--- /dev/null
+From stable+bounces-6799-greg=kroah.com@vger.kernel.org Fri Dec 15 12:15:27 2023
+From: Naveen N Rao <naveen@kernel.org>
+Date: Fri, 15 Dec 2023 16:41:21 +0530
+Subject: powerpc/ftrace: Create a dummy stackframe to fix stack unwind
+To: <stable@vger.kernel.org>
+Cc: Greg KH <gregkh@linuxfoundation.org>, Michael Ellerman <mpe@ellerman.id.au>
+Message-ID: <20231215111122.2361478-1-naveen@kernel.org>
+
+From: Naveen N Rao <naveen@kernel.org>
+
+commit 41a506ef71eb38d94fe133f565c87c3e06ccc072 upstream.
+
+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@vger.kernel.org
+Signed-off-by: Naveen N Rao <naveen@kernel.org>
+Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
+Link: https://msgid.link/20230621051349.759567-1-naveen@kernel.org
+Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
+---
+ arch/powerpc/kernel/trace/ftrace_64_mprofile.S | 7 ++++++-
+ 1 file changed, 6 insertions(+), 1 deletion(-)
+
+--- a/arch/powerpc/kernel/trace/ftrace_64_mprofile.S
++++ b/arch/powerpc/kernel/trace/ftrace_64_mprofile.S
+@@ -41,6 +41,9 @@ _GLOBAL(ftrace_caller)
+ /* Save the original return address in A's stack frame */
+ std r0,LRSAVE(r1)
+
++ /* Create a minimal stack frame for representing B */
++ stdu r1, -STACK_FRAME_MIN_SIZE(r1)
++
+ /* Create our stack frame + pt_regs */
+ stdu r1,-SWITCH_FRAME_SIZE(r1)
+
+@@ -64,6 +67,8 @@ _GLOBAL(ftrace_caller)
+ mflr r7
+ /* Save it as pt_regs->nip */
+ std r7, _NIP(r1)
++ /* Also save it in B's stackframe header for proper unwind */
++ std r7, LRSAVE+SWITCH_FRAME_SIZE(r1)
+ /* Save the read LR in pt_regs->link */
+ std r0, _LINK(r1)
+
+@@ -146,7 +151,7 @@ ftrace_call:
+ ld r2, 24(r1)
+
+ /* Pop our stack frame */
+- addi r1, r1, SWITCH_FRAME_SIZE
++ addi r1, r1, SWITCH_FRAME_SIZE+STACK_FRAME_MIN_SIZE
+
+ #ifdef CONFIG_LIVEPATCH
+ /*
--- /dev/null
+From stable+bounces-6800-greg=kroah.com@vger.kernel.org Fri Dec 15 12:15:29 2023
+From: Naveen N Rao <naveen@kernel.org>
+Date: Fri, 15 Dec 2023 16:41:22 +0530
+Subject: powerpc/ftrace: Fix stack teardown in ftrace_no_trace
+To: <stable@vger.kernel.org>
+Cc: Greg KH <gregkh@linuxfoundation.org>, Michael Ellerman <mpe@ellerman.id.au>
+Message-ID: <20231215111122.2361478-2-naveen@kernel.org>
+
+From: Naveen N Rao <naveen@kernel.org>
+
+commit 4b3338aaa74d7d4ec5b6734dc298f0db94ec83d2 upstream.
+
+Commit 41a506ef71eb ("powerpc/ftrace: Create a dummy stackframe to fix
+stack unwind") added use of a new stack frame on ftrace entry to fix
+stack unwind. However, the commit missed updating the offset used while
+tearing down the ftrace stack when ftrace is disabled. Fix the same.
+
+In addition, the commit missed saving the correct stack pointer in
+pt_regs. Update the same.
+
+Fixes: 41a506ef71eb ("powerpc/ftrace: Create a dummy stackframe to fix stack unwind")
+Cc: stable@vger.kernel.org # v6.5+
+Signed-off-by: Naveen N Rao <naveen@kernel.org>
+Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
+Link: https://msgid.link/20231130065947.2188860-1-naveen@kernel.org
+Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
+---
+ arch/powerpc/kernel/trace/ftrace_64_mprofile.S | 2 +-
+ 1 file changed, 1 insertion(+), 1 deletion(-)
+
+--- a/arch/powerpc/kernel/trace/ftrace_64_mprofile.S
++++ b/arch/powerpc/kernel/trace/ftrace_64_mprofile.S
+@@ -54,7 +54,7 @@ _GLOBAL(ftrace_caller)
+ SAVE_10GPRS(22, r1)
+
+ /* Save previous stack pointer (r1) */
+- addi r8, r1, SWITCH_FRAME_SIZE
++ addi r8, r1, SWITCH_FRAME_SIZE+STACK_FRAME_MIN_SIZE
+ std r8, GPR1(r1)
+
+ /* Load special regs for save below */
projects / thirdparty / kernel / stable-queue.git / commitdiff
