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

[Xen patchbot-unstable <patchbot-unstable@xxxxxxxxxxxxxxxxxxx>]

# HG changeset patch
# User kaf24@xxxxxxxxxxxxxxxxxxxx
# Node ID d9f63f9361c4b933215b4e3a70a5600ba3f6f370
# Parent  4dcb93547710d1071e6d2e77c6d7b7890760fb4a
[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@xxxxxxxxxxxxx>
---
 tools/libxc/xc_load_elf.c |   40 +++++++++++++++++++---------------------
 xen/common/elf.c          |   40 +++++++++++++++++++---------------------
 2 files changed, 38 insertions(+), 42 deletions(-)

diff -r 4dcb93547710 -r d9f63f9361c4 tools/libxc/xc_load_elf.c
--- a/tools/libxc/xc_load_elf.c Sun May 21 09:55:15 2006 +0100
+++ b/tools/libxc/xc_load_elf.c Sun May 21 18:55:14 2006 +0100
@@ -58,10 +58,10 @@ static int parseelfimage(const char *ima
     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 *ima
 
     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 -r 4dcb93547710 -r d9f63f9361c4 xen/common/elf.c
--- a/xen/common/elf.c  Sun May 21 09:55:15 2006 +0100
+++ b/xen/common/elf.c  Sun May 21 18:55:14 2006 +0100
@@ -23,10 +23,10 @@ int parseelfimage(struct domain_setup_in
     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_in
     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 )

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