Re: [PATCH v3 09/19] unwind: Introduce sframe user space unwinding

From: Steven Rostedt
Date: Wed Nov 13 2024 - 17:25:28 EST


On Wed, 13 Nov 2024 17:21:18 -0500
Steven Rostedt <rostedt@xxxxxxxxxxx> wrote:

> > diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c
> > index 434c548f0837..64cc3c1188ca 100644
> > --- a/fs/binfmt_elf.c
> > +++ b/fs/binfmt_elf.c
> > @@ -842,7 +842,8 @@ static int load_elf_binary(struct linux_binprm *bprm)
> > int first_pt_load = 1;
> > unsigned long error;
> > struct elf_phdr *elf_ppnt, *elf_phdata, *interp_elf_phdata = NULL;
> > - struct elf_phdr *elf_property_phdata = NULL, *sframe_phdr = NULL;
> > + struct elf_phdr *elf_property_phdata = NULL;
> > + unsigned long sframe_vaddr = 0;
>
> Could not just save the pointer to the sframe phd, as it gets freed before we need it.
^^^
phdr


> > diff --git a/kernel/unwind/sframe.c b/kernel/unwind/sframe.c
> > index 933e47696e29..ca4ef0b72772 100644
> > --- a/kernel/unwind/sframe.c
> > +++ b/kernel/unwind/sframe.c
> > @@ -73,15 +73,15 @@ static int find_fde(struct sframe_section *sec, unsigned long ip,
> > struct sframe_fde *fde)
> > {
> > struct sframe_fde __user *first, *last, *found = NULL;
> > - u32 ip_off, func_off_low = 0, func_off_high = -1;
> > + s32 ip_off, func_off_low = INT_MIN, func_off_high = INT_MAX;
>
> The ip_off is a signed it. I wrote a program to dump out the sframe section
^^
int


> of files, and I had:
>
> ffffed88: (1020) size: 16 off: 146 num: 2 info: 1 rep:16
> ffffed98: (1030) size: 336 off: 154 num: 2 info:17 rep:16
> ffffefe1: (1279) size: 113 off: 0 num: 4 info: 0 rep: 0
> fffff052: (12ea) size: 54 off: 15 num: 3 info: 0 rep: 0
> fffff088: (1320) size: 167 off: 26 num: 3 info: 0 rep: 0
> fffff12f: (13c7) size: 167 off: 37 num: 4 info: 0 rep: 0
> fffff1d6: (146e) size: 167 off: 52 num: 4 info: 0 rep: 0
> fffff27d: (1515) size: 22 off: 67 num: 4 info: 0 rep: 0
> fffff293: (152b) size: 141 off: 82 num: 4 info: 0 rep: 0
> fffff320: (15b8) size: 81 off: 97 num: 4 info: 0 rep: 0
> fffff371: (1609) size: 671 off: 112 num: 4 info: 1 rep: 0
> fffff610: (18a8) size: 171 off: 131 num: 4 info: 0 rep: 0
>
> The above turns was created by a loop of:
^^^^^^^^^
items were

No idea why I typed that :-p


I can't blame jetlag anymore.

-- Steve