Hi Simon
Thanks for your review!
On Thu, 30 Mar 2023 at 09:49, Simon Horman horms@kernel.org wrote:
On Mon, Mar 27, 2023 at 05:06:53PM +0200, Ricardo Ribalda wrote:
Clang16 links the purgatory text in two sections:
[ 1] .text PROGBITS 0000000000000000 00000040 00000000000011a1 0000000000000000 AX 0 0 16 [ 2] .rela.text RELA 0000000000000000 00003498 0000000000000648 0000000000000018 I 24 1 8 ... [17] .text.hot. PROGBITS 0000000000000000 00003220 000000000000020b 0000000000000000 AX 0 0 1 [18] .rela.text.hot. RELA 0000000000000000 00004428 0000000000000078 0000000000000018 I 24 17 8
And both of them have their range [sh_addr ... sh_addr+sh_size] on the area pointed by `e_entry`.
This causes that image->start is calculated twice, once for .text and another time for .text.hot. The second calculation leaves image->start in a random location.
Because of this, the system crashes inmediatly after:
s/inmediatly/immediately/
kexec_core: Starting new kernel
Cc: stable@vger.kernel.org
Maybe a fixes tag is warranted here.
Reviewed-by: Ross Zwisler zwisler@google.com Signed-off-by: Ricardo Ribalda ribalda@chromium.org
kernel/kexec_file.c | 13 ++++++++++++- 1 file changed, 12 insertions(+), 1 deletion(-)
diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c index f1a0e4e3fb5c..25a37d8f113a 100644 --- a/kernel/kexec_file.c +++ b/kernel/kexec_file.c @@ -901,10 +901,21 @@ static int kexec_purgatory_setup_sechdrs(struct purgatory_info *pi, }
offset = ALIGN(offset, align);
/** Check if the segment contains the entry point, if so,* calculate the value of image->start based on it.* If the compiler has produced more than one .text sectionsnit: s/sections/section/
* (Eg: .text.hot), they are generally after the main .textIf this is the general case, then are there cases where this doesn't hold?
When looking at this issue, I have only seen .text.hot after .text. But I cannot warantee that future versions of llvm or gcc decide to swap the order.
I am going to add a WARN whenever there are two overlapping .text sections so the user has the chance to update their linker script.
* section, and they shall not be used to calculate* image->start. So do not re-calculate image->start if it* is not set to the initial value.*/ if (sechdrs[i].sh_flags & SHF_EXECINSTR && pi->ehdr->e_entry >= sechdrs[i].sh_addr && pi->ehdr->e_entry < (sechdrs[i].sh_addr
+ sechdrs[i].sh_size)) {
+ sechdrs[i].sh_size) &&kbuf->image->start == pi->ehdr->e_entry) { kbuf->image->start -= sechdrs[i].sh_addr; kbuf->image->start += kbuf->mem + offset; }-- 2.40.0.348.gf938b09366-goog-b4-0.11.0-dev-696ae
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-- Ricardo Ribalda