6.11-stable review patch. If anyone has any objections, please let me know.
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From: Andy Shevchenko andriy.shevchenko@linux.intel.com
[ Upstream commit be4ca6c53e66cb275cf0d71f32dac0c4606b9dc0 ]
The init_size description of boot protocol has an example of the runtime start address for the compressed bzImage. For non-relocatable kernel it relies on the pref_address value (if not 0), but for relocatable case only pays respect to the load_addres and kernel_alignment, and it is inaccurate for the latter. Boot loader must consider the pref_address as the Linux kernel relocates to it before being decompressed as nicely described in this commit message a year ago:
43b1d3e68ee7 ("kexec: Allocate kernel above bzImage's pref_address")
Due to this documentation inaccuracy some of the bootloaders (*) made a mistake in the calculations and if kernel image is big enough, this may lead to unbootable configurations.
*) In particular, kexec-tools missed that and resently got a couple of changes which will be part of v2.0.30 release. For the record, commit 43b1d3e68ee7 only fixed the kernel kexec implementation and also missed to update the init_size description.
While at it, make an example C-like looking as it's done elsewhere in the document and fix indentation as presribed by the reStructuredText specifications, so the syntax highliting will work properly.
Fixes: 43b1d3e68ee7 ("kexec: Allocate kernel above bzImage's pref_address") Fixes: d297366ba692 ("x86: document new bzImage fields") Signed-off-by: Andy Shevchenko andriy.shevchenko@linux.intel.com Signed-off-by: Ingo Molnar mingo@kernel.org Acked-by: Randy Dunlap rdunlap@infradead.org Cc: "H. Peter Anvin" hpa@zytor.com Link: https://lore.kernel.org/r/20241125105005.1616154-1-andriy.shevchenko@linux.i... Signed-off-by: Sasha Levin sashal@kernel.org --- Documentation/arch/x86/boot.rst | 17 +++++++++++++---- 1 file changed, 13 insertions(+), 4 deletions(-)
diff --git a/Documentation/arch/x86/boot.rst b/Documentation/arch/x86/boot.rst index 4fd492cb49704..ad2d8ddad27fe 100644 --- a/Documentation/arch/x86/boot.rst +++ b/Documentation/arch/x86/boot.rst @@ -896,10 +896,19 @@ Offset/size: 0x260/4
The kernel runtime start address is determined by the following algorithm::
- if (relocatable_kernel) - runtime_start = align_up(load_address, kernel_alignment) - else - runtime_start = pref_address + if (relocatable_kernel) { + if (load_address < pref_address) + load_address = pref_address; + runtime_start = align_up(load_address, kernel_alignment); + } else { + runtime_start = pref_address; + } + +Hence the necessary memory window location and size can be estimated by +a boot loader as:: + + memory_window_start = runtime_start; + memory_window_size = init_size;
============ =============== Field name: handover_offset