FAILED: patch "[PATCH] powerpc/ftrace: Create a dummy stackframe to fix stack unwind" failed to apply to 4.19-stable tree

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



The patch below does not apply to the 4.19-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 <stable@xxxxxxxxxxxxxxx>.

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-4.19.y
git checkout FETCH_HEAD
git cherry-pick -x 41a506ef71eb38d94fe133f565c87c3e06ccc072
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@xxxxxxxxxxxxxxx>' --in-reply-to '2023080739-bonehead-overexert-ce34@gregkh' --subject-prefix 'PATCH 4.19.y' HEAD^..

Possible dependencies:

41a506ef71eb ("powerpc/ftrace: Create a dummy stackframe to fix stack unwind")
a5f04d1f2724 ("powerpc/ftrace: Regroup PPC64 specific operations in ftrace_mprofile.S")
228216716cb5 ("powerpc/ftrace: Refactor ftrace_{regs_}caller")
9bdb2eec3dde ("powerpc/ftrace: Don't use lmw/stmw in ftrace_regs_caller()")
76b372814b08 ("powerpc/ftrace: Style cleanup in ftrace_mprofile.S")
fc75f8733798 ("powerpc/ftrace: Have arch_ftrace_get_regs() return NULL unless FL_SAVE_REGS is set")
34d8dac807f0 ("powerpc/ftrace: Also save r1 in ftrace_caller()")
4ee83a2cfbc4 ("powerpc/ftrace: Remove ftrace_32.S")
41315494beed ("powerpc/ftrace: Prepare ftrace_64_mprofile.S for reuse by PPC32")
830213786c49 ("powerpc/ftrace: directly call of function graph tracer by ftrace caller")
0c81ed5ed438 ("powerpc/ftrace: Refactor ftrace_{en/dis}able_ftrace_graph_caller")
40b035efe288 ("powerpc/ftrace: Implement CONFIG_DYNAMIC_FTRACE_WITH_ARGS")
c75388a8ceff ("powerpc/ftrace: Prepare PPC64's ftrace_caller() for CONFIG_DYNAMIC_FTRACE_WITH_ARGS")
d95bf254be5f ("powerpc/ftrace: Prepare PPC32's ftrace_caller() for CONFIG_DYNAMIC_FTRACE_WITH_ARGS")
7bdb478c1d15 ("powerpc/ftrace: Simplify PPC32's return_to_handler()")
7875bc9b07cd ("powerpc/ftrace: Don't save again LR in ftrace_regs_caller() on PPC32")
c545b9f040f3 ("powerpc/inst: Define ppc_inst_t")
aebd1fb45c62 ("powerpc: flexible GPR range save/restore macros")
7dfbfb87c243 ("powerpc/ftrace: Activate HAVE_DYNAMIC_FTRACE_WITH_REGS on PPC32")
c93d4f6ecf4b ("powerpc/ftrace: Add module_trampoline_target() for PPC32")

thanks,

greg k-h

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

>From 41a506ef71eb38d94fe133f565c87c3e06ccc072 Mon Sep 17 00:00:00 2001
From: Naveen N Rao <naveen@xxxxxxxxxx>
Date: Wed, 21 Jun 2023 10:43:49 +0530
Subject: [PATCH] powerpc/ftrace: Create a dummy stackframe to fix stack unwind

With ppc64 -mprofile-kernel and ppc32 -pg, profiling instructions to
call into ftrace are emitted right at function entry. The instruction
sequence used is minimal to reduce overhead. Crucially, a stackframe is
not created for the function being traced. This breaks stack unwinding
since the function being traced does not have a stackframe for itself.
As such, it never shows up in the backtrace:

/sys/kernel/debug/tracing # echo 1 > /proc/sys/kernel/stack_tracer_enabled
/sys/kernel/debug/tracing # cat stack_trace
        Depth    Size   Location    (17 entries)
        -----    ----   --------
  0)     4144      32   ftrace_call+0x4/0x44
  1)     4112     432   get_page_from_freelist+0x26c/0x1ad0
  2)     3680     496   __alloc_pages+0x290/0x1280
  3)     3184     336   __folio_alloc+0x34/0x90
  4)     2848     176   vma_alloc_folio+0xd8/0x540
  5)     2672     272   __handle_mm_fault+0x700/0x1cc0
  6)     2400     208   handle_mm_fault+0xf0/0x3f0
  7)     2192      80   ___do_page_fault+0x3e4/0xbe0
  8)     2112     160   do_page_fault+0x30/0xc0
  9)     1952     256   data_access_common_virt+0x210/0x220
 10)     1696     400   0xc00000000f16b100
 11)     1296     384   load_elf_binary+0x804/0x1b80
 12)      912     208   bprm_execve+0x2d8/0x7e0
 13)      704      64   do_execveat_common+0x1d0/0x2f0
 14)      640     160   sys_execve+0x54/0x70
 15)      480      64   system_call_exception+0x138/0x350
 16)      416     416   system_call_common+0x160/0x2c4

Fix this by having ftrace create a dummy stackframe for the function
being traced. With this, backtraces now capture the function being
traced:

/sys/kernel/debug/tracing # cat stack_trace
        Depth    Size   Location    (17 entries)
        -----    ----   --------
  0)     3888      32   _raw_spin_trylock+0x8/0x70
  1)     3856     576   get_page_from_freelist+0x26c/0x1ad0
  2)     3280      64   __alloc_pages+0x290/0x1280
  3)     3216     336   __folio_alloc+0x34/0x90
  4)     2880     176   vma_alloc_folio+0xd8/0x540
  5)     2704     416   __handle_mm_fault+0x700/0x1cc0
  6)     2288      96   handle_mm_fault+0xf0/0x3f0
  7)     2192      48   ___do_page_fault+0x3e4/0xbe0
  8)     2144     192   do_page_fault+0x30/0xc0
  9)     1952     608   data_access_common_virt+0x210/0x220
 10)     1344      16   0xc0000000334bbb50
 11)     1328     416   load_elf_binary+0x804/0x1b80
 12)      912      64   bprm_execve+0x2d8/0x7e0
 13)      848     176   do_execveat_common+0x1d0/0x2f0
 14)      672     192   sys_execve+0x54/0x70
 15)      480      64   system_call_exception+0x138/0x350
 16)      416     416   system_call_common+0x160/0x2c4

This results in two additional stores in the ftrace entry code, but
produces reliable backtraces.

Fixes: 153086644fd1 ("powerpc/ftrace: Add support for -mprofile-kernel ftrace ABI")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Naveen N Rao <naveen@xxxxxxxxxx>
Signed-off-by: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Link: https://msgid.link/20230621051349.759567-1-naveen@xxxxxxxxxx

diff --git a/arch/powerpc/kernel/trace/ftrace_mprofile.S b/arch/powerpc/kernel/trace/ftrace_mprofile.S
index ffb1db386849..1f7d86de1538 100644
--- a/arch/powerpc/kernel/trace/ftrace_mprofile.S
+++ b/arch/powerpc/kernel/trace/ftrace_mprofile.S
@@ -33,6 +33,9 @@
  * and then arrange for the ftrace function to be called.
  */
 .macro	ftrace_regs_entry allregs
+	/* Create a minimal stack frame for representing B */
+	PPC_STLU	r1, -STACK_FRAME_MIN_SIZE(r1)
+
 	/* Create our stack frame + pt_regs */
 	PPC_STLU	r1,-SWITCH_FRAME_SIZE(r1)
 
@@ -42,7 +45,7 @@
 
 #ifdef CONFIG_PPC64
 	/* Save the original return address in A's stack frame */
-	std	r0, LRSAVE+SWITCH_FRAME_SIZE(r1)
+	std	r0, LRSAVE+SWITCH_FRAME_SIZE+STACK_FRAME_MIN_SIZE(r1)
 	/* Ok to continue? */
 	lbz	r3, PACA_FTRACE_ENABLED(r13)
 	cmpdi	r3, 0
@@ -77,6 +80,8 @@
 	mflr	r7
 	/* Save it as pt_regs->nip */
 	PPC_STL	r7, _NIP(r1)
+	/* Also save it in B's stackframe header for proper unwind */
+	PPC_STL	r7, LRSAVE+SWITCH_FRAME_SIZE(r1)
 	/* Save the read LR in pt_regs->link */
 	PPC_STL	r0, _LINK(r1)
 
@@ -142,7 +147,7 @@
 #endif
 
 	/* Pop our stack frame */
-	addi r1, r1, SWITCH_FRAME_SIZE
+	addi r1, r1, SWITCH_FRAME_SIZE+STACK_FRAME_MIN_SIZE
 
 #ifdef CONFIG_LIVEPATCH_64
         /* Based on the cmpd above, if the NIP was altered handle livepatch */




[Index of Archives]     [Linux Kernel]     [Kernel Development Newbies]     [Linux USB Devel]     [Video for Linux]     [Linux Audio Users]     [Yosemite Hiking]     [Linux Kernel]     [Linux SCSI]

  Powered by Linux