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SubjectRe: [PATCH 0/8] use struct pt_regs based syscall calling for x86-64
On Thu, Apr 05, 2018 at 05:19:33PM +0200, Ingo Molnar wrote:
> Ok, this series looks mostly good to me, but AFAICS this breaks the UML build:
>
> make[2]: *** No rule to make target 'archheaders'. Stop.
> arch/um/Makefile:119: recipe for target 'archheaders' failed
> make[1]: *** [archheaders] Error 2
> make[1]: *** Waiting for unfinished jobs....

Ah, that's caused by patch 8/8 which I did and do not like all that much
anyway: UML re-uses syscall_64.tbl which now has x86-specific entries like
__sys_x86_pread64, but expects the generic syscall stub sys_pread64
referenced there. Fixup patch below; could be folded with patch 8/8. Or
patch 8/8 could simply be dropped from the series altogether...

Thanks,
Dominik

--------------------------------------------------------------------------
From f5049ea4e1e5e7751e72a22cbc1b3a9389959a04 Mon Sep 17 00:00:00 2001
From: Dominik Brodowski <linux@dominikbrodowski.net>
Date: Thu, 5 Apr 2018 22:16:23 +0200
Subject: [PATCH] syscalls/x86: fix UML syscall table

To differentiate the different calling regime used on x86, the syscall
functions received __sys_x86_ as prefix (instead of sys_). This breaks
the build of UML on 64-bit x86, as it re-uses the same syscall table.

To fix this, replace the __sys_x86_ prefix with sys_ during the generation
of <asm/syscalls_64.h>.

Fixes: syscalls/x86: rename struct pt_regs-based sys_*() to __sys_x86_*()
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: x86@kernel.org
Signed-off-by: Dominik Brodowski <linux@dominikbrodowski.net>

diff --git a/arch/x86/entry/syscalls/syscalltbl.sh b/arch/x86/entry/syscalls/syscalltbl.sh
index d71ef4bd3615..d6376b87ecb2 100644
--- a/arch/x86/entry/syscalls/syscalltbl.sh
+++ b/arch/x86/entry/syscalls/syscalltbl.sh
@@ -20,17 +20,47 @@ syscall_macro() {
echo "__SYSCALL_${abi}($nr, $real_entry, $qualifier)"
}

-emit() {
+emit64() {
abi="$1"
nr="$2"
entry="$3"
compat="$4"

- if [ "$abi" = "64" -a -n "$compat" ]; then
+ if [ "$abi" = "I386" ]; then
+ echo "emit64() called for a 32-bit syscall" >&2
+ exit 1
+ fi
+
+ if [ -n "$compat" ]; then
echo "a compat entry for a 64-bit syscall makes no sense" >&2
exit 1
fi

+ if [ -n "$entry" ]; then
+ # For CONFIG_UML, we need to strip the __sys_x86 prefix
+ if [ "${entry}" = "${entry#__compat_sys}" ]; then
+ umlentry="sys${entry#__sys_x86}"
+ fi
+
+ echo "#ifdef CONFIG_X86"
+ syscall_macro "$abi" "$nr" "$entry"
+ echo "#else /* CONFIG_UML */"
+ syscall_macro "$abi" "$nr" "$umlentry"
+ echo "#endif"
+ fi
+}
+
+emit32() {
+ abi="$1"
+ nr="$2"
+ entry="$3"
+ compat="$4"
+
+ if [ "$abi" = "64" ]; then
+ echo "emit32() called for a 64-bit syscall" >&2
+ exit 1
+ fi
+
if [ -z "$compat" ]; then
if [ -n "$entry" ]; then
syscall_macro "$abi" "$nr" "$entry"
@@ -53,14 +83,14 @@ grep '^[0-9]' "$in" | sort -n | (
# COMMON is the same as 64, except that we don't expect X32
# programs to use it. Our expectation has nothing to do with
# any generated code, so treat them the same.
- emit 64 "$nr" "$entry" "$compat"
+ emit64 64 "$nr" "$entry" "$compat"
elif [ "$abi" = "X32" ]; then
# X32 is equivalent to 64 on an X32-compatible kernel.
echo "#ifdef CONFIG_X86_X32_ABI"
- emit 64 "$nr" "$entry" "$compat"
+ emit64 64 "$nr" "$entry" "$compat"
echo "#endif"
elif [ "$abi" = "I386" ]; then
- emit "$abi" "$nr" "$entry" "$compat"
+ emit32 "$abi" "$nr" "$entry" "$compat"
else
echo "Unknown abi $abi" >&2
exit 1
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