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

From: Steven Rostedt
Date: Wed Nov 13 2024 - 17:13:19 EST


On Wed, 13 Nov 2024 13:15:35 -0800
Josh Poimboeuf <jpoimboe@xxxxxxxxxx> wrote:

> On Wed, Nov 13, 2024 at 03:50:40PM -0500, Steven Rostedt wrote:
> > On Thu, 7 Nov 2024 17:59:08 +0100
> > Jens Remus <jremus@xxxxxxxxxxxxx> wrote:
> >
> > > On 28.10.2024 22:47, Josh Poimboeuf wrote:
> > > ...
> > > > diff --git a/kernel/unwind/sframe.c b/kernel/unwind/sframe.c
> > > ...
> > > > +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;
> > > > +
> > > > + ip_off = ip - sec->sframe_addr;
> > > > +
> > > > + first = (void __user *)sec->fdes_addr;
> > > > + last = first + sec->fdes_nr;
> > >
> > > Could it be that this needs to be:
> > >
> > > last = first + sec->fdes_nr - 1;
> >
> > Yep, I discovered the same issue.
>
> Indeed, thanks.
>

BTW, the following changes were needed to make it work for me:

-- Steve

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;
unsigned long elf_brk;
int retval, i;
unsigned long elf_entry;
@@ -951,7 +952,7 @@ static int load_elf_binary(struct linux_binprm *bprm)
break;

case PT_GNU_SFRAME:
- sframe_phdr = elf_ppnt;
+ sframe_vaddr = elf_ppnt->p_vaddr;
break;

case PT_LOPROC ... PT_HIPROC:
@@ -1344,8 +1345,8 @@ static int load_elf_binary(struct linux_binprm *bprm)
task_pid_nr(current), retval);
}

- if (sframe_phdr)
- sframe_add_section(load_bias + sframe_phdr->p_vaddr,
+ if (sframe_vaddr)
+ sframe_add_section(load_bias + sframe_vaddr,
start_code, end_code);

regs = current_pt_regs();
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;

ip_off = ip - sec->sframe_addr;

first = (void __user *)sec->fdes_addr;
- last = first + sec->fdes_nr;
+ last = first + sec->fdes_nr - 1;
while (first <= last) {
struct sframe_fde __user *mid;
- u32 func_off;
+ s32 func_off;

mid = first + ((last - first) / 2);

diff --git a/kernel/unwind/user.c b/kernel/unwind/user.c
index 11aadfade005..d9cd820150c5 100644
--- a/kernel/unwind/user.c
+++ b/kernel/unwind/user.c
@@ -97,7 +97,7 @@ int unwind_user_start(struct unwind_user_state *state)

if (current_has_sframe())
state->type = UNWIND_USER_TYPE_SFRAME;
- else if (IS_ENABLED(CONFIG_UNWIND_USER_FP))
+ else if (IS_ENABLED(CONFIG_HAVE_UNWIND_USER_FP))
state->type = UNWIND_USER_TYPE_FP;
else
state->type = UNWIND_USER_TYPE_NONE;
@@ -138,7 +138,7 @@ int unwind_user(struct unwind_stacktrace *trace, unsigned int max_entries)
static u64 ctx_to_cookie(u64 cpu, u64 ctx)
{
BUILD_BUG_ON(NR_CPUS > 65535);
- return (ctx & ((1UL << 48) - 1)) | cpu;
+ return (ctx & ((1UL << 48) - 1)) | (cpu << 48);
}

/*