[LOADER] Another change to the elf_paddr_offset/virt_base logic.

This avoids using zero to indicate 'undefined'. Instead we use
an explicit boolean to indicate whether suitable defaults should
be used. As well as making the logic clearer (I believe) it also
avoids problems if anyone ever explicitly specifies virt_base
(and also elf_paddr_offset) as zero.

Signed-off-by: Keir Fraser <keir@xensource.com>

diff --git a/tools/libxc/xc_load_elf.c b/tools/libxc/xc_load_elf.c
index 80256d18f861aa70eb28c20b3015b187b0d00c89..1cb821b8b93495bce4fe00f5ed168b63105423c8 100644 (file)
--- a/tools/libxc/xc_load_elf.c
+++ b/tools/libxc/xc_load_elf.c
@@ -58,10 +58,10 @@ static int parseelfimage(const char *image,
     Elf_Ehdr *ehdr = (Elf_Ehdr *)image;
     Elf_Phdr *phdr;
     Elf_Shdr *shdr;
-    unsigned long kernstart = ~0UL, kernend=0UL, vaddr, virt_base;
+    unsigned long kernstart = ~0UL, kernend=0UL, vaddr, virt_base, elf_pa_off;
     const char *shstrtab;
     char *guestinfo=NULL, *p;
-    int h;
+    int h, virt_base_defined, elf_pa_off_defined;
 
     if ( !IS_ELF(*ehdr) )
     {
@@ -148,37 +148,35 @@ static int parseelfimage(const char *image,
 
     dsi->xen_guest_string = guestinfo;
 
-    virt_base = 0;
-    if ( (p = strstr(guestinfo, "VIRT_BASE=")) != NULL )
-        virt_base = strtoul(p+10, &p, 0);
-    dsi->elf_paddr_offset = virt_base;
-    if ( (p = strstr(guestinfo, "ELF_PADDR_OFFSET=")) != NULL )
-        dsi->elf_paddr_offset = strtoul(p+17, &p, 0);
+    /* Initial guess for virt_base is 0 if it is not explicitly defined. */
+    p = strstr(guestinfo, "VIRT_BASE=");
+    virt_base_defined = (p != NULL);
+    virt_base = virt_base_defined ? strtoul(p+10, &p, 0) : 0;
+
+    /* Initial guess for elf_pa_off is virt_base if not explicitly defined. */
+    p = strstr(guestinfo, "ELF_PADDR_OFFSET=");
+    elf_pa_off_defined = (p != NULL);
+    elf_pa_off = elf_pa_off_defined ? strtoul(p+17, &p, 0) : virt_base;
 
     for ( h = 0; h < ehdr->e_phnum; h++ )
     {
         phdr = (Elf_Phdr *)(image + ehdr->e_phoff + (h*ehdr->e_phentsize));
         if ( !is_loadable_phdr(phdr) )
             continue;
-        vaddr = phdr->p_paddr - dsi->elf_paddr_offset + virt_base;
+        vaddr = phdr->p_paddr - elf_pa_off + virt_base;
         if ( vaddr < kernstart )
             kernstart = vaddr;
         if ( (vaddr + phdr->p_memsz) > kernend )
             kernend = vaddr + phdr->p_memsz;
     }
 
-    dsi->v_start = virt_base;
-    if ( dsi->v_start == 0 )
-    {
-        /*
-         * Legacy compatibility and images with no __xen_guest section:
-         * assume header addresses are virtual addresses, and that 
-         * guest memory should be mapped starting at kernel load address.
-         */
-        dsi->v_start = kernstart;
-        if ( dsi->elf_paddr_offset == 0 )
-            dsi->elf_paddr_offset = dsi->v_start;
-    }
+    /*
+     * Legacy compatibility and images with no __xen_guest section: assume
+     * header addresses are virtual addresses, and that guest memory should be
+     * mapped starting at kernel load address.
+     */
+    dsi->v_start          = virt_base_defined  ? virt_base  : kernstart;
+    dsi->elf_paddr_offset = elf_pa_off_defined ? elf_pa_off : dsi->v_start;
 
     dsi->v_kernentry = ehdr->e_entry;
     if ( (p = strstr(guestinfo, "VIRT_ENTRY=")) != NULL )

diff --git a/xen/common/elf.c b/xen/common/elf.c
index ef74673ab3f058dec0d1139e931e03a6ca9dc78f..6fad5c5437dabba348c36d216dd99c742d34c9ca 100644 (file)
--- a/xen/common/elf.c
+++ b/xen/common/elf.c
@@ -23,10 +23,10 @@ int parseelfimage(struct domain_setup_info *dsi)
     Elf_Ehdr *ehdr = (Elf_Ehdr *)dsi->image_addr;
     Elf_Phdr *phdr;
     Elf_Shdr *shdr;
-    unsigned long kernstart = ~0UL, kernend=0UL, vaddr, virt_base;
+    unsigned long kernstart = ~0UL, kernend=0UL, vaddr, virt_base, elf_pa_off;
     char *shstrtab, *guestinfo=NULL, *p;
     char *elfbase = (char *)dsi->image_addr;
-    int h;
+    int h, virt_base_defined, elf_pa_off_defined;
 
     if ( !elf_sanity_check(ehdr) )
         return -EINVAL;
@@ -84,37 +84,35 @@ int parseelfimage(struct domain_setup_info *dsi)
     if ( guestinfo == NULL )
         guestinfo = "";
 
-    virt_base = 0;
-    if ( (p = strstr(guestinfo, "VIRT_BASE=")) != NULL )
-        virt_base = simple_strtoul(p+10, &p, 0);
-    dsi->elf_paddr_offset = virt_base;
-    if ( (p = strstr(guestinfo, "ELF_PADDR_OFFSET=")) != NULL )
-        dsi->elf_paddr_offset = simple_strtoul(p+17, &p, 0);
+    /* Initial guess for virt_base is 0 if it is not explicitly defined. */
+    p = strstr(guestinfo, "VIRT_BASE=");
+    virt_base_defined = (p != NULL);
+    virt_base = virt_base_defined ? simple_strtoul(p+10, &p, 0) : 0;
+
+    /* Initial guess for elf_pa_off is virt_base if not explicitly defined. */
+    p = strstr(guestinfo, "ELF_PADDR_OFFSET=");
+    elf_pa_off_defined = (p != NULL);
+    elf_pa_off = elf_pa_off_defined ? simple_strtoul(p+17, &p, 0) : virt_base;
 
     for ( h = 0; h < ehdr->e_phnum; h++ )
     {
         phdr = (Elf_Phdr *)(elfbase + ehdr->e_phoff + (h*ehdr->e_phentsize));
         if ( !is_loadable_phdr(phdr) )
             continue;
-        vaddr = phdr->p_paddr - dsi->elf_paddr_offset + virt_base;
+        vaddr = phdr->p_paddr - elf_pa_off + virt_base;
         if ( vaddr < kernstart )
             kernstart = vaddr;
         if ( (vaddr + phdr->p_memsz) > kernend )
             kernend = vaddr + phdr->p_memsz;
     }
 
-    dsi->v_start = virt_base;
-    if ( dsi->v_start == 0 )
-    {
-        /*
-         * Legacy compatibility and images with no __xen_guest section:
-         * assume header addresses are virtual addresses, and that 
-         * guest memory should be mapped starting at kernel load address.
-         */
-        dsi->v_start = kernstart;
-        if ( dsi->elf_paddr_offset == 0 )
-            dsi->elf_paddr_offset = dsi->v_start;
-    }
+    /*
+     * Legacy compatibility and images with no __xen_guest section: assume
+     * header addresses are virtual addresses, and that guest memory should be
+     * mapped starting at kernel load address.
+     */
+    dsi->v_start          = virt_base_defined  ? virt_base  : kernstart;
+    dsi->elf_paddr_offset = elf_pa_off_defined ? elf_pa_off : dsi->v_start;
 
     dsi->v_kernentry = ehdr->e_entry;
     if ( (p = strstr(guestinfo, "VIRT_ENTRY=")) != NULL )