[PATCH 1/2] powerpc/32: fix syscall wrappers with 64-bit arguments of unaligned register-pairs
Nicholas Piggin
npiggin at gmail.com
Wed Oct 12 14:53:34 AEDT 2022
powerpc 32-bit system call (and function) calling convention for 64-bit
arguments requires the next available odd-pair (two sequential registers
with the first being odd-numbered) from the standard register argument
allocation.
The first argument register is r3, so a 64-bit argument that appears at
an even position in the argument list must skip a register (unless there
were preceeding 64-bit arguments, which might throw things off). This
requires non-standard compat definitions to deal with the holes in the
argument register allocation.
With pt_regs syscall wrappers which use a standard mapper to map pt_regs
GPRs to function arguments, 32-bit kernels hit the same basic problem,
the standard definitions don't cope with the unused argument registers.
Fix this by having 32-bit kernels share those syscall definitions with
compat.
Thanks to Jason for spending a lot of time finding and bisecting this and
developing a trivial reproducer. The perfect bug report.
Reported-by: Jason A. Donenfeld <Jason at zx2c4.com>
Signed-off-by: Nicholas Piggin <npiggin at gmail.com>
---
Since posting the patch in the bug thread:
- dropped sync_file_range2 from the ppc32 syscalls.
- updated some comments on sys_ppc32.c, which now has a different
purpose.
- still have not explicitly tested all convrted syscalls on ppc32
(I don't have a great ppc32 environment to test such things,
will have to try rectify that...).
- Build fixes from mpe.
- Thanks to jms and mpe for helping with debugging.
Thanks,
Nick
arch/powerpc/include/asm/syscalls.h | 16 ++++++++++
arch/powerpc/kernel/Makefile | 1 +
arch/powerpc/kernel/sys_ppc32.c | 38 ++++++++++++++++++------
arch/powerpc/kernel/syscalls/syscall.tbl | 16 ++++++----
4 files changed, 56 insertions(+), 15 deletions(-)
diff --git a/arch/powerpc/include/asm/syscalls.h b/arch/powerpc/include/asm/syscalls.h
index 9840d572da55..a1142496cd58 100644
--- a/arch/powerpc/include/asm/syscalls.h
+++ b/arch/powerpc/include/asm/syscalls.h
@@ -89,6 +89,22 @@ long compat_sys_rt_sigreturn(void);
* responsible for combining parameter pairs.
*/
+#ifdef CONFIG_PPC32
+long sys_ppc_pread64(unsigned int fd,
+ char __user *ubuf, compat_size_t count,
+ u32 reg6, u32 pos1, u32 pos2);
+long sys_ppc_pwrite64(unsigned int fd,
+ const char __user *ubuf, compat_size_t count,
+ u32 reg6, u32 pos1, u32 pos2);
+long sys_ppc_readahead(int fd, u32 r4,
+ u32 offset1, u32 offset2, u32 count);
+long sys_ppc_truncate64(const char __user *path, u32 reg4,
+ unsigned long len1, unsigned long len2);
+long sys_ppc_ftruncate64(unsigned int fd, u32 reg4,
+ unsigned long len1, unsigned long len2);
+long sys_ppc32_fadvise64(int fd, u32 unused, u32 offset1, u32 offset2,
+ size_t len, int advice);
+#endif
#ifdef CONFIG_COMPAT
long compat_sys_mmap2(unsigned long addr, size_t len,
unsigned long prot, unsigned long flags,
diff --git a/arch/powerpc/kernel/Makefile b/arch/powerpc/kernel/Makefile
index 1f121c188805..d382564034a7 100644
--- a/arch/powerpc/kernel/Makefile
+++ b/arch/powerpc/kernel/Makefile
@@ -73,6 +73,7 @@ obj-y := cputable.o syscalls.o \
obj-y += ptrace/
obj-$(CONFIG_PPC64) += setup_64.o irq_64.o\
paca.o nvram_64.o note.o
+obj-$(CONFIG_PPC32) += sys_ppc32.o
obj-$(CONFIG_COMPAT) += sys_ppc32.o signal_32.o
obj-$(CONFIG_VDSO32) += vdso32_wrapper.o
obj-$(CONFIG_PPC_WATCHDOG) += watchdog.o
diff --git a/arch/powerpc/kernel/sys_ppc32.c b/arch/powerpc/kernel/sys_ppc32.c
index dcc3c9fd4cfd..6bdfe11a7689 100644
--- a/arch/powerpc/kernel/sys_ppc32.c
+++ b/arch/powerpc/kernel/sys_ppc32.c
@@ -1,13 +1,23 @@
// SPDX-License-Identifier: GPL-2.0-or-later
/*
- * sys_ppc32.c: Conversion between 32bit and 64bit native syscalls.
+ * sys_ppc32.c: 32-bit system calls with complex calling conventions.
*
* Copyright (C) 2001 IBM
* Copyright (C) 1997,1998 Jakub Jelinek (jj at sunsite.mff.cuni.cz)
* Copyright (C) 1997 David S. Miller (davem at caip.rutgers.edu)
*
- * These routines maintain argument size conversion between 32bit and 64bit
- * environment.
+ * 32-bit system calls with 64-bit arguments pass those in register pairs.
+ * This must be specially dealt with on 64-bit kernels. The compat_arg_u64_dual
+ * in generic compat syscalls is not always usable because the register
+ * pairing is constrained depending on preceeding arguments.
+ *
+ * An analogous problem exists on 32-bit kernels with ARCH_HAS_SYSCALL_WRAPPER,
+ * the defined system call functions take the pt_regs as an argument, and there
+ * is a mapping macro which maps registers to arguments
+ * (SC_POWERPC_REGS_TO_ARGS) which also does not deal with these 64-bit
+ * arguments.
+ *
+ * This file contains these system calls.
*/
#include <linux/kernel.h>
@@ -47,7 +57,17 @@
#include <asm/syscalls.h>
#include <asm/switch_to.h>
-COMPAT_SYSCALL_DEFINE6(ppc_pread64,
+#ifdef CONFIG_PPC32
+#define PPC32_SYSCALL_DEFINE4 SYSCALL_DEFINE4
+#define PPC32_SYSCALL_DEFINE5 SYSCALL_DEFINE5
+#define PPC32_SYSCALL_DEFINE6 SYSCALL_DEFINE6
+#else
+#define PPC32_SYSCALL_DEFINE4 COMPAT_SYSCALL_DEFINE4
+#define PPC32_SYSCALL_DEFINE5 COMPAT_SYSCALL_DEFINE5
+#define PPC32_SYSCALL_DEFINE6 COMPAT_SYSCALL_DEFINE6
+#endif
+
+PPC32_SYSCALL_DEFINE6(ppc_pread64,
unsigned int, fd,
char __user *, ubuf, compat_size_t, count,
u32, reg6, u32, pos1, u32, pos2)
@@ -55,7 +75,7 @@ COMPAT_SYSCALL_DEFINE6(ppc_pread64,
return ksys_pread64(fd, ubuf, count, merge_64(pos1, pos2));
}
-COMPAT_SYSCALL_DEFINE6(ppc_pwrite64,
+PPC32_SYSCALL_DEFINE6(ppc_pwrite64,
unsigned int, fd,
const char __user *, ubuf, compat_size_t, count,
u32, reg6, u32, pos1, u32, pos2)
@@ -63,28 +83,28 @@ COMPAT_SYSCALL_DEFINE6(ppc_pwrite64,
return ksys_pwrite64(fd, ubuf, count, merge_64(pos1, pos2));
}
-COMPAT_SYSCALL_DEFINE5(ppc_readahead,
+PPC32_SYSCALL_DEFINE5(ppc_readahead,
int, fd, u32, r4,
u32, offset1, u32, offset2, u32, count)
{
return ksys_readahead(fd, merge_64(offset1, offset2), count);
}
-COMPAT_SYSCALL_DEFINE4(ppc_truncate64,
+PPC32_SYSCALL_DEFINE4(ppc_truncate64,
const char __user *, path, u32, reg4,
unsigned long, len1, unsigned long, len2)
{
return ksys_truncate(path, merge_64(len1, len2));
}
-COMPAT_SYSCALL_DEFINE4(ppc_ftruncate64,
+PPC32_SYSCALL_DEFINE4(ppc_ftruncate64,
unsigned int, fd, u32, reg4,
unsigned long, len1, unsigned long, len2)
{
return ksys_ftruncate(fd, merge_64(len1, len2));
}
-COMPAT_SYSCALL_DEFINE6(ppc32_fadvise64,
+PPC32_SYSCALL_DEFINE6(ppc32_fadvise64,
int, fd, u32, unused, u32, offset1, u32, offset2,
size_t, len, int, advice)
{
diff --git a/arch/powerpc/kernel/syscalls/syscall.tbl b/arch/powerpc/kernel/syscalls/syscall.tbl
index 2bca64f96164..e9e0df4f9a61 100644
--- a/arch/powerpc/kernel/syscalls/syscall.tbl
+++ b/arch/powerpc/kernel/syscalls/syscall.tbl
@@ -228,8 +228,10 @@
176 64 rt_sigtimedwait sys_rt_sigtimedwait
177 nospu rt_sigqueueinfo sys_rt_sigqueueinfo compat_sys_rt_sigqueueinfo
178 nospu rt_sigsuspend sys_rt_sigsuspend compat_sys_rt_sigsuspend
-179 common pread64 sys_pread64 compat_sys_ppc_pread64
-180 common pwrite64 sys_pwrite64 compat_sys_ppc_pwrite64
+179 32 pread64 sys_ppc_pread64 compat_sys_ppc_pread64
+179 64 pread64 sys_pread64
+180 32 pwrite64 sys_ppc_pwrite64 compat_sys_ppc_pwrite64
+180 64 pwrite64 sys_pwrite64
181 common chown sys_chown
182 common getcwd sys_getcwd
183 common capget sys_capget
@@ -242,10 +244,11 @@
188 common putpmsg sys_ni_syscall
189 nospu vfork sys_vfork
190 common ugetrlimit sys_getrlimit compat_sys_getrlimit
-191 common readahead sys_readahead compat_sys_ppc_readahead
+191 32 readahead sys_ppc_readahead compat_sys_ppc_readahead
+191 64 readahead sys_readahead
192 32 mmap2 sys_mmap2 compat_sys_mmap2
-193 32 truncate64 sys_truncate64 compat_sys_ppc_truncate64
-194 32 ftruncate64 sys_ftruncate64 compat_sys_ppc_ftruncate64
+193 32 truncate64 sys_ppc_truncate64 compat_sys_ppc_truncate64
+194 32 ftruncate64 sys_ppc_ftruncate64 compat_sys_ppc_ftruncate64
195 32 stat64 sys_stat64
196 32 lstat64 sys_lstat64
197 32 fstat64 sys_fstat64
@@ -288,7 +291,8 @@
230 common io_submit sys_io_submit compat_sys_io_submit
231 common io_cancel sys_io_cancel
232 nospu set_tid_address sys_set_tid_address
-233 common fadvise64 sys_fadvise64 compat_sys_ppc32_fadvise64
+233 32 fadvise64 sys_ppc32_fadvise64 compat_sys_ppc32_fadvise64
+233 64 fadvise64 sys_fadvise64
234 nospu exit_group sys_exit_group
235 nospu lookup_dcookie sys_lookup_dcookie compat_sys_lookup_dcookie
236 common epoll_create sys_epoll_create
--
2.37.2
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