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Subject[RFC v5 26/57] objtool: arm64: Decode brk instruction
Date
Add decoding brk instructions. Associate known immediate values with
their kernel/compiler semantics.

Suggested-by: Raphael Gault <raphael.gault@arm.com>
Signed-off-by: Julien Thierry <jthierry@redhat.com>
---
tools/objtool/arch/arm64/decode.c | 33 +++++++++++++++++++++++++++++++
1 file changed, 33 insertions(+)

diff --git a/tools/objtool/arch/arm64/decode.c b/tools/objtool/arch/arm64/decode.c
index aa00de725686..1609750cc4b9 100644
--- a/tools/objtool/arch/arm64/decode.c
+++ b/tools/objtool/arch/arm64/decode.c
@@ -507,6 +507,7 @@ int arm_decode_except_gen(u32 instr, enum insn_type *type,
#define INSN_SVC 0b00000001
#define INSN_HVC 0b00000010
#define INSN_SMC 0b00000011
+#define INSN_BRK 0b00100000

switch (decode_field) {
case INSN_SVC:
@@ -518,6 +519,38 @@ int arm_decode_except_gen(u32 instr, enum insn_type *type,
*/
*type = INSN_NOP;
return 0;
+ case INSN_BRK:
+ /* Based on arch/arm64/include/asm/brk-imm.h */
+ switch (imm16) {
+ case 0x004: /* KPROBES_BRK_IMM */
+ case 0x005: /* UPROBES_BRK_IMM */
+ case 0x400: /* KGDB_DYN_DBG_BRK_IMM */
+ case 0x401: /* KGDB_COMPILED_DBG_BRK_IMM */
+ *type = INSN_OTHER;
+ break;
+ case 0x800: /* BUG_BRK_IMM */
+ /*
+ * brk #0x800 is generated by the BUG()/WARN() linux API
+ * and is thus a particular case. Since those are not
+ * necessarily compiled in, the surrounding code should
+ * work properly without it. We thus consider it as a
+ * nop.
+ */
+ *type = INSN_NOP;
+ break;
+ case 0x3e8:
+ /*
+ * Similar to the use of "ud2" on x86, GCC inserts
+ * "brk #0x38e" instructions for certain divide-by-zero
+ * cases.
+ */
+ *type = INSN_BUG;
+ break;
+ default:
+ *type = INSN_CONTEXT_SWITCH;
+ break;
+ }
+ return 0;
default:
return arm_decode_unknown(instr, type, immediate, ops_list);
}
--
2.21.0
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