Em Wed, Sep 28, 2022 at 08:25:51AM -0700, Nathan Chancellor escreveu: > On Wed, Sep 28, 2022 at 10:42:53AM -0300, Arnaldo Carvalho de Melo wrote: > > Can you please provide the vmlinux file where this takes place? > > Sure thing, it is compressed to save some bandwidth while downloading: > > https://1drv.ms/u/s!AsQNYeB-IEbqnnzsULjM1pXmOlI5?e=qHKjuW So, fixed the case reported, DW_TAG_label outside a DW_TAG_lexblock, on asm DW_TAG_compile_unit DWARF containers, now I noticed that pahole suports encoding BTF_KIND_TAG (18) but not _decoding_ those, so off I go to work on it on btf_loader.c, looking at what btf_encoder.c does. Good that you got me this vmlinux built by clang 15 :-) Now we can BTF encode a vmlinux (-J) using all the CPUs in the system (-j), and then we end up with a kernel with BTF_KIND_TAG that can't be properly grokked by pahole when loading from BTF: ⬢[acme@toolbox pahole]$ pahole -j -J vmlinux-pahole-warnings ⬢[acme@toolbox pahole]$ pahole -F btf vmlinux-pahole-warnings > pahole-pretty-printed-from-btf BTF: idx: 277, Unknown kind 18 BTF: idx: 281, Unknown kind 18 BTF: idx: 331, Unknown kind 18 BTF: idx: 689, Unknown kind 18 BTF: idx: 692, Unknown kind 18 For instance: ⬢[acme@toolbox pahole]$ pahole -C __sifields -F btf vmlinux-pahole-warnings BTF: idx: 277, Unknown kind 18 BTF: idx: 281, Unknown kind 18 BTF: idx: 331, Unknown kind 18 BTF: idx: 689, Unknown kind 18 <BIG SNIP> BTF: idx: 128403, Unknown kind 18 BTF: idx: 128409, Unknown kind 18 union __sifields { struct { __kernel_pid_t _pid; /* 0 4 */ __kernel_uid32_t _uid; /* 4 4 */ } _kill; /* 0 8 */ struct { __kernel_timer_t _tid; /* 0 4 */ int _overrun; /* 4 4 */ sigval_t _sigval; /* 8 8 */ int _sys_private; /* 16 4 */ } _timer; /* 0 24 */ struct { __kernel_pid_t _pid; /* 0 4 */ __kernel_uid32_t _uid; /* 4 4 */ sigval_t _sigval; /* 8 8 */ } _rt; /* 0 16 */ struct { __kernel_pid_t _pid; /* 0 4 */ __kernel_uid32_t _uid; /* 4 4 */ int _status; /* 8 4 */ /* XXX 4 bytes hole, try to pack */ __kernel_clock_t _utime; /* 16 8 */ __kernel_clock_t _stime; /* 24 8 */ } _sigchld; /* 0 32 */ struct { <ERROR > _addr; /* 0 8 */ union { int _trapno; /* 8 4 */ short _addr_lsb; /* 8 2 */ struct { char _dummy_bnd[8]; /* 8 8 */ <ERROR> _lower; /* 16 8 */ <ERROR> _upper; /* 24 8 */ } _addr_bnd; /* 8 24 */ struct { char _dummy_pkey[8]; /* 8 8 */ __u32 _pkey; /* 16 4 */ } _addr_pkey; /* 8 12 */ struct { unsigned long _data; /* 8 8 */ __u32 _type; /* 16 4 */ __u32 _flags; /* 20 4 */ } _perf; /* 8 16 */ }; /* 8 24 */ } _sigfault; /* 0 32 */ struct { long _band; /* 0 8 */ int _fd; /* 8 4 */ } _sigpoll; /* 0 16 */ struct { <ERROR > _call_addr; /* 0 8 */ int _syscall; /* 8 4 */ unsigned int _arch; /* 12 4 */ } _sigsys; /* 0 16 */ }; ⬢[acme@toolbox pahole]$ And if we look from DWARF: ⬢[acme@toolbox pahole]$ pahole -C __sifields -F dwarf vmlinux-pahole-warnings | grep -w _addr -B2 -A2 } _sigchld; /* 0 32 */ struct { user * _addr; /* 0 8 */ union { int _trapno; /* 8 4 */ ⬢[acme@toolbox pahole]$ And from the source code: /* SIGILL, SIGFPE, SIGSEGV, SIGBUS, SIGTRAP, SIGEMT */ struct { void __user *_addr; /* faulting insn/memory ref. */ #ifdef __ia64__ int _imm; /* immediate value for "break" */ unsigned int _flags; /* see ia64 si_flags */ unsigned long _isr; /* isr */ #endif #define __ADDR_BND_PKEY_PAD (__alignof__(void *) < sizeof(short) ? \ sizeof(short) : __alignof__(void *)) union { /* used on alpha and sparc */ int _trapno; /* TRAP # which caused the signal */ /* * used when si_code=BUS_MCEERR_AR or * used when si_code=BUS_MCEERR_AO */ short _addr_lsb; /* LSB of the reported address */ /* used when si_code=SEGV_BNDERR */ struct { char _dummy_bnd[__ADDR_BND_PKEY_PAD]; void __user *_lower; void __user *_upper; } _addr_bnd; Ok: # define __user BTF_TYPE_TAG(user) #if defined(CONFIG_DEBUG_INFO_BTF) && defined(CONFIG_PAHOLE_HAS_BTF_TAG) && \ __has_attribute(btf_type_tag) # define BTF_TYPE_TAG(value) __attribute__((btf_type_tag(#value))) #else # define BTF_TYPE_TAG(value) /* nothing */ #endif Ok, homework to do: we need to better support btf_type_tag in both pahole pretty printer and in its BTF loader. :-) One of the new features will be: pahole --types_with_user_members - Arnaldo
