File kdump-large-phdrs.patch of Package kdump

From: Petr Tesarik <ptesarik@suse.cz>
Subject: Handle dump files with many program headers
References: bsc#932339
Patch-mainline: not yet

To reduce memory requirements, kdumptool reads only the beginning of
the dump file. If there are too many program headers, this size is
insufficient, and the program header table appears truncated.

Unfortunately, gelf_getehdr() cannot be used, because it fails when
program headers are truncated. Raw ELF headers must be examined.

Signed-off-by: Petr Tesarik <ptesarik@suse.cz>
---
 kdumptool/util.cc |   77 +++++++++++++++++++++++++++++++++++++-----------------
 1 file changed, 54 insertions(+), 23 deletions(-)

--- a/kdumptool/util.cc
+++ b/kdumptool/util.cc
@@ -235,12 +235,39 @@ static off_t FindElfNoteByName(int fd, o
 // -----------------------------------------------------------------------------
 #define ELF_HEADER_MAPSIZE          (128*1024)
 
+static void *map_elf(int fd, size_t len)
+{
+    void *map;
+    map = mmap(NULL, len, PROT_READ, MAP_PRIVATE, fd, 0);
+    if (map == MAP_FAILED) {
+	map = mmap(NULL, len, PROT_READ | PROT_WRITE,
+		   MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
+	if (map == MAP_FAILED)
+	    throw KSystemError("Cannot allocate ELF headers", errno);
+
+	size_t to_read = len;
+	char *p = reinterpret_cast<char *>(map);
+	while (to_read) {
+	    ssize_t bytes_read = read(fd, p, to_read);
+	    if (bytes_read < 0)
+		throw KSystemError("ELF read error", errno);
+	    else if (!bytes_read)
+		break;
+
+	    to_read -= bytes_read;
+	    p += bytes_read;
+	}
+    }
+    return map;
+}
+
 bool Util::isXenCoreDump(int fd)
     throw (KError)
 {
     void *map = MAP_FAILED;
     Elf *elf = (Elf*)0;
     bool ret = false;
+    size_t mapsize = ELF_HEADER_MAPSIZE;
 
     Debug::debug()->trace("isXenCoreDump(%d)", fd);
 
@@ -248,41 +275,45 @@ bool Util::isXenCoreDump(int fd)
         throw KError("libelf is out of date.");
 
     try {
-        map = mmap(NULL, ELF_HEADER_MAPSIZE, PROT_READ, MAP_PRIVATE, fd, 0);
-        if (map == MAP_FAILED) {
-            map = mmap(NULL, ELF_HEADER_MAPSIZE, PROT_READ,
-                       MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
-            if (map == MAP_FAILED)
-                throw KSystemError("Cannot allocate ELF headers", errno);
-
-            size_t to_read = ELF_HEADER_MAPSIZE;
-            char *p = reinterpret_cast<char *>(map);
-            while (to_read) {
-                ssize_t bytes_read = read(fd, p, to_read);
-                if (bytes_read < 0)
-                    throw KSystemError("ELF read error", errno);
-                else if (!bytes_read)
-                    break;
-
-                to_read -= bytes_read;
-                p += bytes_read;
-            }
-        }
-        elf = elf_memory(reinterpret_cast<char *>(map), ELF_HEADER_MAPSIZE);
+        map = map_elf(fd, mapsize);
+        elf = elf_memory(reinterpret_cast<char *>(map), mapsize);
         if (!elf)
             throw KELFError("elf_memory() failed", elf_errno());
 
         if (elf_kind(elf) != ELF_K_ELF)
             return false;
 
+        size_t endphdr;
+        Elf32_Ehdr *ehdr32;
+        Elf64_Ehdr *ehdr64;
+
         switch (gelf_getclass(elf)) {
         case ELFCLASS32:
+            ehdr32 = reinterpret_cast<Elf32_Ehdr*>(map);
+            endphdr = ehdr32->e_phoff + ehdr32->e_phentsize * ehdr32->e_phnum;
+            break;
         case ELFCLASS64:
+            ehdr64 = reinterpret_cast<Elf64_Ehdr*>(map);
+            endphdr = ehdr64->e_phoff + ehdr64->e_phentsize * ehdr64->e_phnum;
             break;
         default:
             throw KError("Unrecognized ELF class");
         }
 
+        if (endphdr > mapsize) {
+            elf_end(elf);
+            munmap(map, mapsize);
+
+            long pagesize = sysconf(_SC_PAGESIZE);
+            mapsize = (endphdr + pagesize - 1) & ~(pagesize - 1);
+            Debug::debug()->dbg("Enlarging map size to %zu bytes", mapsize);
+
+            map = map_elf(fd, mapsize);
+            elf = elf_memory(reinterpret_cast<char *>(map), mapsize);
+            if (!elf)
+                throw KELFError("elf_memory() failed", elf_errno());
+        }
+
         size_t phnum, i;
         if (elf_getphdrnum(elf, &phnum))
             throw KELFError("Cannot count ELF program headers", elf_errno());
@@ -304,11 +335,11 @@ bool Util::isXenCoreDump(int fd)
         if (elf)
             elf_end(elf);
         if (map != MAP_FAILED)
-            munmap(map, ELF_HEADER_MAPSIZE);
+            munmap(map, mapsize);
         throw;
     }
 
-    munmap(map, ELF_HEADER_MAPSIZE);
+    munmap(map, mapsize);
     elf_end(elf);
     return ret;
 }