Messages in this thread | | | Date | Thu, 15 Mar 2018 13:10:54 -0500 | From | Josh Poimboeuf <> | Subject | Re: [PATCH 4/9] x86/dumpstack: Improve opcodes dumping in the Code: section |
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On Thu, Mar 15, 2018 at 04:44:43PM +0100, Borislav Petkov wrote: > From: Borislav Petkov <bp@suse.de> > > The code used to iterate byte-by-byte over the bytes around RIP and that > is expensive: disabling pagefaults around it, copy_from_user, etc... > > Make it read the whole buffer of OPCODE_BUFSIZE size in one go. Use a > statically allocated 64 bytes buffer so that concurrent show_opcodes() > do not interleave in the output even though in the majority of the cases > we sync on die_lock. Except the #PF path which doesn't... > > Also, do the PAGE_OFFSET check outside of the function because latter > will be reused in other context. > > Signed-off-by: Borislav Petkov <bp@suse.de> > --- > arch/x86/kernel/dumpstack.c | 34 ++++++++++++++++------------------ > 1 file changed, 16 insertions(+), 18 deletions(-) > > diff --git a/arch/x86/kernel/dumpstack.c b/arch/x86/kernel/dumpstack.c > index eb9d6c00a52f..3f781a8dddb8 100644 > --- a/arch/x86/kernel/dumpstack.c > +++ b/arch/x86/kernel/dumpstack.c > @@ -22,8 +22,6 @@ > #include <asm/stacktrace.h> > #include <asm/unwind.h> > > -#define OPCODE_BUFSIZE 64 > - > int panic_on_unrecovered_nmi; > int panic_on_io_nmi; > static int die_counter; > @@ -72,29 +70,25 @@ static void printk_stack_address(unsigned long address, int reliable, > > static void show_opcodes(u8 *rip) > { > - unsigned int code_prologue = OPCODE_BUFSIZE * 43 / 64; > - unsigned int code_len = OPCODE_BUFSIZE; > - unsigned char c; > +#define OPCODE_BUFSIZE 64 > + unsigned int code_prologue = OPCODE_BUFSIZE * 2 / 3; > + u8 opcodes[OPCODE_BUFSIZE];
I liked OPCODE_BUFSIZE where it was before :-) Here it disrupts the readability of the function a bit IMO.
-- Josh
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