From 55ca3cc1746335bb6ef1d3894ddb6d0c729b3518 Mon Sep 17 00:00:00 2001 From: Suresh Siddha Date: Wed, 28 Oct 2009 18:46:57 -0800 Subject: [PATCH] x86_64, ftrace: Make ftrace use kernel identity mapping to modify code On x86_64, kernel text mappings are mapped read-only with CONFIG_DEBUG_RODATA. So use the kernel identity mapping instead of the kernel text mapping to modify the kernel text. Signed-off-by: Suresh Siddha Acked-by: Steven Rostedt Tested-by: Steven Rostedt LKML-Reference: <20091029024821.080941108@sbs-t61.sc.intel.com> Signed-off-by: Ingo Molnar --- arch/x86/kernel/ftrace.c | 17 +++++++++++++++++ arch/x86/mm/pageattr.c | 3 +-- 2 files changed, 18 insertions(+), 2 deletions(-) diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c index 9dbb527e1652..944e9820b4b5 100644 --- a/arch/x86/kernel/ftrace.c +++ b/arch/x86/kernel/ftrace.c @@ -187,9 +187,26 @@ static void wait_for_nmi(void) nmi_wait_count++; } +static inline int +within(unsigned long addr, unsigned long start, unsigned long end) +{ + return addr >= start && addr < end; +} + static int do_ftrace_mod_code(unsigned long ip, void *new_code) { + /* + * On x86_64, kernel text mappings are mapped read-only with + * CONFIG_DEBUG_RODATA. So we use the kernel identity mapping instead + * of the kernel text mapping to modify the kernel text. + * + * For 32bit kernels, these mappings are same and we can use + * kernel identity mapping to modify code. + */ + if (within(ip, (unsigned long)_text, (unsigned long)_etext)) + ip = (unsigned long)__va(__pa(ip)); + mod_code_ip = (void *)ip; mod_code_newcode = new_code; diff --git a/arch/x86/mm/pageattr.c b/arch/x86/mm/pageattr.c index 8d1e8d95ea45..09a140ca7be8 100644 --- a/arch/x86/mm/pageattr.c +++ b/arch/x86/mm/pageattr.c @@ -279,8 +279,7 @@ static inline pgprot_t static_protections(pgprot_t prot, unsigned long address, __pa((unsigned long)__end_rodata) >> PAGE_SHIFT)) pgprot_val(forbidden) |= _PAGE_RW; -#if defined(CONFIG_X86_64) && defined(CONFIG_DEBUG_RODATA) && \ - !defined(CONFIG_DYNAMIC_FTRACE) +#if defined(CONFIG_X86_64) && defined(CONFIG_DEBUG_RODATA) /* * Once the kernel maps the text as RO (kernel_set_to_readonly is set), * kernel text mappings for the large page aligned text, rodata sections -- 2.20.1