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: sta...@vger.kernel.org > Reported-by: Michael Ellerman <m...@ellerman.id.au> > Signed-off-by: Naveen N Rao <nav...@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 <bg...@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 ]---