diff mbox series

[v2] powerpc/ftrace: Ignore ftrace locations in exit text sections

Message ID 20240213175410.1091313-1-naveen@kernel.org (mailing list archive)
State Accepted
Commit ea73179e64131bcd29ba6defd33732abdf8ca14b
Headers show
Series [v2] powerpc/ftrace: Ignore ftrace locations in exit text sections | expand

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Commit Message

Naveen N Rao Feb. 13, 2024, 5:54 p.m. UTC 
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@vger.kernel.org
Reported-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Naveen N Rao <naveen@kernel.org>
Reviewed-by: Benjamin Gray <bgray@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(-)


base-commit: 4ef8376c466ae8b03e632dd8eca1e44315f7dd61

Comments

Michael Ellerman Feb. 15, 2024, 12:57 p.m. UTC | #1 
On Tue, 13 Feb 2024 23:24:10 +0530, Naveen N Rao wrote:
> 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
> 
> [...]

Applied to powerpc/fixes.

[1/1] powerpc/ftrace: Ignore ftrace locations in exit text sections
      https://git.kernel.org/powerpc/c/ea73179e64131bcd29ba6defd33732abdf8ca14b

cheers
diff mbox series

Patch

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);