Re: [PATCH v4 19/39] unwind_user/sframe: Add support for reading .sframe contents

Josh Poimboeuf
2025-02-04T19:42:53Z

On Thu, Jan 30, 2025 at 07:51:15PM +0000, Weinan Liu wrote:
> Nit: swap() might be a simplify way to alternate pointers between two
> fre_addr[] entries.
>
> For example,
>
> static __always_inline int __find_fre(struct sframe_section *sec,
> struct sframe_fde *fde, unsigned long ip,
> struct unwind_user_frame *frame)
> {
> /* intialize fres[] with invalid value */
> struct sframe_fre fres[2] = {0};
> struct sframe_fre *fre = &fres[1], *prev_fre = fres;
>
> for (i = 0; i < fde->fres_num; i++) {
> swap(fre, next_fre);
> ret = __read_fre(sec, fde, fre_addr, fre);

Problem is, if it breaks out early here on the first iteration:

> if (fre->ip_off > ip_off)
> break;
> }
>
> if (fre->size == 0)
> return -EINVAL;

Then fre isn't valid even though it has a nonzero size.

--
Josh