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author | WANG Xuerui <git@xen0n.name> | 2023-05-01 12:19:27 +0300 |
---|---|---|
committer | Huacai Chen <chenhuacai@loongson.cn> | 2023-05-01 12:19:27 +0300 |
commit | c23e7f01cf621290770069d968ca4c8356a50d00 (patch) | |
tree | 9a408cbfdda2c24f4851b48cce2cc9600373be03 /arch/loongarch/kernel/traps.c | |
parent | 325a38b511caff53c10393bab1e59cbd37f15ec2 (diff) | |
download | linux-c23e7f01cf621290770069d968ca4c8356a50d00.tar.xz |
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 <git@xen0n.name>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
Diffstat (limited to 'arch/loongarch/kernel/traps.c')
-rw-r--r-- | arch/loongarch/kernel/traps.c | 92 |
1 files changed, 92 insertions, 0 deletions
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 <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> @@ -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); |