From 279917e27edc293eb645a25428c6ab3f3bca3f86 Mon Sep 17 00:00:00 2001 From: Helge Deller Date: Thu, 4 Nov 2021 20:19:00 +0100 Subject: [PATCH 1/4] parisc: Fix backtrace to always include init funtion names I noticed that sometimes at kernel startup the backtraces did not included the function names of init functions. Their address were not resolved to function names and instead only the address was printed. Debugging shows that the culprit is is_ksym_addr() which is called by the backtrace functions to check if an address belongs to a function in the kernel. The problem occurs only for CONFIG_KALLSYMS_ALL=y. When looking at is_ksym_addr() one can see that for CONFIG_KALLSYMS_ALL=y the function only tries to resolve the address via is_kernel() function, which checks like this: if (addr >= _stext && addr <= _end) return 1; On parisc the init functions are located before _stext, so this check fails. Other platforms seem to have all functions (including init functions) behind _stext. The following patch moves the _stext symbol at the beginning of the kernel and thus includes the init section. This fixes the check and does not seem to have any negative side effects on where the kernel mapping happens in the map_pages() function in arch/parisc/mm/init.c. Signed-off-by: Helge Deller Cc: stable@kernel.org # 5.4+ --- arch/parisc/kernel/vmlinux.lds.S | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/arch/parisc/kernel/vmlinux.lds.S b/arch/parisc/kernel/vmlinux.lds.S index 2769eb991f58..3d208afd15bc 100644 --- a/arch/parisc/kernel/vmlinux.lds.S +++ b/arch/parisc/kernel/vmlinux.lds.S @@ -57,6 +57,8 @@ SECTIONS { . = KERNEL_BINARY_TEXT_START; + _stext = .; /* start of kernel text, includes init code & data */ + __init_begin = .; HEAD_TEXT_SECTION MLONGCALL_DISCARD(INIT_TEXT_SECTION(8)) @@ -80,7 +82,6 @@ SECTIONS /* freed after init ends here */ _text = .; /* Text and read-only data */ - _stext = .; MLONGCALL_KEEP(INIT_TEXT_SECTION(8)) .text ALIGN(PAGE_SIZE) : { TEXT_TEXT From f0d1cfac45abb1c47792cda19ed680c30cee22bb Mon Sep 17 00:00:00 2001 From: Helge Deller Date: Tue, 9 Nov 2021 22:47:24 +0100 Subject: [PATCH 2/4] parisc: Fix implicit declaration of function '__kernel_text_address' Signed-off-by: Helge Deller --- arch/parisc/kernel/stacktrace.c | 1 + 1 file changed, 1 insertion(+) diff --git a/arch/parisc/kernel/stacktrace.c b/arch/parisc/kernel/stacktrace.c index 6b4ca91932cf..023834ef582e 100644 --- a/arch/parisc/kernel/stacktrace.c +++ b/arch/parisc/kernel/stacktrace.c @@ -8,6 +8,7 @@ * * TODO: Userspace stacktrace (CONFIG_USER_STACKTRACE_SUPPORT) */ +#include #include #include From 38860b2c8bb1b92f61396eb06a63adff916fc31d Mon Sep 17 00:00:00 2001 From: John David Anglin Date: Mon, 8 Nov 2021 16:48:16 -0500 Subject: [PATCH 3/4] parisc: Flush kernel data mapping in set_pte_at() when installing pte for user page For years, there have been random segmentation faults in userspace on SMP PA-RISC machines. It occurred to me that this might be a problem in set_pte_at(). MIPS and some other architectures do cache flushes when installing PTEs with the present bit set. Here I have adapted the code in update_mmu_cache() to flush the kernel mapping when the kernel flush is deferred, or when the kernel mapping may alias with the user mapping. This simplifies calls to update_mmu_cache(). I also changed the barrier in set_pte() from a compiler barrier to a full memory barrier. I know this change is not sufficient to fix the problem. It might not be needed. I have had a few days of operation with 5.14.16 to 5.15.1 and haven't seen any random segmentation faults on rp3440 or c8000 so far. Signed-off-by: John David Anglin Signed-off-by: Helge Deller Cc: stable@kernel.org # 5.12+ --- arch/parisc/include/asm/pgtable.h | 10 ++++++++-- arch/parisc/kernel/cache.c | 4 ++-- 2 files changed, 10 insertions(+), 4 deletions(-) diff --git a/arch/parisc/include/asm/pgtable.h b/arch/parisc/include/asm/pgtable.h index 7badd872f05a..3e7cf882639f 100644 --- a/arch/parisc/include/asm/pgtable.h +++ b/arch/parisc/include/asm/pgtable.h @@ -76,6 +76,8 @@ static inline void purge_tlb_entries(struct mm_struct *mm, unsigned long addr) purge_tlb_end(flags); } +extern void __update_cache(pte_t pte); + /* Certain architectures need to do special things when PTEs * within a page table are directly modified. Thus, the following * hook is made available. @@ -83,11 +85,14 @@ static inline void purge_tlb_entries(struct mm_struct *mm, unsigned long addr) #define set_pte(pteptr, pteval) \ do { \ *(pteptr) = (pteval); \ - barrier(); \ + mb(); \ } while(0) #define set_pte_at(mm, addr, pteptr, pteval) \ do { \ + if (pte_present(pteval) && \ + pte_user(pteval)) \ + __update_cache(pteval); \ *(pteptr) = (pteval); \ purge_tlb_entries(mm, addr); \ } while (0) @@ -303,6 +308,7 @@ extern unsigned long *empty_zero_page; #define pte_none(x) (pte_val(x) == 0) #define pte_present(x) (pte_val(x) & _PAGE_PRESENT) +#define pte_user(x) (pte_val(x) & _PAGE_USER) #define pte_clear(mm, addr, xp) set_pte_at(mm, addr, xp, __pte(0)) #define pmd_flag(x) (pmd_val(x) & PxD_FLAG_MASK) @@ -410,7 +416,7 @@ extern void paging_init (void); #define PG_dcache_dirty PG_arch_1 -extern void update_mmu_cache(struct vm_area_struct *, unsigned long, pte_t *); +#define update_mmu_cache(vms,addr,ptep) __update_cache(*ptep) /* Encode and de-code a swap entry */ diff --git a/arch/parisc/kernel/cache.c b/arch/parisc/kernel/cache.c index c61827e4928a..94150b91c96f 100644 --- a/arch/parisc/kernel/cache.c +++ b/arch/parisc/kernel/cache.c @@ -83,9 +83,9 @@ EXPORT_SYMBOL(flush_cache_all_local); #define pfn_va(pfn) __va(PFN_PHYS(pfn)) void -update_mmu_cache(struct vm_area_struct *vma, unsigned long address, pte_t *ptep) +__update_cache(pte_t pte) { - unsigned long pfn = pte_pfn(*ptep); + unsigned long pfn = pte_pfn(pte); struct page *page; /* We don't have pte special. As a result, we can be called with From 3ec18fc7831e7d79e2d536dd1f3bc0d3ba425e8a Mon Sep 17 00:00:00 2001 From: Sven Schnelle Date: Sat, 13 Nov 2021 20:41:17 +0100 Subject: [PATCH 4/4] parisc/entry: fix trace test in syscall exit path commit 8779e05ba8aa ("parisc: Fix ptrace check on syscall return") fixed testing of TI_FLAGS. This uncovered a bug in the test mask. syscall_restore_rfi is only used when the kernel needs to exit to usespace with single or block stepping and the recovery counter enabled. The test however used _TIF_SYSCALL_TRACE_MASK, which includes a lot of bits that shouldn't be tested here. Fix this by using TIF_SINGLESTEP and TIF_BLOCKSTEP directly. I encountered this bug by enabling syscall tracepoints. Both in qemu and on real hardware. As soon as i enabled the tracepoint (sys_exit_read, but i guess it doesn't really matter which one), i got random page faults in userspace almost immediately. Signed-off-by: Sven Schnelle Signed-off-by: Helge Deller --- arch/parisc/kernel/entry.S | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/parisc/kernel/entry.S b/arch/parisc/kernel/entry.S index 57944d6f9ebb..88c188a965d8 100644 --- a/arch/parisc/kernel/entry.S +++ b/arch/parisc/kernel/entry.S @@ -1805,7 +1805,7 @@ syscall_restore: /* Are we being ptraced? */ LDREG TASK_TI_FLAGS(%r1),%r19 - ldi _TIF_SYSCALL_TRACE_MASK,%r2 + ldi _TIF_SINGLESTEP|_TIF_BLOCKSTEP,%r2 and,COND(=) %r19,%r2,%r0 b,n syscall_restore_rfi