Re: [PATCH v2 5/5] powerpc/signal: Use unsafe_copy_siginfo_to_user()

Christophe Leroy [off-list ref] writes:

Use unsafe_copy_siginfo_to_user() in order to do the copy
within the user access block.

On an mpc 8321 (book3s/32) the improvment is about 5% on a process
sending a signal to itself.

Nacked-by: "Eric W. Biederman" [off-list ref]

copy_siginfo_to_user is not the same as copy_siginfo_to_user32.

As in this patch breaks 32bit userspace on powerpc.

Le 02/09/2021 à 20:38, Eric W. Biederman a écrit :

Christophe Leroy [off-list ref] writes:

quoted

Use unsafe_copy_siginfo_to_user() in order to do the copy
within the user access block.

On an mpc 8321 (book3s/32) the improvment is about 5% on a process
sending a signal to itself.

Nacked-by: "Eric W. Biederman" [off-list ref]

copy_siginfo_to_user is not the same as copy_siginfo_to_user32.

As in this patch breaks 32bit userspace on powerpc.

I don't understand your comment. As you can see below, copy_siginfo_to_user32() is used in the 
compat case (ie 32 bit userspace on PPC64) and unsafe_copy_siginfo_to_user() is used on the 
non-compat case (ie 32 bit userspace on PPC32).

So what's the issue really ?

quoted

Signed-off-by: Christophe Leroy <redacted>
---
  arch/powerpc/kernel/signal_32.c | 13 ++++++-------
  arch/powerpc/kernel/signal_64.c |  5 +----
  2 files changed, 7 insertions(+), 11 deletions(-)

diff --git a/arch/powerpc/kernel/signal_32.c b/arch/powerpc/kernel/signal_32.c
index ff101e2b3bab..f9e16d108bc8 100644
--- a/arch/powerpc/kernel/signal_32.c
+++ b/arch/powerpc/kernel/signal_32.c

@@ -710,12 +710,6 @@ static long restore_tm_user_regs(struct pt_regs *regs, struct mcontext __user *s
  }
  #endif
  
-#ifdef CONFIG_PPC64
-
-#define copy_siginfo_to_user	copy_siginfo_to_user32
-
-#endif /* CONFIG_PPC64 */
-
  /*
   * Set up a signal frame for a "real-time" signal handler
   * (one which gets siginfo).

@@ -779,14 +773,19 @@ int handle_rt_signal32(struct ksignal *ksig, sigset_t *oldset,
  		asm("dcbst %y0; sync; icbi %y0; sync" :: "Z" (mctx->mc_pad[0]));
  	}
  	unsafe_put_sigset_t(&frame->uc.uc_sigmask, oldset, failed);
+#ifndef CONFIG_COMPAT
+	unsafe_copy_siginfo_to_user(&frame->info, &ksig->info, failed);
+#endif
  
  	/* create a stack frame for the caller of the handler */
  	unsafe_put_user(regs->gpr[1], newsp, failed);
  
  	user_access_end();
  
-	if (copy_siginfo_to_user(&frame->info, &ksig->info))
+#ifdef CONFIG_COMPAT
+	if (copy_siginfo_to_user32(&frame->info, &ksig->info))
  		goto badframe;
+#endif
  
  	regs->link = tramp;
  

diff --git a/arch/powerpc/kernel/signal_64.c b/arch/powerpc/kernel/signal_64.c
index 2cca6c8febe1..82b73fbd937d 100644
--- a/arch/powerpc/kernel/signal_64.c
+++ b/arch/powerpc/kernel/signal_64.c

@@ -901,15 +901,12 @@ int handle_rt_signal64(struct ksignal *ksig, sigset_t *set,
  	}
  
  	unsafe_copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set), badframe_block);
+	unsafe_copy_siginfo_to_user(&frame->info, &ksig->info, badframe_block);
  	/* Allocate a dummy caller frame for the signal handler. */
  	unsafe_put_user(regs->gpr[1], newsp, badframe_block);
  
  	user_write_access_end();
  
-	/* Save the siginfo outside of the unsafe block. */
-	if (copy_siginfo_to_user(&frame->info, &ksig->info))
-		goto badframe;
-
  	/* Make sure signal handler doesn't get spurious FP exceptions */
  	tsk->thread.fp_state.fpscr = 0;