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x86/syscall: Mark exit[_group] syscall handlers __noreturn

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The direct-call syscall dispatch function doesn't know that the exit()
and exit_group() syscall handlers don't return, so the call sites aren't
optimized accordingly.

Fix that by marking the exit syscall declarations __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: 1e3ad78334 ("x86/syscall: Don't force use of indirect calls for system calls")
Closes: https://lkml.kernel.org/lkml/6dba9b32-db2c-4e6d-9500-7a08852f17a3@paulmck-laptop
Reported-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Tested-by: Paul E. McKenney <paulmck@kernel.org>
Link: https://lore.kernel.org/r/5d8882bc077d8eadcc7fd1740b56dfb781f12288.1719381528.git.jpoimboe@kernel.org
This commit is contained in:
Josh Poimboeuf 2024-06-25 23:02:00 -07:00 committed by Borislav Petkov (AMD)
parent f2661062f1
commit 9142be9e64
9 changed files with 56 additions and 25 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

6
arch/x86/entry/syscall_32.c
View File

@ -14,10 +14,13 @@
#endif
#define __SYSCALL(nr, sym) extern long __ia32_##sym(const struct pt_regs *);
#define __SYSCALL_NORETURN(nr, sym) extern long __noreturn __ia32_##sym(const struct pt_regs *);
#include <asm/syscalls_32.h>
#undef __SYSCALL
#undef __SYSCALL_NORETURN
#define __SYSCALL_NORETURN __SYSCALL
/*
* The sys_call_table[] is no longer used for system calls, but
* kernel/trace/trace_syscalls.c still wants to know the system
@ -32,7 +35,6 @@ const sys_call_ptr_t sys_call_table[] = {
#endif
#define __SYSCALL(nr, sym) case nr: return __ia32_##sym(regs);
long ia32_sys_call(const struct pt_regs *regs, unsigned int nr)
{
switch (nr) {

5
arch/x86/entry/syscall_64.c
View File

@ -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
/*
* The sys_call_table[] is no longer used for system calls, but
* kernel/trace/trace_syscalls.c still wants to know the system
@ -23,7 +27,6 @@ const sys_call_ptr_t sys_call_table[] = {
#undef __SYSCALL
#define __SYSCALL(nr, sym) case nr: return __x64_##sym(regs);
long x64_sys_call(const struct pt_regs *regs, unsigned int nr)
{
switch (nr) {

5
arch/x86/entry/syscall_x32.c
View File

@ -8,11 +8,14 @@
#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
#define __SYSCALL(nr, sym) case nr: return __x64_##sym(regs);
#undef __SYSCALL_NORETURN
#define __SYSCALL_NORETURN __SYSCALL
#define __SYSCALL(nr, sym) case nr: return __x64_##sym(regs);
long x32_sys_call(const struct pt_regs *regs, unsigned int nr)
{
switch (nr) {

6
arch/x86/entry/syscalls/syscall_32.tbl
View File

@ -2,7 +2,7 @@
# 32-bit system call numbers and entry vectors
#
# The format is:
# <number> <abi> <name> <entry point> <compat entry point>
# <number> <abi> <name> <entry point> [<compat entry point> [noreturn]]
#
# The __ia32_sys and __ia32_compat_sys stubs are created on-the-fly for
# sys_*() system calls and compat_sys_*() compat system calls if
@ -12,7 +12,7 @@
# The abi is always "i386" for this file.
#
0 i386 restart_syscall sys_restart_syscall
1 i386 exit sys_exit
1 i386 exit sys_exit - noreturn
2 i386 fork sys_fork
3 i386 read sys_read
4 i386 write sys_write
@ -263,7 +263,7 @@
249 i386 io_cancel sys_io_cancel
250 i386 fadvise64 sys_ia32_fadvise64
# 251 is available for reuse (was briefly sys_set_zone_reclaim)
252 i386 exit_group sys_exit_group
252 i386 exit_group sys_exit_group - noreturn
253 i386 lookup_dcookie
254 i386 epoll_create sys_epoll_create
255 i386 epoll_ctl sys_epoll_ctl

6
arch/x86/entry/syscalls/syscall_64.tbl
View File

@ -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> [<compat entry point> [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 - 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 - noreturn
232 common epoll_wait sys_epoll_wait
233 common epoll_ctl sys_epoll_ctl
234 common tgkill sys_tgkill

10
arch/x86/um/sys_call_table_32.c
View File

@ -9,6 +9,10 @@
#include <linux/cache.h>
#include <asm/syscall.h>
extern asmlinkage long sys_ni_syscall(unsigned long, unsigned long,
unsigned long, unsigned long,
unsigned long, unsigned long);
/*
* Below you can see, in terms of #define's, the differences between the x86-64
* and the UML syscall table.
@ -22,15 +26,13 @@
#define sys_vm86 sys_ni_syscall
#define __SYSCALL_WITH_COMPAT(nr, native, compat) __SYSCALL(nr, native)
#define __SYSCALL_NORETURN __SYSCALL
#define __SYSCALL(nr, sym) extern asmlinkage long sym(unsigned long, unsigned long, unsigned long, unsigned long, unsigned long, unsigned long);
#include <asm/syscalls_32.h>
#undef __SYSCALL
#define __SYSCALL(nr, sym) sym,
extern asmlinkage long sys_ni_syscall(unsigned long, unsigned long, unsigned long, unsigned long, unsigned long, unsigned long);
const sys_call_ptr_t sys_call_table[] ____cacheline_aligned = {
#include <asm/syscalls_32.h>
};

11
arch/x86/um/sys_call_table_64.c
View File

@ -9,6 +9,10 @@
#include <linux/cache.h>
#include <asm/syscall.h>
extern asmlinkage long sys_ni_syscall(unsigned long, unsigned long,
unsigned long, unsigned long,
unsigned long, unsigned long);
/*
* Below you can see, in terms of #define's, the differences between the x86-64
* and the UML syscall table.
@ -18,14 +22,13 @@
#define sys_iopl sys_ni_syscall
#define sys_ioperm sys_ni_syscall
#define __SYSCALL_NORETURN __SYSCALL
#define __SYSCALL(nr, sym) extern asmlinkage long sym(unsigned long, unsigned long, unsigned long, unsigned long, unsigned long, unsigned long);
#include <asm/syscalls_64.h>
#undef __SYSCALL
#define __SYSCALL(nr, sym) sym,
extern asmlinkage long sys_ni_syscall(unsigned long, unsigned long, unsigned long, unsigned long, unsigned long, unsigned long);
const sys_call_ptr_t sys_call_table[] ____cacheline_aligned = {
#include <asm/syscalls_64.h>
};

16
scripts/syscalltbl.sh
View File

@ -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: $infile: syscall table is not sorted or duplicates the same syscall number" >&2
@ -66,7 +66,21 @@ grep -E "^[0-9]+[[:space:]]+$abis" "$infile" | {
nxt=$((nxt + 1))
done
if [ "$compat" = "-" ]; then
unset compat
fi
if [ -n "$noreturn" ]; then
if [ "$noreturn" != "noreturn" ]; then
echo "error: $infile: invalid string \"$noreturn\" in 'noreturn' column"
exit 1
fi
if [ -n "$compat" ]; then
echo "__SYSCALL_COMPAT_NORETURN($nr, $native, $compat)"
else
echo "__SYSCALL_NORETURN($nr, $native)"
fi
elif [ -n "$compat" ]; then
echo "__SYSCALL_WITH_COMPAT($nr, $native, $compat)"
elif [ -n "$native" ]; then
echo "__SYSCALL($nr, $native)"

4
tools/objtool/noreturns.h
View File

@ -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)