powerpc/32: fix syscall wrappers with 64-bit arguments of unaligned register-pairs

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 preceding 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@zx2c4.com>
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Fixes: 7e92e01b72452 ("powerpc: Provide syscall wrapper")
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20221012035335.866440-1-npiggin@gmail.com

1 files changed, 16 insertions, 0 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,