FAILED: patch "[PATCH] powerpc/ftrace: Ignore ftrace locations in exit text sections" failed to apply to 6.6-stable tree

PATCH In review [email protected] 2 participants 3 messages Feb 19, 2024 – Apr 23, 2024

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Stable branch PowerPC ftrace

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2024-02-19 18:23 UTC #0 lore raw

The patch below does not apply to the 6.6-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.6.y
git checkout FETCH_HEAD
git cherry-pick -x ea73179e64131bcd29ba6defd33732abdf8ca14b
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2024021902-authentic-handpick-da09@gregkh' --subject-prefix 'PATCH 6.6.y' HEAD^..

Possible dependencies:

ea73179e6413 ("powerpc/ftrace: Ignore ftrace locations in exit text sections") 2ec36570c358 ("powerpc/ftrace: Fix indentation in ftrace.h")

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From ea73179e64131bcd29ba6defd33732abdf8ca14b Mon Sep 17 00:00:00 2001
From: Naveen N Rao <[email protected]>
Date: Tue, 13 Feb 2024 23:24:10 +0530
Subject: [PATCH] powerpc/ftrace: Ignore ftrace locations in exit text sections

Michael reported that we are seeing an ftrace bug on bootup when KASAN is enabled and 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 [email protected] # v6.6+

Reported-by Michael Ellerman <[email protected]>

Signed-off-by Naveen N Rao <[email protected]>

Reviewed-by Benjamin Gray <[email protected]>

Signed-off-by Michael Ellerman <[email protected]>

Link https://msgid.link/[email protected] open here

arch/powerpc/include/asm/ftrace.h +2 -8

index 1ebd2ca97f12..107fc5a48456 100644
@@ -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__ */

arch/powerpc/include/asm/sections.h +1 -0

index ea26665f82cf..f43f3a6b0051 100644
@@ -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;

arch/powerpc/kernel/trace/ftrace.c +12 -0

index 82010629cf88..d8d6b4fd9a14 100644
@@ -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;

arch/powerpc/kernel/trace/ftrace_64_pg.c +5 -0

index 7b85c3b460a3..12fab1803bcf 100644
@@ -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)
 {

arch/powerpc/kernel/vmlinux.lds.S +2 -0

index 1c5970df3233..f420df7888a7 100644
@@ -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);

Naveen N Rao

2024-04-23 08:53 UTC #1 lore raw

PATCH 1/1 powerpc/ftrace: Ignore ftrace locations in exit text sections

commit ea73179e64131bcd29ba6defd33732abdf8ca14b upstream.