[PATCH RFC 2/4] signal: Introduce TRAP_PERF si_code and si_perf to siginfo

From: Marco Elver
Date: Tue Feb 23 2021 - 09:36:44 EST

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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.

Signed-off-by: Marco Elver <elver@xxxxxxxxxx>
---
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 5ad8566534e7..943c98782634 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;
@@ -3333,6 +3335,10 @@ 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;
@@ -3413,6 +3419,10 @@ 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;
@@ -4593,6 +4603,7 @@ 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);
--
2.30.0.617.g56c4b15f3c-goog

Next message: Marco Elver: "[PATCH RFC 3/4] perf/core: Add support for SIGTRAP on perf events"
Previous message: Marco Elver: "[PATCH RFC 1/4] perf/core: Apply PERF_EVENT_IOC_MODIFY_ATTRIBUTES to children"
In reply to: Dmitry Vyukov: "Re: [PATCH RFC 1/4] perf/core: Apply PERF_EVENT_IOC_MODIFY_ATTRIBUTES to children"
Next in thread: Geert Uytterhoeven: "Re: [PATCH RFC 2/4] signal: Introduce TRAP_PERF si_code and si_perf to siginfo"
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