Re: [PATCH v3 03/21] perf llvm: Fix arm64 adrp instruction disassembly mismatch with objdump

[Tengda Wu]

On 2026/7/9 14:18, Namhyung Kim wrote:
> On Wed, Jul 01, 2026 at 03:53:37AM +0000, Tengda Wu wrote:
>> The operands of 'adrp' instructions parsed by libllvm are currently
>> represented as raw immediates rather than the "address <symbol+offset>"
>> format used by objdump. This inconsistency causes arm64_mov__parse()
>> to fail when parsing these instructions during post-processing.
>>
>> Example of the mismatch:
>>   Current: adrp x18, 8014
>>   Fix:     adrp x18, ffff800081f5f000 <this_cpu_vector>
>>
>> Fix this by manually extracting the target address from the raw adrp
>> instruction via symbol_lookup_callback(). The address is then converted
>> to a specific symbol during symbol__disassemble_llvm() and formatted
>> to match objdump's output, ensuring compatibility with existing
>> parsers.
>>
>> Signed-off-by: Tengda Wu <wutengda@xxxxxxxxxxxxxxx>
>> ---
>>  tools/perf/util/llvm.c | 50 ++++++++++++++++++++++++++++++++++++++++++
>>  1 file changed, 50 insertions(+)
>>
>> diff --git a/tools/perf/util/llvm.c b/tools/perf/util/llvm.c
>> index a0deb742a733..533d47e8084d 100644
>> --- a/tools/perf/util/llvm.c
>> +++ b/tools/perf/util/llvm.c
>> @@ -94,6 +94,7 @@ static void init_llvm(void)
>>  struct symbol_lookup_storage {
>>  	u64 branch_addr;
>>  	u64 pcrel_load_addr;
>> +	u64 pcrel_adrp_addr;
>>  };
>>  
>>  static const char *
>> @@ -108,6 +109,18 @@ symbol_lookup_callback(void *disinfo, uint64_t value,
>>  		storage->branch_addr = value;
>>  	else if (*ref_type == LLVMDisassembler_ReferenceType_In_PCrel_Load)
>>  		storage->pcrel_load_addr = value;
> 
> Is this used by arm64?  If not, would be possible to reuse
> pcrel_load_addr unless it'd complicate the code significantly?
> 
> I think it's the common concept of PC-relative addressing while it
> requires two instructions to set up the final address on arm64.
> 
> Thanks,
> Namhyung
> 
> 

I initially tried to reuse it directly, but it didn't seem to work properly
in some cases. After checking the LLVM interface implementation, I came up
with this change. I'll take another look at the details. If reuse is feasible,
I'll optimize this patch.

Thanks,
Tengda


>> +	else if (*ref_type == LLVMDisassembler_ReferenceType_In_ARM64_ADRP) {
>> +		uint64_t adrp_imm;
>> +
>> +		/* immhi (bits 23:5) and immlo (bits 30:29) */
>> +		adrp_imm = ((value & 0x00ffffe0) >> 3) | ((value >> 29) & 0x3);
>> +		/* Sign-extend the 21-bit immediate to 64-bit */
>> +		if (adrp_imm & (1ULL << 20))
>> +			adrp_imm |= ~((1ULL << 21) - 1);
>> +
>> +		/* Calculate the target page address */
>> +		storage->pcrel_adrp_addr = (address & ~0xFFFLL) + (adrp_imm << 12);
>> +	}
>>  	*ref_type = LLVMDisassembler_ReferenceType_InOut_None;
>>  	return NULL;
>>  }
>> @@ -204,6 +217,7 @@ int symbol__disassemble_llvm(const char *filename, struct symbol *sym,
>>  
>>  		storage.branch_addr = 0;
>>  		storage.pcrel_load_addr = 0;
>> +		storage.pcrel_adrp_addr = 0;
>>  
>>  		/*
>>  		 * LLVM's API has the code be disassembled as non-const, cast
>> @@ -227,6 +241,42 @@ int symbol__disassemble_llvm(const char *filename, struct symbol *sym,
>>  				free(name);
>>  			}
>>  		}
>> +		if (storage.pcrel_adrp_addr != 0) {
>> +			/*
>> +			 * ADRP (Address Page) instructions encode a 21-bit signed
>> +			 * immediate offset relative to the current PC's page.
>> +			 *
>> +			 * To maintain consistency with standard objdump output,
>> +			 * we truncate the raw encoded immediate at the comma
>> +			 * and replace it with the resolved absolute page address.
>> +			 *
>> +			 * Example conversion:
>> +			 * From: adrp x18, 8014
>> +			 * To:   adrp x18, ffff800081f5f000 <this_cpu_vector>
>> +			 */
>> +			char *name;
>> +			char *s = strchr(disasm_buf, ',');
>> +
>> +			if (s == NULL)
>> +				goto err;
>> +
>> +			s++;
>> +			*s = '\0';
>> +			disasm_len = strlen(disasm_buf);
>> +			disasm_len += scnprintf(disasm_buf + disasm_len,
>> +						sizeof(disasm_buf) - disasm_len,
>> +						" %"PRIx64,
>> +						storage.pcrel_adrp_addr);
>> +			name = llvm_name_for_data(dso, filename,
>> +						  storage.pcrel_adrp_addr);
>> +			if (name) {
>> +				disasm_len += scnprintf(disasm_buf + disasm_len,
>> +							sizeof(disasm_buf) -
>> +							disasm_len,
>> +							" <%s>", name);
>> +				free(name);
>> +			}
>> +		}
>>  		if (storage.pcrel_load_addr != 0) {
>>  			char *name = llvm_name_for_data(dso, filename,
>>  							storage.pcrel_load_addr);
>> -- 
>> 2.34.1
>>