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Date: Tue, 31 Aug 2021 16:40:58 +0200 From: Alexander Lobakin <alexandr.lobakin@...el.com> To: linux-hardening@...r.kernel.org Cc: "Kristen C Accardi" <kristen.c.accardi@...el.com>, Kristen Carlson Accardi <kristen@...ux.intel.com>, Kees Cook <keescook@...omium.org>, Masahiro Yamada <masahiroy@...nel.org>, "H. Peter Anvin" <hpa@...or.com>, Jessica Yu <jeyu@...nel.org>, Nathan Chancellor <nathan@...nel.org>, Nick Desaulniers <ndesaulniers@...gle.com>, Marios Pomonis <pomonis@...gle.com>, Sami Tolvanen <samitolvanen@...gle.com>, Tony Luck <tony.luck@...el.com>, Ard Biesheuvel <ardb@...nel.org>, Jesse Brandeburg <jesse.brandeburg@...el.com>, Lukasz Czapnik <lukasz.czapnik@...el.com>, "Marta A Plantykow" <marta.a.plantykow@...el.com>, Michal Kubiak <michal.kubiak@...el.com>, Michal Swiatkowski <michal.swiatkowski@...el.com>, Alexander Lobakin <alexandr.lobakin@...el.com>, linux-kbuild@...r.kernel.org, linux-arch@...r.kernel.org, linux-kernel@...r.kernel.org, clang-built-linux@...glegroups.com Subject: [PATCH v6 kspp-next 06/22] x86/boot: Allow a "silent" kaslr random byte fetch From: Kees Cook <keescook@...omium.org> Under earlyprintk, each RNG call produces a debug report line. When shuffling hundreds of functions, this is not useful information (each line is identical and tells us nothing new). Instead, allow for a NULL "purpose" to suppress the debug reporting. Signed-off-by: Kees Cook <keescook@...omium.org> Signed-off-by: Kristen Carlson Accardi <kristen@...ux.intel.com> Signed-off-by: Alexander Lobakin <alexandr.lobakin@...el.com> --- arch/x86/lib/kaslr.c | 18 ++++++++++++------ 1 file changed, 12 insertions(+), 6 deletions(-) diff --git a/arch/x86/lib/kaslr.c b/arch/x86/lib/kaslr.c index a53665116458..2b3eb8c948a3 100644 --- a/arch/x86/lib/kaslr.c +++ b/arch/x86/lib/kaslr.c @@ -56,11 +56,14 @@ unsigned long kaslr_get_random_long(const char *purpose) unsigned long raw, random = get_boot_seed(); bool use_i8254 = true; - debug_putstr(purpose); - debug_putstr(" KASLR using"); + if (purpose) { + debug_putstr(purpose); + debug_putstr(" KASLR using"); + } if (has_cpuflag(X86_FEATURE_RDRAND)) { - debug_putstr(" RDRAND"); + if (purpose) + debug_putstr(" RDRAND"); if (rdrand_long(&raw)) { random ^= raw; use_i8254 = false; @@ -68,7 +71,8 @@ unsigned long kaslr_get_random_long(const char *purpose) } if (has_cpuflag(X86_FEATURE_TSC)) { - debug_putstr(" RDTSC"); + if (purpose) + debug_putstr(" RDTSC"); raw = rdtsc(); random ^= raw; @@ -76,7 +80,8 @@ unsigned long kaslr_get_random_long(const char *purpose) } if (use_i8254) { - debug_putstr(" i8254"); + if (purpose) + debug_putstr(" i8254"); random ^= i8254(); } @@ -86,7 +91,8 @@ unsigned long kaslr_get_random_long(const char *purpose) : "a" (random), "rm" (mix_const)); random += raw; - debug_putstr("...\n"); + if (purpose) + debug_putstr("...\n"); return random; } -- 2.31.1
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