Le 09/02/2024 à 08:59, Naveen N Rao a écrit : > 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[];
Should we try to at least use the same symbols as others, or best try to move this into include/asm-generic/sections.h, just like inittext ? $ git grep exittext arch/arm64/include/asm/sections.h:extern char __exittext_begin[], __exittext_end[]; arch/arm64/kernel/patching.c: addr >= (unsigned long)__exittext_begin && arch/arm64/kernel/patching.c: addr < (unsigned long)__exittext_end; arch/arm64/kernel/vmlinux.lds.S: __exittext_begin = .; arch/arm64/kernel/vmlinux.lds.S: __exittext_end = .; arch/riscv/include/asm/sections.h:extern char __exittext_begin[], __exittext_end[]; arch/riscv/kernel/patch.c:static inline bool is_kernel_exittext(uintptr_t addr) arch/riscv/kernel/patch.c: addr >= (uintptr_t)__exittext_begin && arch/riscv/kernel/patch.c: addr < (uintptr_t)__exittext_end; arch/riscv/kernel/patch.c: if (core_kernel_text(uintaddr) || is_kernel_exittext(uintaddr)) arch/riscv/kernel/vmlinux-xip.lds.S: __exittext_begin = .; arch/riscv/kernel/vmlinux-xip.lds.S: __exittext_end = .; arch/riscv/kernel/vmlinux.lds.S: __exittext_begin = .; arch/riscv/kernel/vmlinux.lds.S: __exittext_end = .; > > /* 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; Then arm64 has a function called is_exit_text() and riscv has is_kernel_exittext(). Can we refactor ? > + > + 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