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

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Message-ID: <20241113171326.6d1ddc83@gandalf.local.home>
Date: Wed, 13 Nov 2024 17:13:26 -0500
From: Steven Rostedt <rostedt@...dmis.org>
To: Josh Poimboeuf <jpoimboe@...nel.org>
Cc: Jens Remus <jremus@...ux.ibm.com>, x86@...nel.org, Peter Zijlstra
 <peterz@...radead.org>, Ingo Molnar <mingo@...nel.org>, Arnaldo Carvalho de
 Melo <acme@...nel.org>, linux-kernel@...r.kernel.org, Indu Bhagat
 <indu.bhagat@...cle.com>, Mark Rutland <mark.rutland@....com>, Alexander
 Shishkin <alexander.shishkin@...ux.intel.com>, Jiri Olsa
 <jolsa@...nel.org>, Namhyung Kim <namhyung@...nel.org>, Ian Rogers
 <irogers@...gle.com>, Adrian Hunter <adrian.hunter@...el.com>,
 linux-perf-users@...r.kernel.org, Mark Brown <broonie@...nel.org>,
 linux-toolchains@...r.kernel.org, Jordan Rome <jordalgo@...a.com>, Sam
 James <sam@...too.org>, linux-trace-kernel@...r.kerne.org, Andrii Nakryiko
 <andrii.nakryiko@...il.com>, Mathieu Desnoyers
 <mathieu.desnoyers@...icios.com>, Florian Weimer <fweimer@...hat.com>, Andy
 Lutomirski <luto@...nel.org>, Heiko Carstens <hca@...ux.ibm.com>, Vasily
 Gorbik <gor@...ux.ibm.com>
Subject: Re: [PATCH v3 09/19] unwind: Introduce sframe user space unwinding

On Wed, 13 Nov 2024 13:15:35 -0800
Josh Poimboeuf <jpoimboe@...nel.org> 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@...ux.ibm.com> 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);
 }
 
 /*