load_linux: Don't use size heuristic for non-relocatable kernels

For non-relocatable kernels, it really makes no sense to estimate how
much space the kernel is going to need, as if we fail, there is really
nothing we can do about it.  Furthermore, it is actively wrong for
zImage kernels (which aren't decompressed in place) and for non-Linux
kernels.

Additionally, tweak the code for assigning an address to the command
line to handle a few more corner cases correctly, be simpler, and not
need to build the memory map again since we already are doing that
elsewhere.

Reported-and-tested-by: Christian Hesse <list@eworm.de>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>

1 files changed, 40 insertions, 33 deletions

diff --git a/com32/lib/syslinux/load_linux.c b/com32/lib/syslinux/load_linux.c
index df934e40..06ae2a97 100644
--- a/com32/lib/syslinux/load_linux.c
+++ b/com32/lib/syslinux/load_linux.c
@@ -124,32 +124,29 @@ static int map_initramfs(struct syslinux_movelist **fraglist,
     return 0;
 }
 
-static size_t calc_cmdline_offset(struct linux_header *hdr,
+static size_t calc_cmdline_offset(const struct syslinux_memmap *mmap,
+				  const struct linux_header *hdr,
 				  size_t cmdline_size, addr_t base,
 				  addr_t start)
 {
-    if (hdr->version < 0x0202 || !(hdr->loadflags & 0x01)) {
-	struct syslinux_memmap *mmap;
-
-	mmap = syslinux_memory_map();
-	if (mmap && !syslinux_memmap_highest(mmap, SMT_FREE, &start,
-					     cmdline_size, 0xa0000, 16)) {
-	    syslinux_free_memmap(mmap);
-	    return start - base;
-	}
+    size_t max_offset;
 
-	if (mmap && !syslinux_memmap_highest(mmap, SMT_TERMINAL, &start,
-					     cmdline_size, 0xa0000, 16)) {
-	    syslinux_free_memmap(mmap);
-	    return start - base;
-	}
+    if (hdr->version >= 0x0202 && (hdr->loadflags & LOAD_HIGH))
+	max_offset = 0x10000;
+    else
+	max_offset = 0xfff0 - cmdline_size;
+
+    if (!syslinux_memmap_highest(mmap, SMT_FREE, &start,
+				 cmdline_size, 0xa0000, 16) ||
+	!syslinux_memmap_highest(mmap, SMT_TERMINAL, &start,
+				 cmdline_size, 0xa0000, 16)) {
+	
 
-	syslinux_free_memmap(mmap);
-	dprintf("Unable to find lowmem for cmdline\n");
-	return (0x9ff0 - cmdline_size) & ~15;
+	return min(start - base, max_offset) & ~15;
     }
 
-    return 0x10000;
+    dprintf("Unable to find lowmem for cmdline\n");
+    return (0x9ff0 - cmdline_size) & ~15; /* Legacy value: pure hope... */
 }
 
 int bios_boot_linux(void *kernel_buf, size_t kernel_size,
@@ -159,7 +156,7 @@ int bios_boot_linux(void *kernel_buf, size_t kernel_size,
 {
     struct linux_header hdr, *whdr;
     size_t real_mode_size, prot_mode_size, base;
-    addr_t real_mode_base, prot_mode_base;
+    addr_t real_mode_base, prot_mode_base, prot_mode_max;
     addr_t irf_size;
     size_t cmdline_size, cmdline_offset;
     struct setup_data *sdp;
@@ -243,9 +240,19 @@ int bios_boot_linux(void *kernel_buf, size_t kernel_size,
     real_mode_size = (hdr.setup_sects + 1) << 9;
     real_mode_base = (hdr.loadflags & LOAD_HIGH) ? 0x10000 : 0x90000;
     prot_mode_base = (hdr.loadflags & LOAD_HIGH) ? 0x100000 : 0x10000;
+    prot_mode_max  = (hdr.loadflags & LOAD_HIGH) ? (addr_t)-1 : 0x8ffff;
     prot_mode_size = kernel_size - real_mode_size;
 
-    cmdline_offset = calc_cmdline_offset(&hdr, cmdline_size, real_mode_base,
+    /* Get the memory map */
+    mmap = syslinux_memory_map();	/* Memory map for shuffle_boot */
+    amap = syslinux_dup_memmap(mmap);	/* Keep track of available memory */
+    if (!mmap || !amap) {
+	errno = ENOMEM;
+	goto bail;
+    }
+
+    cmdline_offset = calc_cmdline_offset(mmap, &hdr, cmdline_size,
+					 real_mode_base,
 					 real_mode_base + real_mode_size);
     dprintf("cmdline_offset at 0x%x\n", real_mode_base + cmdline_offset);
 
@@ -281,14 +288,6 @@ int bios_boot_linux(void *kernel_buf, size_t kernel_size,
 	}
     }
 
-    /* Get the memory map */
-    mmap = syslinux_memory_map();	/* Memory map for shuffle_boot */
-    amap = syslinux_dup_memmap(mmap);	/* Keep track of available memory */
-    if (!mmap || !amap) {
-	errno = ENOMEM;
-	goto bail;
-    }
-
     dprintf("Initial memory map:\n");
     syslinux_dump_memmap(mmap);
 
@@ -304,13 +303,21 @@ int bios_boot_linux(void *kernel_buf, size_t kernel_size,
 
     /* Place the kernel in memory */
 
-    /* First, find a suitable place for the protected-mode code */
+    /*
+     * First, find a suitable place for the protected-mode code.  If
+     * the kernel image is not relocatable, just worry if it fits (it
+     * might not even be a Linux image, after all, and for !LOAD_HIGH
+     * we end up decompressing into a different location anyway), but
+     * if it is, make sure everything fits.
+     */
     base = prot_mode_base;
     if (prot_mode_size &&
-	syslinux_memmap_find(amap, &base, hdr.init_size,
+	syslinux_memmap_find(amap, &base,
+			     hdr.relocatable_kernel ?
+			     hdr.init_size : prot_mode_size,
 			     hdr.relocatable_kernel, hdr.kernel_alignment,
-			     prot_mode_base, (addr_t)-1,
-			     prot_mode_base, (addr_t)-1)) {
+			     prot_mode_base, prot_mode_max,
+			     prot_mode_base, prot_mode_max)) {
 	dprintf("Could not find location for protected-mode code\n");
 	goto bail;
     }