lkml.org 
[lkml]   [2009]   [Nov]   [2]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    Date
    From
    Subject[tip:x86/mm] x86_64, ftrace: Make ftrace use kernel identity mapping to modify code
    Commit-ID:  55ca3cc1746335bb6ef1d3894ddb6d0c729b3518
    Gitweb: http://git.kernel.org/tip/55ca3cc1746335bb6ef1d3894ddb6d0c729b3518
    Author: Suresh Siddha <suresh.b.siddha@intel.com>
    AuthorDate: Wed, 28 Oct 2009 18:46:57 -0800
    Committer: Ingo Molnar <mingo@elte.hu>
    CommitDate: Mon, 2 Nov 2009 17:16:36 +0100

    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 <suresh.b.siddha@intel.com>
    Acked-by: Steven Rostedt <rostedt@goodmis.org>
    Tested-by: Steven Rostedt <rostedt@goodmis.org>
    LKML-Reference: <20091029024821.080941108@sbs-t61.sc.intel.com>
    Signed-off-by: Ingo Molnar <mingo@elte.hu>
    ---
    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 9dbb527..944e982 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 8d1e8d9..09a140c 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

    \
     
     \ /
      Last update: 2009-11-02 19:59    [W:0.025 / U:91.880 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site