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arm64: insn: Add return statements after BUG_ON()

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Following a recent series of enhancements to the insn code the ARMv8
allnoconfig build has been generating a large number of warnings in the
form of:

arch/arm64/kernel/insn.c:689:8: warning: 'insn' may be used uninitialized in this function [-Wmaybe-uninitialized]

This is because BUG() and related macros can be compiled out so we get
execution paths which normally result in a panic compiling out to noops
instead.

I wasn't able to immediately identify a sensible return value to use in
these cases so just return AARCH64_BREAK_FAULT - this is all "should
never happen" code so hopefully it never has a practical impact.

Signed-off-by: Mark Brown <broonie@kernel.org>
[catalin.marinas@arm.com: AARCH64_BREAK_FAULT definition contributed by Daniel Borkmann]
[catalin.marinas@arm.com: replace return 0 with AARCH64_BREAK_FAULT]
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
This commit is contained in:
Mark Brown 2014-09-16 17:42:33 +01:00 committed by Catalin Marinas
parent 1059c6bf85
commit a9ae04c9fa
2 changed files with 33 additions and 0 deletions
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8
arch/arm64/include/asm/debug-monitors.h
View File

@ -48,9 +48,11 @@
/*
* #imm16 values used for BRK instruction generation
* Allowed values for kgbd are 0x400 - 0x7ff
* 0x100: for triggering a fault on purpose (reserved)
* 0x400: for dynamic BRK instruction
* 0x401: for compile time BRK instruction
*/
#define FAULT_BRK_IMM 0x100
#define KGDB_DYN_DGB_BRK_IMM 0x400
#define KDBG_COMPILED_DBG_BRK_IMM 0x401
@ -60,6 +62,12 @@
*/
#define AARCH64_BREAK_MON 0xd4200000
/*
* BRK instruction for provoking a fault on purpose
* Unlike kgdb, #imm16 value with unallocated handler is used for faulting.
*/
#define AARCH64_BREAK_FAULT (AARCH64_BREAK_MON | (FAULT_BRK_IMM << 5))
/*
* Extract byte from BRK instruction
*/

25
arch/arm64/kernel/insn.c
View File

@ -22,7 +22,9 @@
#include <linux/smp.h>
#include <linux/stop_machine.h>
#include <linux/uaccess.h>
#include <asm/cacheflush.h>
#include <asm/debug-monitors.h>
#include <asm/insn.h>
#define AARCH64_INSN_SF_BIT BIT(31)
@ -388,6 +390,7 @@ u32 __kprobes aarch64_insn_gen_branch_imm(unsigned long pc, unsigned long addr,
break;
default:
BUG_ON(1);
return AARCH64_BREAK_FAULT;
}
return aarch64_insn_encode_immediate(AARCH64_INSN_IMM_26, insn,
@ -413,6 +416,7 @@ u32 aarch64_insn_gen_comp_branch_imm(unsigned long pc, unsigned long addr,
break;
default:
BUG_ON(1);
return AARCH64_BREAK_FAULT;
}
switch (variant) {
@ -423,6 +427,7 @@ u32 aarch64_insn_gen_comp_branch_imm(unsigned long pc, unsigned long addr,
break;
default:
BUG_ON(1);
return AARCH64_BREAK_FAULT;
}
insn = aarch64_insn_encode_register(AARCH64_INSN_REGTYPE_RT, insn, reg);
@ -475,6 +480,7 @@ u32 aarch64_insn_gen_branch_reg(enum aarch64_insn_register reg,
break;
default:
BUG_ON(1);
return AARCH64_BREAK_FAULT;
}
return aarch64_insn_encode_register(AARCH64_INSN_REGTYPE_RN, insn, reg);
@ -497,6 +503,7 @@ u32 aarch64_insn_gen_load_store_reg(enum aarch64_insn_register reg,
break;
default:
BUG_ON(1);
return AARCH64_BREAK_FAULT;
}
insn = aarch64_insn_encode_ldst_size(size, insn);
@ -535,6 +542,7 @@ u32 aarch64_insn_gen_load_store_pair(enum aarch64_insn_register reg1,
break;
default:
BUG_ON(1);
return AARCH64_BREAK_FAULT;
}
switch (variant) {
@ -553,6 +561,7 @@ u32 aarch64_insn_gen_load_store_pair(enum aarch64_insn_register reg1,
break;
default:
BUG_ON(1);
return AARCH64_BREAK_FAULT;
}
insn = aarch64_insn_encode_register(AARCH64_INSN_REGTYPE_RT, insn,
@ -590,6 +599,7 @@ u32 aarch64_insn_gen_add_sub_imm(enum aarch64_insn_register dst,
break;
default:
BUG_ON(1);
return AARCH64_BREAK_FAULT;
}
switch (variant) {
@ -600,6 +610,7 @@ u32 aarch64_insn_gen_add_sub_imm(enum aarch64_insn_register dst,
break;
default:
BUG_ON(1);
return AARCH64_BREAK_FAULT;
}
BUG_ON(imm & ~(SZ_4K - 1));
@ -632,6 +643,7 @@ u32 aarch64_insn_gen_bitfield(enum aarch64_insn_register dst,
break;
default:
BUG_ON(1);
return AARCH64_BREAK_FAULT;
}
switch (variant) {
@ -644,6 +656,7 @@ u32 aarch64_insn_gen_bitfield(enum aarch64_insn_register dst,
break;
default:
BUG_ON(1);
return AARCH64_BREAK_FAULT;
}
BUG_ON(immr & ~mask);
@ -677,6 +690,7 @@ u32 aarch64_insn_gen_movewide(enum aarch64_insn_register dst,
break;
default:
BUG_ON(1);
return AARCH64_BREAK_FAULT;
}
BUG_ON(imm & ~(SZ_64K - 1));
@ -692,6 +706,7 @@ u32 aarch64_insn_gen_movewide(enum aarch64_insn_register dst,
break;
default:
BUG_ON(1);
return AARCH64_BREAK_FAULT;
}
insn |= (shift >> 4) << 21;
@ -725,6 +740,7 @@ u32 aarch64_insn_gen_add_sub_shifted_reg(enum aarch64_insn_register dst,
break;
default:
BUG_ON(1);
return AARCH64_BREAK_FAULT;
}
switch (variant) {
@ -737,6 +753,7 @@ u32 aarch64_insn_gen_add_sub_shifted_reg(enum aarch64_insn_register dst,
break;
default:
BUG_ON(1);
return AARCH64_BREAK_FAULT;
}
@ -769,6 +786,7 @@ u32 aarch64_insn_gen_data1(enum aarch64_insn_register dst,
break;
default:
BUG_ON(1);
return AARCH64_BREAK_FAULT;
}
switch (variant) {
@ -779,6 +797,7 @@ u32 aarch64_insn_gen_data1(enum aarch64_insn_register dst,
break;
default:
BUG_ON(1);
return AARCH64_BREAK_FAULT;
}
insn = aarch64_insn_encode_register(AARCH64_INSN_REGTYPE_RD, insn, dst);
@ -815,6 +834,7 @@ u32 aarch64_insn_gen_data2(enum aarch64_insn_register dst,
break;
default:
BUG_ON(1);
return AARCH64_BREAK_FAULT;
}
switch (variant) {
@ -825,6 +845,7 @@ u32 aarch64_insn_gen_data2(enum aarch64_insn_register dst,
break;
default:
BUG_ON(1);
return AARCH64_BREAK_FAULT;
}
insn = aarch64_insn_encode_register(AARCH64_INSN_REGTYPE_RD, insn, dst);
@ -852,6 +873,7 @@ u32 aarch64_insn_gen_data3(enum aarch64_insn_register dst,
break;
default:
BUG_ON(1);
return AARCH64_BREAK_FAULT;
}
switch (variant) {
@ -862,6 +884,7 @@ u32 aarch64_insn_gen_data3(enum aarch64_insn_register dst,
break;
default:
BUG_ON(1);
return AARCH64_BREAK_FAULT;
}
insn = aarch64_insn_encode_register(AARCH64_INSN_REGTYPE_RD, insn, dst);
@ -911,6 +934,7 @@ u32 aarch64_insn_gen_logical_shifted_reg(enum aarch64_insn_register dst,
break;
default:
BUG_ON(1);
return AARCH64_BREAK_FAULT;
}
switch (variant) {
@ -923,6 +947,7 @@ u32 aarch64_insn_gen_logical_shifted_reg(enum aarch64_insn_register dst,
break;
default:
BUG_ON(1);
return AARCH64_BREAK_FAULT;
}