[PATCH] i386/x86-64: rename is_at_popf(), add iret to tests and fix

is_at_popf() needs to test for the iret instruction as well as
popf.  So add that test and rename it to is_setting_trap_flag().

Also change max insn length from 16 to 15 to match reality.

LAHF / SAHF can't affect TF, so the comment in x86_64 is removed.

Signed-off-by: Chuck Ebbert <76306.1226@compuserve.com>
Signed-off-by: Andi Kleen <ak@suse.de>

diff --git a/arch/i386/kernel/ptrace.c b/arch/i386/kernel/ptrace.c
index d3db03f..775f50e 100644 (file)
--- a/arch/i386/kernel/ptrace.c
+++ b/arch/i386/kernel/ptrace.c
@@ -185,17 +185,17 @@ static unsigned long convert_eip_to_linear(struct task_struct *child, struct pt_
        return addr;
 }
 
-static inline int is_at_popf(struct task_struct *child, struct pt_regs *regs)
+static inline int is_setting_trap_flag(struct task_struct *child, struct pt_regs *regs)
 {
        int i, copied;
-       unsigned char opcode[16];
+       unsigned char opcode[15];
        unsigned long addr = convert_eip_to_linear(child, regs);
 
        copied = access_process_vm(child, addr, opcode, sizeof(opcode), 0);
        for (i = 0; i < copied; i++) {
                switch (opcode[i]) {
-               /* popf */
-               case 0x9d:
+               /* popf and iret */
+               case 0x9d: case 0xcf:
                        return 1;
                /* opcode and address size prefixes */
                case 0x66: case 0x67:
@@ -247,7 +247,7 @@ static void set_singlestep(struct task_struct *child)
         * don't mark it as being "us" that set it, so that we
         * won't clear it by hand later.
         */
-       if (is_at_popf(child, regs))
+       if (is_setting_trap_flag(child, regs))
                return;
        
        child->ptrace |= PT_DTRACE;

diff --git a/arch/x86_64/kernel/ptrace.c b/arch/x86_64/kernel/ptrace.c
index 412c6a8..addc14a 100644 (file)
--- a/arch/x86_64/kernel/ptrace.c
+++ b/arch/x86_64/kernel/ptrace.c
@@ -116,17 +116,17 @@ unsigned long convert_rip_to_linear(struct task_struct *child, struct pt_regs *r
        return addr;
 }
 
-static int is_at_popf(struct task_struct *child, struct pt_regs *regs)
+static int is_setting_trap_flag(struct task_struct *child, struct pt_regs *regs)
 {
        int i, copied;
-       unsigned char opcode[16];
+       unsigned char opcode[15];
        unsigned long addr = convert_rip_to_linear(child, regs);
 
        copied = access_process_vm(child, addr, opcode, sizeof(opcode), 0);
        for (i = 0; i < copied; i++) {
                switch (opcode[i]) {
-               /* popf */
-               case 0x9d:
+               /* popf and iret */
+               case 0x9d: case 0xcf:
                        return 1;
 
                        /* CHECKME: 64 65 */
@@ -189,10 +189,8 @@ static void set_singlestep(struct task_struct *child)
         * ..but if TF is changed by the instruction we will trace,
         * don't mark it as being "us" that set it, so that we
         * won't clear it by hand later.
-        *
-        * AK: this is not enough, LAHF and IRET can change TF in user space too.
         */
-       if (is_at_popf(child, regs))
+       if (is_setting_trap_flag(child, regs))
                return;
 
        child->ptrace |= PT_DTRACE;