From c23e7f01cf621290770069d968ca4c8356a50d00 Mon Sep 17 00:00:00 2001 From: WANG Xuerui Date: Mon, 1 May 2023 17:19:27 +0800 Subject: LoongArch: Relay BCE exceptions to userland as SIGSEGV with si_code=SEGV_BNDERR SEGV_BNDERR was introduced initially for supporting the Intel MPX, but fell into disuse after the MPX support was removed. The LoongArch bounds-checking instructions behave very differently than MPX, but overall the interface is still kind of suitable for conveying the information to userland when bounds-checking assertions trigger, so we wouldn't have to invent more UAPI. Specifically, when the BCE triggers, a SEGV_BNDERR is sent to userland, with si_addr set to the out-of-bounds address or value (in asrt{gt,le}'s case), and one of si_lower or si_upper set to the configured bound depending on the faulting instruction. The other bound is set to either 0 or ULONG_MAX to resemble a range with both lower and upper bounds. Note that it is possible to have si_addr == si_lower in case of a failing asrtgt or {ld,st}gt, because those instructions test for strict greater-than relationship. This should not pose a problem for userland, though, because the faulting PC is available for the application to associate back to the exact instruction for figuring out the expectation. Example exception context generated by a faulting `asrtgt.d t0, t1` (assert t0 > t1 or BCE) with t0=100 and t1=200: > pc 00005555558206a4 ra 00007ffff2d854fc tp 00007ffff2f2f180 sp 00007ffffbf9fb80 > a0 0000000000000002 a1 00007ffffbf9fce8 a2 00007ffffbf9fd00 a3 00007ffff2ed4558 > a4 0000000000000000 a5 00007ffff2f044c8 a6 00007ffffbf9fce0 a7 fffffffffffff000 > t0 0000000000000064 t1 00000000000000c8 t2 00007ffffbfa2d5e t3 00007ffff2f12aa0 > t4 00007ffff2ed6158 t5 00007ffff2ed6158 t6 000000000000002e t7 0000000003d8f538 > t8 0000000000000005 u0 0000000000000000 s9 0000000000000000 s0 00007ffffbf9fce8 > s1 0000000000000002 s2 0000000000000000 s3 00007ffff2f2c038 s4 0000555555820610 > s5 00007ffff2ed5000 s6 0000555555827e38 s7 00007ffffbf9fd00 s8 0000555555827e38 > ra: 00007ffff2d854fc > ERA: 00005555558206a4 > CRMD: 000000b0 (PLV0 -IE -DA +PG DACF=CC DACM=CC -WE) > PRMD: 00000007 (PPLV3 +PIE -PWE) > EUEN: 00000000 (-FPE -SXE -ASXE -BTE) > ECFG: 0007181c (LIE=2-4,11-12 VS=7) > ESTAT: 000a0000 [BCE] (IS= ECode=10 EsubCode=0) > PRID: 0014c010 (Loongson-64bit, Loongson-3A5000) Signed-off-by: WANG Xuerui Signed-off-by: Huacai Chen --- arch/loongarch/include/asm/inst.h | 26 +++++++++++ arch/loongarch/kernel/genex.S | 1 + arch/loongarch/kernel/traps.c | 92 +++++++++++++++++++++++++++++++++++++++ 3 files changed, 119 insertions(+) (limited to 'arch/loongarch') diff --git a/arch/loongarch/include/asm/inst.h b/arch/loongarch/include/asm/inst.h index a04fe755d719..b09887ffcd15 100644 --- a/arch/loongarch/include/asm/inst.h +++ b/arch/loongarch/include/asm/inst.h @@ -121,6 +121,8 @@ enum reg2bstrd_op { }; enum reg3_op { + asrtle_op = 0x02, + asrtgt_op = 0x03, addw_op = 0x20, addd_op = 0x21, subw_op = 0x22, @@ -176,6 +178,30 @@ enum reg3_op { amord_op = 0x70c7, amxorw_op = 0x70c8, amxord_op = 0x70c9, + fldgts_op = 0x70e8, + fldgtd_op = 0x70e9, + fldles_op = 0x70ea, + fldled_op = 0x70eb, + fstgts_op = 0x70ec, + fstgtd_op = 0x70ed, + fstles_op = 0x70ee, + fstled_op = 0x70ef, + ldgtb_op = 0x70f0, + ldgth_op = 0x70f1, + ldgtw_op = 0x70f2, + ldgtd_op = 0x70f3, + ldleb_op = 0x70f4, + ldleh_op = 0x70f5, + ldlew_op = 0x70f6, + ldled_op = 0x70f7, + stgtb_op = 0x70f8, + stgth_op = 0x70f9, + stgtw_op = 0x70fa, + stgtd_op = 0x70fb, + stleb_op = 0x70fc, + stleh_op = 0x70fd, + stlew_op = 0x70fe, + stled_op = 0x70ff, }; enum reg3sa2_op { diff --git a/arch/loongarch/kernel/genex.S b/arch/loongarch/kernel/genex.S index 44ff1ff64260..78f066384657 100644 --- a/arch/loongarch/kernel/genex.S +++ b/arch/loongarch/kernel/genex.S @@ -82,6 +82,7 @@ SYM_FUNC_END(except_vec_cex) BUILD_HANDLER ade ade badv BUILD_HANDLER ale ale badv + BUILD_HANDLER bce bce none BUILD_HANDLER bp bp none BUILD_HANDLER fpe fpe fcsr BUILD_HANDLER fpu fpu none diff --git a/arch/loongarch/kernel/traps.c b/arch/loongarch/kernel/traps.c index 569c3a5bb052..8db26e4ca447 100644 --- a/arch/loongarch/kernel/traps.c +++ b/arch/loongarch/kernel/traps.c @@ -36,6 +36,7 @@ #include #include #include +#include #include #include #include @@ -51,6 +52,7 @@ extern asmlinkage void handle_ade(void); extern asmlinkage void handle_ale(void); +extern asmlinkage void handle_bce(void); extern asmlinkage void handle_sys(void); extern asmlinkage void handle_bp(void); extern asmlinkage void handle_ri(void); @@ -588,6 +590,95 @@ static void bug_handler(struct pt_regs *regs) } } +asmlinkage void noinstr do_bce(struct pt_regs *regs) +{ + bool user = user_mode(regs); + unsigned long era = exception_era(regs); + u64 badv = 0, lower = 0, upper = ULONG_MAX; + union loongarch_instruction insn; + irqentry_state_t state = irqentry_enter(regs); + + if (regs->csr_prmd & CSR_PRMD_PIE) + local_irq_enable(); + + current->thread.trap_nr = read_csr_excode(); + + die_if_kernel("Bounds check error in kernel code", regs); + + /* + * Pull out the address that failed bounds checking, and the lower / + * upper bound, by minimally looking at the faulting instruction word + * and reading from the correct register. + */ + if (__get_inst(&insn.word, (u32 *)era, user)) + goto bad_era; + + switch (insn.reg3_format.opcode) { + case asrtle_op: + if (insn.reg3_format.rd != 0) + break; /* not asrtle */ + badv = regs->regs[insn.reg3_format.rj]; + upper = regs->regs[insn.reg3_format.rk]; + break; + + case asrtgt_op: + if (insn.reg3_format.rd != 0) + break; /* not asrtgt */ + badv = regs->regs[insn.reg3_format.rj]; + lower = regs->regs[insn.reg3_format.rk]; + break; + + case ldleb_op: + case ldleh_op: + case ldlew_op: + case ldled_op: + case stleb_op: + case stleh_op: + case stlew_op: + case stled_op: + case fldles_op: + case fldled_op: + case fstles_op: + case fstled_op: + badv = regs->regs[insn.reg3_format.rj]; + upper = regs->regs[insn.reg3_format.rk]; + break; + + case ldgtb_op: + case ldgth_op: + case ldgtw_op: + case ldgtd_op: + case stgtb_op: + case stgth_op: + case stgtw_op: + case stgtd_op: + case fldgts_op: + case fldgtd_op: + case fstgts_op: + case fstgtd_op: + badv = regs->regs[insn.reg3_format.rj]; + lower = regs->regs[insn.reg3_format.rk]; + break; + } + + force_sig_bnderr((void __user *)badv, (void __user *)lower, (void __user *)upper); + +out: + if (regs->csr_prmd & CSR_PRMD_PIE) + local_irq_disable(); + + irqentry_exit(regs, state); + return; + +bad_era: + /* + * Cannot pull out the instruction word, hence cannot provide more + * info than a regular SIGSEGV in this case. + */ + force_sig(SIGSEGV); + goto out; +} + asmlinkage void noinstr do_bp(struct pt_regs *regs) { bool user = user_mode(regs); @@ -955,6 +1046,7 @@ void __init trap_init(void) set_handler(EXCCODE_ADE * VECSIZE, handle_ade, VECSIZE); set_handler(EXCCODE_ALE * VECSIZE, handle_ale, VECSIZE); + set_handler(EXCCODE_BCE * VECSIZE, handle_bce, VECSIZE); set_handler(EXCCODE_SYS * VECSIZE, handle_sys, VECSIZE); set_handler(EXCCODE_BP * VECSIZE, handle_bp, VECSIZE); set_handler(EXCCODE_INE * VECSIZE, handle_ri, VECSIZE); -- cgit v1.2.3