Michael Ellerman <m...@ellerman.id.au> writes:
> From: Balbir Singh <bsinghar...@gmail.com>
>
> It would be nice to be able to dump page tables in a particular
> context.
>
> eg: dumping vmalloc space:
>
> 0:mon> dv 0xd00037fffff00000
> pgd @ 0xc0000000017c0000
> pgdp @ 0xc0000000017c00d8 = 0x00000000f10b1000
> pudp @ 0xc0000000f10b13f8 = 0x00000000f10d0000
> pmdp @ 0xc0000000f10d1ff8 = 0x00000000f1102000
> ptep @ 0xc0000000f1102780 = 0xc0000000f1ba018e
> Maps physical address = 0x00000000f1ba0000
> Flags = Accessed Dirty Read Write
>
> This patch does not replicate the complex code of dump_pagetable and
> has no support for bolted linear mapping, thats why I've it's called
> dump virtual page table support. The format of the PTE can be expanded
> even further to add more useful information about the flags in the PTE
> if required.
>
> Signed-off-by: Balbir Singh <bsinghar...@gmail.com>
> [mpe: Bike shed the output format, show the pgdir]
> Signed-off-by: Michael Ellerman <m...@ellerman.id.au>
> ---
> arch/powerpc/xmon/xmon.c | 111
> +++++++++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 111 insertions(+)
>
> diff --git a/arch/powerpc/xmon/xmon.c b/arch/powerpc/xmon/xmon.c
> index a41392dec822..d84bead0ac28 100644
> --- a/arch/powerpc/xmon/xmon.c
> +++ b/arch/powerpc/xmon/xmon.c
> @@ -127,6 +127,7 @@ static void byterev(unsigned char *, int);
> static void memex(void);
> static int bsesc(void);
> static void dump(void);
> +static void show_pte(unsigned long);
> static void prdump(unsigned long, long);
> static int ppc_inst_dump(unsigned long, long, int);
> static void dump_log_buf(void);
> @@ -234,6 +235,7 @@ Commands:\n\
> #endif
> "\
> dr dump stream of raw bytes\n\
> + dv dump virtual address translation \n\
> dt dump the tracing buffers (uses printk)\n\
> dtc dump the tracing buffers for current CPU (uses printk)\n\
> "
> @@ -2639,6 +2641,9 @@ dump(void)
> dump_log_buf();
> } else if (c == 'o') {
> dump_opal_msglog();
> + } else if (c == 'v') {
> + /* dump virtual to physical translation */
> + show_pte(adrs);
> } else if (c == 'r') {
> scanhex(&ndump);
> if (ndump == 0)
> @@ -2972,6 +2977,112 @@ static void show_task(struct task_struct *tsk)
> tsk->comm);
> }
>
> +void format_pte(void *ptep, unsigned long pte)
> +{
> + printf("ptep @ 0x%016lx = 0x%016lx\n", (unsigned long)ptep, pte);;
> + printf("Maps physical address = 0x%016lx\n", pte & PTE_RPN_MASK);
> +
> + printf("Flags = %s%s%s%s%s\n",
> + (pte & _PAGE_ACCESSED) ? "Accessed " : "",
> + (pte & _PAGE_DIRTY) ? "Dirty " : "",
> + (pte & _PAGE_READ) ? "Read " : "",
> + (pte & _PAGE_WRITE) ? "Write " : "",
> + (pte & _PAGE_EXEC) ? "Exec " : "");
> +}
> +
> +static void show_pte(unsigned long addr)
> +{
> + unsigned long tskv = 0;
> + struct task_struct *tsk = NULL;
> + struct mm_struct *mm;
> + pgd_t *pgdp, *pgdir;
> + pud_t *pudp;
> + pmd_t *pmdp;
> + pte_t *ptep;
> +
> + if (!scanhex(&tskv))
> + mm = &init_mm;
> + else
> + tsk = (struct task_struct *)tskv;
> +
> + if (tsk == NULL)
> + mm = &init_mm;
> + else
> + mm = tsk->active_mm;
> +
> + if (setjmp(bus_error_jmp) != 0) {
> + catch_memory_errors = 0;
> + printf("*** Error dumping pte for task %p\n", tsk);
> + return;
> + }
> +
> + catch_memory_errors = 1;
> + sync();
> +
> + if (mm == &init_mm) {
> + pgdp = pgd_offset_k(addr);
> + pgdir = pgd_offset_k(0);
> + } else {
> + pgdp = pgd_offset(mm, addr);
> + pgdir = pgd_offset(mm, 0);
> + }
> +
> + if (pgd_none(*pgdp)) {
> + printf("no linux page table for address\n");
> + return;
> + }
> +
> + printf("pgd @ 0x%016lx\n", pgdir);
> +
> + if (pgd_huge(*pgdp)) {
> + format_pte(pgdp, pgd_val(*pgdp));
> + return;
> + }
> + printf("pgdp @ 0x%016lx = 0x%016lx\n", pgdp, pgd_val(*pgdp));
> +
> + pudp = pud_offset(pgdp, addr);
> +
> + if (pud_none(*pudp)) {
> + printf("No valid PUD\n");
> + return;
> + }
> +
> +#ifdef CONFIG_HUGETLB_PAGE
> + if (pud_huge(*pudp)) {
> + format_pte(pudp, pud_val(*pudp));
> + return;
> + }
> +#endif
For page table walking code we don't need to put #ifdef here. Also how
should we handle address that we map at pmd level even if hugetlb page
is disabled ? (kernel linear mapping). Also where do we handle THP
mapping ? You may want to look at __find_linux_pte() to write a page
table walking code. or better use the helper.
-aneesh
