Re: [PATCH] powerpc/ftrace: Ignore ftrace locations in exit text sections
From: Christophe Leroy <hidden>
Date: 2024-02-12 19:32:18
Le 09/02/2024 à 08:59, Naveen N Rao a écrit :
quoted hunk ↗ jump to hunk
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@vger.kernel.org Reported-by: Michael Ellerman <mpe@ellerman.id.au> Signed-off-by: Naveen N Rao <naveen@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 = .;
quoted hunk ↗ jump to hunk
/* 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 ?
quoted hunk ↗ jump to hunk
+ + 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