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Message-ID: <m1o8drfs1m.fsf@fess.ebiederm.org>
Date: Mon, 03 May 2021 16:04:05 -0500
From: ebiederm@...ssion.com (Eric W. Biederman)
To: Marco Elver <elver@...gle.com>
Cc: Arnd Bergmann <arnd@...db.de>, Florian Weimer <fweimer@...hat.com>,
"David S. Miller" <davem@...emloft.net>,
Peter Zijlstra <peterz@...radead.org>,
Ingo Molnar <mingo@...nel.org>,
Thomas Gleixner <tglx@...utronix.de>,
Peter Collingbourne <pcc@...gle.com>,
Dmitry Vyukov <dvyukov@...gle.com>,
Alexander Potapenko <glider@...gle.com>,
sparclinux <sparclinux@...r.kernel.org>,
linux-arch <linux-arch@...r.kernel.org>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
Linux API <linux-api@...r.kernel.org>,
kasan-dev <kasan-dev@...glegroups.com>
Subject: Re: [PATCH 10/12] signal: Redefine signinfo so 64bit fields are possible
"Eric W. Beiderman" <ebiederm@...ssion.com> writes:
> From: "Eric W. Biederman" <ebiederm@...ssion.com>
>
> The si_perf code really wants to add a u64 field. This change enables
> that by reorganizing the definition of siginfo_t, so that a 64bit
> field can be added without increasing the alignment of other fields.
I decided to include this change because it is not that complicated,
and it allows si_perf_data to have the definition that was originally
desired.
If this looks difficult to make in the userspace definitions,
or is otherwise a problem I don't mind dropping this change. I just
figured since it was not too difficult and we are changing things
anyway I should try for everything.
Eric
> Signed-off-by: "Eric W. Biederman" <ebiederm@...ssion.com>
> ---
> arch/x86/kernel/signal_compat.c | 9 +++----
> include/linux/compat.h | 28 +++++++++++++-------
> include/uapi/asm-generic/siginfo.h | 42 ++++++++++++++++++++----------
> 3 files changed, 49 insertions(+), 30 deletions(-)
>
> diff --git a/arch/x86/kernel/signal_compat.c b/arch/x86/kernel/signal_compat.c
> index a9fcabd8a5e5..a5cd01c52dfb 100644
> --- a/arch/x86/kernel/signal_compat.c
> +++ b/arch/x86/kernel/signal_compat.c
> @@ -17,8 +17,6 @@
> */
> static inline void signal_compat_build_tests(void)
> {
> - int _sifields_offset = offsetof(compat_siginfo_t, _sifields);
> -
> /*
> * If adding a new si_code, there is probably new data in
> * the siginfo. Make sure folks bumping the si_code
> @@ -40,8 +38,7 @@ static inline void signal_compat_build_tests(void)
> * in the ABI, of course. Make sure none of them ever
> * move and are always at the beginning:
> */
> - BUILD_BUG_ON(offsetof(compat_siginfo_t, _sifields) != 3 * sizeof(int));
> -#define CHECK_CSI_OFFSET(name) BUILD_BUG_ON(_sifields_offset != offsetof(compat_siginfo_t, _sifields.name))
> +#define CHECK_CSI_OFFSET(name) BUILD_BUG_ON(0 != offsetof(compat_siginfo_t, _sifields.name))
>
> BUILD_BUG_ON(offsetof(siginfo_t, si_signo) != 0);
> BUILD_BUG_ON(offsetof(siginfo_t, si_errno) != 4);
> @@ -63,8 +60,8 @@ static inline void signal_compat_build_tests(void)
> * structure stays within the padding size (checked
> * above).
> */
> -#define CHECK_CSI_SIZE(name, size) BUILD_BUG_ON(size != sizeof(((compat_siginfo_t *)0)->_sifields.name))
> -#define CHECK_SI_SIZE(name, size) BUILD_BUG_ON(size != sizeof(((siginfo_t *)0)->_sifields.name))
> +#define CHECK_CSI_SIZE(name, size) BUILD_BUG_ON(((3*sizeof(int))+(size)) != sizeof(((compat_siginfo_t *)0)->_sifields.name))
> +#define CHECK_SI_SIZE(name, size) BUILD_BUG_ON(((4*sizeof(int))+(size)) != sizeof(((siginfo_t *)0)->_sifields.name))
>
> CHECK_CSI_OFFSET(_kill);
> CHECK_CSI_SIZE (_kill, 2*sizeof(int));
> diff --git a/include/linux/compat.h b/include/linux/compat.h
> index 6af7bef15e94..d81493248bf3 100644
> --- a/include/linux/compat.h
> +++ b/include/linux/compat.h
> @@ -158,27 +158,28 @@ typedef union compat_sigval {
> compat_uptr_t sival_ptr;
> } compat_sigval_t;
>
> -typedef struct compat_siginfo {
> - int si_signo;
> -#ifndef __ARCH_HAS_SWAPPED_SIGINFO
> - int si_errno;
> - int si_code;
> -#else
> - int si_code;
> - int si_errno;
> -#endif
> +#define __COMPAT_SIGINFO_COMMON \
> + ___SIGINFO_COMMON; \
> + int _common_pad[__alignof__(compat_uptr_t) != __alignof__(int)]
>
> +typedef struct compat_siginfo {
> + union {
> + struct {
> + __COMPAT_SIGINFO_COMMON;
> + };
> union {
> - int _pad[128/sizeof(int) - 3];
> + int _pad[128/sizeof(int)];
>
> /* kill() */
> struct {
> + __COMPAT_SIGINFO_COMMON;
> compat_pid_t _pid; /* sender's pid */
> __compat_uid32_t _uid; /* sender's uid */
> } _kill;
>
> /* POSIX.1b timers */
> struct {
> + __COMPAT_SIGINFO_COMMON;
> compat_timer_t _tid; /* timer id */
> int _overrun; /* overrun count */
> compat_sigval_t _sigval; /* same as below */
> @@ -186,6 +187,7 @@ typedef struct compat_siginfo {
>
> /* POSIX.1b signals */
> struct {
> + __COMPAT_SIGINFO_COMMON;
> compat_pid_t _pid; /* sender's pid */
> __compat_uid32_t _uid; /* sender's uid */
> compat_sigval_t _sigval;
> @@ -193,6 +195,7 @@ typedef struct compat_siginfo {
>
> /* SIGCHLD */
> struct {
> + __COMPAT_SIGINFO_COMMON;
> compat_pid_t _pid; /* which child */
> __compat_uid32_t _uid; /* sender's uid */
> int _status; /* exit code */
> @@ -203,6 +206,7 @@ typedef struct compat_siginfo {
> #ifdef CONFIG_X86_X32_ABI
> /* SIGCHLD (x32 version) */
> struct {
> + __COMPAT_SIGINFO_COMMON;
> compat_pid_t _pid; /* which child */
> __compat_uid32_t _uid; /* sender's uid */
> int _status; /* exit code */
> @@ -213,6 +217,7 @@ typedef struct compat_siginfo {
>
> /* SIGILL, SIGFPE, SIGSEGV, SIGBUS, SIGTRAP, SIGEMT */
> struct {
> + __COMPAT_SIGINFO_COMMON;
> compat_uptr_t _addr; /* faulting insn/memory ref. */
> #define __COMPAT_ADDR_BND_PKEY_PAD (__alignof__(compat_uptr_t) < sizeof(short) ? \
> sizeof(short) : __alignof__(compat_uptr_t))
> @@ -242,16 +247,19 @@ typedef struct compat_siginfo {
>
> /* SIGPOLL */
> struct {
> + __COMPAT_SIGINFO_COMMON;
> compat_long_t _band; /* POLL_IN, POLL_OUT, POLL_MSG */
> int _fd;
> } _sigpoll;
>
> struct {
> + __COMPAT_SIGINFO_COMMON;
> compat_uptr_t _call_addr; /* calling user insn */
> int _syscall; /* triggering system call number */
> unsigned int _arch; /* AUDIT_ARCH_* of syscall */
> } _sigsys;
> } _sifields;
> + };
> } compat_siginfo_t;
>
> struct compat_rlimit {
> diff --git a/include/uapi/asm-generic/siginfo.h b/include/uapi/asm-generic/siginfo.h
> index e663bf117b46..1fcede623a73 100644
> --- a/include/uapi/asm-generic/siginfo.h
> +++ b/include/uapi/asm-generic/siginfo.h
> @@ -29,15 +29,33 @@ typedef union sigval {
> #define __ARCH_SI_ATTRIBUTES
> #endif
>
> +#ifndef __ARCH_HAS_SWAPPED_SIGINFO
> +#define ___SIGINFO_COMMON \
> + int si_signo; \
> + int si_errno; \
> + int si_code
> +#else
> +#define ___SIGINFO_COMMON \
> + int si_signo; \
> + int si_code; \
> + int si_errno
> +#endif /* __ARCH_HAS_SWAPPED_SIGINFO */
> +
> +#define __SIGINFO_COMMON \
> + ___SIGINFO_COMMON; \
> + int _common_pad[__alignof__(void *) != __alignof(int)]
> +
> union __sifields {
> /* kill() */
> struct {
> + __SIGINFO_COMMON;
> __kernel_pid_t _pid; /* sender's pid */
> __kernel_uid32_t _uid; /* sender's uid */
> } _kill;
>
> /* POSIX.1b timers */
> struct {
> + __SIGINFO_COMMON;
> __kernel_timer_t _tid; /* timer id */
> int _overrun; /* overrun count */
> sigval_t _sigval; /* same as below */
> @@ -46,6 +64,7 @@ union __sifields {
>
> /* POSIX.1b signals */
> struct {
> + __SIGINFO_COMMON;
> __kernel_pid_t _pid; /* sender's pid */
> __kernel_uid32_t _uid; /* sender's uid */
> sigval_t _sigval;
> @@ -53,6 +72,7 @@ union __sifields {
>
> /* SIGCHLD */
> struct {
> + __SIGINFO_COMMON;
> __kernel_pid_t _pid; /* which child */
> __kernel_uid32_t _uid; /* sender's uid */
> int _status; /* exit code */
> @@ -62,6 +82,7 @@ union __sifields {
>
> /* SIGILL, SIGFPE, SIGSEGV, SIGBUS, SIGTRAP, SIGEMT */
> struct {
> + __SIGINFO_COMMON;
> void __user *_addr; /* faulting insn/memory ref. */
> #ifdef __ia64__
> int _imm; /* immediate value for "break" */
> @@ -97,35 +118,28 @@ union __sifields {
>
> /* SIGPOLL */
> struct {
> + __SIGINFO_COMMON;
> __ARCH_SI_BAND_T _band; /* POLL_IN, POLL_OUT, POLL_MSG */
> int _fd;
> } _sigpoll;
>
> /* SIGSYS */
> struct {
> + __SIGINFO_COMMON;
> void __user *_call_addr; /* calling user insn */
> int _syscall; /* triggering system call number */
> unsigned int _arch; /* AUDIT_ARCH_* of syscall */
> } _sigsys;
> };
>
> -#ifndef __ARCH_HAS_SWAPPED_SIGINFO
> -#define __SIGINFO \
> -struct { \
> - int si_signo; \
> - int si_errno; \
> - int si_code; \
> - union __sifields _sifields; \
> -}
> -#else
> +
> #define __SIGINFO \
> -struct { \
> - int si_signo; \
> - int si_code; \
> - int si_errno; \
> +union { \
> + struct { \
> + __SIGINFO_COMMON; \
> + }; \
> union __sifields _sifields; \
> }
> -#endif /* __ARCH_HAS_SWAPPED_SIGINFO */
>
> typedef struct siginfo {
> union {
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