Re: [PATCH v3 11/12] signal: Deliver all of the siginfo perf data in _perf

From: Marco Elver
Date: Wed May 05 2021 - 13:57:31 EST

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On Wed, 5 May 2021 at 16:11, Eric W. Beiderman <ebiederm@xxxxxxxxxxxx> wrote:
> From: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx>
>
> Don't abuse si_errno and deliver all of the perf data in _perf member
> of siginfo_t.
>
> The data field in the perf data structures in a u64 to allow a pointer
> to be encoded without needed to implement a 32bit and 64bit version of
> the same structure. There already exists a 32bit and 64bit versions
> siginfo_t, and the 32bit version can not include a 64bit member as it
> only has 32bit alignment. So unsigned long is used in siginfo_t
> instead of a u64 as unsigned long can encode a pointer on all
> architectures linux supports.

Since there is no functional change (we already had the unsigned long
here), the explanation made me think there was a change in that area
(but there wasn't). (Can leave as-is, but a "Note: " or similar if you
deem it appropriate.)

> v1: https://lkml.kernel.org/r/m11rarqqx2.fsf_-_@xxxxxxxxxxxxxxxxx
> v2: https://lkml.kernel.org/r/20210503203814.25487-10-ebiederm@xxxxxxxxxxxx
> Signed-off-by: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx>

Reviewed-by: Marco Elver <elver@xxxxxxxxxx>

Thank you!

> ---
> arch/arm/kernel/signal.c | 3 ++-
> arch/arm64/kernel/signal.c | 3 ++-
> arch/arm64/kernel/signal32.c | 3 ++-
> arch/sparc/kernel/signal32.c | 3 ++-
> arch/sparc/kernel/signal_64.c | 3 ++-
> arch/x86/kernel/signal_compat.c | 6 ++++--
> fs/signalfd.c | 3 ++-
> include/linux/compat.h | 5 ++++-
> include/uapi/asm-generic/siginfo.h | 8 +++++--
> include/uapi/linux/signalfd.h | 4 ++--
> kernel/signal.c | 21 ++++++++++++-------
> .../selftests/perf_events/sigtrap_threads.c | 12 +++++------
> 12 files changed, 47 insertions(+), 27 deletions(-)
>
> diff --git a/arch/arm/kernel/signal.c b/arch/arm/kernel/signal.c
> index 643bcb0f091b..f3800c0f428b 100644
> --- a/arch/arm/kernel/signal.c
> +++ b/arch/arm/kernel/signal.c
> @@ -757,7 +757,8 @@ static_assert(offsetof(siginfo_t, si_addr_lsb) == 0x10);
> static_assert(offsetof(siginfo_t, si_lower) == 0x14);
> static_assert(offsetof(siginfo_t, si_upper) == 0x18);
> static_assert(offsetof(siginfo_t, si_pkey) == 0x14);
> -static_assert(offsetof(siginfo_t, si_perf) == 0x10);
> +static_assert(offsetof(siginfo_t, si_perf_data) == 0x10);
> +static_assert(offsetof(siginfo_t, si_perf_type) == 0x14);
> static_assert(offsetof(siginfo_t, si_band) == 0x0c);
> static_assert(offsetof(siginfo_t, si_fd) == 0x10);
> static_assert(offsetof(siginfo_t, si_call_addr) == 0x0c);
> diff --git a/arch/arm64/kernel/signal.c b/arch/arm64/kernel/signal.c
> index ad4bd27fc044..b3978b468bd4 100644
> --- a/arch/arm64/kernel/signal.c
> +++ b/arch/arm64/kernel/signal.c
> @@ -1005,7 +1005,8 @@ static_assert(offsetof(siginfo_t, si_addr_lsb) == 0x18);
> static_assert(offsetof(siginfo_t, si_lower) == 0x20);
> static_assert(offsetof(siginfo_t, si_upper) == 0x28);
> static_assert(offsetof(siginfo_t, si_pkey) == 0x20);
> -static_assert(offsetof(siginfo_t, si_perf) == 0x18);
> +static_assert(offsetof(siginfo_t, si_perf_data) == 0x18);
> +static_assert(offsetof(siginfo_t, si_perf_type) == 0x20);
> static_assert(offsetof(siginfo_t, si_band) == 0x10);
> static_assert(offsetof(siginfo_t, si_fd) == 0x18);
> static_assert(offsetof(siginfo_t, si_call_addr) == 0x10);
> diff --git a/arch/arm64/kernel/signal32.c b/arch/arm64/kernel/signal32.c
> index ee6c7484e130..d3be01c46bec 100644
> --- a/arch/arm64/kernel/signal32.c
> +++ b/arch/arm64/kernel/signal32.c
> @@ -489,7 +489,8 @@ static_assert(offsetof(compat_siginfo_t, si_addr_lsb) == 0x10);
> static_assert(offsetof(compat_siginfo_t, si_lower) == 0x14);
> static_assert(offsetof(compat_siginfo_t, si_upper) == 0x18);
> static_assert(offsetof(compat_siginfo_t, si_pkey) == 0x14);
> -static_assert(offsetof(compat_siginfo_t, si_perf) == 0x10);
> +static_assert(offsetof(compat_siginfo_t, si_perf_data) == 0x10);
> +static_assert(offsetof(compat_siginfo_t, si_perf_type) == 0x14);
> static_assert(offsetof(compat_siginfo_t, si_band) == 0x0c);
> static_assert(offsetof(compat_siginfo_t, si_fd) == 0x10);
> static_assert(offsetof(compat_siginfo_t, si_call_addr) == 0x0c);
> diff --git a/arch/sparc/kernel/signal32.c b/arch/sparc/kernel/signal32.c
> index 5573722e34ad..4276b9e003ca 100644
> --- a/arch/sparc/kernel/signal32.c
> +++ b/arch/sparc/kernel/signal32.c
> @@ -778,6 +778,7 @@ static_assert(offsetof(compat_siginfo_t, si_addr_lsb) == 0x10);
> static_assert(offsetof(compat_siginfo_t, si_lower) == 0x14);
> static_assert(offsetof(compat_siginfo_t, si_upper) == 0x18);
> static_assert(offsetof(compat_siginfo_t, si_pkey) == 0x14);
> -static_assert(offsetof(compat_siginfo_t, si_perf) == 0x10);
> +static_assert(offsetof(compat_siginfo_t, si_perf_data) == 0x10);
> +static_assert(offsetof(compat_siginfo_t, si_perf_type) == 0x14);
> static_assert(offsetof(compat_siginfo_t, si_band) == 0x0c);
> static_assert(offsetof(compat_siginfo_t, si_fd) == 0x10);
> diff --git a/arch/sparc/kernel/signal_64.c b/arch/sparc/kernel/signal_64.c
> index a69a78984c36..cea23cf95600 100644
> --- a/arch/sparc/kernel/signal_64.c
> +++ b/arch/sparc/kernel/signal_64.c
> @@ -588,6 +588,7 @@ static_assert(offsetof(siginfo_t, si_addr_lsb) == 0x18);
> static_assert(offsetof(siginfo_t, si_lower) == 0x20);
> static_assert(offsetof(siginfo_t, si_upper) == 0x28);
> static_assert(offsetof(siginfo_t, si_pkey) == 0x20);
> -static_assert(offsetof(siginfo_t, si_perf) == 0x18);
> +static_assert(offsetof(siginfo_t, si_perf_data) == 0x18);
> +static_assert(offsetof(siginfo_t, si_perf_type) == 0x20);
> static_assert(offsetof(siginfo_t, si_band) == 0x10);
> static_assert(offsetof(siginfo_t, si_fd) == 0x14);
> diff --git a/arch/x86/kernel/signal_compat.c b/arch/x86/kernel/signal_compat.c
> index c9601f092a1e..b52407c56000 100644
> --- a/arch/x86/kernel/signal_compat.c
> +++ b/arch/x86/kernel/signal_compat.c
> @@ -147,8 +147,10 @@ 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);
> + BUILD_BUG_ON(offsetof(siginfo_t, si_perf_data) != 0x18);
> + BUILD_BUG_ON(offsetof(siginfo_t, si_perf_type) != 0x20);
> + BUILD_BUG_ON(offsetof(compat_siginfo_t, si_perf_data) != 0x10);
> + BUILD_BUG_ON(offsetof(compat_siginfo_t, si_perf_type) != 0x14);
>
> CHECK_CSI_OFFSET(_sigpoll);
> CHECK_CSI_SIZE (_sigpoll, 2*sizeof(int));
> diff --git a/fs/signalfd.c b/fs/signalfd.c
> index 83130244f653..335ad39f3900 100644
> --- a/fs/signalfd.c
> +++ b/fs/signalfd.c
> @@ -134,7 +134,8 @@ static int signalfd_copyinfo(struct signalfd_siginfo __user *uinfo,
> break;
> case SIL_FAULT_PERF_EVENT:
> new.ssi_addr = (long) kinfo->si_addr;
> - new.ssi_perf = kinfo->si_perf;
> + new.ssi_perf_type = kinfo->si_perf_type;
> + new.ssi_perf_data = kinfo->si_perf_data;
> break;
> case SIL_CHLD:
> new.ssi_pid = kinfo->si_pid;
> diff --git a/include/linux/compat.h b/include/linux/compat.h
> index 6af7bef15e94..a27fffaae121 100644
> --- a/include/linux/compat.h
> +++ b/include/linux/compat.h
> @@ -236,7 +236,10 @@ typedef struct compat_siginfo {
> u32 _pkey;
> } _addr_pkey;
> /* used when si_code=TRAP_PERF */
> - compat_ulong_t _perf;
> + struct {
> + compat_ulong_t _data;
> + u32 _type;
> + } _perf;
> };
> } _sigfault;
>
> diff --git a/include/uapi/asm-generic/siginfo.h b/include/uapi/asm-generic/siginfo.h
> index 3503282021aa..3ba180f550d7 100644
> --- a/include/uapi/asm-generic/siginfo.h
> +++ b/include/uapi/asm-generic/siginfo.h
> @@ -96,7 +96,10 @@ union __sifields {
> __u32 _pkey;
> } _addr_pkey;
> /* used when si_code=TRAP_PERF */
> - unsigned long _perf;
> + struct {
> + unsigned long _data;
> + __u32 _type;
> + } _perf;
> };
> } _sigfault;
>
> @@ -159,7 +162,8 @@ 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_perf_data _sifields._sigfault._perf._data
> +#define si_perf_type _sifields._sigfault._perf._type
> #define si_band _sifields._sigpoll._band
> #define si_fd _sifields._sigpoll._fd
> #define si_call_addr _sifields._sigsys._call_addr
> diff --git a/include/uapi/linux/signalfd.h b/include/uapi/linux/signalfd.h
> index 7e333042c7e3..e78dddf433fc 100644
> --- a/include/uapi/linux/signalfd.h
> +++ b/include/uapi/linux/signalfd.h
> @@ -39,8 +39,8 @@ struct signalfd_siginfo {
> __s32 ssi_syscall;
> __u64 ssi_call_addr;
> __u32 ssi_arch;
> - __u32 __pad3;
> - __u64 ssi_perf;
> + __u32 ssi_perf_type;
> + __u64 ssi_perf_data;
>
> /*
> * Pad strcture to 128 bytes. Remember to update the
> diff --git a/kernel/signal.c b/kernel/signal.c
> index 49560ceac048..7fec9d1c5b11 100644
> --- a/kernel/signal.c
> +++ b/kernel/signal.c
> @@ -1758,11 +1758,13 @@ int force_sig_perf(void __user *addr, u32 type, u64 sig_data)
> struct kernel_siginfo info;
>
> clear_siginfo(&info);
> - info.si_signo = SIGTRAP;
> - info.si_errno = type;
> - info.si_code = TRAP_PERF;
> - info.si_addr = addr;
> - info.si_perf = sig_data;
> + info.si_signo = SIGTRAP;
> + info.si_errno = 0;
> + info.si_code = TRAP_PERF;
> + info.si_addr = addr;
> + info.si_perf_data = sig_data;
> + info.si_perf_type = type;
> +
> return force_sig_info(&info);
> }
>
> @@ -3380,7 +3382,8 @@ void copy_siginfo_to_external32(struct compat_siginfo *to,
> break;
> case SIL_FAULT_PERF_EVENT:
> to->si_addr = ptr_to_compat(from->si_addr);
> - to->si_perf = from->si_perf;
> + to->si_perf_data = from->si_perf_data;
> + to->si_perf_type = from->si_perf_type;
> break;
> case SIL_CHLD:
> to->si_pid = from->si_pid;
> @@ -3456,7 +3459,8 @@ static int post_copy_siginfo_from_user32(kernel_siginfo_t *to,
> break;
> case SIL_FAULT_PERF_EVENT:
> to->si_addr = compat_ptr(from->si_addr);
> - to->si_perf = from->si_perf;
> + to->si_perf_data = from->si_perf_data;
> + to->si_perf_type = from->si_perf_type;
> break;
> case SIL_CHLD:
> to->si_pid = from->si_pid;
> @@ -4639,7 +4643,8 @@ static inline void siginfo_buildtime_checks(void)
> CHECK_OFFSET(si_lower);
> CHECK_OFFSET(si_upper);
> CHECK_OFFSET(si_pkey);
> - CHECK_OFFSET(si_perf);
> + CHECK_OFFSET(si_perf_data);
> + CHECK_OFFSET(si_perf_type);
>
> /* sigpoll */
> CHECK_OFFSET(si_band);
> diff --git a/tools/testing/selftests/perf_events/sigtrap_threads.c b/tools/testing/selftests/perf_events/sigtrap_threads.c
> index 78ddf5e11625..fde123066a8c 100644
> --- a/tools/testing/selftests/perf_events/sigtrap_threads.c
> +++ b/tools/testing/selftests/perf_events/sigtrap_threads.c
> @@ -164,8 +164,8 @@ TEST_F(sigtrap_threads, enable_event)
> EXPECT_EQ(ctx.signal_count, NUM_THREADS);
> EXPECT_EQ(ctx.tids_want_signal, 0);
> EXPECT_EQ(ctx.first_siginfo.si_addr, &ctx.iterate_on);
> - EXPECT_EQ(ctx.first_siginfo.si_errno, PERF_TYPE_BREAKPOINT);
> - EXPECT_EQ(ctx.first_siginfo.si_perf, TEST_SIG_DATA(&ctx.iterate_on));
> + EXPECT_EQ(ctx.first_siginfo.si_perf_type, PERF_TYPE_BREAKPOINT);
> + EXPECT_EQ(ctx.first_siginfo.si_perf_data, TEST_SIG_DATA(&ctx.iterate_on));
>
> /* Check enabled for parent. */
> ctx.iterate_on = 0;
> @@ -183,8 +183,8 @@ TEST_F(sigtrap_threads, modify_and_enable_event)
> EXPECT_EQ(ctx.signal_count, NUM_THREADS);
> EXPECT_EQ(ctx.tids_want_signal, 0);
> EXPECT_EQ(ctx.first_siginfo.si_addr, &ctx.iterate_on);
> - EXPECT_EQ(ctx.first_siginfo.si_errno, PERF_TYPE_BREAKPOINT);
> - EXPECT_EQ(ctx.first_siginfo.si_perf, TEST_SIG_DATA(&ctx.iterate_on));
> + EXPECT_EQ(ctx.first_siginfo.si_perf_type, PERF_TYPE_BREAKPOINT);
> + EXPECT_EQ(ctx.first_siginfo.si_perf_data, TEST_SIG_DATA(&ctx.iterate_on));
>
> /* Check enabled for parent. */
> ctx.iterate_on = 0;
> @@ -203,8 +203,8 @@ TEST_F(sigtrap_threads, signal_stress)
> EXPECT_EQ(ctx.signal_count, NUM_THREADS * ctx.iterate_on);
> EXPECT_EQ(ctx.tids_want_signal, 0);
> EXPECT_EQ(ctx.first_siginfo.si_addr, &ctx.iterate_on);
> - EXPECT_EQ(ctx.first_siginfo.si_errno, PERF_TYPE_BREAKPOINT);
> - EXPECT_EQ(ctx.first_siginfo.si_perf, TEST_SIG_DATA(&ctx.iterate_on));
> + EXPECT_EQ(ctx.first_siginfo.si_perf_type, PERF_TYPE_BREAKPOINT);
> + EXPECT_EQ(ctx.first_siginfo.si_perf_data, TEST_SIG_DATA(&ctx.iterate_on));
> }
>
> TEST_HARNESS_MAIN
> --
> 2.30.1
>

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