From mboxrd@z Thu Jan 1 00:00:00 1970 From: Masami Hiramatsu Date: Thu, 15 Jun 2006 13:26:47 +0000 Subject: [RFC][PATCH]fix search_extable() to find correct entry Message-Id: <44916017.5050006@sdl.hitachi.co.jp> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: linux-ia64@vger.kernel.org Hi, Tony I found a suspicious buggy code in the linux kernel on IA64 arch. As far as I can see, search_extable() doesn't work correctly, because the lookup routine expects that the address format of the exception_table_entry is "IP + slot", but the compiler (gcc-3.4.5) generates it as "IP + (slot << 2)". Thus the lookup routine always fails to find the corresponding entry. You can check it by dumping __ex_table section of vmlinux. I made a patch to fix this bug attached in this mail. This patch is against 2.6.17-rc6-mm2. Please review it. Description: Fix search_extable() and ia64_handle_exception() to handle the address format of exception_table_entry correctly. Thanks, -- Masami HIRAMATSU 2nd Research Dept. Hitachi, Ltd., Systems Development Laboratory E-mail: hiramatu@sdl.hitachi.co.jp Signed-off-by: Masami Hiramatsu arch/ia64/mm/extable.c | 7 ++++--- include/asm-ia64/uaccess.h | 4 ++-- 2 files changed, 6 insertions(+), 5 deletions(-) diff --exclude=CVS -Narup a/arch/ia64/mm/extable.c b/arch/ia64/mm/extable.c --- a/arch/ia64/mm/extable.c 2005-10-28 09:02:08.000000000 +0900 +++ b/arch/ia64/mm/extable.c 2006-06-14 14:59:11.000000000 +0900 @@ -63,9 +63,10 @@ search_extable (const struct exception_t unsigned long mid_ip; long diff; + ip = (ip & ~0xf) + ((ip & 0x3) << 2); while (first <= last) { mid = &first[(last - first)/2]; - mid_ip = (u64) &mid->addr + mid->addr; + mid_ip = ((u64) &mid->addr + mid->addr) & ~0x3; diff = mid_ip - ip; if (diff = 0) return mid; @@ -83,8 +84,8 @@ ia64_handle_exception (struct pt_regs *r long fix = (u64) &e->cont + e->cont; regs->r8 = -EFAULT; - if (fix & 4) + if (fix & 2) regs->r9 = 0; regs->cr_iip = fix & ~0xf; - ia64_psr(regs)->ri = fix & 0x3; /* set continuation slot number */ + ia64_psr(regs)->ri = (fix & 0xc) >> 2; /* set continuation slot number */ } diff --exclude=CVS -Narup a/include/asm-ia64/uaccess.h b/include/asm-ia64/uaccess.h --- a/include/asm-ia64/uaccess.h 2005-10-28 09:02:08.000000000 +0900 +++ b/include/asm-ia64/uaccess.h 2006-06-14 23:54:55.000000000 +0900 @@ -139,7 +139,7 @@ do { \ register long __gu_r8 asm ("r8") = 0; \ register long __gu_r9 asm ("r9"); \ asm ("\n[1:]\tld"#n" %0=%2%P2\t// %0 and %1 get overwritten by exception handler\n" \ - "\t.xdata4 \"__ex_table\", 1b-., 1f-.+4\n" \ + "\t.xdata4 \"__ex_table\", 1b-., 1f-.+2\n" \ "[1:]" \ : "=r"(__gu_r9), "=r"(__gu_r8) : "m"(__m(addr)), "1"(__gu_r8)); \ (err) = __gu_r8; \ @@ -346,7 +346,7 @@ extern unsigned long __strnlen_user (con struct exception_table_entry { int addr; /* location-relative address of insn this fixup is for */ - int cont; /* location-relative continuation addr.; if bit 2 is set, r9 is set to 0 */ + int cont; /* location-relative continuation addr.; if bit 1 is set, r9 is set to 0 */ }; extern void ia64_handle_exception (struct pt_regs *regs, const struct exception_table_entry *e);