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Date: Sat, 12 Mar 2022 16:14:34 -0800 From: Joe Perches <joe@...ches.com> To: Alexey Dobriyan <adobriyan@...il.com>, x86@...nel.org Cc: tglx@...utronix.de, mingo@...hat.com, bp@...en8.de, dave.hansen@...ux.intel.com, hpa@...or.com, linux-kernel@...r.kernel.org Subject: Re: [PATCH 1/5] x86/alternative: simplify DUMP_BYTES macro On Sat, 2022-03-12 at 08:36 -0800, Joe Perches wrote: > On Fri, 2022-03-11 at 17:43 +0300, Alexey Dobriyan wrote: > > Avoid zero length check with clever whitespace placement in the format > > string. > [] > > diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c > [] > > @@ -66,13 +66,10 @@ do { \ > > if (unlikely(debug_alternative)) { \ > > int j; \ > > \ > > - if (!(len)) \ > > - break; \ > > - \ > > printk(KERN_DEBUG pr_fmt(fmt), ##args); \ > > - for (j = 0; j < (len) - 1; j++) \ > > - printk(KERN_CONT "%02hhx ", buf[j]); \ > > - printk(KERN_CONT "%02hhx\n", buf[j]); \ > > + for (j = 0; j < (len); j++) \ > > + printk(KERN_CONT " %02hhx", buf[j]); \ > > + printk(KERN_CONT "\n"); \ > > } \ > > This could also use %02x and not %02hhx > > And MAX_PATCH_LEN is 255 but is that really possible? > > Maybe if the actual patch length is always <= 64 this could use > printk(KERN_CONT "%*ph\n", (int)len, buf); > instead and avoid all possible interleaving? Another possibility would be to raise the arbitrary 64 byte limit on %*ph to 256. --- Documentation/core-api/printk-formats.rst | 6 +++--- lib/vsprintf.c | 2 +- 2 files changed, 4 insertions(+), 4 deletions(-) diff --git a/Documentation/core-api/printk-formats.rst b/Documentation/core-api/printk-formats.rst index 5e89497ba314e..39f787e9b26e1 100644 --- a/Documentation/core-api/printk-formats.rst +++ b/Documentation/core-api/printk-formats.rst @@ -289,9 +289,9 @@ Raw buffer as a hex string %*phD 00-01-02- ... -3f %*phN 000102 ... 3f -For printing small buffers (up to 64 bytes long) as a hex string with a -certain separator. For larger buffers consider using -:c:func:`print_hex_dump`. +For printing small buffers (up to 256 bytes long) as a hex string with a +certain separator. For buffers larger than 64 bytes consider using +:c:func:`print_hex_dump` as its output can be more easily counted. MAC/FDDI addresses ------------------ diff --git a/lib/vsprintf.c b/lib/vsprintf.c index 2a6c767cc2709..be6fa9fab1be8 100644 --- a/lib/vsprintf.c +++ b/lib/vsprintf.c @@ -1194,7 +1194,7 @@ char *hex_string(char *buf, char *end, u8 *addr, struct printf_spec spec, } if (spec.field_width > 0) - len = min_t(int, spec.field_width, 64); + len = min_t(int, spec.field_width, 256); for (i = 0; i < len; ++i) { if (buf < end)
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