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x86-64, compat: Test %rax for the syscall number, not %eax

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On 64 bits, we always, by necessity, jump through the system call
table via %rax.  For 32-bit system calls, in theory the system call
number is stored in %eax, and the code was testing %eax for a valid
system call number.  At one point we loaded the stored value back from
the stack to enforce zero-extension, but that was removed in checkin
d4d6715016.  An actual 32-bit process
will not be able to introduce a non-zero-extended number, but it can
happen via ptrace.

Instead of re-introducing the zero-extension, test what we are
actually going to use, i.e. %rax.  This only adds a handful of REX
prefixes to the code.

Reported-by: Ben Hawkes <hawkes@sota.gen.nz>
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
Cc: <stable@kernel.org>
Cc: Roland McGrath <roland@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
H. Peter Anvin 2010-09-14 12:42:41 -07:00
parent c41d68a513
commit 36d001c70d
1 changed files with 7 additions and 7 deletions
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14
arch/x86/ia32/ia32entry.S
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@ -153,7 +153,7 @@ ENTRY(ia32_sysenter_target)
testl $_TIF_WORK_SYSCALL_ENTRY,TI_flags(%r10)
CFI_REMEMBER_STATE
jnz sysenter_tracesys
cmpl $(IA32_NR_syscalls-1),%eax
cmpq $(IA32_NR_syscalls-1),%rax
ja ia32_badsys
sysenter_do_call:
IA32_ARG_FIXUP
@ -195,7 +195,7 @@ sysexit_from_sys_call:
movl $AUDIT_ARCH_I386,%edi /* 1st arg: audit arch */
call audit_syscall_entry
movl RAX-ARGOFFSET(%rsp),%eax /* reload syscall number */
cmpl $(IA32_NR_syscalls-1),%eax
cmpq $(IA32_NR_syscalls-1),%rax
ja ia32_badsys
movl %ebx,%edi /* reload 1st syscall arg */
movl RCX-ARGOFFSET(%rsp),%esi /* reload 2nd syscall arg */
@ -248,7 +248,7 @@ sysenter_tracesys:
call syscall_trace_enter
LOAD_ARGS32 ARGOFFSET /* reload args from stack in case ptrace changed it */
RESTORE_REST
cmpl $(IA32_NR_syscalls-1),%eax
cmpq $(IA32_NR_syscalls-1),%rax
ja int_ret_from_sys_call /* sysenter_tracesys has set RAX(%rsp) */
jmp sysenter_do_call
CFI_ENDPROC
@ -314,7 +314,7 @@ ENTRY(ia32_cstar_target)
testl $_TIF_WORK_SYSCALL_ENTRY,TI_flags(%r10)
CFI_REMEMBER_STATE
jnz cstar_tracesys
cmpl $IA32_NR_syscalls-1,%eax
cmpq $IA32_NR_syscalls-1,%rax
ja ia32_badsys
cstar_do_call:
IA32_ARG_FIXUP 1
@ -367,7 +367,7 @@ cstar_tracesys:
LOAD_ARGS32 ARGOFFSET, 1 /* reload args from stack in case ptrace changed it */
RESTORE_REST
xchgl %ebp,%r9d
cmpl $(IA32_NR_syscalls-1),%eax
cmpq $(IA32_NR_syscalls-1),%rax
ja int_ret_from_sys_call /* cstar_tracesys has set RAX(%rsp) */
jmp cstar_do_call
END(ia32_cstar_target)
@ -425,7 +425,7 @@ ENTRY(ia32_syscall)
orl $TS_COMPAT,TI_status(%r10)
testl $_TIF_WORK_SYSCALL_ENTRY,TI_flags(%r10)
jnz ia32_tracesys
cmpl $(IA32_NR_syscalls-1),%eax
cmpq $(IA32_NR_syscalls-1),%rax
ja ia32_badsys
ia32_do_call:
IA32_ARG_FIXUP
@ -444,7 +444,7 @@ ia32_tracesys:
call syscall_trace_enter
LOAD_ARGS32 ARGOFFSET /* reload args from stack in case ptrace changed it */
RESTORE_REST
cmpl $(IA32_NR_syscalls-1),%eax
cmpq $(IA32_NR_syscalls-1),%rax
ja int_ret_from_sys_call /* ia32_tracesys has set RAX(%rsp) */
jmp ia32_do_call
END(ia32_syscall)