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powerpc/book3s64/kuap: Improve error reporting with KUAP

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With hash translation use DSISR_KEYFAULT to identify a wrong access.
With Radix we look at the AMR value and type of fault.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20201127044424.40686-17-aneesh.kumar@linux.ibm.com
This commit is contained in:
Aneesh Kumar K.V 2020-11-27 10:14:18 +05:30 committed by Michael Ellerman
parent 4d6c551e9f
commit eb232b1624
5 changed files with 29 additions and 12 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

4
arch/powerpc/include/asm/book3s/32/kup.h
View file

@ -177,8 +177,8 @@ static inline void restore_user_access(unsigned long flags)
allow_user_access(to, to, end - addr, KUAP_READ_WRITE);
}
static inline bool
bad_kuap_fault(struct pt_regs *regs, unsigned long address, bool is_write)
static inline bool bad_kuap_fault(struct pt_regs *regs, unsigned long address,
bool is_write, unsigned long error_code)
{
unsigned long begin = regs->kuap & 0xf0000000;
unsigned long end = regs->kuap << 28;

27
arch/powerpc/include/asm/book3s/64/kup.h
View file

@ -303,12 +303,29 @@ static inline void set_kuap(unsigned long value)
isync();
}
static inline bool
bad_kuap_fault(struct pt_regs *regs, unsigned long address, bool is_write)
#define RADIX_KUAP_BLOCK_READ UL(0x4000000000000000)
#define RADIX_KUAP_BLOCK_WRITE UL(0x8000000000000000)
static inline bool bad_kuap_fault(struct pt_regs *regs, unsigned long address,
bool is_write, unsigned long error_code)
{
return WARN(mmu_has_feature(MMU_FTR_BOOK3S_KUAP) &&
(regs->kuap & (is_write ? AMR_KUAP_BLOCK_WRITE : AMR_KUAP_BLOCK_READ)),
"Bug: %s fault blocked by AMR!", is_write ? "Write" : "Read");
if (!mmu_has_feature(MMU_FTR_BOOK3S_KUAP))
return false;
if (radix_enabled()) {
/*
* Will be a storage protection fault.
* Only check the details of AMR[0]
*/
return WARN((regs->kuap & (is_write ? RADIX_KUAP_BLOCK_WRITE : RADIX_KUAP_BLOCK_READ)),
"Bug: %s fault blocked by AMR!", is_write ? "Write" : "Read");
}
/*
* We don't want to WARN here because userspace can setup
* keys such that a kernel access to user address can cause
* fault
*/
return !!(error_code & DSISR_KEYFAULT);
}
static __always_inline void allow_user_access(void __user *to, const void __user *from,

4
arch/powerpc/include/asm/kup.h
View file

@ -59,8 +59,8 @@ void setup_kuap(bool disabled);
#else
static inline void setup_kuap(bool disabled) { }
static inline bool
bad_kuap_fault(struct pt_regs *regs, unsigned long address, bool is_write)
static inline bool bad_kuap_fault(struct pt_regs *regs, unsigned long address,
bool is_write, unsigned long error_code)
{
return false;
}

4
arch/powerpc/include/asm/nohash/32/kup-8xx.h
View file

@ -60,8 +60,8 @@ static inline void restore_user_access(unsigned long flags)
mtspr(SPRN_MD_AP, flags);
}
static inline bool
bad_kuap_fault(struct pt_regs *regs, unsigned long address, bool is_write)
static inline bool bad_kuap_fault(struct pt_regs *regs, unsigned long address,
bool is_write, unsigned long error_code)
{
return WARN(!((regs->kuap ^ MD_APG_KUAP) & 0xff000000),
"Bug: fault blocked by AP register !");

2
arch/powerpc/mm/fault.c
View file

@ -227,7 +227,7 @@ static bool bad_kernel_fault(struct pt_regs *regs, unsigned long error_code,
// Read/write fault in a valid region (the exception table search passed
// above), but blocked by KUAP is bad, it can never succeed.
if (bad_kuap_fault(regs, address, is_write))
if (bad_kuap_fault(regs, address, is_write, error_code))
return true;
// What's left? Kernel fault on user in well defined regions (extable