
> +}
> +EXPORT_SYMBOL_GPL(unwind_get_return_address);
> +
> +static bool update_stack_state(struct unwind_state *state, void *addr,
> + size_t len)
> +{
> + struct stack_info *info = &state->stack_info;
> +
> + if (on_stack(info, addr, len))
> + return true;
> +
> + if (get_stack_info(info->next_sp, state->task, info,
> + &state->stack_mask))
> + goto unknown;
> +
> + if (!on_stack(info, addr, len))
> + goto unknown;
> +
> + return true;
> +
> +unknown:
> + info->type = STACK_TYPE_UNKNOWN;
> + return false;
> +}
> +
> +bool unwind_next_frame(struct unwind_state *state)
> +{
> + unsigned long *next_bp;
> +
> + if (unwind_done(state))
> + return false;
> +
> + next_bp = (unsigned long *)*state->bp;
> +
> + /*
> + * Make sure the next frame is on a valid stack and can be accessed
> + * safely.
> + */
> + if (!update_stack_state(state, next_bp, FRAME_HEADER_SIZE))
> + return false;
> +
> + /* move to the next frame */
> + state->bp = next_bp;
> + return true;
> +}
> +EXPORT_SYMBOL_GPL(unwind_next_frame);
> +
> +void __unwind_start(struct unwind_state *state, struct task_struct *task,
> + struct pt_regs *regs, unsigned long *sp)
> +{
> + memset(state, 0, sizeof(*state));
> +
> + state->task = task;
> + state->bp = get_frame_pointer(task, regs);
> +
> + get_stack_info(state->bp, state->task, &state->stack_info,
> + &state->stack_mask);
> + update_stack_state(state, state->bp, FRAME_HEADER_SIZE);
> +
> + /* unwind to the first frame after the specified stack pointer */
> + while (state->bp < sp && !unwind_done(state))
> + unwind_next_frame(state);
Do we unwind all the frames here? It seems strange to me that in a
function named __unwind_start(), we unwind all the frames.
> +}
> +EXPORT_SYMBOL_GPL(__unwind_start);
> diff --git a/arch/x86/kernel/unwind_guess.c b/arch/x86/kernel/unwind_guess.c
> new file mode 100644
> index 0000000..e03df5a
> --- /dev/null
> +++ b/arch/x86/kernel/unwind_guess.c
> @@ -0,0 +1,40 @@
> +#include <linux/sched.h>
> +#include <linux/ftrace.h>
> +#include <asm/ptrace.h>
> +#include <asm/bitops.h>
> +#include <asm/stacktrace.h>
> +#include <asm/unwind.h>
> +
> +bool unwind_next_frame(struct unwind_state *state)
> +{
> + struct stack_info *info = &state->stack_info;
> +
> + if (info->type == STACK_TYPE_UNKNOWN)
> + return false;
> +
> + do {
> + for (state->sp++; state->sp < info->end; state->sp++)
> + if (__kernel_text_address(*state->sp))
> + return true;
> +
> + state->sp = info->next_sp;
> +
> + } while (!get_stack_info(state->sp, state->task, info,
> + &state->stack_mask));
> +
> + return false;
> +}
> +
> +void __unwind_start(struct unwind_state *state, struct task_struct *task,
> + struct pt_regs *regs, unsigned long *sp)
> +{
> + memset(state, 0, sizeof(*state));
> +
> + state->task = task;
> + state->sp = sp;
> +
> + get_stack_info(sp, state->task, &state->stack_info,
> &state->stack_mask);
> +
> + if (!__kernel_text_address(*sp))
> + unwind_next_frame(state);
> +}
> --
> 2.7.4
>
Why is it that you need to export symbols in unwind_frame.c but not in
unwind_guess.c. As per the Makefile, we would be compiling either of
those two files. Should not EXPORT_SYMBOL_GPL(__unwind_start) appear
in both files?
--
Nilay
