From: "Paul E. McKenney" <paulmck@kernel.org>
To: Josh Poimboeuf <jpoimboe@kernel.org>
Cc: x86@kernel.org, linux-kernel@vger.kernel.org,
Linus Torvalds <torvalds@linux-foundation.org>,
Daniel Sneddon <daniel.sneddon@linux.intel.com>,
Pawan Gupta <pawan.kumar.gupta@linux.intel.com>,
Thomas Gleixner <tglx@linutronix.de>,
Alexandre Chartre <alexandre.chartre@oracle.com>,
Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
Peter Zijlstra <peterz@infradead.org>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Sean Christopherson <seanjc@google.com>,
Andrew Cooper <andrew.cooper3@citrix.com>,
Dave Hansen <dave.hansen@linux.intel.com>,
Nikolay Borisov <nik.borisov@suse.com>,
KP Singh <kpsingh@kernel.org>, Waiman Long <longman@redhat.com>,
Borislav Petkov <bp@alien8.de>, Ingo Molnar <mingo@kernel.org>
Subject: Re: [PATCH v4 3/5] x86/syscall: Mark exit[_group] syscall handlers __noreturn
Date: Sat, 20 Apr 2024 06:58:58 -0700 [thread overview]
Message-ID: <0c410ba5-0e42-43b6-80b8-a69c5419a97d@paulmck-laptop> (raw)
In-Reply-To: <3b99cb2919c88ab3d353337423b2f0f1b9173f0a.1713559768.git.jpoimboe@kernel.org>
On Fri, Apr 19, 2024 at 02:09:49PM -0700, Josh Poimboeuf wrote:
> The direct-call syscall dispatch functions don't know that the exit()
> and exit_group() syscall handlers don't return. As a result the call
> sites aren't optimized accordingly.
>
> Fix that by marking those exit syscall declarations as __noreturn.
>
> Fixes the following warnings:
>
> vmlinux.o: warning: objtool: x64_sys_call+0x2804: __x64_sys_exit() is missing a __noreturn annotation
> vmlinux.o: warning: objtool: ia32_sys_call+0x29b6: __ia32_sys_exit_group() is missing a __noreturn annotation
>
> Fixes: 7390db8aea0d ("x86/bhi: Add support for clearing branch history at syscall entry")
> Reported-by: "Paul E. McKenney" <paulmck@kernel.org>
> Closes: https://lkml.kernel.org/lkml/6dba9b32-db2c-4e6d-9500-7a08852f17a3@paulmck-laptop
> Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Looks good, but it does not apply on top of current -next and I don't
trust myself to hand-apply it (something about having just got off of
a flight across the big pond).
Could you please let me know what else do I need to pull in to be able
to cleanly apply this one?
Thanx, Paul
> ---
> arch/x86/entry/syscall_64.c | 4 ++++
> arch/x86/entry/syscall_x32.c | 4 ++++
> arch/x86/entry/syscalls/syscall_64.tbl | 6 +++---
> arch/x86/um/sys_call_table_32.c | 1 +
> arch/x86/um/sys_call_table_64.c | 1 +
> scripts/syscalltbl.sh | 6 ++++--
> tools/objtool/noreturns.h | 4 ++++
> 7 files changed, 21 insertions(+), 5 deletions(-)
>
> diff --git a/arch/x86/entry/syscall_64.c b/arch/x86/entry/syscall_64.c
> index 96ea1f8a1d3f..ff36a993a07e 100644
> --- a/arch/x86/entry/syscall_64.c
> +++ b/arch/x86/entry/syscall_64.c
> @@ -8,9 +8,13 @@
> #include <asm/syscall.h>
>
> #define __SYSCALL(nr, sym) extern long __x64_##sym(const struct pt_regs *);
> +#define __SYSCALL_NORETURN(nr, sym) extern long __noreturn __x64_##sym(const struct pt_regs *);
> #include <asm/syscalls_64.h>
> #undef __SYSCALL
>
> +#undef __SYSCALL_NORETURN
> +#define __SYSCALL_NORETURN __SYSCALL
> +
> #define __SYSCALL(nr, sym) __x64_##sym,
> const sys_call_ptr_t sys_call_table[] = {
> #include <asm/syscalls_64.h>
> diff --git a/arch/x86/entry/syscall_x32.c b/arch/x86/entry/syscall_x32.c
> index 5aef4230faca..4221ecce6e68 100644
> --- a/arch/x86/entry/syscall_x32.c
> +++ b/arch/x86/entry/syscall_x32.c
> @@ -8,9 +8,13 @@
> #include <asm/syscall.h>
>
> #define __SYSCALL(nr, sym) extern long __x64_##sym(const struct pt_regs *);
> +#define __SYSCALL_NORETURN(nr, sym) extern long __noreturn __x64_##sym(const struct pt_regs *);
> #include <asm/syscalls_x32.h>
> #undef __SYSCALL
>
> +#undef __SYSCALL_NORETURN
> +#define __SYSCALL_NORETURN __SYSCALL
> +
> #define __SYSCALL(nr, sym) __x64_##sym,
> const sys_call_ptr_t x32_sys_call_table[] = {
> #include <asm/syscalls_x32.h>
> diff --git a/arch/x86/entry/syscalls/syscall_64.tbl b/arch/x86/entry/syscalls/syscall_64.tbl
> index 7e8d46f4147f..6695105d21b5 100644
> --- a/arch/x86/entry/syscalls/syscall_64.tbl
> +++ b/arch/x86/entry/syscalls/syscall_64.tbl
> @@ -2,7 +2,7 @@
> # 64-bit system call numbers and entry vectors
> #
> # The format is:
> -# <number> <abi> <name> <entry point>
> +# <number> <abi> <name> <entry point> [0 noreturn]
> #
> # The __x64_sys_*() stubs are created on-the-fly for sys_*() system calls
> #
> @@ -68,7 +68,7 @@
> 57 common fork sys_fork
> 58 common vfork sys_vfork
> 59 64 execve sys_execve
> -60 common exit sys_exit
> +60 common exit sys_exit 0 noreturn
> 61 common wait4 sys_wait4
> 62 common kill sys_kill
> 63 common uname sys_newuname
> @@ -239,7 +239,7 @@
> 228 common clock_gettime sys_clock_gettime
> 229 common clock_getres sys_clock_getres
> 230 common clock_nanosleep sys_clock_nanosleep
> -231 common exit_group sys_exit_group
> +231 common exit_group sys_exit_group 0 noreturn
> 232 common epoll_wait sys_epoll_wait
> 233 common epoll_ctl sys_epoll_ctl
> 234 common tgkill sys_tgkill
> diff --git a/arch/x86/um/sys_call_table_32.c b/arch/x86/um/sys_call_table_32.c
> index 89df5d89d664..c7d4bf955d2b 100644
> --- a/arch/x86/um/sys_call_table_32.c
> +++ b/arch/x86/um/sys_call_table_32.c
> @@ -24,6 +24,7 @@
> #define __SYSCALL_WITH_COMPAT(nr, native, compat) __SYSCALL(nr, native)
>
> #define __SYSCALL(nr, sym) extern asmlinkage long sym(unsigned long, unsigned long, unsigned long, unsigned long, unsigned long, unsigned long);
> +#define __SYSCALL_NORETURN __SYSCALL
> #include <asm/syscalls_32.h>
>
> #undef __SYSCALL
> diff --git a/arch/x86/um/sys_call_table_64.c b/arch/x86/um/sys_call_table_64.c
> index b0b4cfd2308c..4760c40ae5cd 100644
> --- a/arch/x86/um/sys_call_table_64.c
> +++ b/arch/x86/um/sys_call_table_64.c
> @@ -19,6 +19,7 @@
> #define sys_ioperm sys_ni_syscall
>
> #define __SYSCALL(nr, sym) extern asmlinkage long sym(unsigned long, unsigned long, unsigned long, unsigned long, unsigned long, unsigned long);
> +#define __SYSCALL_NORETURN __SYSCALL
> #include <asm/syscalls_64.h>
>
> #undef __SYSCALL
> diff --git a/scripts/syscalltbl.sh b/scripts/syscalltbl.sh
> index 6abe143889ef..16487d47e06a 100755
> --- a/scripts/syscalltbl.sh
> +++ b/scripts/syscalltbl.sh
> @@ -54,7 +54,7 @@ nxt=0
>
> grep -E "^[0-9]+[[:space:]]+$abis" "$infile" | {
>
> - while read nr abi name native compat ; do
> + while read nr abi name native compat noreturn; do
>
> if [ $nxt -gt $nr ]; then
> echo "error: $infile: syscall table is not sorted or duplicates the same syscall number" >&2
> @@ -66,7 +66,9 @@ grep -E "^[0-9]+[[:space:]]+$abis" "$infile" | {
> nxt=$((nxt + 1))
> done
>
> - if [ -n "$compat" ]; then
> + if [ -n "$noreturn" ]; then
> + echo "__SYSCALL_NORETURN($nr, $native)"
> + elif [ -n "$compat" ]; then
> echo "__SYSCALL_WITH_COMPAT($nr, $native, $compat)"
> elif [ -n "$native" ]; then
> echo "__SYSCALL($nr, $native)"
> diff --git a/tools/objtool/noreturns.h b/tools/objtool/noreturns.h
> index 7ebf29c91184..1e8141ef1b15 100644
> --- a/tools/objtool/noreturns.h
> +++ b/tools/objtool/noreturns.h
> @@ -7,12 +7,16 @@
> * Yes, this is unfortunate. A better solution is in the works.
> */
> NORETURN(__fortify_panic)
> +NORETURN(__ia32_sys_exit)
> +NORETURN(__ia32_sys_exit_group)
> NORETURN(__kunit_abort)
> NORETURN(__module_put_and_kthread_exit)
> NORETURN(__reiserfs_panic)
> NORETURN(__stack_chk_fail)
> NORETURN(__tdx_hypercall_failed)
> NORETURN(__ubsan_handle_builtin_unreachable)
> +NORETURN(__x64_sys_exit)
> +NORETURN(__x64_sys_exit_group)
> NORETURN(arch_cpu_idle_dead)
> NORETURN(bch2_trans_in_restart_error)
> NORETURN(bch2_trans_restart_error)
> --
> 2.44.0
>
next prev parent reply other threads:[~2024-04-20 13:59 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-19 21:09 [PATCH 0/5] x86/bugs: more BHI fixes Josh Poimboeuf
2024-04-19 21:09 ` [PATCH v4 1/5] x86/bugs: Only harden syscalls when needed Josh Poimboeuf
2024-04-22 8:09 ` Yujie Liu
2024-05-07 5:17 ` Josh Poimboeuf
2024-05-20 5:21 ` Yujie Liu
2024-04-19 21:09 ` [PATCH v4 2/5] cpu/speculation: Fix CPU mitigation defaults for !x86 Josh Poimboeuf
2024-04-20 0:09 ` Sean Christopherson
2024-04-23 14:10 ` Sean Christopherson
2024-04-24 5:35 ` Josh Poimboeuf
2024-04-19 21:09 ` [PATCH v4 3/5] x86/syscall: Mark exit[_group] syscall handlers __noreturn Josh Poimboeuf
2024-04-20 13:58 ` Paul E. McKenney [this message]
2024-04-21 5:25 ` Josh Poimboeuf
2024-04-21 20:40 ` Paul McKenney
2024-04-21 21:47 ` Paul McKenney
2024-05-02 23:48 ` Paul McKenney
2024-05-03 15:38 ` Paul E. McKenney
2024-05-03 19:56 ` Josh Poimboeuf
2024-05-03 20:44 ` Josh Poimboeuf
2024-05-03 23:33 ` Paul E. McKenney
2024-05-03 23:48 ` Josh Poimboeuf
2024-05-04 16:48 ` Paul E. McKenney
2024-04-19 21:09 ` [PATCH v4 4/5] x86/bugs: Remove duplicate Spectre cmdline option descriptions Josh Poimboeuf
2024-04-19 21:09 ` [PATCH v4 5/5] x86/bugs: Add 'spectre_bhi=vmexit' cmdline option Josh Poimboeuf
2024-04-19 21:46 ` Josh Poimboeuf
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