From a5f7a5bb3b7f28ba7e4fa246775b29a0e5537255 Mon Sep 17 00:00:00 2001 From: Jinke Han Date: Tue, 8 Sep 2026 15:37:42 +0800 Subject: x86/kprobes: Fix crash when probing CS CALL instructions When using eBPF to probe CS CALL instructions within a function, a crash can be triggered. The eBPF tool probes offset 257 of the __hrtimer_run_queues() function: <__hrtimer_run_queues+249>: nopl 0x0(%rax,%rax,1) <__hrtimer_run_queues+254>: mov %r14,%rdi <__hrtimer_run_queues+257>: cs call <__x86_indirect_thunk_r12> <__hrtimer_run_queues+263>: mov %eax,%r12d <__hrtimer_run_queues+266>: xchg %ax,%ax <__hrtimer_run_queues+268>: mov %r13,%rdi Which triggers this crash: BUG: unable to handle page fault for address: 00000000000f41c9 #PF: supervisor write access in kernel mode #PF: error_code(0x0002) - not-present page PGD 0 P4D 0 Oops: 0002 [#1] SMP NOPTI CPU: 1 PID: 0 Comm: swapper/1 Kdump: loaded Tainted: P RIP: 0010:__hrtimer_run_queues+0x106/0x230 Note that __hrtimer_run_queues+0x106 is __hrtimer_run_queues+262, which is at the 6th byte of the above CS CALL instruction. Since the CS CALL instruction occupies 6 bytes, the exception occurred in the middle of that call instruction. The root cause is that when using eBPF tools to probe in the middle of a function, a kprobe with INT3 is used as the underlying implementation. During single-step emulation of the original CALL instruction, int3_emulate_call() assumes that the probed CALL instruction is 5 bytes long. However, the actual CS-prefixed CALL instruction occupies 6 bytes, so it constructs an incorrect exception return address. When the CPU returns from the kprobe handler, the next instruction to be executed is at the address of the last byte of that CS CALL instruction. Coincidentally, starting from that address, the CPU fetches and decodes a completely different instruction, which ultimately triggers a kernel crash. Fix the issue by using the actual instruction length obtained from the instruction decoder when constructing the exception return address, rather than relying on the hardcoded CALL_INSN_SIZE macro. [ mingo: Refined the changelog ] Fixes: 6256e668b7af ("x86/kprobes: Use int3 instead of debug trap for single-step") Suggested-by: Masami Hiramatsu (Google) Signed-off-by: Jinke Han Signed-off-by: Ingo Molnar Reviewed-by: Masami Hiramatsu (Google) Acked-by: Yafang Shao Acked-by: Borislav Petkov Cc: Peter Zijlstra Link: https://patch.msgid.link/20260908073742.GA10517@didi-ThinkCentre-M920t-N000 --- arch/powerpc/math-emu/math.c | 461 +++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 461 insertions(+) create mode 100644 arch/powerpc/math-emu/math.c (limited to 'arch/powerpc/math-emu/math.c') diff --git a/arch/powerpc/math-emu/math.c b/arch/powerpc/math-emu/math.c new file mode 100644 index 000000000..936a9a149 --- /dev/null +++ b/arch/powerpc/math-emu/math.c @@ -0,0 +1,461 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Copyright (C) 1999 Eddie C. Dost (ecd@atecom.com) + */ + +#include +#include + +#include +#include +#include + +#include +#include + +#define FLOATFUNC(x) extern int x(void *, void *, void *, void *) + +/* The instructions list which may be not implemented by a hardware FPU */ +FLOATFUNC(fre); +FLOATFUNC(frsqrtes); +FLOATFUNC(fsqrt); +FLOATFUNC(fsqrts); +FLOATFUNC(mtfsf); +FLOATFUNC(mtfsfi); + +#ifdef CONFIG_MATH_EMULATION_HW_UNIMPLEMENTED +#undef FLOATFUNC +#define FLOATFUNC(x) static inline int x(void *op1, void *op2, void *op3, \ + void *op4) { return 0; } +#endif + +FLOATFUNC(fadd); +FLOATFUNC(fadds); +FLOATFUNC(fdiv); +FLOATFUNC(fdivs); +FLOATFUNC(fmul); +FLOATFUNC(fmuls); +FLOATFUNC(fsub); +FLOATFUNC(fsubs); + +FLOATFUNC(fmadd); +FLOATFUNC(fmadds); +FLOATFUNC(fmsub); +FLOATFUNC(fmsubs); +FLOATFUNC(fnmadd); +FLOATFUNC(fnmadds); +FLOATFUNC(fnmsub); +FLOATFUNC(fnmsubs); + +FLOATFUNC(fctiw); +FLOATFUNC(fctiwz); +FLOATFUNC(frsp); + +FLOATFUNC(fcmpo); +FLOATFUNC(fcmpu); + +FLOATFUNC(mcrfs); +FLOATFUNC(mffs); +FLOATFUNC(mtfsb0); +FLOATFUNC(mtfsb1); + +FLOATFUNC(lfd); +FLOATFUNC(lfs); + +FLOATFUNC(stfd); +FLOATFUNC(stfs); +FLOATFUNC(stfiwx); + +FLOATFUNC(fabs); +FLOATFUNC(fmr); +FLOATFUNC(fnabs); +FLOATFUNC(fneg); + +/* Optional */ +FLOATFUNC(fres); +FLOATFUNC(frsqrte); +FLOATFUNC(fsel); + + +#define OP31 0x1f /* 31 */ +#define LFS 0x30 /* 48 */ +#define LFSU 0x31 /* 49 */ +#define LFD 0x32 /* 50 */ +#define LFDU 0x33 /* 51 */ +#define STFS 0x34 /* 52 */ +#define STFSU 0x35 /* 53 */ +#define STFD 0x36 /* 54 */ +#define STFDU 0x37 /* 55 */ +#define OP59 0x3b /* 59 */ +#define OP63 0x3f /* 63 */ + +/* Opcode 31: */ +/* X-Form: */ +#define LFSX 0x217 /* 535 */ +#define LFSUX 0x237 /* 567 */ +#define LFDX 0x257 /* 599 */ +#define LFDUX 0x277 /* 631 */ +#define STFSX 0x297 /* 663 */ +#define STFSUX 0x2b7 /* 695 */ +#define STFDX 0x2d7 /* 727 */ +#define STFDUX 0x2f7 /* 759 */ +#define STFIWX 0x3d7 /* 983 */ + +/* Opcode 59: */ +/* A-Form: */ +#define FDIVS 0x012 /* 18 */ +#define FSUBS 0x014 /* 20 */ +#define FADDS 0x015 /* 21 */ +#define FSQRTS 0x016 /* 22 */ +#define FRES 0x018 /* 24 */ +#define FMULS 0x019 /* 25 */ +#define FRSQRTES 0x01a /* 26 */ +#define FMSUBS 0x01c /* 28 */ +#define FMADDS 0x01d /* 29 */ +#define FNMSUBS 0x01e /* 30 */ +#define FNMADDS 0x01f /* 31 */ + +/* Opcode 63: */ +/* A-Form: */ +#define FDIV 0x012 /* 18 */ +#define FSUB 0x014 /* 20 */ +#define FADD 0x015 /* 21 */ +#define FSQRT 0x016 /* 22 */ +#define FSEL 0x017 /* 23 */ +#define FRE 0x018 /* 24 */ +#define FMUL 0x019 /* 25 */ +#define FRSQRTE 0x01a /* 26 */ +#define FMSUB 0x01c /* 28 */ +#define FMADD 0x01d /* 29 */ +#define FNMSUB 0x01e /* 30 */ +#define FNMADD 0x01f /* 31 */ + +/* X-Form: */ +#define FCMPU 0x000 /* 0 */ +#define FRSP 0x00c /* 12 */ +#define FCTIW 0x00e /* 14 */ +#define FCTIWZ 0x00f /* 15 */ +#define FCMPO 0x020 /* 32 */ +#define MTFSB1 0x026 /* 38 */ +#define FNEG 0x028 /* 40 */ +#define MCRFS 0x040 /* 64 */ +#define MTFSB0 0x046 /* 70 */ +#define FMR 0x048 /* 72 */ +#define MTFSFI 0x086 /* 134 */ +#define FNABS 0x088 /* 136 */ +#define FABS 0x108 /* 264 */ +#define MFFS 0x247 /* 583 */ +#define MTFSF 0x2c7 /* 711 */ + + +#define AB 2 +#define AC 3 +#define ABC 4 +#define D 5 +#define DU 6 +#define X 7 +#define XA 8 +#define XB 9 +#define XCR 11 +#define XCRB 12 +#define XCRI 13 +#define XCRL 16 +#define XE 14 +#define XEU 15 +#define XFLB 10 + +static int +record_exception(struct pt_regs *regs, int eflag) +{ + u32 fpscr; + + fpscr = __FPU_FPSCR; + + if (eflag) { + fpscr |= FPSCR_FX; + if (eflag & EFLAG_OVERFLOW) + fpscr |= FPSCR_OX; + if (eflag & EFLAG_UNDERFLOW) + fpscr |= FPSCR_UX; + if (eflag & EFLAG_DIVZERO) + fpscr |= FPSCR_ZX; + if (eflag & EFLAG_INEXACT) + fpscr |= FPSCR_XX; + if (eflag & EFLAG_INVALID) + fpscr |= FPSCR_VX; + if (eflag & EFLAG_VXSNAN) + fpscr |= FPSCR_VXSNAN; + if (eflag & EFLAG_VXISI) + fpscr |= FPSCR_VXISI; + if (eflag & EFLAG_VXIDI) + fpscr |= FPSCR_VXIDI; + if (eflag & EFLAG_VXZDZ) + fpscr |= FPSCR_VXZDZ; + if (eflag & EFLAG_VXIMZ) + fpscr |= FPSCR_VXIMZ; + if (eflag & EFLAG_VXVC) + fpscr |= FPSCR_VXVC; + if (eflag & EFLAG_VXSOFT) + fpscr |= FPSCR_VXSOFT; + if (eflag & EFLAG_VXSQRT) + fpscr |= FPSCR_VXSQRT; + if (eflag & EFLAG_VXCVI) + fpscr |= FPSCR_VXCVI; + } + +// fpscr &= ~(FPSCR_VX); + if (fpscr & (FPSCR_VXSNAN | FPSCR_VXISI | FPSCR_VXIDI | + FPSCR_VXZDZ | FPSCR_VXIMZ | FPSCR_VXVC | + FPSCR_VXSOFT | FPSCR_VXSQRT | FPSCR_VXCVI)) + fpscr |= FPSCR_VX; + + fpscr &= ~(FPSCR_FEX); + if (((fpscr & FPSCR_VX) && (fpscr & FPSCR_VE)) || + ((fpscr & FPSCR_OX) && (fpscr & FPSCR_OE)) || + ((fpscr & FPSCR_UX) && (fpscr & FPSCR_UE)) || + ((fpscr & FPSCR_ZX) && (fpscr & FPSCR_ZE)) || + ((fpscr & FPSCR_XX) && (fpscr & FPSCR_XE))) + fpscr |= FPSCR_FEX; + + __FPU_FPSCR = fpscr; + + return (fpscr & FPSCR_FEX) ? 1 : 0; +} + +int +do_mathemu(struct pt_regs *regs) +{ + void *op0 = NULL, *op1 = NULL, *op2 = NULL, *op3 = NULL; + unsigned long pc = regs->nip; + signed short sdisp; + u32 insn = 0; + int idx = 0; + int (*func)(void *, void *, void *, void *); + int type = 0; + int eflag, trap; + + if (get_user(insn, (u32 __user *)pc)) + return -EFAULT; + + switch (insn >> 26) { + case LFS: func = lfs; type = D; break; + case LFSU: func = lfs; type = DU; break; + case LFD: func = lfd; type = D; break; + case LFDU: func = lfd; type = DU; break; + case STFS: func = stfs; type = D; break; + case STFSU: func = stfs; type = DU; break; + case STFD: func = stfd; type = D; break; + case STFDU: func = stfd; type = DU; break; + + case OP31: + switch ((insn >> 1) & 0x3ff) { + case LFSX: func = lfs; type = XE; break; + case LFSUX: func = lfs; type = XEU; break; + case LFDX: func = lfd; type = XE; break; + case LFDUX: func = lfd; type = XEU; break; + case STFSX: func = stfs; type = XE; break; + case STFSUX: func = stfs; type = XEU; break; + case STFDX: func = stfd; type = XE; break; + case STFDUX: func = stfd; type = XEU; break; + case STFIWX: func = stfiwx; type = XE; break; + default: + goto illegal; + } + break; + + case OP59: + switch ((insn >> 1) & 0x1f) { + case FDIVS: func = fdivs; type = AB; break; + case FSUBS: func = fsubs; type = AB; break; + case FADDS: func = fadds; type = AB; break; + case FSQRTS: func = fsqrts; type = XB; break; + case FRES: func = fres; type = XB; break; + case FMULS: func = fmuls; type = AC; break; + case FRSQRTES: func = frsqrtes;type = XB; break; + case FMSUBS: func = fmsubs; type = ABC; break; + case FMADDS: func = fmadds; type = ABC; break; + case FNMSUBS: func = fnmsubs; type = ABC; break; + case FNMADDS: func = fnmadds; type = ABC; break; + default: + goto illegal; + } + break; + + case OP63: + if (insn & 0x20) { + switch ((insn >> 1) & 0x1f) { + case FDIV: func = fdiv; type = AB; break; + case FSUB: func = fsub; type = AB; break; + case FADD: func = fadd; type = AB; break; + case FSQRT: func = fsqrt; type = XB; break; + case FRE: func = fre; type = XB; break; + case FSEL: func = fsel; type = ABC; break; + case FMUL: func = fmul; type = AC; break; + case FRSQRTE: func = frsqrte; type = XB; break; + case FMSUB: func = fmsub; type = ABC; break; + case FMADD: func = fmadd; type = ABC; break; + case FNMSUB: func = fnmsub; type = ABC; break; + case FNMADD: func = fnmadd; type = ABC; break; + default: + goto illegal; + } + break; + } + + switch ((insn >> 1) & 0x3ff) { + case FCMPU: func = fcmpu; type = XCR; break; + case FRSP: func = frsp; type = XB; break; + case FCTIW: func = fctiw; type = XB; break; + case FCTIWZ: func = fctiwz; type = XB; break; + case FCMPO: func = fcmpo; type = XCR; break; + case MTFSB1: func = mtfsb1; type = XCRB; break; + case FNEG: func = fneg; type = XB; break; + case MCRFS: func = mcrfs; type = XCRL; break; + case MTFSB0: func = mtfsb0; type = XCRB; break; + case FMR: func = fmr; type = XB; break; + case MTFSFI: func = mtfsfi; type = XCRI; break; + case FNABS: func = fnabs; type = XB; break; + case FABS: func = fabs; type = XB; break; + case MFFS: func = mffs; type = X; break; + case MTFSF: func = mtfsf; type = XFLB; break; + default: + goto illegal; + } + break; + + default: + goto illegal; + } + + switch (type) { + case AB: + op0 = (void *)¤t->thread.TS_FPR((insn >> 21) & 0x1f); + op1 = (void *)¤t->thread.TS_FPR((insn >> 16) & 0x1f); + op2 = (void *)¤t->thread.TS_FPR((insn >> 11) & 0x1f); + break; + + case AC: + op0 = (void *)¤t->thread.TS_FPR((insn >> 21) & 0x1f); + op1 = (void *)¤t->thread.TS_FPR((insn >> 16) & 0x1f); + op2 = (void *)¤t->thread.TS_FPR((insn >> 6) & 0x1f); + break; + + case ABC: + op0 = (void *)¤t->thread.TS_FPR((insn >> 21) & 0x1f); + op1 = (void *)¤t->thread.TS_FPR((insn >> 16) & 0x1f); + op2 = (void *)¤t->thread.TS_FPR((insn >> 11) & 0x1f); + op3 = (void *)¤t->thread.TS_FPR((insn >> 6) & 0x1f); + break; + + case D: + idx = (insn >> 16) & 0x1f; + sdisp = (insn & 0xffff); + op0 = (void *)¤t->thread.TS_FPR((insn >> 21) & 0x1f); + op1 = (void *)((idx ? regs->gpr[idx] : 0) + sdisp); + break; + + case DU: + idx = (insn >> 16) & 0x1f; + if (!idx) + goto illegal; + + sdisp = (insn & 0xffff); + op0 = (void *)¤t->thread.TS_FPR((insn >> 21) & 0x1f); + op1 = (void *)(regs->gpr[idx] + sdisp); + break; + + case X: + op0 = (void *)¤t->thread.TS_FPR((insn >> 21) & 0x1f); + break; + + case XA: + op0 = (void *)¤t->thread.TS_FPR((insn >> 21) & 0x1f); + op1 = (void *)¤t->thread.TS_FPR((insn >> 16) & 0x1f); + break; + + case XB: + op0 = (void *)¤t->thread.TS_FPR((insn >> 21) & 0x1f); + op1 = (void *)¤t->thread.TS_FPR((insn >> 11) & 0x1f); + break; + + case XE: + idx = (insn >> 16) & 0x1f; + op0 = (void *)¤t->thread.TS_FPR((insn >> 21) & 0x1f); + op1 = (void *)((idx ? regs->gpr[idx] : 0) + + regs->gpr[(insn >> 11) & 0x1f]); + break; + + case XEU: + idx = (insn >> 16) & 0x1f; + if (!idx) + goto illegal; + op0 = (void *)¤t->thread.TS_FPR((insn >> 21) & 0x1f); + op1 = (void *)(regs->gpr[idx] + + regs->gpr[(insn >> 11) & 0x1f]); + break; + + case XCR: + op0 = (void *)®s->ccr; + op1 = (void *)(long)((insn >> 23) & 0x7); + op2 = (void *)¤t->thread.TS_FPR((insn >> 16) & 0x1f); + op3 = (void *)¤t->thread.TS_FPR((insn >> 11) & 0x1f); + break; + + case XCRL: + op0 = (void *)®s->ccr; + op1 = (void *)(long)((insn >> 23) & 0x7); + op2 = (void *)(long)((insn >> 18) & 0x7); + break; + + case XCRB: + op0 = (void *)(long)((insn >> 21) & 0x1f); + break; + + case XCRI: + op0 = (void *)(long)((insn >> 23) & 0x7); + op1 = (void *)(long)((insn >> 12) & 0xf); + break; + + case XFLB: + op0 = (void *)(long)((insn >> 17) & 0xff); + op1 = (void *)¤t->thread.TS_FPR((insn >> 11) & 0x1f); + break; + + default: + goto illegal; + } + + /* + * If we support a HW FPU, we need to ensure the FP state + * is flushed into the thread_struct before attempting + * emulation + */ + flush_fp_to_thread(current); + + eflag = func(op0, op1, op2, op3); + + if (insn & 1) { + regs->ccr &= ~(0x0f000000); + regs->ccr |= (__FPU_FPSCR >> 4) & 0x0f000000; + } + + trap = record_exception(regs, eflag); + if (trap) + return 1; + + switch (type) { + case DU: + case XEU: + regs->gpr[idx] = (unsigned long)op1; + break; + + default: + break; + } + + regs_add_return_ip(regs, 4); + return 0; + +illegal: + return -ENOSYS; +} -- cgit v1.3.1