[PATCH] arm64: Show three registers per line

[PATCH] arm64: Show three registers per line

[Matthew Wilcox (Oracle)]

Displaying two registers per line takes 15 lines.  That improves to just
10 lines if we display three registers per line, which reduces the amount
of information lost when oopses are cut off.  It stays within 80 columns
and matches x86-64.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
---
 arch/arm64/kernel/process.c | 9 +++------
 1 file changed, 3 insertions(+), 6 deletions(-)

diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c
index 6e60aa3b5ea9..aff5a2c12297 100644
--- a/arch/arm64/kernel/process.c
+++ b/arch/arm64/kernel/process.c
@@ -294,13 +294,10 @@ void __show_regs(struct pt_regs *regs)
 	i = top_reg;
 
 	while (i >= 0) {
-		printk("x%-2d: %016llx ", i, regs->regs[i]);
-		i--;
+		printk("x%-2d: %016llx", i, regs->regs[i]);
 
-		if (i % 2 == 0) {
-			pr_cont("x%-2d: %016llx ", i, regs->regs[i]);
-			i--;
-		}
+		while (i-- % 3)
+			pr_cont(" x%-2d: %016llx", i, regs->regs[i]);
 
 		pr_cont("\n");
 	}
-- 
2.30.2

Re: [PATCH] arm64: Show three registers per line

[Kees Cook]

On Tue, Apr 20, 2021 at 06:22:45PM +0100, Matthew Wilcox (Oracle) wrote:
> Displaying two registers per line takes 15 lines.  That improves to just
> 10 lines if we display three registers per line, which reduces the amount
> of information lost when oopses are cut off.  It stays within 80 columns
> and matches x86-64.
> 
> Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>

Reviewed-by: Kees Cook <keescook@chromium.org>

-- 
Kees Cook

RE: [PATCH] arm64: Show three registers per line

[David Laight]

From: Matthew Wilcox
> Sent: 20 April 2021 18:23
>
> Displaying two registers per line takes 15 lines.  That improves to just
> 10 lines if we display three registers per line, which reduces the amount
> of information lost when oopses are cut off.  It stays within 80 columns
> and matches x86-64.
> 
> Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
> ---
>  arch/arm64/kernel/process.c | 9 +++------
>  1 file changed, 3 insertions(+), 6 deletions(-)
> 
> diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c
> index 6e60aa3b5ea9..aff5a2c12297 100644
> --- a/arch/arm64/kernel/process.c
> +++ b/arch/arm64/kernel/process.c
> @@ -294,13 +294,10 @@ void __show_regs(struct pt_regs *regs)
>  	i = top_reg;
> 
>  	while (i >= 0) {
> -		printk("x%-2d: %016llx ", i, regs->regs[i]);
> -		i--;
> +		printk("x%-2d: %016llx", i, regs->regs[i]);
> 
> -		if (i % 2 == 0) {
> -			pr_cont("x%-2d: %016llx ", i, regs->regs[i]);
> -			i--;
> -		}
> +		while (i-- % 3)
> +			pr_cont(" x%-2d: %016llx", i, regs->regs[i]);
> 
>  		pr_cont("\n");
>  	}

I think I'd avoid pr_cont() to avoid 'mishaps' during concurrent oops.
This probably needs something like:
	for (; i >= 0; i -= 3) {
		switch (i) {
		case 0:
			printk("x%-2d: %016llx\n", i, regs->regs[i]);
			break;
		case 1:
			printk("x%-2d: %016llx x%-2d: %016llx\n",
			       i, regs->regs[i], i - 1, regs->regs[i - 1]);
			break;
		default:
			printk("x%-2d: %016llx x%-2d: %016llx x%-2d: %016llx\n",
			       i, regs->regs[i], i - 1, regs->regs[i - 1],
				 i - 2, regs->regs[i - 2]);
			continue;
		}
		break;
	}

	David

-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)

Re: [PATCH] arm64: Show three registers per line

[Will Deacon]

On Tue, Apr 20, 2021 at 06:22:45PM +0100, Matthew Wilcox (Oracle) wrote:
> Displaying two registers per line takes 15 lines.  That improves to just
> 10 lines if we display three registers per line, which reduces the amount
> of information lost when oopses are cut off.  It stays within 80 columns
> and matches x86-64.
> 
> Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
> ---
>  arch/arm64/kernel/process.c | 9 +++------
>  1 file changed, 3 insertions(+), 6 deletions(-)

Acked-by: Will Deacon <will@kernel.org>

Will

Re: [PATCH] arm64: Show three registers per line

[Catalin Marinas]

On Tue, 20 Apr 2021 18:22:45 +0100, Matthew Wilcox (Oracle) wrote:
> Displaying two registers per line takes 15 lines.  That improves to just
> 10 lines if we display three registers per line, which reduces the amount
> of information lost when oopses are cut off.  It stays within 80 columns
> and matches x86-64.

Applied to arm64 (for-next/core), thanks!

[1/1] arm64: Show three registers per line
      https://git.kernel.org/arm64/c/0bca3ec846d7

-- 
Catalin