This patch addresses the bpftool issue "Wrong callq address displayed"[0]. The issue stemmed from an incorrect program counter (PC) value used during disassembly with LLVM or libbfd. For LLVM: The PC argument must represent the actual address in the kernel to compute the correct relative address. For libbfd: The relative address can be adjusted by adding func_ksym within the custom info->print_address_func to yield the correct address. Links: [0] https://github.com/libbpf/bpftool/issues/109 Changes: v2 -> v3: * Address comment from Quentin: * Remove the typedef. v1 -> v2: * Fix the broken libbfd disassembler. Fixes: e1947c750ffe ("bpftool: Refactor disassembler for JIT-ed programs") Acked-by: Yonghong Song <yonghong.song@xxxxxxxxx> Signed-off-by: Leon Hwang <leon.hwang@xxxxxxxxx> --- tools/bpf/bpftool/jit_disasm.c | 40 ++++++++++++++++++++++++---------- 1 file changed, 29 insertions(+), 11 deletions(-) diff --git a/tools/bpf/bpftool/jit_disasm.c b/tools/bpf/bpftool/jit_disasm.c index 7b8d9ec89..c032d2c6a 100644 --- a/tools/bpf/bpftool/jit_disasm.c +++ b/tools/bpf/bpftool/jit_disasm.c @@ -80,7 +80,8 @@ symbol_lookup_callback(__maybe_unused void *disasm_info, static int init_context(disasm_ctx_t *ctx, const char *arch, __maybe_unused const char *disassembler_options, - __maybe_unused unsigned char *image, __maybe_unused ssize_t len) + __maybe_unused unsigned char *image, __maybe_unused ssize_t len, + __maybe_unused __u64 func_ksym) { char *triple; @@ -109,12 +110,13 @@ static void destroy_context(disasm_ctx_t *ctx) } static int -disassemble_insn(disasm_ctx_t *ctx, unsigned char *image, ssize_t len, int pc) +disassemble_insn(disasm_ctx_t *ctx, unsigned char *image, ssize_t len, int pc, + __u64 func_ksym) { char buf[256]; int count; - count = LLVMDisasmInstruction(*ctx, image + pc, len - pc, pc, + count = LLVMDisasmInstruction(*ctx, image + pc, len - pc, func_ksym + pc, buf, sizeof(buf)); if (json_output) printf_json(buf); @@ -136,8 +138,21 @@ int disasm_init(void) #ifdef HAVE_LIBBFD_SUPPORT #define DISASM_SPACER "\t" +struct disasm_info { + struct disassemble_info info; + __u64 func_ksym; +}; + +static void disasm_print_addr(bfd_vma addr, struct disassemble_info *info) +{ + struct disasm_info *dinfo = container_of(info, struct disasm_info, info); + + addr += dinfo->func_ksym; + generic_print_address(addr, info); +} + typedef struct { - struct disassemble_info *info; + struct disasm_info *info; disassembler_ftype disassemble; bfd *bfdf; } disasm_ctx_t; @@ -215,7 +230,7 @@ static int fprintf_json_styled(void *out, static int init_context(disasm_ctx_t *ctx, const char *arch, const char *disassembler_options, - unsigned char *image, ssize_t len) + unsigned char *image, ssize_t len, __u64 func_ksym) { struct disassemble_info *info; char tpath[PATH_MAX]; @@ -238,12 +253,13 @@ static int init_context(disasm_ctx_t *ctx, const char *arch, } bfdf = ctx->bfdf; - ctx->info = malloc(sizeof(struct disassemble_info)); + ctx->info = malloc(sizeof(struct disasm_info)); if (!ctx->info) { p_err("mem alloc failed"); goto err_close; } - info = ctx->info; + ctx->info->func_ksym = func_ksym; + info = &ctx->info->info; if (json_output) init_disassemble_info_compat(info, stdout, @@ -272,6 +288,7 @@ static int init_context(disasm_ctx_t *ctx, const char *arch, info->disassembler_options = disassembler_options; info->buffer = image; info->buffer_length = len; + info->print_address_func = disasm_print_addr; disassemble_init_for_target(info); @@ -304,9 +321,10 @@ static void destroy_context(disasm_ctx_t *ctx) static int disassemble_insn(disasm_ctx_t *ctx, __maybe_unused unsigned char *image, - __maybe_unused ssize_t len, int pc) + __maybe_unused ssize_t len, int pc, + __maybe_unused __u64 func_ksym) { - return ctx->disassemble(pc, ctx->info); + return ctx->disassemble(pc, &ctx->info->info); } int disasm_init(void) @@ -331,7 +349,7 @@ int disasm_print_insn(unsigned char *image, ssize_t len, int opcodes, if (!len) return -1; - if (init_context(&ctx, arch, disassembler_options, image, len)) + if (init_context(&ctx, arch, disassembler_options, image, len, func_ksym)) return -1; if (json_output) @@ -360,7 +378,7 @@ int disasm_print_insn(unsigned char *image, ssize_t len, int opcodes, printf("%4x:" DISASM_SPACER, pc); } - count = disassemble_insn(&ctx, image, len, pc); + count = disassemble_insn(&ctx, image, len, pc, func_ksym); if (json_output) { /* Operand array, was started in fprintf_json. Before -- 2.44.0
