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authorWANG Xuerui <git@xen0n.name>2023-05-01 17:19:27 +0800
committerHuacai Chen <chenhuacai@loongson.cn>2023-05-01 17:19:27 +0800
commitc23e7f01cf621290770069d968ca4c8356a50d00 (patch)
tree9a408cbfdda2c24f4851b48cce2cc9600373be03 /arch
parent325a38b511caff53c10393bab1e59cbd37f15ec2 (diff)
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')
-rw-r--r--arch/loongarch/include/asm/inst.h26
-rw-r--r--arch/loongarch/kernel/genex.S1
-rw-r--r--arch/loongarch/kernel/traps.c92
3 files changed, 119 insertions, 0 deletions
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 <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);