From: WANG Xuerui git@xen0n.name
[ Upstream commit c23e7f01cf621290770069d968ca4c8356a50d00 ]
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 git@xen0n.name Signed-off-by: Huacai Chen chenhuacai@loongson.cn Signed-off-by: Sasha Levin sashal@kernel.org --- arch/loongarch/include/asm/inst.h | 26 +++++++++ arch/loongarch/kernel/genex.S | 1 + arch/loongarch/kernel/traps.c | 92 +++++++++++++++++++++++++++++++ 3 files changed, 119 insertions(+)
diff --git a/arch/loongarch/include/asm/inst.h b/arch/loongarch/include/asm/inst.h index 7eedd83fd0d72..8f68def5a2643 100644 --- a/arch/loongarch/include/asm/inst.h +++ b/arch/loongarch/include/asm/inst.h @@ -115,6 +115,8 @@ enum reg2bstrd_op { };
enum reg3_op { + asrtle_op = 0x02, + asrtgt_op = 0x03, addw_op = 0x20, addd_op = 0x21, subw_op = 0x22, @@ -170,6 +172,30 @@ 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 7e5c293ed89f7..0719d2c9b59bc 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 05511203732c3..4e7f8c652218d 100644 --- a/arch/loongarch/kernel/traps.c +++ b/arch/loongarch/kernel/traps.c @@ -35,6 +35,7 @@ #include <asm/break.h> #include <asm/cpu.h> #include <asm/fpu.h> +#include <asm/inst.h> #include <asm/loongarch.h> #include <asm/mmu_context.h> #include <asm/pgtable.h> @@ -50,6 +51,7 @@
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); @@ -430,6 +432,95 @@ 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); @@ -750,6 +841,7 @@ 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);