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author | WANG Xuerui <git@xen0n.name> | 2023-05-01 12:19:27 +0300 |
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committer | Huacai Chen <chenhuacai@loongson.cn> | 2023-05-01 12:19:27 +0300 |
commit | c23e7f01cf621290770069d968ca4c8356a50d00 (patch) | |
tree | 9a408cbfdda2c24f4851b48cce2cc9600373be03 /arch/loongarch/kernel/genex.S | |
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/genex.S')
-rw-r--r-- | arch/loongarch/kernel/genex.S | 1 |
1 files changed, 1 insertions, 0 deletions
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 |