[PATCH] powerpc/ftrace: Ignore ftrace locations in exit text sections
Benjamin Gray
bgray at linux.ibm.com
Tue Feb 13 15:20:17 AEDT 2024
On Fri, 2024-02-09 at 13:29 +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
>
> 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>
> ---
> arch/powerpc/include/asm/ftrace.h | 9 +--------
> arch/powerpc/include/asm/sections.h | 1 +
> arch/powerpc/kernel/trace/ftrace.c | 12 ++++++++++++
> arch/powerpc/kernel/vmlinux.lds.S | 2 ++
> 4 files changed, 16 insertions(+), 8 deletions(-)
>
> diff --git a/arch/powerpc/include/asm/ftrace.h
> b/arch/powerpc/include/asm/ftrace.h
> index 1ebd2ca97f12..d6babd083202 100644
> --- a/arch/powerpc/include/asm/ftrace.h
> +++ b/arch/powerpc/include/asm/ftrace.h
> @@ -20,14 +20,7 @@
> #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 ftrace_call_adjust(unsigned long addr);
> unsigned long prepare_ftrace_return(unsigned long parent, unsigned
> long ip,
> unsigned long sp);
>
> diff --git a/arch/powerpc/include/asm/sections.h
> b/arch/powerpc/include/asm/sections.h
> index ea26665f82cf..d389dcecdb0b 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 _sexittext[], _eexittext[];
>
> /* 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..b5efd8d7bc01 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)_sexittext && addr < (unsigned
> long)_eexittext)
> + 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/vmlinux.lds.S
> b/arch/powerpc/kernel/vmlinux.lds.S
> index 1c5970df3233..9c376ae6857d 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) {
> + _sexittext = .;
> EXIT_TEXT
> + _eexittext = .;
> }
>
> . = ALIGN(PAGE_SIZE);
>
> base-commit: 4ef8376c466ae8b03e632dd8eca1e44315f7dd61
Reviewed-by: Benjamin Gray <bgray at linux.ibm.com>
Fixes what I assume is the same bug I was seeing for a while
[ 0.000000][ T0] ftrace-powerpc: 0xc0000000030f4f38: No module provided for non-kernel address
[ 0.000000][ T0] ------------[ ftrace bug ]------------
[ 0.000000][ T0] ftrace faulted on modifying
[ 0.000000][ T0] [<c0000000030f4f38>] _sub_D_65535_0+0xc/0x40
[ 0.000000][ T0] Initializing ftrace call sites
[ 0.000000][ T0] ftrace record flags: 0
[ 0.000000][ T0] (0)
[ 0.000000][ T0] expected tramp: c0000000000a8548
[ 0.000000][ T0] ------------[ cut here ]------------
[ 0.000000][ T0] WARNING: CPU: 0 PID: 0 at kernel/trace/ftrace.c:2179 ftrace_bug+0x16c/0x3a0
[ 0.000000][ T0] Modules linked in:
[ 0.000000][ T0] CPU: 0 PID: 0 Comm: swapper Not tainted 6.8.0-rc3-02361-g892886f9f5b7-dirty #11
[ 0.000000][ T0] Hardware name: IBM pSeries (emulated by qemu) POWER9 (raw) 0x4e1202 0xf000005 of:SLOF,HEAD hv:linux,kvm pSeries
[ 0.000000][ T0] NIP: c00000000048a96c LR: c00000000048a968 CTR: 0000000000000000
[ 0.000000][ T0] REGS: c000000004fa7ae0 TRAP: 0700 Not tainted (6.8.0-rc3-02361-g892886f9f5b7-dirty)
[ 0.000000][ T0] MSR: 8000000002021033 <SF,VEC,ME,IR,DR,RI,LE> CR: 28028440 XER: 00000000
[ 0.000000][ T0] CFAR: c00000000031db34 IRQMASK: 3
[ 0.000000][ T0] GPR00: c00000000048a968 c000000004fa7d80 c000000002645600 0000000000000022
[ 0.000000][ T0] GPR04: 0000000000000008 0000000000000001 c000000000326dc4 0000000000000000
[ 0.000000][ T0] GPR08: c000000002535600 0000000000000001 c00000000440bee0 0000000048028444
[ 0.000000][ T0] GPR12: 0000000000000000 c000000006250000 0000000000000000 0000000000000000
[ 0.000000][ T0] GPR16: 0000000000000000 0000000000000003 0000000000000001 0000000000000000
[ 0.000000][ T0] GPR20: c000000004fe8af8 c000000010030428 c0000000045b90c0 0000000000000000
[ 0.000000][ T0] GPR24: 0000000000000000 c000000010030430 c000000010030420 0000000000000000
[ 0.000000][ T0] GPR28: c000000001dd9a40 c000000001dd8bc0 c0000000102a5b00 c0000000102a5b08
[ 0.000000][ T0] NIP [c00000000048a96c] ftrace_bug+0x16c/0x3a0
[ 0.000000][ T0] LR [c00000000048a968] ftrace_bug+0x168/0x3a0
[ 0.000000][ T0] Call Trace:
[ 0.000000][ T0] [c000000004fa7d80] [c00000000048a968] ftrace_bug+0x168/0x3a0 (unreliable)
[ 0.000000][ T0] [c000000004fa7e20] [c00000000048aeec] ftrace_process_locs+0x34c/0x780
[ 0.000000][ T0] [c000000004fa7ec0] [c0000000030655c0] ftrace_init+0xc8/0x27c
[ 0.000000][ T0] [c000000004fa7f40] [c00000000300d458] start_kernel+0x1bc/0x528
[ 0.000000][ T0] [c000000004fa7fe0] [c00000000000eaa0] start_here_common+0x1c/0x20
[ 0.000000][ T0] Code: 7fe3fb78 483a31e5 60000000 e93e0008 75290800 40820150 7fc3f378 4bfffc95 7c641b78 387d0f40 4be93189 60000000 <0fe00000> 382100a0 3d22fda6 39000001
[ 0.000000][ T0] irq event stamp: 0
[ 0.000000][ T0] hardirqs last enabled at (0): [<0000000000000000>] 0x0
[ 0.000000][ T0] hardirqs last disabled at (0): [<0000000000000000>] 0x0
[ 0.000000][ T0] softirqs last enabled at (0): [<0000000000000000>] 0x0
[ 0.000000][ T0] softirqs last disabled at (0): [<0000000000000000>] 0x0
[ 0.000000][ T0] ---[ end trace 0000000000000000 ]---
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