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Subject[PATCH v2 03/14] x86/fault: Fold mm_fault_error() into do_user_addr_fault()
Date
mm_fault_error() is logically just the end of do_user_addr_fault().
Combine the functions. This makes the code easier to read.

Most of the churn here is from renaming hw_error_code to error_code in
do_user_addr_fault().

This makes no difference at all to the generated code (objdump -dr) as
compared to changing noinline to __always_inline in the definition of
mm_fault_error().

Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Andy Lutomirski <luto@kernel.org>
---
arch/x86/mm/fault.c | 97 +++++++++++++++++++++------------------------
1 file changed, 45 insertions(+), 52 deletions(-)

diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index 818902b08c52..91cf7a672c04 100644
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -981,40 +981,6 @@ do_sigbus(struct pt_regs *regs, unsigned long error_code, unsigned long address,
force_sig_fault(SIGBUS, BUS_ADRERR, (void __user *)address);
}

-static noinline void
-mm_fault_error(struct pt_regs *regs, unsigned long error_code,
- unsigned long address, vm_fault_t fault)
-{
- if (fatal_signal_pending(current) && !(error_code & X86_PF_USER)) {
- no_context(regs, error_code, address, 0, 0);
- return;
- }
-
- if (fault & VM_FAULT_OOM) {
- /* Kernel mode? Handle exceptions or die: */
- if (!(error_code & X86_PF_USER)) {
- no_context(regs, error_code, address,
- SIGSEGV, SEGV_MAPERR);
- return;
- }
-
- /*
- * We ran out of memory, call the OOM killer, and return the
- * userspace (which will retry the fault, or kill us if we got
- * oom-killed):
- */
- pagefault_out_of_memory();
- } else {
- if (fault & (VM_FAULT_SIGBUS|VM_FAULT_HWPOISON|
- VM_FAULT_HWPOISON_LARGE))
- do_sigbus(regs, error_code, address, fault);
- else if (fault & VM_FAULT_SIGSEGV)
- bad_area_nosemaphore(regs, error_code, address);
- else
- BUG();
- }
-}
-
static int spurious_kernel_fault_check(unsigned long error_code, pte_t *pte)
{
if ((error_code & X86_PF_WRITE) && !pte_write(*pte))
@@ -1252,7 +1218,7 @@ NOKPROBE_SYMBOL(do_kern_addr_fault);
/* Handle faults in the user portion of the address space */
static inline
void do_user_addr_fault(struct pt_regs *regs,
- unsigned long hw_error_code,
+ unsigned long error_code,
unsigned long address)
{
struct vm_area_struct *vma;
@@ -1272,8 +1238,8 @@ void do_user_addr_fault(struct pt_regs *regs,
* Reserved bits are never expected to be set on
* entries in the user portion of the page tables.
*/
- if (unlikely(hw_error_code & X86_PF_RSVD))
- pgtable_bad(regs, hw_error_code, address);
+ if (unlikely(error_code & X86_PF_RSVD))
+ pgtable_bad(regs, error_code, address);

/*
* If SMAP is on, check for invalid kernel (supervisor) access to user
@@ -1283,10 +1249,10 @@ void do_user_addr_fault(struct pt_regs *regs,
* enforcement appears to be consistent with the USER bit.
*/
if (unlikely(cpu_feature_enabled(X86_FEATURE_SMAP) &&
- !(hw_error_code & X86_PF_USER) &&
+ !(error_code & X86_PF_USER) &&
!(regs->flags & X86_EFLAGS_AC)))
{
- bad_area_nosemaphore(regs, hw_error_code, address);
+ bad_area_nosemaphore(regs, error_code, address);
return;
}

@@ -1295,7 +1261,7 @@ void do_user_addr_fault(struct pt_regs *regs,
* in a region with pagefaults disabled then we must not take the fault
*/
if (unlikely(faulthandler_disabled() || !mm)) {
- bad_area_nosemaphore(regs, hw_error_code, address);
+ bad_area_nosemaphore(regs, error_code, address);
return;
}

@@ -1316,9 +1282,9 @@ void do_user_addr_fault(struct pt_regs *regs,

perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);

- if (hw_error_code & X86_PF_WRITE)
+ if (error_code & X86_PF_WRITE)
flags |= FAULT_FLAG_WRITE;
- if (hw_error_code & X86_PF_INSTR)
+ if (error_code & X86_PF_INSTR)
flags |= FAULT_FLAG_INSTRUCTION;

#ifdef CONFIG_X86_64
@@ -1334,7 +1300,7 @@ void do_user_addr_fault(struct pt_regs *regs,
* to consider the PF_PK bit.
*/
if (is_vsyscall_vaddr(address)) {
- if (emulate_vsyscall(hw_error_code, regs, address))
+ if (emulate_vsyscall(error_code, regs, address))
return;
}
#endif
@@ -1357,7 +1323,7 @@ void do_user_addr_fault(struct pt_regs *regs,
* Fault from code in kernel from
* which we do not expect faults.
*/
- bad_area_nosemaphore(regs, hw_error_code, address);
+ bad_area_nosemaphore(regs, error_code, address);
return;
}
retry:
@@ -1373,17 +1339,17 @@ void do_user_addr_fault(struct pt_regs *regs,

vma = find_vma(mm, address);
if (unlikely(!vma)) {
- bad_area(regs, hw_error_code, address);
+ bad_area(regs, error_code, address);
return;
}
if (likely(vma->vm_start <= address))
goto good_area;
if (unlikely(!(vma->vm_flags & VM_GROWSDOWN))) {
- bad_area(regs, hw_error_code, address);
+ bad_area(regs, error_code, address);
return;
}
if (unlikely(expand_stack(vma, address))) {
- bad_area(regs, hw_error_code, address);
+ bad_area(regs, error_code, address);
return;
}

@@ -1392,8 +1358,8 @@ void do_user_addr_fault(struct pt_regs *regs,
* we can handle it..
*/
good_area:
- if (unlikely(access_error(hw_error_code, vma))) {
- bad_area_access_error(regs, hw_error_code, address, vma);
+ if (unlikely(access_error(error_code, vma))) {
+ bad_area_access_error(regs, error_code, address, vma);
return;
}

@@ -1415,7 +1381,7 @@ void do_user_addr_fault(struct pt_regs *regs,
/* Quick path to respond to signals */
if (fault_signal_pending(fault, regs)) {
if (!user_mode(regs))
- no_context(regs, hw_error_code, address, SIGBUS,
+ no_context(regs, error_code, address, SIGBUS,
BUS_ADRERR);
return;
}
@@ -1432,11 +1398,38 @@ void do_user_addr_fault(struct pt_regs *regs,
}

mmap_read_unlock(mm);
- if (unlikely(fault & VM_FAULT_ERROR)) {
- mm_fault_error(regs, hw_error_code, address, fault);
+ if (likely(!(fault & VM_FAULT_ERROR)))
+ return;
+
+ if (fatal_signal_pending(current) && !(error_code & X86_PF_USER)) {
+ no_context(regs, error_code, address, 0, 0);
return;
}

+ if (fault & VM_FAULT_OOM) {
+ /* Kernel mode? Handle exceptions or die: */
+ if (!(error_code & X86_PF_USER)) {
+ no_context(regs, error_code, address,
+ SIGSEGV, SEGV_MAPERR);
+ return;
+ }
+
+ /*
+ * We ran out of memory, call the OOM killer, and return the
+ * userspace (which will retry the fault, or kill us if we got
+ * oom-killed):
+ */
+ pagefault_out_of_memory();
+ } else {
+ if (fault & (VM_FAULT_SIGBUS|VM_FAULT_HWPOISON|
+ VM_FAULT_HWPOISON_LARGE))
+ do_sigbus(regs, error_code, address, fault);
+ else if (fault & VM_FAULT_SIGSEGV)
+ bad_area_nosemaphore(regs, error_code, address);
+ else
+ BUG();
+ }
+
check_v8086_mode(regs, address, tsk);
}
NOKPROBE_SYMBOL(do_user_addr_fault);
--
2.29.2
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