[PATCH v4 2/4] RISCV: Fix incorrect virtual address translation in crashdump load

[luo.haiyang at zte.com.cn]

From: Luo Haiyang <luo.haiyang at zte.com.cn>

The kexec shows the following crashdump log:

Elf header: p_type = 1, p_offset = 0x80100000 p_paddr = 0x80100000 p_vaddr = 0xcff000 ...
Elf header: p_type = 1, p_offset = 0x100000000 p_paddr = 0x100000000 p_vaddr = 0x80bff000 ...
Elf header: p_type = 1, p_offset = 0x87ffff000 p_paddr = 0x87ffff000 p_vaddr = 0x800bfe000 ...

Obviously, phys_to_virt returns an incorrect virtual address (vaddr). On the RISC-V architecture,
the linear address mapping is defined as:
va = pa + kernel_map.va_pa_offset (kernel_map.va_pa_offset = PAGE_OFFSET - phys_ram_base)
Both PAGE_OFFSET and phys_ram_base can be read from /proc/kcore.

Signed-off-by: Luo Haiyang <luo.haiyang at zte.com.cn>
---
kexec/arch/riscv/Makefile          |  2 ++
kexec/arch/riscv/crashdump-riscv.c | 55 ++++++++++++++++++++++++------
util_lib/elf_info.c                | 41 +++++++++++++++++-----
util_lib/include/elf_info.h        |  1 +
4 files changed, 80 insertions(+), 19 deletions(-)

diff --git a/kexec/arch/riscv/Makefile b/kexec/arch/riscv/Makefile
index 18a997b..e886770 100644
--- a/kexec/arch/riscv/Makefile
+++ b/kexec/arch/riscv/Makefile
@@ -14,6 +14,8 @@ riscv_ARCH_REUSE_INITRD =
riscv_CPPFLAGS += -I $(srcdir)/kexec/
+riscv_PHYS_TO_VIRT =
+
dist += $(riscv_KEXEC_SRCS)                \
kexec/arch/riscv/image-header.h         \
kexec/arch/riscv/include/arch/options.h     \
diff --git a/kexec/arch/riscv/crashdump-riscv.c b/kexec/arch/riscv/crashdump-riscv.c
index e923a71..6875249 100644
--- a/kexec/arch/riscv/crashdump-riscv.c
+++ b/kexec/arch/riscv/crashdump-riscv.c
@@ -1,5 +1,6 @@
#include <errno.h>
#include <elf.h>
+#include <elf_info.h>
#include <unistd.h>
#include "kexec.h"
@@ -22,18 +23,45 @@ static struct memory_ranges crash_mem_ranges = {0};
static struct memory_ranges system_mem_ranges = {0};
struct memory_range elfcorehdr_mem = {0};
-static unsigned long long get_page_offset(struct kexec_info *info)
+static unsigned long long phys_offset;
+
+static int get_page_offset(unsigned long long *page_offset)
{
-   unsigned long long vaddr_off = 0;
-   unsigned long long page_size = sysconf(_SC_PAGESIZE);
-   unsigned long long init_start = get_kernel_sym("_sinittext");
+   int fd, ret = 0;
-   /*
-    * Begining of init section is aligned to page size
-    */
-   vaddr_off = init_start - page_size;
+   if ((fd = open("/proc/kcore", O_RDONLY)) < 0) {
+       fprintf(stderr, "Can't open (%s).\n", "/proc/kcore");
+       return EFAILED;
+   }
+
+   ret = read_page_offset_elf_kcore(fd, (long *)page_offset);
+   if (ret)
+       fprintf(stderr, "Can't get page_offset from /proc/kcore\n");
+
+   close(fd);
+   return ret;
+}
+
+static int get_phys_offset(unsigned long long *phys_offset)
+{
+   int fd, ret = 0;
+
+   if ((fd = open("/proc/kcore", O_RDONLY)) < 0) {
+       fprintf(stderr, "Can't open (%s).\n", "/proc/kcore");
+       return EFAILED;
+   }
+
+   ret = read_phys_offset_elf_kcore(fd, (long *)phys_offset);
+   if (ret)
+       fprintf(stderr, "Can't get phys_offset from /proc/kcore\n");
-   return vaddr_off;
+   close(fd);
+   return ret;
+}
+
+unsigned long phys_to_virt(struct crash_elf_info *elf_info, unsigned long long p)
+{
+   return elf_info->page_offset - phys_offset + p;
}
/*
@@ -124,7 +152,14 @@ int load_elfcorehdr(struct kexec_info *info)
if (crash_get_memory_ranges())
return EFAILED;
-   elf_info.page_offset = get_page_offset(info);
+   if (get_phys_offset(&phys_offset))
+       return EFAILED;
+
+   dbgprintf("phys_offset:   %016llx\n", phys_offset);
+
+   if (get_page_offset(&elf_info.page_offset))
+       return EFAILED;
+
dbgprintf("page_offset:   %016llx\n", elf_info.page_offset);
#if __riscv_xlen == 64
diff --git a/util_lib/elf_info.c b/util_lib/elf_info.c
index 589bc1a..36eb895 100644
--- a/util_lib/elf_info.c
+++ b/util_lib/elf_info.c
@@ -1308,16 +1308,39 @@ int read_phys_offset_elf_kcore(int fd, long *phys_off)
*phys_off = ULONG_MAX;
+   if (phys_offset != UINT64_MAX) {
+       *phys_off = phys_offset;
+       return 0;
+   }
+
+   /* If we have a valid 'PHYS_OFFSET' by now,
+    * return it to the caller now.
+    */
ret = read_elf(fd);
-   if (!ret) {
-       /* If we have a valid 'PHYS_OFFSET' by now,
-        * return it to the caller now.
-        */
-       if (phys_offset != UINT64_MAX) {
-           *phys_off = phys_offset;
-           return ret;
-       }
+   if (!ret && phys_offset != UINT64_MAX) {
+       *phys_off = phys_offset;
+       return 0;
+   }
+
+   return -EFAULT;
+}
+
+int read_page_offset_elf_kcore(int fd, long *page_off)
+{
+   int ret;
+
+   *page_off = ULONG_MAX;
+
+   if (page_offset != UINT64_MAX) {
+       *page_off = page_offset;
+       return 0;
+   }
+
+   ret = read_elf(fd);
+   if (!ret && page_offset != UINT64_MAX) {
+       *page_off = page_offset;
+       return 0;
}
-   return 2;
+   return -EFAULT;
}
diff --git a/util_lib/include/elf_info.h b/util_lib/include/elf_info.h
index fdf4c3d..3ccc950 100644
--- a/util_lib/include/elf_info.h
+++ b/util_lib/include/elf_info.h
@@ -29,6 +29,7 @@ int get_pt_load(int idx,
unsigned long long *virt_start,
unsigned long long *virt_end);
int read_phys_offset_elf_kcore(int fd, long *phys_off);
+int read_page_offset_elf_kcore(int fd, long *page_off);
int read_elf(int fd);
void dump_dmesg(int fd, void (*handler)(char*, unsigned int));
extern void (*arch_scan_vmcoreinfo)(char *pos);
--
2.27.0