Re: [PATCH v4 05/10] signal: Introduce TRAP_PERF si_code and si_perf to siginfo

Hi Marco,

On 08.04.2021 12:36, Marco Elver wrote:

Introduces the TRAP_PERF si_code, and associated siginfo_t field si_perf. These will be used by the perf event subsystem to send signals (if requested) to the task where an event occurred.

Acked-by: Geert Uytterhoeven geert@linux-m68k.org # m68k Acked-by: Arnd Bergmann arnd@arndb.de # asm-generic Signed-off-by: Marco Elver elver@google.com

This patch landed in linux-next as commit fb6cc127e0b6 ("signal: Introduce TRAP_PERF si_code and si_perf to siginfo"). It causes regression on my test systems (arm 32bit and 64bit). Most systems fails to boot in the given time frame. I've observed that there is a timeout waiting for udev to populate /dev and then also during the network interfaces configuration. Reverting this commit, together with 97ba62b27867 ("perf: Add support for SIGTRAP on perf events") to let it compile, on top of next-20210420 fixes the issue.

---

arch/m68k/kernel/signal.c | 3 +++ arch/x86/kernel/signal_compat.c | 5 ++++- fs/signalfd.c | 4 ++++ include/linux/compat.h | 2 ++ include/linux/signal.h | 1 + include/uapi/asm-generic/siginfo.h | 6 +++++- include/uapi/linux/signalfd.h | 4 +++- kernel/signal.c | 11 +++++++++++ 8 files changed, 33 insertions(+), 3 deletions(-)

diff --git a/arch/m68k/kernel/signal.c b/arch/m68k/kernel/signal.c index 349570f16a78..a4b7ee1df211 100644 --- a/arch/m68k/kernel/signal.c +++ b/arch/m68k/kernel/signal.c @@ -622,6 +622,9 @@ static inline void siginfo_build_tests(void) /* _sigfault._addr_pkey */ BUILD_BUG_ON(offsetof(siginfo_t, si_pkey) != 0x12);

• /* _sigfault._perf */
• BUILD_BUG_ON(offsetof(siginfo_t, si_perf) != 0x10);
• /* _sigpoll */ BUILD_BUG_ON(offsetof(siginfo_t, si_band) != 0x0c); BUILD_BUG_ON(offsetof(siginfo_t, si_fd) != 0x10);

diff --git a/arch/x86/kernel/signal_compat.c b/arch/x86/kernel/signal_compat.c index a5330ff498f0..0e5d0a7e203b 100644 --- a/arch/x86/kernel/signal_compat.c +++ b/arch/x86/kernel/signal_compat.c @@ -29,7 +29,7 @@ static inline void signal_compat_build_tests(void) BUILD_BUG_ON(NSIGFPE != 15); BUILD_BUG_ON(NSIGSEGV != 9); BUILD_BUG_ON(NSIGBUS != 5);

• BUILD_BUG_ON(NSIGTRAP != 5);

• BUILD_BUG_ON(NSIGTRAP != 6); BUILD_BUG_ON(NSIGCHLD != 6); BUILD_BUG_ON(NSIGSYS != 2);

@@ -138,6 +138,9 @@ static inline void signal_compat_build_tests(void) BUILD_BUG_ON(offsetof(siginfo_t, si_pkey) != 0x20); BUILD_BUG_ON(offsetof(compat_siginfo_t, si_pkey) != 0x14);

• BUILD_BUG_ON(offsetof(siginfo_t, si_perf) != 0x18);
• BUILD_BUG_ON(offsetof(compat_siginfo_t, si_perf) != 0x10);
• CHECK_CSI_OFFSET(_sigpoll); CHECK_CSI_SIZE (_sigpoll, 2*sizeof(int)); CHECK_SI_SIZE (_sigpoll, 4*sizeof(int));

diff --git a/fs/signalfd.c b/fs/signalfd.c index 456046e15873..040a1142915f 100644 --- a/fs/signalfd.c +++ b/fs/signalfd.c @@ -134,6 +134,10 @@ static int signalfd_copyinfo(struct signalfd_siginfo __user *uinfo, #endif new.ssi_addr_lsb = (short) kinfo->si_addr_lsb; break;

• case SIL_PERF_EVENT:

• new.ssi_addr = (long) kinfo->si_addr;
  

• new.ssi_perf = kinfo->si_perf;
  

• break;
  

  case SIL_CHLD: new.ssi_pid = kinfo->si_pid; new.ssi_uid = kinfo->si_uid;

diff --git a/include/linux/compat.h b/include/linux/compat.h index 6e65be753603..c8821d966812 100644 --- a/include/linux/compat.h +++ b/include/linux/compat.h @@ -236,6 +236,8 @@ typedef struct compat_siginfo { char _dummy_pkey[__COMPAT_ADDR_BND_PKEY_PAD]; u32 _pkey; } _addr_pkey;

• 		/* used when si_code=TRAP_PERF */
  

• 		compat_u64 _perf;
  };
  

  } _sigfault;

diff --git a/include/linux/signal.h b/include/linux/signal.h index 205526c4003a..1e98548d7cf6 100644 --- a/include/linux/signal.h +++ b/include/linux/signal.h @@ -43,6 +43,7 @@ enum siginfo_layout { SIL_FAULT_MCEERR, SIL_FAULT_BNDERR, SIL_FAULT_PKUERR,

• SIL_PERF_EVENT, SIL_CHLD, SIL_RT, SIL_SYS,

diff --git a/include/uapi/asm-generic/siginfo.h b/include/uapi/asm-generic/siginfo.h index d2597000407a..d0bb9125c853 100644 --- a/include/uapi/asm-generic/siginfo.h +++ b/include/uapi/asm-generic/siginfo.h @@ -91,6 +91,8 @@ union __sifields { char _dummy_pkey[__ADDR_BND_PKEY_PAD]; __u32 _pkey; } _addr_pkey;

• 	/* used when si_code=TRAP_PERF */
  

• 	__u64 _perf;
  

  }; } _sigfault;

@@ -155,6 +157,7 @@ typedef struct siginfo { #define si_lower _sifields._sigfault._addr_bnd._lower #define si_upper _sifields._sigfault._addr_bnd._upper #define si_pkey _sifields._sigfault._addr_pkey._pkey +#define si_perf _sifields._sigfault._perf #define si_band _sifields._sigpoll._band #define si_fd _sifields._sigpoll._fd #define si_call_addr _sifields._sigsys._call_addr @@ -253,7 +256,8 @@ typedef struct siginfo { #define TRAP_BRANCH 3 /* process taken branch trap */ #define TRAP_HWBKPT 4 /* hardware breakpoint/watchpoint */ #define TRAP_UNK 5 /* undiagnosed trap */ -#define NSIGTRAP 5 +#define TRAP_PERF 6 /* perf event with sigtrap=1 */ +#define NSIGTRAP 6 /*

• There is an additional set of SIGTRAP si_codes used by ptrace

diff --git a/include/uapi/linux/signalfd.h b/include/uapi/linux/signalfd.h index 83429a05b698..7e333042c7e3 100644 --- a/include/uapi/linux/signalfd.h +++ b/include/uapi/linux/signalfd.h @@ -39,6 +39,8 @@ struct signalfd_siginfo { __s32 ssi_syscall; __u64 ssi_call_addr; __u32 ssi_arch;

• __u32 __pad3;
• __u64 ssi_perf;

/* * Pad strcture to 128 bytes. Remember to update the @@ -49,7 +51,7 @@ struct signalfd_siginfo { * comes out of a read(2) and we really don't want to have * a compat on read(2). */

• __u8 __pad[28];

• __u8 __pad[16]; };

diff --git a/kernel/signal.c b/kernel/signal.c index f2718350bf4b..7061e4957650 100644 --- a/kernel/signal.c +++ b/kernel/signal.c @@ -1199,6 +1199,7 @@ static inline bool has_si_pid_and_uid(struct kernel_siginfo *info) case SIL_FAULT_MCEERR: case SIL_FAULT_BNDERR: case SIL_FAULT_PKUERR:

• case SIL_PERF_EVENT: case SIL_SYS: ret = false; break;

@@ -2531,6 +2532,7 @@ static void hide_si_addr_tag_bits(struct ksignal *ksig) case SIL_FAULT_MCEERR: case SIL_FAULT_BNDERR: case SIL_FAULT_PKUERR:

• case SIL_PERF_EVENT: ksig->info.si_addr = arch_untagged_si_addr( ksig->info.si_addr, ksig->sig, ksig->info.si_code); break;

@@ -3341,6 +3343,10 @@ void copy_siginfo_to_external32(struct compat_siginfo *to, #endif to->si_pkey = from->si_pkey; break;

• case SIL_PERF_EVENT:

• to->si_addr = ptr_to_compat(from->si_addr);
  

• to->si_perf = from->si_perf;
  

• break;
  

  case SIL_CHLD: to->si_pid = from->si_pid; to->si_uid = from->si_uid;

@@ -3421,6 +3427,10 @@ static int post_copy_siginfo_from_user32(kernel_siginfo_t *to, #endif to->si_pkey = from->si_pkey; break;

• case SIL_PERF_EVENT:

• to->si_addr = compat_ptr(from->si_addr);
  

• to->si_perf = from->si_perf;
  

• break;
  

  case SIL_CHLD: to->si_pid = from->si_pid; to->si_uid = from->si_uid;

@@ -4601,6 +4611,7 @@ static inline void siginfo_buildtime_checks(void) CHECK_OFFSET(si_lower); CHECK_OFFSET(si_upper); CHECK_OFFSET(si_pkey);

• CHECK_OFFSET(si_perf);

/* sigpoll */ CHECK_OFFSET(si_band);

Best regards