From a9ae04c9faeff1ad617e4f4492af3143d8c5ad9b Mon Sep 17 00:00:00 2001 From: Mark Brown Date: Tue, 16 Sep 2014 17:42:33 +0100 Subject: [PATCH] arm64: insn: Add return statements after BUG_ON() 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 [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 --- arch/arm64/include/asm/debug-monitors.h | 8 ++++++++ arch/arm64/kernel/insn.c | 25 +++++++++++++++++++++++++ 2 files changed, 33 insertions(+) diff --git a/arch/arm64/include/asm/debug-monitors.h b/arch/arm64/include/asm/debug-monitors.h index 7fb343779498..230132f9a7d8 100644 --- a/arch/arm64/include/asm/debug-monitors.h +++ b/arch/arm64/include/asm/debug-monitors.h @@ -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 */ diff --git a/arch/arm64/kernel/insn.c b/arch/arm64/kernel/insn.c index 0668ee5c5bf9..e007714ded04 100644 --- a/arch/arm64/kernel/insn.c +++ b/arch/arm64/kernel/insn.c @@ -22,7 +22,9 @@ #include #include #include + #include +#include #include #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; } -- 2.39.5