[PATCH v2] powerpc/ftrace: Ignore ftrace locations in exit text sections
Naveen N Rao
naveen at kernel.org
Wed Feb 14 04:54:10 AEDT 2024
Michael reported that we are seeing ftrace bug on bootup when KASAN is
enabled, and if we are using -fpatchable-function-entry:
ftrace: allocating 47780 entries in 18 pages
ftrace-powerpc: 0xc0000000020b3d5c: No module provided for non-kernel address
------------[ ftrace bug ]------------
ftrace faulted on modifying
[<c0000000020b3d5c>] 0xc0000000020b3d5c
Initializing ftrace call sites
ftrace record flags: 0
(0)
expected tramp: c00000000008cef4
------------[ cut here ]------------
WARNING: CPU: 0 PID: 0 at kernel/trace/ftrace.c:2180 ftrace_bug+0x3c0/0x424
Modules linked in:
CPU: 0 PID: 0 Comm: swapper Not tainted 6.5.0-rc3-00120-g0f71dcfb4aef #860
Hardware name: IBM pSeries (emulated by qemu) POWER9 (raw) 0x4e1202 0xf000005 of:SLOF,HEAD hv:linux,kvm pSeries
NIP: c0000000003aa81c LR: c0000000003aa818 CTR: 0000000000000000
REGS: c0000000033cfab0 TRAP: 0700 Not tainted (6.5.0-rc3-00120-g0f71dcfb4aef)
MSR: 8000000002021033 <SF,VEC,ME,IR,DR,RI,LE> CR: 28028240 XER: 00000000
CFAR: c0000000002781a8 IRQMASK: 3
...
NIP [c0000000003aa81c] ftrace_bug+0x3c0/0x424
LR [c0000000003aa818] ftrace_bug+0x3bc/0x424
Call Trace:
ftrace_bug+0x3bc/0x424 (unreliable)
ftrace_process_locs+0x5f4/0x8a0
ftrace_init+0xc0/0x1d0
start_kernel+0x1d8/0x484
With CONFIG_FTRACE_MCOUNT_USE_PATCHABLE_FUNCTION_ENTRY=y and
CONFIG_KASAN=y, compiler emits nops in functions that it generates for
registering and unregistering global variables (unlike with -pg and
-mprofile-kernel where calls to _mcount() are not generated in those
functions). Those functions then end up in INIT_TEXT and EXIT_TEXT
respectively. We don't expect to see any profiled functions in
EXIT_TEXT, so ftrace_init_nop() assumes that all addresses that aren't
in the core kernel text belongs to a module. Since these functions do
not match that criteria, we see the above bug.
Address this by having ftrace ignore all locations in the text exit
sections of vmlinux.
Fixes: 0f71dcfb4aef ("powerpc/ftrace: Add support for -fpatchable-function-entry")
Cc: stable at vger.kernel.org
Reported-by: Michael Ellerman <mpe at ellerman.id.au>
Signed-off-by: Naveen N Rao <naveen at kernel.org>
Reviewed-by: Benjamin Gray <bgray at linux.ibm.com>
---
v2:
- Rename exit text section variable name to match other architectures
- Fix clang builds
I've collected Benjamin's Reviewed-by tag since those parts of the patch
remain the same.
- Naveen
arch/powerpc/include/asm/ftrace.h | 10 ++--------
arch/powerpc/include/asm/sections.h | 1 +
arch/powerpc/kernel/trace/ftrace.c | 12 ++++++++++++
arch/powerpc/kernel/trace/ftrace_64_pg.c | 5 +++++
arch/powerpc/kernel/vmlinux.lds.S | 2 ++
5 files changed, 22 insertions(+), 8 deletions(-)
diff --git a/arch/powerpc/include/asm/ftrace.h b/arch/powerpc/include/asm/ftrace.h
index 1ebd2ca97f12..107fc5a48456 100644
--- a/arch/powerpc/include/asm/ftrace.h
+++ b/arch/powerpc/include/asm/ftrace.h
@@ -20,14 +20,6 @@
#ifndef __ASSEMBLY__
extern void _mcount(void);
-static inline unsigned long ftrace_call_adjust(unsigned long addr)
-{
- if (IS_ENABLED(CONFIG_ARCH_USING_PATCHABLE_FUNCTION_ENTRY))
- addr += MCOUNT_INSN_SIZE;
-
- return addr;
-}
-
unsigned long prepare_ftrace_return(unsigned long parent, unsigned long ip,
unsigned long sp);
@@ -142,8 +134,10 @@ static inline u8 this_cpu_get_ftrace_enabled(void) { return 1; }
#ifdef CONFIG_FUNCTION_TRACER
extern unsigned int ftrace_tramp_text[], ftrace_tramp_init[];
void ftrace_free_init_tramp(void);
+unsigned long ftrace_call_adjust(unsigned long addr);
#else
static inline void ftrace_free_init_tramp(void) { }
+static inline unsigned long ftrace_call_adjust(unsigned long addr) { return addr; }
#endif
#endif /* !__ASSEMBLY__ */
diff --git a/arch/powerpc/include/asm/sections.h b/arch/powerpc/include/asm/sections.h
index ea26665f82cf..f43f3a6b0051 100644
--- a/arch/powerpc/include/asm/sections.h
+++ b/arch/powerpc/include/asm/sections.h
@@ -14,6 +14,7 @@ typedef struct func_desc func_desc_t;
extern char __head_end[];
extern char __srwx_boundary[];
+extern char __exittext_begin[], __exittext_end[];
/* Patch sites */
extern s32 patch__call_flush_branch_caches1;
diff --git a/arch/powerpc/kernel/trace/ftrace.c b/arch/powerpc/kernel/trace/ftrace.c
index 82010629cf88..d8d6b4fd9a14 100644
--- a/arch/powerpc/kernel/trace/ftrace.c
+++ b/arch/powerpc/kernel/trace/ftrace.c
@@ -27,10 +27,22 @@
#include <asm/ftrace.h>
#include <asm/syscall.h>
#include <asm/inst.h>
+#include <asm/sections.h>
#define NUM_FTRACE_TRAMPS 2
static unsigned long ftrace_tramps[NUM_FTRACE_TRAMPS];
+unsigned long ftrace_call_adjust(unsigned long addr)
+{
+ if (addr >= (unsigned long)__exittext_begin && addr < (unsigned long)__exittext_end)
+ return 0;
+
+ if (IS_ENABLED(CONFIG_ARCH_USING_PATCHABLE_FUNCTION_ENTRY))
+ addr += MCOUNT_INSN_SIZE;
+
+ return addr;
+}
+
static ppc_inst_t ftrace_create_branch_inst(unsigned long ip, unsigned long addr, int link)
{
ppc_inst_t op;
diff --git a/arch/powerpc/kernel/trace/ftrace_64_pg.c b/arch/powerpc/kernel/trace/ftrace_64_pg.c
index 7b85c3b460a3..12fab1803bcf 100644
--- a/arch/powerpc/kernel/trace/ftrace_64_pg.c
+++ b/arch/powerpc/kernel/trace/ftrace_64_pg.c
@@ -37,6 +37,11 @@
#define NUM_FTRACE_TRAMPS 8
static unsigned long ftrace_tramps[NUM_FTRACE_TRAMPS];
+unsigned long ftrace_call_adjust(unsigned long addr)
+{
+ return addr;
+}
+
static ppc_inst_t
ftrace_call_replace(unsigned long ip, unsigned long addr, int link)
{
diff --git a/arch/powerpc/kernel/vmlinux.lds.S b/arch/powerpc/kernel/vmlinux.lds.S
index 1c5970df3233..f420df7888a7 100644
--- a/arch/powerpc/kernel/vmlinux.lds.S
+++ b/arch/powerpc/kernel/vmlinux.lds.S
@@ -281,7 +281,9 @@ SECTIONS
* to deal with references from __bug_table
*/
.exit.text : AT(ADDR(.exit.text) - LOAD_OFFSET) {
+ __exittext_begin = .;
EXIT_TEXT
+ __exittext_end = .;
}
. = ALIGN(PAGE_SIZE);
base-commit: 4ef8376c466ae8b03e632dd8eca1e44315f7dd61
--
2.43.0
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