Re: [PATCH v7 2/7] arm64: Add more test functions to insn.c

From: David Long
Date: Mon Jun 29 2015 - 20:07:04 EST

On 06/29/15 13:23, Steve Capper wrote:
Hi David,
Some comments below.

On 15 June 2015 at 20:07, David Long <dave.long@xxxxxxxxxx> wrote:
From: "David A. Long" <dave.long@xxxxxxxxxx>

Certain instructions are hard to execute correctly out-of-line (as in
kprobes). Test functions are added to insn.[hc] to identify these. The
instructions include any that use PC-relative addressing, change the PC,
or change interrupt masking. For efficiency and simplicity test
functions are also added for small collections of related instructions.

Signed-off-by: David A. Long <dave.long@xxxxxxxxxx>
---
arch/arm64/include/asm/insn.h | 18 ++++++++++++++++++
arch/arm64/kernel/insn.c | 28 ++++++++++++++++++++++++++++
2 files changed, 46 insertions(+)

diff --git a/arch/arm64/include/asm/insn.h b/arch/arm64/include/asm/insn.h
index f81b328..1fdd237 100644
--- a/arch/arm64/include/asm/insn.h
+++ b/arch/arm64/include/asm/insn.h
@@ -223,8 +223,13 @@ static __always_inline bool aarch64_insn_is_##abbr(u32 code) \
static __always_inline u32 aarch64_insn_get_##abbr##_value(void) \
{ return (val); }

+__AARCH64_INSN_FUNCS(adr_adrp, 0x1F000000, 0x10000000)
+__AARCH64_INSN_FUNCS(prfm_lit, 0xFF000000, 0xD8000000)
__AARCH64_INSN_FUNCS(str_reg, 0x3FE0EC00, 0x38206800)
__AARCH64_INSN_FUNCS(ldr_reg, 0x3FE0EC00, 0x38606800)
+__AARCH64_INSN_FUNCS(ldr_lit, 0xBF000000, 0x18000000)
+__AARCH64_INSN_FUNCS(ldrsw_lit, 0xFF000000, 0x98000000)
+__AARCH64_INSN_FUNCS(exclusive, 0x3F000000, 0x08000000)

Going one step back, if we're worried about the exclusive monitors
then we'll be worried about instructions in-between the monitor pairs
too?


Yes, but I don't see anything we can reasonably do about that.


__AARCH64_INSN_FUNCS(stp_post, 0x7FC00000, 0x28800000)
__AARCH64_INSN_FUNCS(ldp_post, 0x7FC00000, 0x28C00000)
__AARCH64_INSN_FUNCS(stp_pre, 0x7FC00000, 0x29800000)
@@ -264,19 +269,29 @@ __AARCH64_INSN_FUNCS(ands, 0x7F200000, 0x6A000000)
__AARCH64_INSN_FUNCS(bics, 0x7F200000, 0x6A200000)
__AARCH64_INSN_FUNCS(b, 0xFC000000, 0x14000000)
__AARCH64_INSN_FUNCS(bl, 0xFC000000, 0x94000000)
+__AARCH64_INSN_FUNCS(b_bl, 0x7C000000, 0x14000000)
+__AARCH64_INSN_FUNCS(cb, 0x7E000000, 0x34000000)
__AARCH64_INSN_FUNCS(cbz, 0x7F000000, 0x34000000)
__AARCH64_INSN_FUNCS(cbnz, 0x7F000000, 0x35000000)
+__AARCH64_INSN_FUNCS(tb, 0x7E000000, 0x36000000)
__AARCH64_INSN_FUNCS(tbz, 0x7F000000, 0x36000000)
__AARCH64_INSN_FUNCS(tbnz, 0x7F000000, 0x37000000)
+__AARCH64_INSN_FUNCS(b_bl_cb_tb, 0x5C000000, 0x14000000)
__AARCH64_INSN_FUNCS(bcond, 0xFF000010, 0x54000000)
__AARCH64_INSN_FUNCS(svc, 0xFFE0001F, 0xD4000001)
__AARCH64_INSN_FUNCS(hvc, 0xFFE0001F, 0xD4000002)
__AARCH64_INSN_FUNCS(smc, 0xFFE0001F, 0xD4000003)
__AARCH64_INSN_FUNCS(brk, 0xFFE0001F, 0xD4200000)
+__AARCH64_INSN_FUNCS(exception, 0xFF000000, 0xD4000000)
__AARCH64_INSN_FUNCS(hint, 0xFFFFF01F, 0xD503201F)
__AARCH64_INSN_FUNCS(br, 0xFFFFFC1F, 0xD61F0000)
__AARCH64_INSN_FUNCS(blr, 0xFFFFFC1F, 0xD63F0000)
+__AARCH64_INSN_FUNCS(br_blr, 0xFFDFFC1F, 0xD61F0000)
__AARCH64_INSN_FUNCS(ret, 0xFFFFFC1F, 0xD65F0000)
+__AARCH64_INSN_FUNCS(msr_imm, 0xFFF8F000, 0xD5004000)

Should this not be:
__AARCH64_INSN_FUNCS(msr_imm, 0xFFF8F01F, 0xD500401F)
As the lower 5 bits of an MSR (immediate) are all 1?


Yeah, that does look more correct.

+__AARCH64_INSN_FUNCS(msr_reg, 0xFFF00000, 0xD5100000)
+__AARCH64_INSN_FUNCS(set_clr_daif, 0xFFFFF0DF, 0xD50340DF)

Looks good, just an MSR immediate with either DAIFSet or DAIFClr.

+__AARCH64_INSN_FUNCS(rd_wr_daif, 0xFFDFFFE0, 0xD51B4220)

Looks good, either MRS or MSR (register) where systemreg = DAIF.


#undef __AARCH64_INSN_FUNCS

@@ -285,6 +300,9 @@ bool aarch64_insn_is_nop(u32 insn);
int aarch64_insn_read(void *addr, u32 *insnp);
int aarch64_insn_write(void *addr, u32 insn);
enum aarch64_insn_encoding_class aarch64_get_insn_class(u32 insn);
+bool aarch64_insn_uses_literal(u32 insn);
+bool aarch64_insn_is_branch(u32 insn);
+bool aarch64_insn_is_daif_access(u32 insn);
u64 aarch64_insn_decode_immediate(enum aarch64_insn_imm_type type, u32 insn);
u32 aarch64_insn_encode_immediate(enum aarch64_insn_imm_type type,
u32 insn, u64 imm);
diff --git a/arch/arm64/kernel/insn.c b/arch/arm64/kernel/insn.c
index 9249020..ecd8882 100644
--- a/arch/arm64/kernel/insn.c
+++ b/arch/arm64/kernel/insn.c
@@ -155,6 +155,34 @@ static bool __kprobes __aarch64_insn_hotpatch_safe(u32 insn)
aarch64_insn_is_nop(insn);
}

+bool __kprobes aarch64_insn_uses_literal(u32 insn)
+{
+ /* ldr/ldrsw (literal), prfm */
+
+ return aarch64_insn_is_ldr_lit(insn) ||
+ aarch64_insn_is_ldrsw_lit(insn) ||
+ aarch64_insn_is_adr_adrp(insn) ||
+ aarch64_insn_is_prfm_lit(insn);
+}
+
+bool __kprobes aarch64_insn_is_branch(u32 insn)
+{
+ /* b, bl, cb*, tb*, b.cond, br, blr */
+
+ return aarch64_insn_is_b_bl_cb_tb(insn) ||
+ aarch64_insn_is_br_blr(insn) ||
+ aarch64_insn_is_ret(insn) ||
+ aarch64_insn_is_bcond(insn);
+}
+
+bool __kprobes aarch64_insn_is_daif_access(u32 insn)
+{
+ /* msr daif, mrs daif, msr daifset, msr daifclr */
+
+ return aarch64_insn_is_rd_wr_daif(insn) ||
+ aarch64_insn_is_set_clr_daif(insn);
+}
+
/*
* ARM Architecture Reference Manual for ARMv8 Profile-A, Issue A.a
* Section B2.6.5 "Concurrent modification and execution of instructions":
--
1.8.1.2


--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/